Document:

Flexible Deferral Plan

 Exhibit 10(ab) 
 SIGMA-ALDRICH CORPORATION 
 2005 FLEXIBLE DEFERRAL PLAN 

WHEREAS, Sigma-Aldrich Corporation, a Delaware corporation (hereinafter the “Company”), 3050 Spruce Street, St. Louis, Missouri
63103, previously adopted the Sigma- Aldrich Corporation Flexible Deferral Plan (“Plan”); and 
 WHEREAS, the Company
reserved the right to amend the Plan pursuant to Section 10 thereof; and 
 WHEREAS, effective January 1, 2009, the
Company desires to amend and restate the Plan to incorporate provisions required by Section 409A of the Internal Revenue Code of 1986, as amended; and 
 WHEREAS, the Company intends that amounts deferred under the Plan as of December 31, 2004 and any earnings attributable to such deferrals shall be “grandfathered” and governed by the Plan
document as in effect as of December 31, 2004 (“2003 Flexible Deferral Plan”); and 
 WHEREAS, the Company
intends that amounts deferred on or after January 1, 2005 and any earnings attributable to such deferrals, which have not been paid on or before December 31, 2008, shall be governed by the Plan as amended and restated, effective
January 1, 2009 (“2005 Flexible Deferral Plan”) and any subsequent amendments thereto; 
 NOW THEREFORE, the Plan
is amended and restated, effective January 1, 2009, as the 2005 Flexible Deferral Plan to read as follows: 
 1.
Establishment and Purposes. 
 a. Establishment. In recognition of the valuable services performed by certain
employees, the Company established the Plan. The Participants participating in this Plan constitute a select group of management or highly compensated employees. It is the intention of the parties that this arrangement is unfunded for tax purposes
and for purposes of Title I of ERISA. 

 b. Name. The Plan shall be known as the “Sigma-Aldrich Corporation 2005 Flexible
Deferral Plan.” 
 c. Purpose. The purpose of this Plan is to allow Participants to defer a portion of their
compensation so that such amounts may be paid to the Participants (or their Beneficiaries) as specified pursuant to this Plan. 

2. Definitions. 
 Except as otherwise provided herein, the following terms shall have the definitions hereinafter indicated wherever used in this Plan with initial capital letters: 

a. Beneficiary: Any person, entity, or any combination thereof, designated by a Participant in accordance with Section 7.h.
of this Plan, to receive benefits under this Plan in the event of the Participant’s death, or in the absence of any such designation, his or her estate. The term “Beneficiary” shall include one or more Beneficiaries, including all
contingent Beneficiaries designated. 
 b. Board of Directors: The Company’s Board of Directors or other governing
body at any time. 
 c. Company: Sigma-Aldrich Corporation, a Delaware corporation, and any corporation or other entity
having purchased all or substantially all of the assets and other property of Sigma-Aldrich Corporation or any successor corporation or other entity resulting from a merger or consolidation with Sigma-Aldrich Corporation. 

d. Code: The Internal Revenue Code of 1986, as amended. 

  
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 e. Committee: The Committee shall mean and be comprised of the same individuals as
may then be serving, at any time or from time to time, as members of the Pension Plan Committee under the Company’s Sigma-Aldrich Corporation Retirement Security Value Plan, as amended. 

f. Deferral Election Form: A written document under which a Participant elects to defer a portion of his or her compensation in
substantially the form of Exhibit 1 attached hereto (or such other form or by any other means, electronically or otherwise, as the Company may designate from time to time). 
 g. Deferred Compensation Account: Deferred Compensation Account shall have the meaning set forth in Section 6 of this Plan. 

h. ERISA: The Employee Retirement Income Security Act of 1974, as amended. 

i. In-Service Account: In-Service Account shall have the meaning set forth in Section 6 of this Plan. 

j. Participant: An employee of the Company, or a subsidiary of the Company, selected by the Company (or a Committee or other group
designated by the Company), in its discretion, to participate in this Plan, provided that all chosen employees shall be members of a select group of management or highly compensated employees. 

k. Plan: Plan shall mean this Sigma-Aldrich Corporation Flexible Deferral Plan. 

l. Retirement: Retirement shall mean a Participant’s termination of employment on or after attainment of age 55. A
Participant shall be deemed to have terminated employment only if the Company and the Participant reasonably anticipate a permanent 

  
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reduction in his or her level of bona fide services to a level less than 50% of the average level of bona fide services provided by the Participant in the immediately preceding thirty-six
(36) months. 
 m. Retirement Account: Retirement Account shall have the meaning set forth in Section 6 of this
Plan. 
 n. Trust or Trust Fund: Any trust established to hold amounts set aside by the Company in accordance with
Section 6. 
 o. Trustee: The institution appointed by the Company and by any additional or successor trustee of the
Trust Fund. 
 3. Participation in the Plan. 
 a. Eligibility. Employees of the Company, or a subsidiary of the Company, selected by the Company (or a Committee or other group designated by the Company), in its discretion, to participate in the
Plan, from time to time shall be eligible to participate in this Plan. Notwithstanding any other provision herein, only individuals who are members of a select group of management or highly compensated employees may participate in this Plan. The
Company hereby designates the Committee to designate, in its discretion, the individuals entitled to participate under this Plan, provided that all individuals participating hereunder must be members of a select group of management or highly
compensated employees of the Company, or a subsidiary of the Company. At any time the Company may designate a different Committee or group to make such designations, or may make such designations itself. 

b. Participation. Participants may elect to commence their participation in this Plan and defer payment of part of their
compensation as provided herein by executing a Deferral Election Form in substantially the form of Exhibit 1 attached hereto (or such other form or by any other means, electronically or otherwise, as the Company may designate from time to time) and
delivering said Deferral Election Form to the Company. 

  
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 c. Deferral Amounts. Each Deferral Election Form executed under this Plan shall
specify the percentage of salary and/or bonus which is to be deferred for each year. A Participant can defer a minimum of one percent (1%), but no more than fifty percent (50%), in increments of one percent (1%), of his or her salary for any year,
and a Participant may defer a minimum of one percent (1%) or up to one hundred percent (100%) of any bonus for any year designated by the Company as eligible for deferral under this Plan; provided, however, no Participant shall be allowed
to defer any part or all of his or her bonus which has been classified by the Company as a “special bonus”. A Participant may elect to defer none of his or her salary and/or none of his or her bonus. For the purposes of this Plan, salary
means the aggregate compensation paid to a Participant by the Company or by a subsidiary of the Company employing the Participant, including base salary, overtime pay, commissions, and all other items that constitute wages within the meaning of
Section 3401(a) of the Code, but does not include any bonuses or other amounts contributed to, or received under, any other plan of deferred compensation. Compensation excludes all stock option transactions, expense account reimbursements,
automobile allowances and moving expense reimbursements. 
 d. Election Periods. For each calendar year in which a
Participant desires to defer his or her compensation under the Plan, he or she must execute and deliver a Deferral Election Form in the form and manner directed by the Company before any deferrals can become effective. The Deferral Election Form
must be made by the date set forth by the Company, which shall be no later than the December 31 prior to the calendar year for which such compensation would otherwise be earned. However, in the year in which an employee is first

  
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eligible to participate in the Plan, such Deferral Election Form shall be filed within thirty (30) days of the date on which the employee is first eligible to participate in the Plan but
such election shall apply only to the base salary earned during the remainder of the calendar year. Notwithstanding the foregoing, in the case of any bonus which is determined to be performance- based compensation under Code Section 409A, the
Company may permit a Deferral Election Form to be filed up until the date that is six months before the end of the performance period, provided (i) the performance criteria are defined in writing no later than ninety (90) days after the
commencement of the period of service to which the criteria relates; (ii) the Participant has performed services for the Company continuously from the later of the beginning of the performance period to which the bonus relates or the date upon
which the performance criteria are established; and (iii) the bonus has not become both substantially certain to be paid and readily ascertainable. The portion of Deferral Election Form indicating the amount of compensation to be deferred for
an upcoming deferral period becomes irrevocable as of the latest date on which it could be made for such year. 
 e.
Effective Elections. All elections provided for in subparagraphs (a) through (d) in this Section shall only be effective if filed with or delivered to the Company (or its designee under Section 8 hereunder) in the manner
requested or directed by the Company. 
 4. Participant Elective Deferrals and Designation of Schedule for Payment of
Benefits. 
 a. Compensation Deferral. Subject to the limits specified in Section 3 herein, during each payroll
period in which a Participant has elected to defer compensation under a Deferral Election Form, the Company shall defer payment of such part of the Participant’s compensation as is specified in the Deferral Election Form (herein the
“Participant Elective 

  
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Deferrals”). Such deferred amounts shall be credited to a Participant’s Deferred Compensation Account on a monthly basis (or more frequently in the Company’s discretion). However,
in the case of compensation which is paid less frequently than monthly, any deferred amount shall be credited to a Participant’s Deferred Compensation Account no later than one month following the date such compensation would have been paid to
the Participant in the absence of a deferral election. 
 b. Deferral Election Form. In addition to electing the amount
of his or her compensation that shall be deferred pursuant to the Deferral Election Form, a Participant must also designate the applicable percentages of such amount (in whole percentage(s) only) to be allocated his or her Retirement Account and/or
each In-Service Account(s). In the absence of such an election, the entire amount of the Participant’s Elective Deferrals shall be credited to the Participant’s Retirement Account. In the event a Participant elects to have all or any
portion of Participant Elective Deferrals allocated to a new In-Service Account, such Participant must also designate on the Deferral Election form the distribution date for such account. The date must be an objectively determinable date and must be
at least five (5) years from the date such In-Service Account is established. 
 5. Earnings Amounts. In addition to
the Participant Elective Deferrals which shall be credited to a Participant’s Deferred Compensation Account, the Company shall also credit (or reduce) a Participant’s Deferred Compensation Account by an amount equal to the amount that
would have been earned (or lost) if the amounts deferred under this Plan had been invested in hypothetical investments designated by the Participant from time to time, based on a list of hypothetical investments specified by the Company. The choices
to be selected by the Participant among the list of available hypothetical investments may be different based on the 

  
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Participant’s designation of when a deferral shall become payable (for example, the choices of investments for retirement deferrals may be different from the choices for deferrals to be
distributed while the Participant is still in-service). Such hypothetical earnings shall be referred to in this Plan as the “Earnings Amounts.” The Participant shall designate on his or her Deferral Election Form (or in such other form or
by any other means, electronically or otherwise, as the Company may designate from time to time), the investments used to measure the Earnings Amounts from the list specified by the Company. Such designations shall be made in the manner prescribed
by the Company (for example, the Company may require that all designations be made in one percent (1%) increments). The Participant may change such designations on a daily basis as permitted by the Company. Earnings Amounts shall be credited to
(or deducted from) the Participant’s Deferred Compensation Account at least monthly (or more frequently at the discretion of the Company). Earnings shall be credited (or deducted from) a Deferred Compensation Account until all payments with
respect to such account have been made under this Plan. The Company shall not be liable or otherwise responsible for any decrease in a Participant’s Deferred Compensation Account because of the investment performance of the designated assets.
To the extent that a Participant or his or her Beneficiary acquires a right to receive payments from the Company under the provisions hereof, such right shall be no greater than the right of any unsecured general creditor of the Company or any
subsidiary of the Company. 
 Notwithstanding any provision to the contrary herein, in the event a Participant is permitted to
defer all or a portion of a bonus otherwise payable in shares of Company stock, the earnings and losses on the shares credited under the Plan to the Participant’s Deferred Compensation Account shall be based on the performance of the Company
stock. Furthermore, 

  
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the Company may implement such restrictions and limitations on the Participant’s ability to transfer credited shares of Company stock to other hypothetical investments available under the
Plan as the Company deems appropriate in its sole discretion. 
 6. Deferred Compensation Account. 

a. Deferred Compensation Account. The Company shall cause to be established for each Participant a bookkeeping account (the
“Deferred Compensation Account”) to provide a convenient method of measuring the Company’s obligation to each Participant under this Plan. Each Participant’s Deferred Compensation Account shall be comprised of one or more
subaccounts among which the Company shall record the amounts equal to the Participant’s Elective Deferrals, and the related Earnings Amounts. Such subaccounts shall be limited to an account which shall become payable to the Participant upon his
or her Retirement (“Retirement Account”) and up to five (5) short-term accounts which shall be distributed to the Participant on specified payment dates (“In-Service Accounts”). Deferred Compensation Accounts shall at all
times remain a part of the general assets of the Company and shall remain available for the payment of Company obligations and the obligations of the Company’s subsidiaries. 

b. Unfunded Arrangement. Neither the existence of this Plan nor any Deferred Compensation Account shall be deemed to create a
trust. Any trust referred to in this Plan or created by the Company in connection with this Plan, and any assets held by the trust to assist the Company in meeting its obligations under this Plan, will constitute an unfunded arrangement for tax
purposes and for purposes of Title I of ERISA. Neither the existence of this Plan nor any Deferred Compensation Account shall entitle any Participant, Beneficiary or other person to a claim or lien against the assets of a Deferred Compensation
Account or any other assets of the Company. Any Participant and his or her Beneficiary shall have only the rights of an unsecured general creditor in regard to receiving the benefits payable under this Plan. 

  
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 c. Status of Trust Fund. The Company is under no obligation to segregate any assets
to provide for the Company’s obligations under this Plan. If the Company does elect to segregate assets into a Trust Fund pursuant to subsection (d) of this Section 6, the Deferred Compensation Accounts may be maintained on the books
of the Trust Fund referenced therein. 
 d. Creation of Trust Fund. The Company may, but is not required to, establish a
Trust Fund and make contributions to it corresponding to any or all of the obligations of the Company to make payments under this Plan. These contributions shall be credited with income, expenses, gains and losses in accordance with the investment
experience of the Trust Fund. The Committee may direct the Trustee to establish investment funds within the Trust Fund. The Committee may alter the available funds or procedures for allocating the Deferred Compensation Accounts among them at any
time. All assets of the Trust Funds shall remain the property of the Company. No Participant shall have any priority claim on the Trust Fund or any security interest or other right in or to them superior to the rights of general creditors of the
Company or any subsidiary of the Company. 
 7. Benefit Payments. 

a. Payments Based on Designated Schedule(s). Unless otherwise provided herein, amounts credited to a Participant’s Retirement
Account shall be distributed on the first day of the seventh month immediately following the date of the Participant’s Retirement. Distribution of a Participant’s Retirement Account shall be made in a lump sum unless the Participant has
designated on his or her Deferral Election Form for payment to be made in annual installments between two (2) and fifteen (15) years. If a Participant has elected to receive 

  
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distribution of his or her Retirement Account in annual installments, such Participant may also designate on his or her Deferral Election Form a specific percentage of his or her Retirement
Account balance to be distributed as the first annual installment payment, with the remaining amount to be paid in substantially equal amounts over the remaining distribution period (“First Installment Option”). In the absence of a First
Installment Option election, each annual installment payment will be for substantially equal amounts, except to the extent any increase or decrease in the amount reflects the earnings or losses through the date the amount is paid. 

Unless otherwise provided herein, distribution of a Participant’s In-Service Account shall be made in a lump sum on the date
specified on the Participant’s Deferral Election Form unless the Participant has designated on his or her Deferral Election Form for payment to be made in substantially equal annual installments not to exceed five (5) years. 

b. Payment Election Change. A Participant may elect to (i) extend the deferral period (subject to a minimum of five
(5) additional years) for any In-Service Account and/or (ii) change the method of distribution (for example, the number of annual installments or to elect a First Installment Option) for any In-Service Account or Retirement Account in
accordance with the procedures established by the Company. If a Participant makes such an election, then (a) such change must be made at least twelve (12) months before the original designated distribution date; (ii) such election
change shall not become effective until twelve (12) months after the date the Participant submits the change to the Company and (iii) the first payment with respect to which such election is made shall be deferred for a period of not less
than five (5) years from the date such payment would otherwise have been made. 
 c. Mandatory Lump Sum Payment.
Notwithstanding any other designation by a Participant, if the Participant’s employment with the Company terminates for any reason 

  
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before the Participant’s attainment of age 55, an amount equal to the balance of the Participant’s Deferred Compensation Account at the time shall be paid to the Participant in a lump
sum. Such payment shall be made on the first day of the seventh month immediately following the Participant’s date of termination, and the Company shall have no further liability hereunder. However, if the Participant’s termination of
employment with the Company is on account of his or her death, the lump sum payment shall be made to the Participant’s designated Beneficiary on the first day of the month immediately following the date of the Participant’s death.

 d. Payment Upon the Retired Participant’s Death. If a Participant, who has designated in his or her Deferral
Election Form the payment of his or her Retirement Account and/or any In-Service Account over a number of years, dies at any time following the commencement of his or her payments, the payments shall continue to be made over the then balance of the
years, as designated by the Participant, such payments being paid to the Participant’s Beneficiary. 

e. Fixed Payment Dates. In all cases in which amounts are payable upon a fixed date, payment is deemed to be
made upon the fixed date if the payment is made on such date or a later date within the same calendar year or, if later, by the 15th day of the third calendar month following the specified date (provided the Participant is not permitted, directly or
indirectly, to designate the taxable year of payment). 
 f. Withholding. Notwithstanding any other provision herein, the
Company shall be entitled to withhold from any amount payable hereunder any amount required to be withheld for income, employment or other federal, state or local taxes. 
 g. Payment Only from Company Assets. Except in the case of non-cash compensation deferred under the Plan, all distributions from the Plan to Participants and

  
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Beneficiaries shall be made in cash, unless the Committee determines that other property should be distributed. Any payment of benefits to a Participant or his or her Beneficiary shall be made
from assets which shall continue, for all purposes, to be a part of the general assets of the Company. No person shall have or acquire any interest in such assets by virtue of the provisions of this Plan. To the extent that a Participant or his or
her Beneficiary acquires a right to receive payments from the Company under the provisions hereof, such right shall be no greater than the right of any unsecured general creditor of the Company. This Plan constitutes a mere promise by the Company to
make benefit payments in the future. 
 h. Beneficiaries. A Participant may designate on his or her Deferral Election
Form (or pursuant to such other form or writing or by other means, electronically or otherwise, as the Company may designate from time to time) a Beneficiary or Beneficiaries to receive the amounts as provided herein after his or her death. In the
absence of such a designation, the Company shall pay any such amount to the Participant’s estate. A Beneficiary designation may be revoked or amended by a Participant at any time in accordance with the procedures established by the Company.

 8. Administration of the Plan and Claims Procedure. 

a. Determinations. The Committee, or such other Committee or individual designated by the Company, shall make all determinations
as to rights to benefits under this Plan. The Committee shall have full power and authority to interpret, construe and administer this Plan. The interpretation and construction of this Plan by the Committee, and any action taken pursuant thereto,
shall be binding and conclusive upon all parties in interest. All expenses of the Plan’s administration shall be paid by the Company. 

  
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 The Committee, in carrying out its duties with respect to the administration of the Plan,
shall have, in addition to any other power conferred by the Plan or by law, the following powers: 
 (i) to determine all
questions relating to eligibility to participate in the Plan; 
 (ii) to compute and certify to the Company the amount and kind
of distributions payable to the Participants and Beneficiaries; 
 (iii) to maintain records necessary for the administration
of the Plan that are not maintained by the Company or the Trustee, if any; 
 (iv) to interpret the Plan provisions and to make
and publish such rules with regard to the Plan’s administration not inconsistent with the terms hereof; 
 (v) to
establish and modify the method of accounting for the Plan; 
 (vi) to employ counsel, accountants and other consultants to aid
in exercising its powers and carrying out its duties hereunder; and 
 (vii) to perform any other acts necessary and proper for
the Plan’s administration, except those that are performed by the Trustee, if any, or as otherwise limited by the Company. 

b. Reports. The Company shall provide each Participant with a statement reflecting the amount of the Participant’s Deferred
Compensation Account on at least a quarterly basis. 
 c. No Liability. No Committee member, employee, agent, officer,
member, manager, volunteer or director of the Company (or its designee) shall, in any event, be liable to any person for any action taken or omitted to be taken in connection with the interpretation, construction or administration of this Plan, so
long as such action or omission to act is made in good faith. 

  
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 d. Designation of Committee. The Company hereby designates the Committee to
administer this Plan. Said Committee shall have all the authority as is granted to the Company under the terms of this Plan for the administration of this Plan in accordance with its terms and in ruling on such questions arising out of the
administration, interpretation and application of the Plan. The Committee may approve or disapprove all Deferral Election Forms and elections in connection herewith, and make all other determinations hereunder. Members of the Committee may
participate in the Plan, but no member of the Committee shall be entitled to make decisions which relate solely to his or her own participation. The Company reserves the right to designate a different Committee, or an individual, to administer this
Plan from time to time, or to make any determinations directly at any time. If no such Committee or individual is designated at any time, such functions, as appropriate, may be conducted by the Company’s Board of Directors. The Company’s
Board of Directors hereby reserves the right to revoke such designation at any time and to make other designations (and to revoke such designations) at any time. 
 e. Claims Procedure. The following provisions are hereby made a part of this Plan and are intended to meet the requirements of ERISA: 

(1) The named fiduciary under this Plan is the Company. 
 (2) This Plan is unfunded. The Participants shall defer certain amounts under this Plan, but all benefits shall be paid from the Company’s general assets which at all times shall remain subject to
the claims of the Company’s general creditors. 

  
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 (3) Direct payment by the Company is the basis of payment of benefits under this Plan.

 (4) The following claims procedures shall apply for purposes of this Plan. Any and all persons presenting claims hereunder
(individually or collectively, “Claimant”) must follow these procedures: 
 (A) For claims procedure purposes, the
Committee shall appoint among themselves a chairperson of the Committee (or the chairperson of any other Committee designated by the Company to administer this Plan, or a designated member of the Board of Directors or other governing body of the
Company). 
 (B) A Claimant shall make a claim for benefits hereunder by submitting a written claim to the Company (or its
designee) in the manner set forth herein for providing notice to the Company under this Plan. The Committee shall decide whether the claim shall be allowed, and the following claims procedure shall apply: 

(i) If for any reason a claim for benefits under this Plan is denied by the Committee in whole or in part, the Committee shall deliver
to the Claimant a written explanation setting forth: the specific reason or reasons for the adverse determination; references to specific Plan provisions on which the determination is based; a description of any additional material or information
necessary for the Claimant to perfect the claim and an explanation of why such material or information is necessary; and a description of the Plan’s review procedure including a statement of the Claimant’s rights to bring a civil action
under Section 502 of ERISA following an adverse determination on review, all written in a manner calculated to be understood by the Claimant. For this purpose: 
 (a) The Committee’s claim shall be deemed filed when delivered in writing as provided herein. 

  
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 (b) The Committee’s explanation shall be in writing delivered to the Claimant within
90 days after receipt of the claim by the Plan, unless the Committee determines that special circumstances require an extension of time for processing the claim. If such an extension of time for processing is required, written notice of the
extension shall be furnished to the Claimant prior to the termination of the initial 90 day period. In no event shall such extension exceed a period of 90 days from the end of such initial period. The extension notice shall indicate the special
circumstances requiring an extension of time and the date by which the Committee expects to render the benefit determination. If the period of time is extended because the Claimant has failed to provide necessary information to decide the claim, the
period for making the benefit determination shall be tolled from the date on which the notification of the extension is sent to the Claimant, until the date on which the Claimant provides the information. 

(ii) The Claimant shall have 60 days following his or her receipt of a notice of adverse benefit determination to file with the
Committee a written request for review of the denial. Claimant shall have the opportunity to submit written comments, documents, records, and other information relating to the claim for benefits. Claimant shall be provided, upon request and free of
charge, reasonable access to, and copies of, all documents, records, and other information relevant to the Claimant’s claim for benefits. The review of the claim shall take into account all comments, documents, records, and other information
submitted by the Claimant relating to the claim, without regard to whether such information was submitted or considered in the initial benefit determination. 

  
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 (iii) In the case of a request for review of an adverse benefit determination, the Company
shall designate an individual or Committee (herein the “Reviewer”) to review the claim. On review, the Reviewer shall notify the Claimant not later than 60 days after the Company’s receipt of the request for review, unless the
Reviewer determines that special circumstances require an extension of time for processing the claim, in which case a decision shall be rendered as soon as possible, but not later than 120 days after receipt of the request for review. If such an
extension of time for review is required because of special circumstances, written notice of the extension shall be furnished to the Claimant prior to the commencement of the extension. The extension notice shall indicate the special circumstances
requiring an extension of time and the date by which the Plan expects to render the determination on review. If the period of time is extended because the Claimant has failed to provide necessary information to decide the claim, the period for
making the benefit determination shall be tolled from the date on which the notification of the extension is sent to the Claimant, until the date on which the Claimant provides the information. The decision on review shall be in writing and in the
case of an adverse benefit determination shall include: (1) the specific reason or reasons for the decision; (2) references to the specific Plan provisions on which the benefit determination is based; (3) a statement that the Claimant
is entitled to receive, upon request and free of charge, reasonable access to, and copies of, all documents, records and other information relevant to the Claimant’s claim for benefits; and (4) a statement of the Claimant’s right to
bring an action under Section 502(a) of ERISA, all written in a manner calculated to be understood by the Claimant. If the decision on review is not furnished within such time, the claim shall be deemed denied on review. 

  
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 9. Non-Assignability of Benefits. Neither any Participant nor any Beneficiary under
this Plan shall have any power or right to transfer, assign, anticipate, hypothecate or otherwise encumber any part or all of the amounts payable hereunder. Such amounts shall not be subject to seizure by any creditor of a Participant or any
Beneficiary hereunder, by a proceeding at law or in equity, nor transferable by operation of law in the event of the bankruptcy or insolvency of any Participant or any Beneficiary hereunder. Any such attempted assignment or transfer shall be void
and shall terminate the Participant’s participation in this Plan; the Company shall thereupon have no further liability hereunder with respect to such Participant and his or her Beneficiary. 

10. Amendment and Termination. This Plan may not be amended, altered or modified, retroactively, except by a written instrument
signed by the Company and the impacted Participants or their respective successors. The Company may amend, alter, modify or terminate this Plan on a prospective basis at any time, provided further that no such modification or termination shall
adversely affect a Participant’s entitlement to benefits attributable to amounts credited to his or her Deferred Compensation Account prior to the modification or termination of this Plan. Without limiting the generality of the foregoing, the
Company reserves the right to discontinue this Plan at any time, and/or change the eligibility of the Participants as well as the percentage or amounts Participants may defer. This Plan document sets forth the terms and provisions of this Plan and
any prior written or oral communications regarding the terms of this Plan shall not alter or modify the terms of this Plan. In the event the Plan is terminated, benefits shall become payable due to such termination only to the extent permissible
under the regulations promulgated by the Secretary of Treasury pursuant to Code Section 409A and in the manner set forth therein. 

  
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 11. Impact on Other Benefits. Except as otherwise required by the Code or any other
applicable law, this Plan and the benefits provided herein are in addition to all other benefits which may be provided by the Company to the Participants from time to time, and shall not reduce, replace or otherwise cause any reduction, in any
manner, with regard to any of such other benefits. In no event shall any provision herein be deemed to amend or modify any employment agreement between the Company and any Participant, and no provision herein shall be deemed to entitle any
Participant to continued employment with the Company. 
 12. Notices. Any notice or other communication required or
permitted under this Plan shall be in writing and, if directed to the Company, shall be sent by United States certified mail, return receipt requested, postage prepaid, addressed to: Sigma-Aldrich Corporation, 3050 Spruce Street, St. Louis, Missouri
63103, Attn: Flexible Deferral Plan Committee, and, if directed to a Participant or to a Beneficiary, may be hand-delivered or mailed to such Participant or Beneficiary at the last known address for such person as it appears in the Company’s
records. A notice or other communication sent by United States certified mail, return receipt requested, postage prepaid, addressed as provided above, shall be deemed to have been given on the next business day after mailing. 

13. Governing Law. This Plan shall be governed by and construed in accordance with the laws of the State of Missouri without
regard to its conflict of law rules. 
 14. Headings. The headings of the sections of this Plan are for reference only
and are not to be utilized in construing the Plan. 
 15. Gender. All pronouns of whatever gender refer indifferently to
persons or objects of any gender. 
 16. Singular and Plural. Singular terms refer also the plural number and vice versa.

  
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 17. Severability. If any provision of this Plan is held illegal or invalid for any
reason, the remaining provisions are to remain in full force and effect and to be construed and enforced in accordance with the purposes of the Plan as if the illegal or invalid provision did not exist. 

18. Section 409A Provisions. This Plan shall be interpreted in a manner consistent with the provisions of Section 409A
of the Code and the regulations thereunder. 
 IN WITNESS WHEREOF, the Company has executed and adopted this restatement of the
Plan on this 19 day of December, 2008. 
  

			
	SIGMA-ALDRICH CORPORATION
		
	By:	 	 /s/ Douglas W.
Rau

			
	Print Name:	 	 Douglas W. Rau

	Print Title:	 	 VP Human Resources

  
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 SIGMA-ALDRICH CORPORATION 

DEFERRED COMPENSATION PLAN 
 EXHIBIT 1 
 DEFERRAL ELECTION FORM 

  
 22 

 FIRST AMENDMENT TO THE 

SIGMA-ALDRICH CORPORATION 2005 FLEXIBLE DEFERRAL PLAN 
 WHEREAS, Sigma-Aldrich Corporation, a Delaware corporation (hereinafter the “Company”), 3050 Spruce Street, St. Louis, Missouri 63103, previously adopted the Sigma-Aldrich Corporation 2005
Flexible Deferral Plan (“Plan”); and 
 WHEREAS, the Company reserved the right to amend the Plan pursuant to
Section 10 thereof; and 
 WHEREAS, effective January 1, 2010, the Company desires to amend the Plan to allow for
discretionary Company contributions; 
 NOW THEREFORE, effective January 1, 2010, the Plan shall be amended as follows:

  

	1.	The definition of In-Service Account in Section 1 is deleted in its entirety and replaced with the following: 

“In-Service Account: In-Service Account shall mean a subaccount of the Deferred Compensation Account which
shall be distributed to the Participant on a specified payment date.” 
  

	2.	The following new definition is inserted in Section 1 therein: 

“Company Contribution Account: Company Contribution Account shall mean a subaccount of a Deferred Compensation
Account which shall become payable to the Participant upon his termination of employment.” 
  

	3.	The definition of Retirement Account in Section 1 is deleted in its entirety and replaced with the following: 

“Retirement Account: Retirement Account shall mean a subaccount of the Deferred Compensation Account which
shall become payable to the Participant upon his or her Retirement.” 
  

	4.	The following new subsection (f) is inserted at the end of Section 3 therein: 

“f. Company Contributions. The Company may, in its sole discretion, credit a Participant’s Company
Contribution Account at such times and in such amounts as it may determine (“Company Contribution”). 

(1) Discretionary Match. In its sole discretion, the Company may credit a Participant’s Company Contribution
Account with a discretionary matching contribution in an amount equal to 60% of Participant Elective Deferrals up to a maximum of 6% of compensation. Any such discretionary matching contribution will be credited annually within 90 days following the

 
close of the applicable calendar year. For purposes of this subsection 3(f)(1), “compensation” means the amount of Participant Elective Deferrals that reduces the amount of compensation
taken into account under the Sigma-Aldrich 401(k) Retirement Savings Plan for purposes of determining the maximum matching contribution under such plan. 
 (2) Discretionary Contribution. At the Company’s election, the Company may credit a Participant’s Company Contribution Account with a discretionary contribution in such amount and at such
time as it determines. 
 The Company has no obligation to make a Company Contribution under this subsection
3(f), nor is the Company obligated to make a Company Contribution to all Participants or in the same amounts.” 
 5. The first paragraph of
Subsection 5(a) is deleted in its entirety and replaced with the following: 
 “Earnings Amounts. In addition to the
Participant Elective Deferrals and Company Contributions, if any, which shall be credited to a Participant’s Deferred Compensation Account, the Company shall also credit (or reduce) a Participant’s Deferred Compensation Account by an
amount equal to the amount that would have been earned (or lost) if the amounts credited under this Plan had been invested in the available hypothetical investments specified by the Company. Such hypothetical earnings shall be referred to in this
Plan as the “Earnings Amounts.” With respect to the Participant Elective Deferrals, the Participant shall designate his or her hypothetical investment(s) on the Deferral Election Form (or in such other form or by any other means,
electronically or otherwise, as the Company may designate from time to time) in the manner prescribed by the Company. In the case of Company Contributions, the Company shall designate a rate of return or hypothetical investment on which Earning
Amounts will be based until the Participant makes an hypothetical investment election in accordance with the procedures established by the Company. The available hypothetical investments may be differ among the Retirement Account, Company
Contribution Account and the In-Service Accounts. A Participant may change his or her investment elections on a daily basis as permitted by the Company. Earnings Amounts shall be credited to (or deducted from) the Participant’s Deferred
Compensation Account at least monthly (or more frequently at the discretion of the Company). Earning Amounts shall be credited (or deducted from) a Deferred Compensation Account until all payments with respect to such account have been made under
this Plan. The Company shall not be liable or otherwise responsible for any decrease in a Participant’s Deferred Compensation Account because of the investment performance of the designated assets. To the extent that a Participant or his or her
beneficiary acquires a right to receive payments form the Company under the provisions hereof, such right shall be no greater than the right of any unsecured general creditor of the Company or any [ILLEGIBLE] in its entirety and replaced with
the following: 
 a. Deferred Compensation Account. The Company shall cause to be established for each Participant a
bookkeeping account (the “Deferred Compensation Account”) to 

 
provide a convenient method of measuring the Company’s obligations to each Participant under this Plan. Each Participant’s Deferred Compensation Account shall be comprised of one or
more subaccounts among which the Company shall record the amounts equal to the Participant’s Elective Deferrals, Company Contributions, if any, and the related Earnings Amounts. Such subaccounts shall include a Retirement Account, a Company
Contribution Account and up to five (5) In-Service Accounts. Participants’ Deferred Compensation Accounts shall at all times remain a part of the general assets of the Company and shall remain available for the payment of Company
obligations and the obligations of the Company’s subsidiaries. 
 7. The following is inserted at the end of Section 7(a) as a new
paragraph: 
 “Unless otherwise provided herein, amounts credited to a Participant’s Company Contributions Account, if
any, shall be distributed to the Participant in a lump sum on the first day of the seventh month immediately following the date of the Participant’s termination of employment.” 

IN WITNESS WHEREOF, the Company has caused this amendment to be executed by its duly authorized officer this 29 day of December, 2009.

  

			
	SIGMA-ALDRICH CORPORATION
		
	By:	 	 /s/ Douglas W.
Rau

			
	Print Name:	 	 Douglas W. Rau

	Print Title:	 	 VP Human Resources

 SIGMA-ALDRICH CORPORATION 

FLEXIBLE DEFERRAL PLAN 
 THIS PLAN, effective as of February 1, 2003 (the “Effective Date”), is established by Sigma-Aldrich Corporation, a Delaware corporation (hereinafter the “Company”), 3050 Spruce
Street, St. Louis, Missouri 63103. 
 RECITALS 

The Company recognizes the valuable services performed for it by the employees participating in this Plan (herein the
“Participants”). 
 The Company desires to establish this Plan to permit certain designated employees of the Company
and its subsidiaries to defer payment of a portion of their compensation until the times specified pursuant to this Plan. 
 The
Participants participating in this Plan constitute a select group of management or highly compensated employees. 
 It is the
intention of the parties that this arrangement is unfunded for tax purposes and for purposes of Title I of ERISA. 
 The Company
desires to provide the terms and conditions under which such amounts shall be deferred and paid. 
 AGREEMENTS

 In consideration of these premises, the Company hereby declares: 

1. Establishment and Purposes. 
 a. Establishment. Company hereby establishes this Plan as of the Effective Date. 
 b. Name. The Plan shall be known as the “Sigma-Aldrich Corporation Flexible Deferral Plan.” 

 c. Purpose. The purpose of this Plan is to allow Participants to defer a portion of
their compensation so that such amounts may be paid to the Participants (or their Beneficiaries) as specified pursuant to this Plan. 
 2. Definitions. 
 Except as otherwise provided herein, the following terms
shall have the definitions hereinafter indicated wherever used in this Plan with initial capital letters: 
 a.
Beneficiary: Any person, entity, or any combination thereof, designated by a Participant in a written document in substantially the form of Section 7 of the Deferral Election Form attached to this Plan as Exhibit 1 and hereby made a part
of this Plan (or such other form or by any other means, electronically or otherwise, as the Company may designate from time to time), to receive benefits under this Plan in the event of the Participant’s death, or in the absence of any such
designation, his or her estate. The term “Beneficiary” shall include one or more Beneficiaries, including all contingent Beneficiaries designated. 
 b. Board of Directors: The Company’s Board of Directors or other governing body at any time. 
 c. Company: Sigma-Aldrich Corporation, a Delaware corporation, and any corporation or other entity having purchased all or substantially all of the assets and other property of Sigma-Aldrich
Corporation or any successor corporation or other entity resulting from a merger or consolidation with Sigma-Aldrich Corporation. 
 d. Code: The Internal Revenue Code of 1986, as amended. 
 e. Deferral
Election Form: A written document under which a Participant elects to defer a portion of his or her compensation in substantially the form of Exhibit 1 attached hereto (or such other form or by any other means, electronically or otherwise, as
the Company may designate from time to time). 

  
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 f. Deferred Compensation Account: Deferred Compensation Account shall have the
meaning set forth in Section 6 of this Plan. 
 g. Disability or Disabled: A Participant shall be considered
“Disabled” or to have a “Disability” for purposes of this Plan if he or she has a physical or mental condition which, in the judgment of the Committee, totally and permanently prevents the Participant from engaging in any
substantial remunerative occupation or employment, not including any condition resulting from a Participant’s participation in the commission of a felony, or from injury received or disease contracted in the service of the Armed Forces of the
United States or of any other country. A determination of Disability shall be based upon a certification from a physician selected by the Committee, or a determination under the Federal Social Security Act. 

h. ERISA: The Employee Retirement Income Security Act of 1974, as amended. 

i. Participant: An employee of the Company, or a subsidiary of the Company, selected by the Company (or a Committee or other group
designated by the Company), in its discretion, to participate in this Plan, provided that all chosen employees shall be members of a select group of management or highly compensated employees. 

j. Plan: Plan shall mean this Sigma-Aldrich Corporation Flexible Deferral Plan. 

k. Committee: The Committee shall mean and be comprised of the same individuals as may then be serving, at anytime or from time to
time, as members of the Pension Plan Committee under the Company’s Sigma-Aldrich Corporation Retirement Security Value Plan, as amended. 

  
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 l. Trust or Trust Fund: Any trust established to hold amounts set aside by the
Company in accordance with Section 6. 
 m. Trustee: The institution appointed by the Company and by any additional
or successor trustee of the Trust Fund. 
 3. Participation in the Plan. 

a. Eligibility. Employees of the Company, or a subsidiary of the Company, selected by the Company (or a Committee or other group
designated by the Company), in its discretion, to participate in the Plan, from time to time shall be eligible to participate in this Plan. Notwithstanding any other provision herein, only individuals who are members of a select group of management
or highly compensated employees may participate in this Plan. The Company hereby designates the Committee to designate, in its discretion, the individuals entitled to participate under this Plan, provided that all individuals participating hereunder
must be members of a select group of management or highly compensated employees of the Company, or a subsidiary of the Company. At any time the Company may designate a different Committee or group to make such designations, or may make such
designations itself. 
 b. Deferral Election Form. Participants may elect to commence their participation in this Plan
and defer payment of part of their compensation as provided herein by executing a Deferral Election Form in substantially the form of Exhibit 1 attached hereto (or such other form or by any other means, electronically or otherwise, as the Company
may designate from time to time) and delivering said Deferral Election Form to the Company. The current salary and bonus of a Participant will be thereupon reduced by the amount specified in the Deferral Election Form and said amount credited to the
Deferred Compensation Account. 

  
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 c. Deferral Amounts. Each Deferral Election Form executed under this Plan shall
specify the percentage of base salary and/or bonus which is to be deferred for each year. A Participant can defer a minimum of one percent (1%), but no more than fifty percent (50%), in increments of one percent (1%), of his or her base salary for
any year, and a Participant may defer a minimum of one percent (1%) or up to one hundred percent (100%) of his or her bonus for any year; provided, however, no Participant shall be allowed to defer any part or all of his or her bonus which
has been classified by the Company as a “special bonus”. The amount to be deferred shall be deducted from the compensation otherwise payable to the Participant. A Participant may elect to defer none of his or her base salary and/or none of
his or her bonus. For the purposes of this Plan, base salary means the aggregate compensation paid to a Participant by the Company or by a subsidiary of the Company employing the Participant, including salary, overtime pay, commissions, bonuses
(except as specified herein) and all other items that constitute wages within the meaning of Section 3401(a) of the Code, including the amounts deferred by the Participants under this Plan but does not include any other amounts contributed to,
or received under, any other plan of deferred compensation. Compensation excludes all stock option transactions, expense account reimbursements, automobile allowances and moving expense reimbursements. 

d. Election Periods. At times designated by the Company, each Participant may execute and deliver a Deferral
Election Form with the Company in the form and manner directed by the Company. A base salary and bonus deferral period ends each December 31st and a new deferral period begins January 1st. The election to defer for each new year must be made by
December 15th of the previous year (except in the case of new employees of the Company, or a subsidiary of the Company, becoming eligible to participate in the Plan, the Deferral Election Form shall be executed and delivered within 45 days
following said new Participant’s employment 

  
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commencement date or within such other longer period of time as permitted by the Company from time to time). A Participant who desires to continue to participate in this Plan shall file a
Deferral Election Form each year. Subject to the other provisions of this Plan providing for various specific rights and privileges of Participants to discontinue or otherwise change elections hereunder on a prospective basis, a Deferral Election
Form becomes irrevocable as of the latest date on which it could be made for each year. 
 e. Discontinuance. If a
Participant wishes to discontinue deferrals hereunder, he or she may file a Notice of Discontinuance with the Committee at any time, with such discontinuance becoming effective within fifteen days following the Committee’s receipt of such
Notice of Discontinuance or, if additional time is needed by the Committee to administer or otherwise process such discontinuance, then the effective date of such discontinuance shall be as soon as is administratively convenient to the Committee. A
Participant may change his or her salary deferral election but in no event shall any such changes be given effect by the Company or the Committee more than once per calendar quarter. A Notice of Deferral Election change will be effective within
fifteen (15) days following the Committee’s receipt of such Notice of Deferral Election change or, if additional time is needed by the Committee to administer or otherwise process such change, then the effective date of such change shall
be as soon as is administratively convenient to the Committee. Notwithstanding anything in this subparagraph (e) or elsewhere in the Plan to the contrary, under no circumstances shall any requested discontinuance or other change be effective
with respect to any salary or bonus earned by the electing Participant at any times or for any periods prior to the date the Committee receives the Participant’s Notice of Discontinuance or Notice of Deferral Election change, as the case may
be. 

  
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 f. Recommencement. Participants who had participated in the Plan
and who subsequently discontinue or otherwise terminate their participation may recommence active participation (beginning on January 1st of the next Plan year after 12 consecutive non-deferral months) by filing a new Deferral Election Form as allowed by
the Company. 
 g. Effective Elections. All elections provided for in subparagraphs (a) through (f) in this
Section shall only be effective if filed with or delivered to the Company (or its designee under Section 8 hereunder) in the manner requested or directed by the Company. In addition, all elections provided for in subparagraphs (e) and
(f) in this Section shall be made subject to the prior consent and approval of the Company (or its designee under Section 8 hereunder). 
 4. Participant Elective Deferrals and Designation of Schedule for Payment of Benefits. 
 a. Compensation Deferral. Subject to the limits specified in Section 3 herein, during each payroll period in which a Participant has elected to defer compensation under a Deferral Election
Form, the Company shall defer payment of such part of the Participant’s compensation as is specified in the Deferral Election Form (herein the “Participant Elective Deferrals”). Such deferred amounts shall be credited to a
Participant’s Deferred Compensation Account on a monthly basis (or more frequently in the Company’s discretion). 
 b.
Deferral Election Form. In addition to designating the amount of his or her compensation that shall be deferred in a Deferral Election Form, a Participant may also designate when such amounts shall be paid, as provided in Section 7 of
this Plan. 
 5. Earnings Amounts. In addition to the Participant Elective Deferrals which shall be credited to a
Participant’s Deferred Compensation Account, the Company shall also credit (or reduce) a Participant’s Deferred Compensation Account by an amount equal to the amount that would have been earned (or lost) if the amounts deferred under this
Plan had been invested in 

  
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hypothetical investments designated by the Participant from time to time, based on a list of hypothetical investments specified by the Company. The choices to be selected by the Participant among
the list of available hypothetical investments may be different based on the Participant’s designation of when a deferral shall become payable (for example, the choices of investments for retirement deferrals may be different from the choices
for deferrals to be distributed while the Participant is still in-service). Such hypothetical earnings shall be referred to in this Plan as the “Earnings Amounts.” The Participant shall designate the investments used to measure the
Earnings Amounts from the list specified by the Company, by a written statement (or form or document) in the form of Section 6 of the Deferral Election Form attached hereto, or in such other form or by any other means, electronically or
otherwise, as the Company may designate from time to time. Such designations shall be made in the manner prescribed by the Company (for example, the Company may require that all designations be made in one percent (1%) increments). The
Participant may change such designations on a daily basis as permitted by the Company. Earnings Amounts shall be credited to (or deducted from) the Participant’s Deferred Compensation Account at least monthly (or more frequently at the
discretion of the Company). Earnings shall be credited (or deducted from) a Deferred Compensation Account until all payments with respect to such account have been made under this Plan. The Company shall not be liable or otherwise responsible for
any decrease in a Participant’s Deferred Compensation Account because of the investment performance of the designated assets. To the extent that a Participant or his or her Beneficiary acquires a right to receive payments from the Company under
the provisions hereof, such right shall be no greater than the right of any unsecured general creditor of the Company or any subsidiary of the Company. 

  
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 6. Deferred Compensation Account. 

a. Deferred Compensation Account. The Company shall cause to be established for each Participant a bookkeeping account (the
“Deferred Compensation Account”) to provide a convenient method of measuring the Company’s obligation to each Participant under this Plan. The Company shall record in each account the amounts equal to the Participant Elective
Deferrals, and the related Earnings Amounts. Deferred Compensation Accounts shall at all times remain a part of the general assets of the Company and shall remain available for the payment of Company obligations and the obligations of the
Company’s subsidiaries. In addition, at its discretion, the Company may also establish additional bookkeeping accounts for each Participant, including up to four (4) different in-service accounts in addition to a retirement account.

 b. Unfunded Arrangement. Neither the existence of this Plan nor any Deferred Compensation Account shall be deemed to
create a trust. Any trust referred to in this Plan or created by the Company in connection with this Plan, and any assets held by the trust to assist the Company in meeting its obligations under this Plan, will constitute an unfunded arrangement for
tax purposes and for purposes of Title I of ERISA. Neither the existence of this Plan nor any Deferred Compensation Account shall entitle any Participant, Beneficiary or other person to a claim or lien against the assets of a Deferred Compensation
Account or any other assets of the Company. Any Participant and his or her Beneficiary shall have only the rights of an unsecured general creditor in regard to receiving the benefits payable under this Plan. 

c. Status of Trust Fund. The Company is under no obligation to segregate any assets to provide for the Company’s obligations
under this Plan. If the Company does elect to segregate assets into a Trust Fund pursuant to subsection (d) of this Section 6, the Deferred Compensation Accounts may be maintained on the books of the Trust Fund referenced therein.

  
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 d. Creation of Trust Fund. The Company may, but is not required to, establish a Trust
Fund and make contributions to it corresponding to any or all of the obligations of the Company to make payments under this Plan. These contributions shall be credited with income, expenses, gains and losses in accordance with the investment
experience of the Trust Fund. The Committee may direct the Trustee to establish investment funds within the Trust Fund. The Committee may alter the available funds or procedures for allocating the Deferred Compensation Accounts among them at any
time. All assets of the Trust Funds shall remain the property of the Company. No Participant shall have any priority claim on the Trust Fund or any security interest or other right in or to them superior to the rights of general creditors of the
Company or any subsidiary of the Company. 
 7. Benefit Payments. 

a. Payments Based on Designated Schedule(s). In addition to designating the amount to be deferred, on each Deferral Election Form,
the Participant may designate (among a list of options provided by the Company) when the benefits (equal to the Participant’s Deferred Compensation Account balance) will be paid under this Plan. At a minimum, Participants will have the option
to have the amounts paid at retirement age (hereby designated as age 55), and/or at up to four designated times prior to retirement (thus, up to four “in-service” distributions can be specified). A Participant shall be deemed to have
retired, solely for the purpose of this Plan, if his or her employment terminates after he or she has attained age 55, regardless of his or her prior years of service. Subject to other provisions of this Plan providing for mandatory methods of
distributions in the event of various circumstances giving rise to the right to receive the Deferred Compensation Account, to the extent provided in the applicable Deferral Election Form, the Participant Deferred Compensation Account balance may be
paid out in a lump sum or over a specified period of years. 

  
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In the case of payments to be made upon retirement, the maximum payment period shall be fifteen (15) years. For payments to be made while the Participant is still employed on a full-time
basis by the Company, or a subsidiary of the Company (i.e., in-service distributions), the payments will be made in a lump sum or in installments, with the maximum payment period being five (5) years. Notwithstanding the foregoing, however, in
the case of in-service distributions, the Participant’s Elective Deferrals must be deferred for at least five (5) years from the date the Participant’s Deferred Compensation Account was first established. The method of distribution
(for example, the length of the installment payment period) can be changed by the Participant (in a manner permitted by the Company) at any time more than sixty (60) days before the original designated distribution date. The method of
distribution designated by the Participant will apply if the Participant’s employment with the Company, or a subsidiary of the Company, terminates at anytime after attaining the normal retirement age or in the case of any in-service
distribution designated by the Participant. When applicable, payments shall be made by the Company within sixty (60) days of the designated date. 
 b. Mandatory Lump Sum Payment. Notwithstanding any other designation by a Participant, if the Participant’s employment with the Company terminates for any reason (including the
Participant’s death or Disability) at any time before the Participant has reached the retirement age specified in subparagraph (a) of this Section 7, an amount equal to the balance of the Participant’s Deferred Compensation
Account at the time shall be paid to the Participant in a lump sum, and the Company shall have no further liability hereunder. In the event the Participant dies after such termination, but before receiving such a lump sum payment, an amount equal to
the Participant’s Deferred Compensation Account shall be paid to the Participant’s designated Beneficiary. 

  
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 c. Payment Upon the Retired Participant’s Death. If a Participant, who has
designated in his or her Deferral Election Form the payment of his or her Deferred Compensation Account over a number of years, dies at any time following the commencement of his or her payments, the payments shall continue to be made over the then
balance of the years, as designated by the Participant, such payments being paid to the Participant’s Beneficiary. 
 d.
Withholding. Notwithstanding any other provision herein, the Company shall be entitled to withhold from any amount payable hereunder any amount required to be withheld for income, employment or other federal, state or local taxes. 

e. Payment Only from Company Assets. All distributions from the Plan to Participants and Beneficiaries shall be made in cash,
unless the Committee determines that other property should be distributed. Any payment of benefits to a Participant or his or her Beneficiary shall be made from assets which shall continue, for all purposes, to be a part of the general assets of the
Company. No person shall have or acquire any interest in such assets by virtue of the provisions of this Plan. To the extent that a Participant or his or her Beneficiary acquires a right to receive payments from the Company under the provisions
hereof, such right shall be no greater than the right of any unsecured general creditor of the Company. This Plan constitutes a mere promise by the Company to make benefit payments in the future. 

f. Beneficiaries. A Participant may designate his or her Beneficiary or Beneficiaries to receive the amounts as provided herein
after his or her death by delivering a writing to the Company in substantially the form of Section 7 of the Deferral Election Form attached hereto (or such other form or by other means, electronically or otherwise, as the Company may designate
from time to time), designating a beneficiary or beneficiaries. In the absence of such a designation, the Company shall pay any such amount to the Participant’s estate. 

  
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 8. Administration of the Plan and Claims Procedure. 

a. Determinations. The Committee, or such other Committee or individual designated by the Company, shall make all determinations
as to rights to benefits under this Plan. The Committee shall have full power and authority to interpret, construe and administer this Plan. The interpretation and construction of this Plan by the Committee, and any action taken pursuant thereto,
shall be binding and conclusive upon all parties in interest. All expenses of the Plan’s administration shall be paid by the Company. 
 The Committee, in carrying out its duties with respect to the administration of the Plan, shall have, in addition to any other power conferred by the Plan or by law, the following powers: 

(i) to determine all questions relating to eligibility to participate in the Plan; 

(ii) to compute and certify to the Company the amount and kind of distributions payable to the Participants and Beneficiaries;

 (iii) to maintain records necessary for the administration of the Plan that are not maintained by the Company or the
Trustee, if any; 
 (iv) to interpret the Plan provisions and to make and publish such rules with regard to the Plan’s
administration not inconsistent with the terms hereof; 
 (v) to establish and modify the method of accounting for the Plan;

 (vi) to employ counsel, accountants and other consultants to aid in exercising its powers and carrying out its duties
hereunder; and 

  
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 (vii) to perform any other acts necessary and proper for the Plan’s administration,
except those that are performed by the Trustee, if any, or as otherwise limited by the Company. 
 b. Reports. The
Company shall provide each Participant with a statement reflecting the amount of the Participant’s Deferred Compensation Account on at least a quarterly basis. 
 c. No Liability. No Committee member, employee, agent, officer, member, manager, volunteer or director of the Company (or its designee) shall, in any event, be liable to any person for any action
taken or omitted to be taken in connection with the interpretation, construction or administration of this Plan, so long as such action or omission to act is made in good faith. 

d. Designation of Committee. The Company hereby designates the Committee to administer this Plan. Said Committee shall have all
the authority as is granted to the Company under the terms of this Plan for the administration of this Plan in accordance with its terms and in ruling on such questions arising out of the administration, interpretation and application of the Plan.
The Committee may approve or disapprove all Deferral Election Forms and elections in connection herewith, and make all other determinations hereunder. Members of the Committee may participate in the Plan, but no member of the Committee shall be
entitled to make decisions which relate solely to his or her own participation. The Company reserves the right to designate a different Committee, or an individual, to administer this Plan from time to time, or to make any determinations directly at
any time. If no such Committee or individual is designated at any time, such functions, as appropriate, may be conducted by the Company’s Board of Directors. The Company’s Board of Directors hereby reserves the right to revoke such
designation at any time and to make other designations (and to revoke such designations) at any time. 

  
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 e. Claims Procedure. The following provisions are hereby made a part of this Plan and
are intended to meet the requirements of ERISA: 
 (1) The named fiduciary under this Plan is the Company. 

(2) This Plan is unfunded. The Participants shall defer certain amounts under this Plan, but all benefits shall be paid from the
Company’s general assets which at all times shall remain subject to the claims of the Company’s general creditors. 

(3) Direct payment by the Company is the basis of payment of benefits under this Plan. 

(4) The following claims procedures shall apply for purposes of this Plan. Any and all persons presenting claims hereunder (individually
or collectively, “Claimant”) must follow these procedures: 
 (A) For claims procedure purposes, the Committee shall
appoint among themselves a chairperson of the Committee (or the chairperson of any other Committee designated by the Company to administer this Plan, or a designated member of the Board of Directors or other governing body of the Company).

 (B) A Claimant shall make a claim for benefits hereunder by submitting a written claim to the Company (or its designee) in
the maimer set forth herein for providing notice to the Company under this Plan. The Committee shall decide whether the claim shall be allowed, and the following claims procedure shall apply: 

(i) If for any reason a claim for benefits under this Plan is denied by the Committee in whole or in part, the Committee shall deliver
to the Claimant a written explanation setting forth: the specific reason or reasons for the adverse determination; references to specific Plan provisions on which the determination is based; a description of any additional

  
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material or information necessary for the Claimant to perfect the claim and an explanation of why such material or information is necessary; and a description of the Plan’s review procedure
including a statement of the Claimant’s rights to bring a civil action under Section 502 of ERISA following an adverse determination on review, all written in a manner calculated to be understood by the Claimant. For this purpose:

 (a) The Committee’s claim shall be deemed filed when delivered in writing as provided herein. 

(b) The Committee’s explanation shall be in writing delivered to the Claimant within 90 days after receipt of the claim by the
Plan, unless the Committee determines that special circumstances require an extension of time for processing the claim. If such an extension of time for processing is required, written notice of the extension shall be furnished to the Claimant prior
to the termination of the initial 90 day period. In no event shall such extension exceed a period of 90 days from the end of such initial period. The extension notice shall indicate the special circumstances requiring an extension of time and the
date by which the Committee expects to render the benefit determination. If the period of time is extended because the Claimant has failed to provide necessary information to decide the claim, the period for making the benefit determination shall be
tolled from the date on which the notification of the extension is sent to the Claimant, until the date on which the Claimant provides the information. 
 (ii) The Claimant shall have 60 days following his or her receipt of a notice of adverse benefit determination to file with the Committee a written request for review of the denial. Claimant shall have
the opportunity to submit written comments, documents, records, and other information relating to the claim for benefits. Claimant shall be provided, upon request and free of charge, reasonable access to, and copies of, all documents, records, and
other 

  
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information relevant to the Claimant’s claim for benefits. The review of the claim shall take into account all comments, documents, records, and other information submitted by the Claimant
relating to the claim, without regard to whether such information was submitted or considered in the initial benefit determination. 
 (iii) In the case of a request for review of an adverse benefit determination, the Company shall designate an individual or Committee (herein the “Reviewer”) to review the claim. On review, the
Reviewer shall notify the Claimant not later than 60 days after the Company’s receipt of the request for review, unless the Reviewer determines that special circumstances require an extension of time for processing the claim, in which case a
decision shall be rendered as soon as possible, but not later than 120 days after receipt of the request for review. If such an extension of time for review is required because of special circumstances, written notice of the extension shall be
furnished to the Claimant prior to the commencement of the extension. The extension notice shall indicate the special circumstances requiring an extension of time and the date by which the Plan expects to render the determination on review. If the
period of time is extended because the Claimant has failed to provide necessary information to decide the claim, the period for making the benefit determination shall be tolled from the date on which the notification of the extension is sent to the
Claimant, until the date on which the Claimant provides the information. The decision on review shall be in writing and in the case of an adverse benefit determination shall include: (1) the specific reason or reasons for the decision;
(2) references to the specific Plan provisions on which the benefit determination is based; (3) a statement that the Claimant is entitled to receive, upon request and free of charge, reasonable access to, and copies of, all documents,
records and other information relevant to the Claimant’s claim for benefits; and (4) a statement of the Claimant’s right to bring an action under Section 502(a) of ERISA, all written in a manner calculated to be understood by the
Claimant. If the decision on review is not furnished within such time, the claim shall be deemed denied on review. 

  
 -17-

 9. Non-Assignability of Benefits. Neither any Participant nor any Beneficiary under
this Plan shall have any power or right to transfer, assign, anticipate, hypothecate or otherwise encumber any part or all of the amounts payable hereunder. Such amounts shall not be subject to seizure by any creditor of a Participant or any
Beneficiary hereunder, by a proceeding at law or in equity, nor transferable by operation of law in the event of the bankruptcy or insolvency of any Participant or any Beneficiary hereunder. Any such attempted assignment or transfer shall be void
and shall terminate the Participant’s participation in this Plan; the Company shall thereupon have no further liability hereunder with respect to such Participant and his or her Beneficiary. 

10. Amendment and Termination. This Plan may not be amended, altered or modified, retroactively, except by a written instrument
signed by the Company and the impacted Participants or their respective successors. The Company may amend, alter, modify or terminate this Plan on a prospective basis at any time, provided further that no such modification or termination shall
adversely affect a Participant’s entitlement to benefits attributable to amounts credited to his or her Deferred Compensation Account prior to the modification or termination of this Plan. Without limiting the generality of the foregoing, the
Company reserves the right to discontinue this Plan at any time, and/or change the eligibility of the Participants as well as the percentage or amounts Participants may defer. This Plan document sets forth the terms and provisions of this Plan and
any prior written or oral communications regarding the terms of this Plan shall not alter or modify the terms of this Plan. 

11. Impact on Other Benefits. Except as otherwise required by the Code or any other applicable law, this Plan and the benefits
provided herein are in addition to all other benefits which 

  
 -18-

 
may be provided by the Company to the Participants from time to time, and shall not reduce, replace or otherwise cause any reduction, in any manner, with regard to any of such other benefits. In
no event shall any provision herein be deemed to amend or modify any employment agreement between the Company and any Participant, and no provision herein shall be deemed to entitle any Participant to continued employment with the Company.

 12. Notices. Any notice or other communication required or permitted under this Plan shall be in writing and, if
directed to the Company, shall be sent by United States certified mail, return receipt requested, postage prepaid, addressed to: Sigma-Aldrich Corporation, 3050 Spruce Street, St. Louis, Missouri 63103, Attn: Flexible Deferral Plan Committee, and,
if directed to a Participant or to a Beneficiary, may be hand-delivered or mailed to such Participant or Beneficiary at the last known address for such person as it appears in the Company’s records. A notice or other communication sent by
United States certified mail, return receipt requested, postage prepaid, addressed as provided above, shall be deemed to have been given on the next business day after mailing. 

13. Governing Law. This Plan shall be governed by and construed in accordance with the laws of the State of Missouri without
regard to its conflict of law rules. 
 14. Headings. The headings of the sections of this Plan are for reference only
and are not to be utilized in construing the Plan. 
 15. Gender. All pronouns of whatever gender refer indifferently to
persons or objects of any gender. 
 16. Singular and Plural. Singular terms refer also the plural number and vice versa.

  
 -19-

 17. Severability. If any provision of this Plan is held illegal or invalid for any
reason, the remaining provisions are to remain in full force and effect and to be construed and enforced in accordance with the purposes of the Plan as if the illegal or invalid provision did not exist. 

IN WITNESS WHEREOF, the Company has executed and adopted this Plan as of the Effective Date. 

 

					
	SIGMA-ALDRICH CORPORATION
		
	By:	 	 /s/ Kirk A. Richter

		 	Print Name:	 	 Kirk A. Richter

		 	Print Title:	 	 Treasurer

  
 -20-

 SIGMA-ALDRICH CORPORATION 

DEFERRED COMPENSATION PLAN 
 EXHIBIT 1 
 DEFERRAL ELECTION FORM 

  
 -21-

 Sigma-Aldrich Corporation 
 Flexible Deferral Plan (FDP) 
 2003 Deferral Election Form 

 
 Section 1: Employee Information

  

			
	 Employee’s Name (Last, First, M.I.)

  
	  	 Date of
Birth

	 Social Security Number 
  
	  	 Date of Hire

	 Street 
  
	  	 City

	 State 
  
	  	 Zip

Section 2: Deferral Elections 
  

			
	  

I hereby submit this request to the Company regarding the deferral of Plan Year 2003 compensation. I understand that the amount specified below will be
deducted from my earned income for the Plan Year February 1, 2003, through December 31, 2003, and applied to my FDP account.

	 	 
	 ̈	  	 Deferral — Salary (inclusive of Commissions, if
any)

	 	 
	 	  	 Please deduct
            % of my 2003 salary and commission. (minimum 1%; maximum 50%)

	 	 
	 ̈	  	 Deferral — Bonus (inclusive of Company discretionary bonus,
if any)

	 	 
	 	  	 Please deduct
            % of my 2002 bonus paid in 2003. (minimum 1%; maximum 100%)

	 	 
	 ̈	  	
No Deferral

 

 Section 3: Account Type

  

	
	The Flexible Deferral Plan allows you to
allocate deferrals into two (2) types of accounts – a retirement account and/or a short-term account.
	 
	I request that my Plan Year 2003 deferral(s) be allocated as indicated in
this section. I understand that deferrals will automatically be credited to my retirement account, unless I specify a percentage (%) be directed to the short-term account. (Allocate in 10% increments. Total must equal
100%.)
	 
	 Please allocate
            % of my total deferral to my retirement account.

	 
	 Please allocate
            % of my total deferral to my short-term account.

	 (You must elect a Payment Date in Section 4.)

 Section 4:
Short-Term Account Payment Date 
 (Do not complete if 100% to retirement account.) 

 

	
	
I hereby elect to establish a short-term account. I understand that the Payment Date is irrevocable and that I may establish one short-term account each
year, subject to an overall total of four (4) accounts.
  
 The Payment
Date must be a minimum of five (5) years from the year of your original deferral election into that account. For Plan Year 2003, the earliest payment date is February 1, 2008.

	 
	I elect my short-term account to be payable on
                                         
   .
	
    (Month Day, Year)

  
  

	 Nov 2002 
	 1 

 Sigma-Aldrich Corporation 
 Flexible Deferral Plan (FDP) 
 2003 Deferral Election Form 

 
 Section 5: Payment Options 

 

							
	I request that my FDP Plan Year 2003 deferral(s) be paid according to the option(s) indicated in
this section. I understand that changes can be made up to 60 days before my retirement date or the Payment Date that I have elected in Section 4. I also understand that any payments will commence no later than 60 days after the elected Payment
Date.
	Retirement Account	 	Short-Term Account
	  
  ̈
	 	  
 Lump sum
	 	 ̈	  	Lump sum
	  
  ̈
	 	  
 Annual payments over              years (five (5), 10 or 15)
  
	 	  ̈

 
	  	  
 Annual payments over              years (no more than five (5))
  

 Section 6: Investment Selections 

 

													
	 I
hereby request that my future deferrals be allocated as if invested in the following fund(s) according to the percentage(s) that I have indicated. I understand that this investment election will apply only to my FDP Plan Year 2003 deferral(s) until
I change it.
  
	
   
 

	  	  	Retirement
Account	 	 	  	 	  	Short-Term
Account	 
	  	  	(in 1% increments)	 	 	 	 	  	(in 1% increments)	 
	  

Fidelity Money Market Trust: Retirement
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Intermediate Bond Fund
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Balanced Fund
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Growth & Income Portfolio
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Spartan US Equity Index Fund
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Blue Chip Growth Fund
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Mid-Cap Stock Fund
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Fidelity Diversified International Fund
	  	   
	              
	%   
	 			 	  	   
	              
	% 
 

	  

Total:
	  	 	100	% 	 	 	 	 	  	 	100	% 

  
  

	 Nov 2002 
	 2 

 Sigma-Aldrich Corporation 
 Flexible Deferral Plan (FDP) 
 2003 Deferral Election Form 

 
 Section 7: Employee Beneficiary
Designation 
  

											
	I hereby name the following
person or persons, entity or entities (herein called “Designated Beneficiary(ies)”) to receive such amounts, if any, that are payable under the Plan after my death:
	 					 
	Primary Beneficiary #1	 	  
	  	Name	  		  		  	 
	
 
	  	  
	  		  	 
	  
 %                
	  	  
	  		  	 
	  
 SSN
	  	  
	  		  	 
	Primary Beneficiary #2	 	  
	  	Name	  		  		  	 
	
 
	  	  
	  		  	 
	  
 %                
	  	  
	  		  	 
	  
 SSN
	  	  
	  		  	 
	Contingent Beneficiary #1	 	  
	  	Name	  		  		  	 
	
 
	  	  
	  		  	 
	  
 %                                  
      
	  		  	 
	  
 SSN                        
	  		  	 
	Contingent Beneficiary #2	 	  
	  	Name	  		  		  	 
	
 
	  		  	 
	  
 %                                  
      
	  		  	 
	  
 SSN                        
	  		  	 
	  

If a Trust is designated, include the full name of the Trust, the date of execution, the Trustee’s name, address and
identification.

	 
	I understand that this Beneficiary Designation will apply to
all of my deferral accounts and shall remain in effect until revoked by me in writing or until superseded by my execution and delivery of a substitute Beneficiary Designation Form. I understand that no such revocation or substitute Beneficiary
Designation Form will be effective until it is actually received by the Plan Administrator.
	 		 
	  
	  		  	  

	
(Employee’s Signature)
	  	 	  	 (Date)

 

  
  

	 Nov 2002 
	 3 

 Sigma-Aldrich Corporation 
 Flexible Deferral Plan (FDP) 
 2003 Deferral Election Form 

 
 Section 8: Employee Authorization

  

							
	I acknowledge receipt of a copy
of the Sigma-Aldrich Corporation Flexible Deferral Plan Participant Information Booklet and confirm that I have reviewed and understood all the terms and conditions thereof, which terms, provisions, and conditions are hereby incorporated by
reference into this Deferral Election.
	 			 
	  
	  		  		  	  

	(Employee’s Signature)	  		  		  	(Date)
	 
	This request must be completed and returned
by January 15, 2003, to:
	 The Todd Organization, 701 Market Street, Suite 1000, St. Louis, MO 63101

 

 For Sigma-Aldrich Use Only

  

					
	The Company hereby acknowledges
the receipt and agrees to the deferral requested, subject to the terms and conditions of the Plan.
	 		 
	  
	  	  
	 	  

	 (Date)

 
	  	 (By)

 
	 	 (Title)

 

  

			
	Nov 2002	  	4

 AMENDMENT TO THE SIGMA-ALDRICH CORPORATION FLEXIBLE 

DEFERRAL PLAN 
 WHEREAS, Sigma-Aldrich Corporation (“Company”) previously adopted the Sigma-Aldrich Corporation Flexible Deferral Plan (“Plan”); and 

WHEREAS, the Company reserved the right to amend the Plan pursuant to Section 10 thereof; and 

WHEREAS, the Company desires to amend the Plan in certain respects effective January 1, 2005; 

NOW, THEREFORE, effective January 1, 2005, Section 10 of the Plan is hereby amended to read as follows: 

This Plan may not be amended, altered or modified, retroactively, except by a written instrument signed by the Company and the impacted
Participants or their respective successors. The Company may amend, alter, modify or terminate this Plan on a prospective basis at any time, provided that no such modification or termination shall adversely affect a Participant’s entitlement to
benefits attributable to amounts credited to his or her Deferred Compensation Account prior to the modification or termination of this Plan. (Notwithstanding the foregoing, the Company may amend, alter, modify or terminate this Plan, whether
retroactively or prospectively, to comply with or otherwise address the requirements and provisions of Section 409A of the Code and the guidance and regulations issued thereunder by a written instrument signed by the Company.) Without limiting
the generality of the foregoing, the Company reserves the right to discontinue this Plan at any time, and/or change the eligibility of the Participants as well as the percentage or amounts Participants may defer. This Plan document sets forth the
terms and provisions of this Plan, and any prior written or oral communications regarding the terms of this Plan shall not alter or modify the terms of this Plan. 
 The Company has caused this Amendment to be executed this 23 day of December, 2004. 
  

			
	SIGMA-ALDRICH CORPORATION
	
	 /s/ Kirk A. Richter

	By:	 	 Kirk A. Richter

	Title:	 	 Treasurer

 AMENDMENT TO THE SIGMA-ALDRICH CORPORATION FLEXIBLE 

DEFERRAL PLAN 
 WHEREAS, Sigma-Aldrich Corporation (“Company”) previously adopted the Sigma-Aldrich Corporation Flexible Deferral Plan (“Plan”); and 

WHEREAS, the Company reserved the right to amend the Plan pursuant to Section 10 thereof; and 

WHEREAS, the Company desires to amend the Plan to eliminate Patty Fish’s interest therein; 

NOW, THEREFORE, effective September 16, 2005, the Plan is hereby amended by adding the following sentence at the end of
Section 10: 
 Upon Patty Fish’s termination of employment with the Company, her participation in the Plan was
terminated and, as a result, her entire interest in the Plan was subsequently distributed to her on September 16, 2005. 
 The Company has caused this Amendment to be executed this 15th day of December, 2005. 
  

			
	SIGMA-ALDRICH CORPORATION
	
	 /s/ Kirk A. Richter

	By:	 	 Kirk A. Richter

	Title:	 	 TreasurerSupplemental Retirement Plan

 Exhibit 10(ac) 
 SIGMA-ALDRICH SUPPLEMENTAL RETIREMENT PLAN 
 As Amended and Restated
Effective January 1, 2009 
 WHEREAS, Sigma-Aldrich Corporation (“Company”) previously adopted the
Sigma-Aldrich Supplemental Retirement Plan (“Plan”), effective April 1, 2004, in order to attract and retain selected executives; and 
 WHEREAS, the Company reserved the right to amend the Plan in Section 14 thereof; and 
 WHEREAS, effective January 1, 2009, the Company desires to amend and restate the Plan, to the extent necessary to incorporate the provisions required by Section 409A of the Internal Revenue Code
of 1986, as amended; 
 NOW, THEREFORE, effective January 1, 2009, the Plan is amended and restated in its entirety as
follows: 
  

	1.	PURPOSE 

Sigma-Aldrich Corporation (“Company”) established the Sigma-Aldrich Supplemental Retirement Plan (“Plan”) to provide
eligible key employees of the Company with supplemental retirement income and to provide such employees with competitive retirement and capital accumulation benefits. In addition, the Plan is intended to provide eligible key employees additional
incentive to remain employed by the Company and to attract certain executive-level employees. 
  

	2.	DEFINITIONS 

 The
following definitions shall be applicable throughout the Plan: 
  

	 	2.1	Account. 

“Account” means a bookkeeping account established and maintained by the Company for each Participant reflecting Credits and
earnings and losses thereon in accordance with the Plan. 
  

	 	2.2	Accounting Date. 

“Accounting Date” means each Business Day on which a calculation concerning an Account is performed, or as otherwise defined by
the Committee. 
  

	 	2.3	Active Participant. 

“Active Participant” means an Employee who is (i) an executive of the Company; and (ii) designated by the CEO as an
Active Participant in the Plan for any Plan Year. 

  
 1 

	 	2.4	Affiliate. 

“Affiliate” when used with reference to a Change of Control, shall be defined by reference to the Securities Exchange Act of
1934 and rules in effect thereunder. 
  

	 	2.5	Annual Base Salary. 

“Annual Base Salary” means the base salary of an Active Participant for a given Plan Year, as determined by the Committee.

  

	 	2.6	Annual Credit. 

“Annual Credit” means an annual credit made on behalf of an Active Participant by the Company as more fully described in
Section 7. In the event the Committee elects to credit an Active Participant with an Annual Credit for a Plan Year, the amount of such Annual Credit for any such Plan Year shall be equal to six percent (6%) of such Active
Participant’s Annual Base Salary on January 1 of the applicable Plan Year. The Annual Credit shall be pro rated as specified in Section 2.19 to reflect a partial year of participation with respect to any Employee who becomes an Active
Participant after January 1 of the applicable Plan Year. 
  

	 	2.7	Associate. 

“Associate” when used with reference to a Change of Control, shall be defined by reference to the Securities Exchange Act of
1934 and rules in effect thereunder. 
  

	 	2.8	Beneficial Owner. 

“Beneficial Owner” when used with reference to a Change of Control, shall be defined by reference to the Securities and Exchange
Act of 1934 and rules in effect thereunder. 
  

	 	2.9	Beneficiary. 

“Beneficiary” means the person or persons designated by the Participant to the extent applicable in accordance with the Plan, or
if no person or persons are so designated, the estate of a deceased Participant. 
  

	 	2.10	Board. 

“Board” means the Board of Directors of the Company or its designee. 

 

	 	2.11	Business Day. 

“Business Day” means a day on which the New York Stock Exchange is open for trading activity. 

 

	 	2.12	Cause. 

“Cause” means (i) engaging by a Participant in willful misconduct which is materially injurious to the Company;
(ii) conviction of a Participant by a court of competent jurisdiction of, or entry of a plea of nolo contendere with respect to, a felony; (iii) engaging by a Participant in fraud,

  
 2 

 
material dishonesty or gross misconduct in connection with the business of the Company; (iv) engaging by a Participant in any act of moral turpitude reasonably likely to materially and
adversely affect the Company or its business; or (v) a Participant’s current chronic abuse of or dependency on alcohol or drugs (illicit or otherwise). 
  

	 	2.13	CEO. 

“CEO” means the Chief Executive Officer of the Company. 

 

	 	2.14	Change of Control. 

“Change of Control” occurs if any individual, corporation, partnership or other Person or entity, together with its Affiliates
and Associates, acquires as the Beneficial Owner more than twenty-five percent (25%) in the aggregate of the outstanding shares of the Company entitled to vote in the election of directors, or a majority of directors elected to the Board, or a
majority of the persons constituting a group authorized to hire or terminate employment of officers, if other than the Board, are different from the directors or persons constituting the Board or group just prior to the start of such period, or a
group other than the Board is created to hire or terminate employment of officers. 
  

	 	2.15	Committee. 

“Committee” means the Compensation Committee of the Board. 

 

	 	2.16	Company. 

“Company” means Sigma-Aldrich Corporation. 
  

	 	2.17	Continuous Participation. 

 “Continuous Participation” means a period of continuous employment as a full-time Employee of the Company beginning on the date on which an Employee first becomes an Active Participant and
ending on the Employee’s Termination. In the event an Employee has a Termination and subsequently becomes an Employee and an Active Participant, any Continuous Participation shall begin on the date such individual again becomes an Active
Participant. Any Continuous Participation that may have accrued prior to a Termination shall be forfeited. 
  

	 	2.18	Credit. 

“Credit” means any Annual Credit and/or Discretionary Credit. 

 

	 	2.19	Credit Date. 

“Credit Date” means the first day of each Plan Year. With respect to an Employee who thereafter becomes an Active Participant
after January 1 of any Plan Year, the “Credit Date” for such Plan Year means the first day of the month following the date such Employee becomes an Active Participant. “Credit Date” shall also mean any other date on which
Credits are credited to an Active Participant’s Account in accordance with rules prescribed by the Committee. In the event that the applicable Credit Date is not a day on which the Company is open for business, the applicable Credits shall be
made as soon as administratively feasible after the applicable Credit Date and otherwise in accordance with the Plan, but in any event not later than two Business Days after the applicable Credit Date. 

  
 3 

	 	2.20	Disability or Disabled. 

 A Participant shall be considered “Disabled” or to have a “Disability” if the Participant is determined to have a Disability under the Retirement Plan. In the event that the
Participant does not participate in the Retirement Plan, the Participant shall be disabled for purposes of this Plan if the Participant is determined to be totally and permanently disabled by the Social Security Administration, or comparable agency
in the country of Participant’s employment. 
  

	 	2.21	Discretionary Credit. 

 “Discretionary Credit” means any credit that may be made on behalf of an Active Participant by the Company in addition to the Annual Credit, as determined under this Plan and otherwise by the
sole discretion of the CEO. 
  

	 	2.22	Election. 

“Election” means a Participant’s delivery of a written notice of election to the Committee or its designee electing the
form of payment on Retirement or investment alternatives to the extent there is an Account maintained on his or her behalf under the Plan. 
  

	 	2.23	Employee. 

“Employee” means an individual classified by the Committee as a member of a select group of management or highly compensated
employees of the Company. 
  

	 	2.24	Good Reason. 

“Good Reason” when used with reference to a voluntary termination by a Participant from his or her employment with the Company
within two years after a Change of Control, shall mean (i) a reduction in such Participant’s base salary as in effect immediately prior to a Change of Control; or (ii) a reduction in such Participant’s status, position,
responsibilities or duties as in effect immediately prior to a Change of Control. 
  

	 	2.25	Participant. 

“Participant” includes both (i) an Active Participant and (ii) an Employee who was formerly an Active Participant, had
any Credits credited to an Account on his or her behalf and is continuing in a period of Continuous Participation, despite ceasing to be an Active Participant. 
  

	 	2.26	Payment Form. 

“Payment Form” means one of the following forms of payment on Retirement elected in a Participant’s Election: (i) a
lump sum payment or (ii) annual installments payments (not to exceed fifteen (15) years). 

  
 4 

	 	2.27	Person. 

“Person” means an individual, a partnership, a corporation, an association, a joint stock company, a limited liability company,
a trust, a joint venture, an unincorporated organization or a governmental entity or any department, agency or political subdivision thereof. 
  

	 	2.28	Plan. 

“Plan” means this Sigma-Aldrich Supplemental Retirement Plan as amended from time to time. 

 

	 	2.29	Plan Year. 

“Plan Year” means the annual period commencing January 1 and ending the following December 31. 

 

	 	2.30	Retirement. 

“Retirement” means a Termination on or after the date a Participant attains the earlier of his or her Normal Retirement Date or
Early Retirement Date as defined in accordance with the Retirement Plan. 
  

	 	2.31	Retirement Plan. 

“Retirement Plan” means the Sigma-Aldrich Corporation Retirement Security Value Plan. 

 

	 	2.32	Termination. 

“Termination” means termination of services for any reason. 

 

	 	2.33	Year(s) of Participation. 

 “Year of Participation” means a 12-month period of Continuous Participation. “Years of Participation” means contiguous 12-month periods of Continuous Participation. Any Year(s) of
Participation that accrued prior to a Termination shall be forfeited. 
  

	3.	ADMINISTRATION 

Full power and authority to construe, interpret and administer the Plan shall be vested in the Committee. This power and authority
includes, but is not limited to, selecting investment indices, establishing the level of Discretionary Credits (if any) to the Plan, establishing Annual Credit and Discretionary Credit terms and conditions, receiving and approving beneficiary
designation forms, and adopting modifications, amendments and procedures as maybe deemed necessary, appropriate or convenient by the Committee. Decisions of the Committee shall be final, conclusive and binding on all parties. The Committee, in its
sole discretion, may delegate day-to-day administration of the Plan to an employee or employees of the Company or to a third-party administrator. The Committee may also rely on outside counsel, independent accountants or other consultants or
advisors for advice and assistance in fulfilling its administrative duties under the Plan. Notwithstanding the foregoing, the CEO shall select Employees eligible to participate in the Plan and Participants eligible for a Discretionary Credit (if
any). 

  
 5 

	4.	ELIGIBILITY 

 The
CEO shall have the authority to select from Employees who are executives of the Company those Employees who shall be Active Participants eligible for Annual Credits under the Plan in each Plan Year. The list of Active Participants is set forth in
Appendix A, which shall be amended from time to time by the CEO to reflect then current Active Participants. In addition, the CEO may designate any Active Participant(s) who shall be eligible for Discretionary Credits under the Plan with respect to
a specified Plan Year. The CEO is not obligated to designate any Participant as eligible for Discretionary Credits in any given Plan Year, and may, in his or her sole discretion, designate some but not all Active Participants as eligible for any
Discretionary Credits. A designation as eligible for a Discretionary Credit in one Plan Year does not confer such eligibility upon any Participant in any other Plan Year. 

 

	5.	PARTICIPANT ACCOUNTS 

 There shall be established an Account, to which there shall be credited any Annual Credits as of each Credit Date. In addition, Discretionary Credits, if any, shall be allocated to an Active
Participant’s Account on any applicable Credit Date in accordance with rules prescribed by the Committee. Each such Account shall be credited or debited, as appropriate, on each Accounting Date with income or loss, as appropriate, based upon a
hypothetical investment in any one or more of the investment options available under the Plan, as prescribed by the Committee. The Committee may, in its sole discretion, prescribe investment alternatives under the Plan that are substantially similar
in the aggregate to the investment options available under the Section 401(k) plan maintained by the Company; provided that, an investment alternative reflecting an investment in Company stock shall not be available under this Plan. 

 

	6.	TERMS OF PARTICIPATION 

  

	 	6.1	In General. 

 Any
Employee selected by the CEO to participate in the Plan shall make an Election as to the Payment Form and the investment options which shall be used to credit his or her Account with investment gains or charge his or her Account with losses in
accordance with Section 5 on a form prescribed by the Committee. Such Election must be delivered to the Committee or its designee within 30 days after the date the Employee first becomes eligible to participate in the Plan. An Employee so
selected by the CEO shall begin participation in the Plan on the first day of the month or at such other time as designated by the Committee in which such Employee is designated as an Active Participant and the Employee has made an Election as to
the Payment Form. An Election may not be revoked or modified except as stated in the Plan. 
  

	 	6.2	Investment Alternatives for Existing Balances. 

 A Participant may elect to change an existing Election as to the investment alternatives in effect with respect to existing amounts in his or her Account (in increments prescribed by the Committee) for
any Plan Year, or such other period as prescribed by the Committee, by submitting a new Election prior to the beginning of such Plan Year, or such other period as prescribed by the Committee, and subject to such other restrictions as determined by
the Committee. 

  
 6 

	7.	CREDITS 

 In the
sole discretion of the Committee, the Company shall credit each Active Participant’s Account with an Annual Credit on the applicable Credit Date. In addition, with respect to any Active Participant who has also been designated in accordance
with the Plan as eligible for a Discretionary Credit, the CEO may credit such Active Participant’s Account with a Discretionary Credit (if any) on the applicable Credit Date in an amount to be determined by the CEO’s sole discretion. The
amount of any Discretionary Credits may vary between Active Participants eligible for any such Discretionary Credit in the CEO’s sole discretion. 
  

	 	7.1	Vesting. 

 Each
Participant shall be zero percent (0%) vested in the amount of Credits and earnings and losses thereon credited to such Participant’s Account until such Participant has completed five (5) Years of Participation and shall be fifty percent
(50%) vested in the amount of Credits and earnings (or losses) thereon credited to such Participant’s Account after such Participant has completed five (5) Years of Participation. Each Participant shall continue to vest an additional
ten percent (10%) in the amount of Credits (if any) and earnings (or losses) thereon credited to such Participant’s Account for each additional Year of Participation such Participant completes after his or her initial five (5) Years
of Participation. Each Participant shall be one hundred percent (100%) vested in the amount of Credits and earnings (or losses) to be credited to such Participant’s Account after such Participant has completed ten (10) Years of
Participation. 
 In the event of a Participant’s Termination, other than a Termination by the Company (other than for
Cause) or by the Employee for Good Reason within two (2) years after a Change of Control that occurs while the Participant is employed with the Company, and other than a Termination on account of death, Disability, or Retirement, such
Participant’s Account shall be forfeited to the extent not vested. In the event of a Participant’s Termination by the Company (other than for Cause) or by the Participant for Good Reason within two (2) years after a Change of Control
that occurs while the Participant is employed with the Company, or a Termination on account of death, Disability or Retirement, such Participant shall immediately become one hundred percent (100%) vested in any Credits and earnings or losses
thereon credited to his or her Account as of the date of Termination. 
  

	8.	DISTRIBUTION 

  

	 	8.1	In General. 

Unless otherwise provided herein, payment or commencement of payment of the vested amounts in a Participant’s Account shall occur on
the first day of the seventh month immediately following his or her date of Termination. If the Participant’s Termination is due to any reason other than Retirement, distribution of the Participant’s Account shall be made in a lump sum to
the Participant. In the event the Participant’s Termination is due to Retirement, his or her Account shall be distributed in such Payment Form as designated on the Participant’s Election (or in a lump sum if no Election was made by the
Participant). A Participant may elect to change his Payment Form in accordance with the rules established by the Committee, subject to the following: (i) the change is made at least twelve 12 months before the date the payment is scheduled to be
paid (or in the case of installments, 12 months before the date the first amount was scheduled to be paid); (ii) the change is not effective until at least twelve (12) months after the Participant submits the change to the Committee; and
(iii) the payment with respect to which such change is made is deferred for a period of not less than five (5) years from the date such payment would otherwise have been paid (or in the case of installment payments, five years from the
date the first amount was scheduled to be paid). 

  
 7 

 A Participant shall be deemed to have a Termination if the Company and Participant
reasonably anticipate a permanent reduction in the Participant’s level of bona fide services to a level less than 50% of the average level of bona fide services provided by the Participant in the immediately preceding 36 months. Notwithstanding
the preceding sentence, no termination shall occur while the Participant is on military leave, sick leave, or other bona fide leave-of-absence which does not exceed six months or such longer period during which the Participant retains a right to
reemployment with the Company pursuant to law or by contract. A leave of absence will be a bona fide leave-of-absence only if there is a reasonable expectation that the Participant will return to perform services for the Company. 

 

	 	8.2	Death. 

 In the
event of the Participant’s death, the Company shall pay all vested and unpaid amounts in such Participant’s Account to the Participant’s Beneficiary in a single lump sum on the first day of the month immediately following the
Participant’s death. 
  

	 	8.3	Form of Distribution. 

 Distribution of a Participant’s Account shall be made in cash. 
  

	 	8.4	Payment Date. 

 In
all cases in which amounts are due and payable under this Plan upon a fixed date, payment is deemed to be made upon the fixed date if the payment is made on such date or a later date within the same calendar year or, if later, by the fifteenth day
of the third calendar month following the specified date (provided the Participant or beneficiary is not permitted, directly or indirectly, to designate the taxable year of payment). 

 

	9.	BENEFICIARY DESIGNATION 

 A Participant may designate one or more persons (including a trust) to whom or to which payments are to be made if the Participant dies before receiving distribution of all amounts due under the Plan. A
Participant may, at any time, elect to change the designation of a Beneficiary. A designation of Beneficiary will be effective only after the signed designation of Beneficiary is filed with the Committee or its designee while the Participant is
alive and will cancel all designations of Beneficiary signed and filed earlier. If the Participant fails to designate a Beneficiary as provided above or if all of a Participant’s Beneficiaries predecease him or her and he or she fails to
designate a new Beneficiary, the remaining unpaid amounts shall be paid in one lump sum to the estate of such Participant. If all Beneficiaries of the Participant die after the Participant but before complete payment of all amounts due hereunder,
the remaining unpaid amounts shall be paid in one lump sum to the estate of the last to die of such Beneficiaries. 

  
 8 

	10.	UNSECURED GENERAL CREDITOR STATUS OF EMPLOYEE 

 The payments to Participants and their Beneficiaries hereunder shall be made from the general corporate assets of the Company. No person shall have any interest in any such assets by virtue of the
provisions of this Plan. The Company’s obligation hereunder shall be an unfunded and unsecured promise to pay money in the future. To the extent that any person acquires a right to receive payments from the Company under the provisions hereof,
such right shall be no greater than the right of any unsecured general creditor of the Company; no such person shall have nor acquire any legal or equitable right, interest or claim in or to any property or assets of the Company. Any Accounts
maintained under this Plan shall be hypothetical in nature and shall be maintained for bookkeeping purposes only. Neither the Plan nor any Account shall hold any actual funds or assets. 

 

	11.	INALIENABILITY OF BENEFITS 

 The interests of the Participants and their Beneficiaries under the Plan may not in any way be voluntarily or involuntarily transferred, alienated or assigned, nor subject to attachment, execution,
garnishment or other such equitable or legal process. A Participant or Beneficiary cannot waive the provisions of this Section. 
  

	12.	CLAIMS PROCEDURE 

The following claims procedures shall apply for purposes of this Plan. Any and all persons presenting claims hereunder (individually or
collectively, “Claimant”) must follow these procedures: 
 (i) For claims procedure purposes, the Committee shall
appoint among themselves a chairperson of the Committee (or the chairperson of any other Committee designated by the Company to administer this Plan, or a designated member of the Board of Directors or other governing body of the Company).

 (ii) A Claimant shall make a claim for benefits hereunder by submitting a written claim to the Company (or its designee)
addressed to: Sigma-Aldrich Corporation, 3050 Spruce Street, St. Louis, Missouri 63103, Attn: Supplemental Retirement Plan/Committee. The Committee shall decide whether the claim shall be allowed, and the following claims procedure shall apply:

 a) If for any reason a claim for benefits under this Plan is denied by the Committee in whole or in part, the Committee
shall deliver to the Claimant a written explanation setting forth: the specific reason or reasons for the adverse determination; references to specific Plan provisions on which the determination is based; a description of any additional material or
information necessary for the Claimant to perfect the claim and an explanation of why such material or information is necessary; and a description of the Plan’s review procedure including a statement of the Claimant’s rights to bring a
civil action under Section 502 of ERISA following an adverse determination on review, all written in a manner calculated to be understood by the Claimant. For this purpose: 

(1) The Committee’s claim shall be deemed filed when delivered in writing as provided herein. 

  
 9 

 (2) The Committee’s explanation shall be in writing delivered to the Claimant within
90 days after receipt of the claim by the Plan, unless the Committee determines that special circumstances require an extension of time for processing the claim. If such an extension of time for processing is required, written notice of the
extension shall be furnished to the Claimant prior to the termination of the initial 90 day period. In no event shall such extension exceed a period of 90 days from the end of such initial period. The extension notice shall indicate the special
circumstances requiring an extension of time and the date by which the Committee expects to render the benefit determination. If the period of time is extended because the Claimant has failed to provide necessary information to decide the claim, the
period for making the benefit determination shall be tolled from the date on which the notification of the extension is sent to the Claimant, until the date on which the Claimant provides the information. 

b) The Claimant shall have 60 days following his or her receipt of a notice of adverse benefit determination to file with the Committee
a written request for review of the denial. Claimant shall have the opportunity to submit written comments, documents, records and other information relating to the claim for benefits. Claimant shall be provided, upon request and free of charge,
reasonable access to, and copies of, all documents, records, and other information relevant to the Claimant’s claim for benefits. The review of the claim shall take into account all comments, document, records, and other information submitted
by the Claimant relating to the claim, without regard to whether such information was submitted or considered in the initial benefit determination. 
 c) In the case of a request for review of an adverse benefit determination, the Company shall designate an individual or Committee (herein the “Reviewer”) to review the claim. On review, the
Reviewer shall notify the Claimant not later than 60 days after the Company’s receipt of the request for review, unless the Review determines that special circumstances require an extension of time for processing the claim, in which case a
decision shall be rendered as soon as possible, but not later than 120 days after receipt of other request for review. If such an extension of time for review is required because of special circumstances written notice of the extension shall be
furnished to the Claimant prior to the commencement of the extension. The extension notice shall indicate the special circumstances requiring an extension of time and the date by which the Plan expects to render the determination on review. If the
period of time is extended because the Claimant has failed to provide necessary information to decide the claim, the period for making the benefit determination shall be tolled from the date on which the notification of the extension is sent to the
Claimant, until the date on which the Claimant provides the information. The decision on review shall be in writing and in the case of an adverse benefit determination shall include: (1) the specific reason or reasons for the decision;
(2) references to the specific Plan provisions on which the benefit determination is based; (3) a statement that the Claimant is entitled to receive, upon request and free of charge, reasonable access to, and copies of, all documents,
records and other information relevant to the Claimant’s claim for benefits; and (4) a statement of the Claimant’s right to bring an action under Section 502(a) of ERISA, all written in a manner calculated to be understood by the
Claimant. If the decision on review is not furnished within such time, the claim shall be deemed denied on review. 
 To the
extent permitted by law, a decision on review by the Reviewer shall be binding and conclusive upon all persons whomsoever. Completion of the claims procedure described in this Section shall be a mandatory precondition that must be complied with
prior to commencement of a legal or equitable action in connection with the Plan by a person claiming rights under the Plan, or by another person claiming rights through such a person. 

  
 10 

	13.	GOVERNING LAW 

 To
the extent not preempted by Federal law, the provisions of this Plan shall be interpreted and construed in accordance with the laws of the State of Missouri without regard to conflict of law provisions. 

 

	14.	AMENDMENTS 

 The
Board or the Committee may amend or terminate this Plan at any time in its discretion; provided, however, that such amendment or termination shall not adversely affect Credits and earnings or losses previously credited to a Participant’s
Account. In the event the Plan is terminated, benefits shall become payable due to such termination only to the extent permissible under the regulations promulgated by the Secretary of Treasury pursuant to Code Section 409A and in the manner
set forth therein. 
  

	15.	SECTION 409A PROVISION 

 This Plan shall be interpreted in a manner consistent with the provisions of Section 409A of the Code and the regulations thereunder. 

IN WITNESS WHEREOF, on this 19 day of December, 2008, this restatement of the Plan is adopted effective the first day of January, 2009.

  

			
	SIGMA-ALDRICH CORPORATION
		
	By:	 	 /s/ Douglas W. Rau

	Name:	 	 Douglas W. Rau

	Title:	 	 VP Human Resources

  
 11 

 APPENDIX A 

ACTIVE PARTICIPANTS

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