Exhibit 10(b)

CHANGE IN CONTROL AGREEMENT

This Agreement, dated as of this 30th day of December 2008, is by and between
Jai P. Nagarkatti (“Executive”) and Sigma-Aldrich Corporation and any successor
to its business and/or assets (“Company”).

WHEREAS, the Company considers it essential to the best interests of the Company
that its key employees be encouraged to remain with the Company and to devote
full attention to the Company’s business in the event that any third party
expresses its intention to take action which could result in a change in control
of the Company; and

WHEREAS, Executive serves as a key employee of the Company;

NOW, THEREFORE, to encourage Executive’s continued, undivided attention,
dedication and services to the Company and the availability of Executive’s
advice and counsel notwithstanding the possibility, threat or occurrence of a
change in control of the Company, and to induce Executive to remain in the
employ of the Company, and for other good and valuable consideration, the
adequacy and sufficiency of which are hereby acknowledged, the Company and
Executive agree as follows:

 

  1. Term of Agreement. The term of this Agreement shall commence on the date
first set forth above and shall end on December 31, 2009, and shall continue in
effect for successive periods of one year thereafter unless either the Company
or Executive gives written notice of intent to terminate the Agreement at least
six (6) months prior to the expiration of the then-current term of this
Agreement. The Company is precluded from giving notice of intent to terminate
within six months of a Change in Control or at any time at which a Change in
Control with an identified party is under serious consideration.

 

  2. Definitions. As used herein, the terms identified below shall have the
meanings indicated:

 

  (a) “Applicable Amount” shall mean two times the lesser of:

 

  (1) Executive’s annualized compensation (as defined within the meaning of
Section 409A of the Code) based upon Executive’s annual rate of pay for the year
preceding the year in which Executive’s employment with the Company terminates
(adjusted for any increase during that year that was expected to continue
indefinitely if Executive’s employment had not terminated); or

 

  (2) the maximum amount that may be taken into account under a qualified plan
pursuant to Section 401(a)(17) of the Code for the year in which Executive’s
employment is terminated.

 

  (b) “Base Amount” means “base amount” as defined in Section 280G of the Code.

 

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  (c) “Board” means the Company’s Board of Directors.

 

  (d) “COBRA” shall mean the Consolidated Budget Reconciliation Act of 1985.

 

  (e) “Change in Control” means (1) an acquisition by an individual or entity of
35% of the outstanding common stock or voting power of the Company, (2) a
contested change of a majority of the non-employee directors of the Company,
(3) a merger, sale, acquisition, or other such transaction where the
shareholders of the Company immediately prior to such transaction do not own 60%
of the outstanding common stock of the Company immediately following such
transaction, or (4) shareholder approval of a complete dissolution of the
Company (excluding bankruptcy).

 

  (f) “Cause” means any of the following:

 

  (i) the willful and continuous failure by Executive to substantially perform
Executive’s duties with the Company (other than any such failure resulting from
Executive’s incapacity due to physical or mental illness) thirty (30) days after
a written demand for substantial performance is delivered to Executive by the
Board which specifically identifies the manner in which the Board believes that
Executive has not substantially performed Executive’s duties,

 

  (ii) gross misconduct or gross negligence by Executive provided (A) the Board
has determined that the resulting harm to the Company from Executive’s gross
misconduct or gross negligence cannot be adequately remedied, or (B) Executive
fails to correct any resulting harm to the Company within thirty (30) days after
a written demand for correction is delivered to Executive by the Board which
specifically identifies both the manner in which the Board believes that
Executive has engaged in gross misconduct or gross negligence and an appropriate
method of correcting any resulting harm to the Company, or

 

  (iii) Executive’s conviction of or the entering of a plea of guilty or nolo
contendere to the commission of a felony.

 

  (g) “Code” means the Internal Revenue Code of 1986, as amended, and the
regulations and other guidance promulgated by the Treasury Department and the
Internal Revenue Service thereunder.

 

  (h) “Good Reason” means the occurrence of one or more of the following
conditions without the consent of the Executive:

 

  (i) a diminution in Executive’s authority, duties, or responsibilities;

 

  (ii) a diminution in the authority, duties or responsibilities of the
supervisor to whom the Executive is required to report;

 

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  (iii) a diminution in the budget over which the Executive retains authority;

 

  (iv) a change of at least 50 miles in the geographic location at which the
Executive must perform services for the Company;

 

  (v) any action or inaction that constitutes a material breach by the Company
of the agreement under which the Executive provides services;

 

  (vi) a diminution in Executive’s base compensation.

 

  (i) “Incentive Payment” shall have the meaning as set forth in Section 3.

 

  (j) “Long-Term Incentive Plan” shall mean the 2003 Sigma-Aldrich Long-Term
Incentive Plan and any successor plan thereto.

 

  (k) “Qualifying Termination” shall have the meaning as set forth in Section 5.

 

  (l) “Rabbi Trust” shall mean a trust established or selected by the Company to
pay benefits due to Executive in the circumstances described in this Agreement
or to other Company executives under other nonqualified arrangements that is
intended to constitute an unfunded arrangement that does not affect the status
of the Agreement and any other plan or agreement maintained by the Company as an
unfunded plan maintained for the purpose of providing deferred compensation for
a select group of management or highly compensated employees under Title I of
the Employee Retirement Income Security act of 1974. Any Rabbi Trust established
by the Company shall be subject to the claims of the Company’s creditors in the
event the Company becomes insolvent, until paid to Executive.

 

  (m) “Severance Payment” shall mean the benefit, if any, defined as a
“Severance Payment” and paid to Executive as a lump sum under the Company’s
Executive Severance Plan.

 

  (n) “Short-Term Incentive Plan” shall mean the Sigma-Aldrich Corporation Cash
Bonus Plan and any successor plan thereto.

 

  (o) “Specified Employee” shall mean any Company employee that the Company
determines is a Specified Employee within the meaning of Section 409A of the
Code. The Company shall determine whether an employee is a Specified Employee by
applying reasonable, objectively determinable identification procedures set
forth in a resolution of the Board issued before December 31, 2007.

 

  (p) “Termination Factor” means a factor equal to 2.99.

 

  (q) “Termination Payment” shall have the meaning as set forth in Section 6.

 

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3.

Incentive Payments. In the event of a Change in Control, Executive shall be
entitled to receive an “Incentive Payment.” Subject to the terms hereof, such
payment will be made in a lump-sum sixty (60) days following the date of the
Change in Control or as soon as administratively practicable thereafter but in
no event later than 2 1/2 months after the close of the year in which the Change
in Control occurs. The Incentive Payment shall equal the sum of Executive’s
bonus and incentive compensation otherwise payable under the terms of the
Company’s Short-Term and Long-Term Incentive Plans determined on a pro rata
basis for Executive’s services and performance to the date of the Change in
Control and based on full and immediate vesting as of the date of the Change in
Control. Notwithstanding any provision herein to the contrary, in the event an
Incentive Payment is deferred compensation under Section 409A of the Code, such
Incentive Payment shall be fully vested with respect to the pro rata portion for
Executive’s services and performance to the date of the Change in Control and
paid out pursuant to the terms of the awards and underlying plans.

 

  4. Stock Rights. In the event of a Change in Control, Executive’s
non-qualified stock options, incentive stock options, stock appreciation rights,
restricted stock, performance shares, performance units, and restricted stock
units granted by the Company which are outstanding on the date of the Change in
Control, shall vest and be exercisable pursuant to the terms of the awards and
underlying plans.

 

  5. Qualifying Termination. Benefits only become payable under Sections 6 and 7
below if Executive experiences a “Qualifying Termination”. A Qualifying
Termination shall occur on the later of the following events, provided both such
events occur: (1) the Company terminates Executive’s employment without Cause
or, no later than two years following the event that gives rise to Good Reason,
Executive terminates his or her employment for Good Reason, provided that such
termination of employment (be it without Cause or for Good Reason) occurs either
six months prior or two years following a Change in Control or (2) a Change in
Control occurs. For purpose of a Qualifying Termination involving Good Reason,
the Executive must provide the Company with notice within 90 days of the initial
existence of a condition constituting Good Reason and afford the Company 30 days
in which to remedy the condition. If the Company remedies the condition during
the prescribed 30-day period and the Executive terminates employment, the
Executive will not be deemed to have terminated his or her employment for Good
Reason for purposes of this Section 5.

 

  6. Termination Payment. Except as described below, Executive shall receive a
“Termination Payment” immediately upon the occurrence of a Qualifying
Termination or as soon as administratively possible thereafter. The Termination
Payment shall be subject to deductions for customary withholdings, including,
without limitation, federal and state withholding taxes and social security
taxes. Subject to all other provisions of this Agreement, including Section 9
hereof, the Termination Payment shall equal the sum of the following amounts
less any “Severance Payment”:

 

  (a) All previously earned and accrued but unpaid base salary up to the date of
Executive’s termination of employment;

 

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  (b) An amount equal to the Termination Factor multiplied by Executive’s annual
base salary as of the date of Executive’s termination of employment; and

 

  (c) An amount equal to the Termination Factor multiplied by the full-year
Short Term Incentive Target of the year in which Executive terminates
employment.

The portion of the Termination Payment described in subsections (b) and
(c) shall be paid to an Executive who is a Specified Employee on the first day
of the seventh month following the date Executive terminates employment with the
Company, or, if earlier, the date Executive dies following the Qualifying
Termination. Any Termination Payment made to an Executive who is a Specified
Employee that is to be delayed pursuant to this Section 6 shall be held in a
Rabbi Trust with reasonable interest accruing from the date of the Qualifying
Termination until payment to Executive.

If the Company determines that the termination of employment causing the
Qualifying Termination constitutes an involuntary separation from service as
defined by Section 409A of the Code, the sum of the Termination Payment
described in subsections (b) and (c) and the “Severance Payments” shall, to the
extent it does not exceed the Applicable Amount, be paid without regard to such
six month delay.

 

  7. Continuation of Benefits. Executive shall receive the following benefits
beginning upon the occurrence of a Qualifying Termination or as soon as
administratively possible thereafter. Such benefits (including the right to
reimbursements) shall, unless otherwise noted, continue for a period of years
equal to the Termination Factor multiplied by one year. Any reimbursements
listed below shall be paid no later than the end of Executive’s third taxable
year following the taxable year in which Executive terminates employment. To the
extent that the right to reimbursements extends beyond Executive’s second
taxable year following the year in which Executive’s employment was terminated,
the portion of reimbursements provided after such period shall be reimbursed by
the end of Executive’s taxable year following the end of Executive’s taxable
year in which the expense was incurred.

 

  (a) The Company will maintain Director and Officer insurance for the benefit
of Executive on the same basis as if Executive were actively employed with the
Company; and

 

  (b) The Company will indemnify Executive for all of the expenses incurred or
damages paid or payable with respect to a bona fide claim against Executive,
including settlement payments, where such claim is based on actions or failures
to act by Executive in his or her capacity as an employee of the Company.

 

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  8. Cap on Certain Payments by the Company. In the event that any payment or
benefit of any type by the Company to or for the benefit of Executive, whether
paid or payable or distributed or distributable pursuant to the terms of this
Agreement or otherwise, would not exceed 110% of the greatest amount that could
be paid to the Executive such that receipt of such payment or benefit would not
be subject to the excise tax imposed by Section 4999 of the of the Code,
Executive shall receive, subject to the conditions of this Agreement and in full
satisfaction of any and all rights under this Agreement, only such payments and
benefits which do not, in the aggregate, exceed the product of 2.99 and
Executive’s “Base Amount.” However, no amounts or benefits which constitute
nonqualified deferred compensation subject to Code section 409A shall be
forfeited or reduced pursuant to this Section 8 until all amounts and benefits
not subject to Code Section 409A have been forfeited.

 

  9. Non-Disclosure of Confidential Information and Noncompete.

 

  (a) Executive expressly recognizes and acknowledges that during Executive’s
employment with the Company, Executive became entrusted with, had access to, or
gained possession of confidential and proprietary information, data, documents,
records, materials, and other trade secrets and/or other proprietary business
information of the Company that is not readily available to competitors, outside
third parties and/or the public, including without limitation, information about
(i) current or prospective customers and/or suppliers, (ii) employees, research,
goodwill, production, and prices, (iii) business methods, processes, practices
or procedures; (iv) computer software and technology development, and
(v) business strategy, including acquisition, merger and/or divestiture
strategies, (collectively or with respect to any of the foregoing, the
“Confidential Information”). Executive agrees, by acceptance of the benefits
under this Agreement, to protect all Confidential Information concerning the
business activities of the Company which were acquired in connection with or as
a result of the performance of service for the Company.

 

  (b) Executive recognizes that the Company is engaged in the business of
research, development, manufacture and sale of chemicals and chemical products
in laboratory proportions throughout the world (the “Company’s Business”), which
business requires for its successful operation the fullest security of its
Confidential Information of which Executive will acquire knowledge during the
course of his employment.

 

  (c) Executive shall not, directly or indirectly (whether as owner, partner,
consultant, employee or otherwise), at any time during his employment with the
Company and for a period of two (2) years following any termination of his
employment with the Company which gives rise to a Termination Payment under
Section 6, regardless of how or why Executive’s employment terminates,
(i) engage in or invest in any business that is primarily engaged in any work or
activity that is then competitive with and the same as or similar to the
Company’s Business, or with respect to which Executive had access to
Confidential Information while with the Company, or (ii) otherwise compete
against the Company’s Business, provided, however, that the foregoing shall not
prohibit Executive from owning 2% or less of the outstanding equity securities
of a publicly traded entity.

 

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  (d) Executive understands that the intention of this Section of this Agreement
is not to prevent the Executive from earning a livelihood and Executive agrees
nothing in this Agreement would prevent Executive from earning a livelihood
utilizing his general purchasing, sales, professional or technical skills in any
of the hospitals, businesses, research or manufacturing facilities of companies
which are not directly or indirectly in competition with the Company.

 

  (e) Executive’s breach of Section 9 of this Agreement shall relieve Company of
its obligations (if any) to pay that portion of any Termination Payment equal to
the sum of three (3) times the Executive’s annual base salary as of the date of
Executive’s termination of employment plus three (3) times the full-year Short
Term Incentive Target of the year in which Executive terminates employment
(“Noncompete Payments”). In the event that Executive breaches this Section 9
after he has received the Termination Payment, he shall immediately return the
full amount of the Noncompete Payments to the Company, with interest from the
date Executive received such amounts.

 

  10. Employment Agreement. The Company and Executive acknowledge that
Executive’s employment, other than with respect to the terms explicitly
addressed in this Agreement, is and shall continue to be governed by the
separate Executive Employment Agreement entered between the Company and
Executive, dated as of January 1, 2006 (as modified, or substituted by new
agreements, from time to time, the “Employment Agreement”). This Agreement is
not a contract of employment and does not, apart from the Employment Agreement,
guarantee Executive employment for any particular period of time. If Executive’s
employment terminates for any reason, Executive shall not be entitled to any
payments, benefits, damages, awards or compensation other than as provided by
this Agreement and the Employment Agreement, or as may otherwise be available in
accordance with the Company’s established employee plans and practices or other
agreements with the Company at the time of termination.

 

  11. General Reimbursement Procedure. To the extent that Executive is entitled
to any reimbursements under this Agreement and the procedures for such
reimbursements are not otherwise set forth herein, such reimbursements shall be
made as soon as administratively practicable but in no event later than (1) the
end of a two year period following the date Executive terminates employment with
the Company or, if later, (2) the end of Executive’s taxable year following the
Taxable year in which Executive incurred the expense giving rise the
reimbursement right. Notwithstanding the foregoing, any Executive who is a
Specified Employee at the time his or her employment with the Company is
terminated shall not receive reimbursements under this Section 11 prior to the
first day of the seventh month following termination of employment (or, if
earlier, the date of death of Executive). Any benefits payable under this
Agreement which are subject to the six-month deferral provision shall be held in
a Rabbi Trust with reasonable interest accruing from the date of the Qualifying
Termination until payment to Executive.

 

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  12. Arbitration; Litigation Expenses. All claims, disputes and other matters
in question between the parties arising under this Agreement shall be decided by
arbitration in accordance with the rules of the American Arbitration Association
(“AAA”), unless the parties mutually agree otherwise. The determination reached
in such arbitration shall be final and biding on both parties without any right
of appeal of further dispute. Execution of the determination by such arbitrator
may be sought in any court of competent jurisdiction. The arbitrators shall not
be bound by judicial formalities and may abstain from following the strict rules
of evidence and shall interpret this Agreement as an honorable engagement and
not merely as a legal obligation. Unless otherwise agreed by the parties, any
such arbitration shall be conducted in accordance with the Rules of the AAA and
the proceedings shall be private and confidential.

The party seeking arbitration shall notify the other party in writing and
request the AAA to submit a list of 5 or 7 potential arbitrators. In the event
the parties do not agree upon an arbitrator, each party shall, in turn, strike
one arbitrator from the list, the Corporation having the first strike, until
only one arbitrator remains, who shall arbitrate the dispute. The arbitration
hearing shall be conducted within 30 days of the selection of an arbitrator or
at the earliest date thereafter that the arbitrator is available.

The administrative costs of the arbitration shall be borne equally by the
parties; however, the prevailing party in any such arbitration shall be entitled
to a recovery of his/its reasonable attorneys fees. For purposes of this
agreement, the prevailing party shall be the party that substantially prevails
in the action after the resolution of all claims. The arbitrator shall retain
jurisdiction of the dispute to determine any prevailing party issues.

 

  13. General Creditor. Any and all amounts payable hereunder to Executive shall
be made from assets which shall continue, for all purposes, to be part of the
general, unrestricted assets of the Company; no person shall have nor acquire
any interest in any such asset by virtue of the provisions of this Agreement.
The Company’s obligation hereunder shall be an unfunded and unsecured promise to
pay money in the future. To the extent that Executive or 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.

 

  14.

Severability and Interpretation. In the event of a conflict between the terms of
this Agreement and any of the definitions or provisions in the Company’s
Severance Plan or Executive Severance Plan, or otherwise, the terms of this
Agreement shall prevail. Whenever possible, each provision of this Agreement and
any portion hereof shall be interpreted in such a manner as to be effective and
valid under applicable law, rules and regulations. If any covenant or other
provision of this

 

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Agreement (or portion thereof) shall be held to be invalid, illegal, or
incapable of being enforced, by reason of any rule of law, rule, regulation,
administrative order, judicial decision or public policy, all other conditions
and provisions of this Agreement shall, nevertheless, remain in full force and
effect, and no covenant or provision shall be deemed dependent upon any other
covenant or provision (or portion) unless so expressed herein. The parties
hereto desire and consent that the court or other body making such determination
shall, to the extent necessary to avoid any unenforceability, so reform such
covenant or other provision or portions of this Agreement to the minimum extent
necessary so as to render the same enforceable in accordance with the intent
herein expressed.

 

  15. No Assignments. This Agreement shall inure to the benefit of, and be
binding upon, the Company and any successor to the Company, but neither this
Agreement nor any rights hereunder shall be assigned by Executive.

 

  16. Prior Agreements. Upon execution by both parties, this Agreement shall
supersede and replace all prior employment agreements between the Company and
Executive, other than the Employment Agreement, and this Agreement shall
constitute the entire agreement between the parties, except as expressly
provided herein, concerning the effect of a Change in Control on the employment
relationship between the Company and Executive.

 

  17. Entire Agreement. This Agreement represents the entire and integrated
Change in Control Agreement between Executive and the Company and supersedes all
prior negotiations, representations and agreements, either written or oral, with
respect thereto.

 

  18. Waiver and Releases. In consideration of the covenants under this
Agreement and as a condition precedent to receiving any payments under this
Agreement, Executive agrees to execute a Release of employment claims in such
form as requested by the Company.

 

  19. Notice. All notices and other communications hereunder shall be in writing
and shall be given by hand delivery to the other party, by registered or
certified mail, return receipt requested, postage prepaid, or by overnight
courier, addressed as set forth in this Section 19 or to such other address as
may hereafter be notified by such party to the other party. Notices and
communications shall be effective at the time they are given in the foregoing
manner.

If to Executive:

Jai P. Nagarkatti

14967 Straub Hill Lane

Chesterfield, MO 63017

 

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If to the Company:

Sigma-Aldrich Corporation

ATTN: General Counsel

3050 Spruce Street

St. Louis, MO 63103

(314) 286-7442

 

  20. Amendments and Waivers. No modification, amendment or waiver of any of the
provisions of this Agreement shall be effective unless in writing specifically
referring hereto, and signed by the parties hereto.

 

  21. Governing Law. The parties agree that this Agreement shall be interpreted
in accordance with and governed by the laws of the State of Missouri, without
regard for any conflict of law principles. Subject to Section 12, any action
concerning this Agreement shall be brought in a court of competent jurisdiction
in Saint Louis County, Missouri and each party consents to the venue and
jurisdiction of such courts.

 

  22. Headings. Section headings are provided in this Agreement for convenience
only and shall not be deemed to substantively alter the content of such
sections.

 

  23. Section 409A Savings Clause. This Agreement is intended to comply with the
provisions of 409A of the Code. If any compensation or benefits provided by this
Agreement may result in the application of Section 409A of the Code, the Company
shall, in consultation with Executive, modify the Agreement in the least
restrictive manner necessary in order to exclude such compensation from the
definition of “deferred compensation” within the meaning of such Section 409A of
the Code or in order to comply with the provisions of Section 409A of the Code,
other applicable provision(s) of the Code and/or any rules, regulations or other
regulatory guidance issued under such statutory provisions and without any
diminution in the value of the payments to Executive.

IN WITNESS WHEREOF, the parties have executed this Change in Control Agreement
this 30th day of December 2008.

 

SIGMA-ALDRICH CORPORATION     EXECUTIVE By  

/s/ Richard A. Keffer

    By  

/s/ Jai Nagarkatti

  Richard A. Keffer       Jai Nagarkatti   Vice President, General Counsel &
Secretary      

 

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