Document:

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                                                                  Exhibit 10 (e)
                                                                  --------------
                             THIRD AMENDMENT TO THE
                             ----------------------
              SIGMA-ALDRICH CORPORATION SHARE OPTION PLAN OF 1987
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          This Third Amendment to the Share Option Plan of 1987 is hereby
approved and adopted by Sigma-Aldrich Corporation (the "Company") effective as
of November 1, 1999.

          WHEREAS, the Company established its Share Option Plan of 1987 (the
"Plan") to provide for the granting of options to purchase common stock of the
Company to certain key employees of the Company and its subsidiaries; and

          WHEREAS, the Company desires to clarify that the employees of a
subsidiary which is sold will be treated in the same manner as employees whose
employment is terminated pursuant to the sale of assets; and

          WHEREAS, the Company desires to amend the Plan to provide twelve
months rather than three months after (i) termination of employment by
retirement or (ii) termination of employment by the Company without cause for an
optionee to exercise the unexercised portion of an option provided that in no
event shall the original ten year termination date of such option be extended;
and
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          WHEREAS, the Plan provides that each option shall be exercisable in
such manner, at such time or times and subject to such conditions or limitations
as shall be fixed by the Compensation Committee of the Board (the "Committee"),
in its sole discretion at the time such option is granted; and

          WHEREAS, the Company desires to clarify that the Committee, in certain
circumstances, may amend the terms and conditions with respect to which an
option is exercisable after the time an option is granted; and

          WHEREAS, the Plan established by the Company and approved by the
shareholders of the Company contemplated that with certain exceptions no option
would be exercisable within twelve months of grant; and

          WHEREAS, the Company desires to create exceptions to such twelve month
rule.

          NOW, THEREFORE, the following amendments and modifications are hereby
made a part of the Plan:

          1.   The first two sentences of paragraph 6 of the Plan are hereby
deleted and the following three sentences are inserted in their place:

          Except as provided in paragraphs 8(b)(ii) and 8(b)(v), no option
          granted under this Plan may be exercised prior to the expiration of
          twelve (12) months from the date it is granted. The Committee may
          specify a longer period of time during which an option may not be
          exercised at the time each option is granted. Any period of non-
          exercise (whether shortened as provided in paragraphs 8(b)(ii) and
          8(b)(v) or lengthened as provided in the preceding sentence) is
          hereinafter referred to as the "Non-exercise Period."

          2.   Paragraph 8(b)(i) of the Plan is hereby amended and restated as
follows:

     (b)  Termination of Employment After the Non-exercise Period
          -------------------------------------------------------

          (1)  By Retirement or Termination of Employment by the Company
               ---------------------------------------------------------
               Without Cause
               -------------
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          If the Non-exercise Period shall have elapsed and the optionee's
     employment with the Company and every subsidiary of the Company shall have
     been terminated by the Company thereafter without cause (as hereinafter
     defined) or shall terminate because of the retirement of an optionee on a
     permitted Retirement Date from the Company and all subsidiaries, the
     optionee shall have the right to exercise the unexercised portion of the
     option at any time during a period of twelve (12) months after the date of
     termination or retirement, in whole or in part, to the extent the optionee
     could have exercised such option had he remained in the employ of the
     Company during the twelve (12) month period.  If a subsidiary of the
     Company ceases to be a subsidiary of the Company, an optionee who is
     employed by such former subsidiary and is no longer employed by either the
     Company or any current subsidiary of the Company shall be deemed to have
     terminated employment with the Company and every subsidiary of the Company
     and such termination shall be deemed to have been made by the Company
     without cause.  The unexercised portion of the option shall terminate no
     later than twelve (12) months after an optionee ceases to be an employee
     for any of the foregoing reasons, and any unexercised portion shall
     terminate immediately if and when the optionee becomes an employee, agent
     or principal of a competitor of the Company, or of any subsidiary of the
     Company, without the consent of the Company.

          If an optionee dies within such twelve (12) month period at a time
     when the optionee is not an employee, agent or principal of a competitor of
     the Company or of any subsidiary (or when the Company has consented to such
     relationship with a competitor), the option may be exercised at any time
     during the period of twelve (12) months after the date of the death of the
     optionee by a designee, for the number of Shares which the deceased
     optionee could have acquired by the exercise of such option had the
     deceased optionee survived for the twelve (12) month period, without regard
     to the requirement of exercise within twelve (12) months after termination
     of employment.

          The Committee may, in its sole and absolute discretion, amend existing
     options, which provide only three (3) months for exercise after termination
     by retirement or termination by the Company without cause, to conform the
     provisions of this Paragraph 8(b)(i) as amended.

          For purposes of this Plan, the term "designee" means the deceased
     optionee's personal representative or any person who acquired the right to
     exercise such option by bequest or inheritance or by reason of the laws of
     descent and distribution.  The term "Retirement Date" shall have the
     meaning set forth in the Employees' Retirement Plan, as in effect from time
     to time, of the optionee's employer, and shall include, where applicable,
     the Normal Retirement Date, the Early Retirement Date, and Retirement By
     Reason of Disability as defined in such Plan, or, if the optionee's
     employer has no such plan, the term shall have the meaning set forth in the
     Federal Social Security Act, as in effect from time to time.

          3.   A new paragraph 8(b)(v) is added immediately following paragraph
8(b)(iv) as follows:
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          (v)  Certain Corporate Transactions.  If an optionee's employment is
               ------------------------------
     terminated or deemed terminated with the Company and every subsidiary of
     the Company solely as a result of:

               (1)  the sale of a subsidiary of the Company,

               (2)  the sale of the assets of a portion of the business of the
                    Company or a subsidiary of the Company, or

               (3)  a corporation reorganization or restructuring, the Committee
                    may, in its sole and absolute discretion, allow the optionee
                    to exercise options (i) which are not yet otherwise
                    exercisable and (ii) which have not been granted at least
                    twelve (12) months prior to the date of such transaction.

          IN WITNESS WHEREOF, the Company has executed this Third Amendment to
the Share Option Plan of 1987 as of the day and year first above written.

                              SIGMA-ALDRICH CORPORATION

                              By    /s/ David R. Harvey
                                    --------------------------
                                            President<PAGE>

                                                                  Exhibit 10 (f)
                            FOURTH AMENDMENT TO THE
                           SIGMA-ALDRICH CORPORATION
                           SHARE OPTION PLAN OF 1987

     This Fourth Amendment to the Sigma-Aldrich Corporation Share Option Plan of
1987 is hereby adopted by Sigma-Aldrich Corporation (the "Company") effective as
of February 20, 2001.

          WHEREAS, the Company established its Share Option Plan of 1987 (the
"Plan") to provide for the granting of options to purchase common stock of the
Company to certain key employees of the Company and its subsidiaries;

          WHEREAS, Paragraph 15 of the Plan provides that the Board of Directors
may make such amendments and modifications as it deems advisable, in its sole
discretion, subject to certain exceptions;

          WHEREAS, the Board of Directors desires to amend the Plan to provide
that options shall become vested and exercisable upon (i) termination of
employment by retirement or (ii) termination of employment by reason of death or
disability, subject to the terms and conditions of the Plan;  and

          WHEREAS, the Plan provides that each option shall be exercisable in
such manner, at such time or times and subject to such conditions or limitations
as shall be fixed by the Compensation Committee of the Board (the "Committee"),
in its sole discretion at the time such option is granted or after the time an
option is granted;

          NOW, THEREFORE, the following amendments and modifications are hereby
made a part of the Plan:

     1.   The first three sentences of Paragraph 6 are hereby deleted and
replaced with the following:

          "Except as provided in Paragraph 8, no option granted under this Plan
          may be exercised prior to the expiration of twelve (12) months from
          the date it is granted.  The Committee may specify a longer period of
          time during which an option may not be exercised at the time each
          option is granted.  Any period of non-exercise (whether shortened as
          provided in Paragraph 8 or lengthened as provided in the preceding
          sentence) is hereinafter referred to as the 'Non-exercise Period.'"

     2.   Paragraph 8(a) is hereby deleted and replaced with the following:

          "(a)  Termination of Employment During the Non-exercise Period
                --------------------------------------------------------

          "Except as provided in Paragraph 8(b) hereof, if, during the Non-
          exercise Period, the optionee's employment with the Company and every
          subsidiary of the Company shall terminate for any reason, the
          optionee's right to exercise the option shall terminate and all rights
          thereunder shall cease."
<PAGE>

     3.   The first three paragraphs of Paragraph 8(b)(i) are hereby deleted and
replaced with the following:

          "If the Non-exercise Period shall have elapsed and the optionee's
          employment with the Company and every subsidiary of the Company shall
          have been terminated by the Company thereafter without cause (as
          hereinafter defined) or shall terminate because of the retirement of
          an optionee on a permitted Retirement Date from the Company and all
          subsidiaries, the optionee shall have the right to exercise the
          unexercised portion of the option at any time during a period of
          twelve (12) months after the date of termination or retirement, in
          whole or in part, (x) in the case of  termination of the optionee's
          employment by the Company without cause, to the extent the optionee
          could have exercised such option had he remained in the employ of the
          Company during the twelve (12) month period or (y) in the case of
          termination because of retirement of an optionee on a permitted
          Retirement Date, to the extent of any or all the options held by the
          optionee, whether or not the Non-exercise Period shall have elapsed
          with respect to such options.  If a subsidiary of the Company ceases
          to be a subsidiary of the Company, an optionee who is employed by such
          former subsidiary and is no longer employed by either the Company or
          any current subsidiary of the Company shall be deemed to have
          terminated employment with the Company and every subsidiary of the
          Company and such termination shall be deemed to have been made by the
          Company without cause.  The unexercised portion of the option shall
          terminate no later than twelve (12) months after an optionee ceases to
          be an employee for any of the foregoing reasons, and any unexercised
          portion shall terminate immediately if and when the optionee becomes
          an employee, agent or principal of a competitor of the Company or of
          any subsidiary of the Company without the consent of the Company.

          "If an optionee dies within such twelve (12) month period at a time
          when the optionee is not an employee, agent or principal of a
          competitor of the Company or of any subsidiary (or when the Company
          has consented to such relationship with a competitor), the option may
          be exercised at any time during the period of twelve (12) months after
          the date of the death of the optionee by his designee, (x) in the case
          of termination of the optionee's employment by the Company without
          cause, for the number of Shares which the deceased optionee could have
          acquired by the exercise of such option had the deceased optionee
          survived for the twelve (12) month period, without regard to the
          requirement of exercise within twelve (12) months after termination of
          employment or (y) in the case of termination because of retirement of
          an optionee on a permitted Retirement Date, for the number of Shares
          subject to any or all the options held by the deceased optionee,
          whether or not the Non-exercise Period shall have elapsed with respect
          to such options, without regard to the requirement of exercise within
          twelve (12) months after termination of employment.
<PAGE>

          "The Committee may, in its sole and absolute discretion, amend
          existing options to conform to the provisions of this Paragraph
          8(b)(i) as amended."

     4.   Paragraph 8(b)(ii) is hereby deleted and replaced with the following:

          "(ii)  By Death or Permanent and Total Disability
                 ------------------------------------------

          "If an optionee dies or is totally and permanently disabled (within
          the meaning of Section 22(e)(3) of the Internal Revenue Code) while in
          the employ of the Company or any subsidiary, the option may be
          exercised by the optionee or by his personal representative at any
          time during the twelve (12) month period after the date of such death
          or disability for the total number of Shares subject to such person's
          options, whether or not the Non-exercise Period shall have elapsed
          with respect to such options."

     5.   In all other respects, the Plan, as amended, is hereby ratified and
confirmed.

<PAGE>

          IN WITNESS WHEREOF, the Company has executed this Fourth Amendment to
the Share Option Plan of 1987 as of the day and year first above written.

                                   SIGMA-ALDRICH CORPORATION

                                   By   /s/ David R. Harvey
                                        -------------------
                                        President

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