INDEMNIFICATION AGREEMENT


             This Agreement is made as of November 4, 1996 between Thermo
        Instrument Systems Inc., a Delaware corporation ("THI"), and
        Thermo Optek Corporation, a Delaware corporation ("TOC").

             WHEREAS, on March 29, 1996 THI, directly and through its
        subsidiaries, purchased certain businesses of Fisons plc (the
        "Fisons Businesses") pursuant to an Amended and Restated Asset
        and Stock Purchase Agreement dated as of such date (the "Restated
        Agreement"); and

             WHEREAS, THI and TOC have agreed that the ARL and Elemental
        Fisons Businesses (the "TOC Businesses") shall be sold by THI to
        TOC; and

             WHEREAS, the sale by THI, and the purchase by TOC, of the
        TOC Businesses shall be made pursuant to a number of purchase and
        sale agreements among subsidiaries of TOC, THI and subsidiaries
        of THI (the "Transfer Agreements"); and

             WHEREAS, THI and TOC desire to make certain provisions for
        (i) THI's indemnification of TOC and its subsidiaries for certain
        liabilities of the TOC Businesses and (ii) TOC's indemnification
        of THI and its subsidiaries for certain liabilities of the TOC
        Businesses.

             NOW, THEREFORE, THI and TOC hereby agree as follows:

             1.   Indemnification.
                  ---------------

                  (a)  THI shall indemnify and hold harmless TOC and its
        subsidiaries from any and all damages, losses, liabilities, costs
        and expenses (including, without limitation, settlement costs and
        any reasonable legal, accounting or other expenses for
        investigating or defending any actions or threatened actions)
        incurred by TOC or any of its subsidiaries as a result of:

                       (i)  any third party claims based on the acts or
        omissions of THI or any of its subsidiaries (including any
        subsidiaries subsequently sold to TOC) on or after March 29, 1996
        and prior to the date hereof; or

                       (ii) the breach by THI or any of its subsidiaries
        of any representation, warranty, covenant or agreement contained
        in any of the Transfer Agreements.

                  (b)  TOC shall indemnify and hold harmless THI and its
        subsidiaries form any and all damages, losses, liabilities, costs
        and expenses (including, without limitation, settlement costs and
        any reasonable legal, accounting or other expenses for
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        investigating or defending any actions or threatened actions)
        incurred by THI or any of its subsidiaries (other than
        subsidiaries acquired by TOC) as a result of any liability of the
        TOC Businesses other than a liability (i) as to which TOC and its
        subsidiaries are entitled to indemnification by THI hereunder or
        (ii) that is expressly retained by THI or any of its subsidiaries
        pursuant to any Transfer Agreement.

                  (c)  Whenever any claim shall arise for indemnification
        hereunder, the party seeking indemnification (the "Indemnified
        Party") shall promptly notify the other party (the "Indemnifying
        Party") of the claim and, when known, the facts constituting the
        basis for such claim.  In the event of any such claim for
        indemnification hereunder resulting from or in connection with
        any claim or legal proceedings by a third party, the notice to
        the Indemnifying Party shall specify, if known, the amount or an
        estimate of the amount of the liability arising therefrom.  The
        Indemnified Party shall not settle or compromise any claim by a
        third party for which the Indemnified Party is entitled to
        indemnification hereunder without the prior consent of the
        Indemnifying Party, unless suit shall have been instituted
        against the Indemnified Party and the Indemnifying Party shall
        not have taken control of such suit after notification thereof as
        provided in Section 2(d) of this Agreement.

                  (d)  In connection with any claim giving rise to
        indemnity hereunder resulting from or arising out of any claim or
        legal proceeding by a person who is not a party to this
        Agreement, the Indemnifying Party at its sole cost and expense
        may, upon notice to the Indemnified Party, assume the defense of
        any such claim or legal proceeding if it acknowledges to the
        Indemnified Party its obligations to indemnify the Indemnified
        Party with respect to all elements of such claim.  The
        Indemnified Party shall be entitled to participate in (but not
        control) the defense of any such action, with its counsel and at
        its own expense.  If the Indemnifying Party does not assume the
        defense of any such claim or litigation resulting therefrom
        within 30 days after the date the Indemnifying Party is notified
        of such claim pursuant to Paragraph 2(c) hereof, (i) the
        Indemnified Party may defend against such claim or litigation,
        after giving notice of the same to the Indemnifying Party, on
        such terms as are appropriate in the Indemnified Party's
        reasonable judgment, and (ii) the Indemnifying Party shall be
        entitled to participate in (but not control) the defense of such
        action, with its counsel and at its own expense.

             3.   Restated Agreement.  THI hereby assigns to TOC, and TOC
        hereby accepts and assumes, the rights and obligations of THI
        under the Restated Agreement, and any agreements or instruments
        executed by THI in connection therewith, but only to the extent
        such rights and obligations relate primarily to the TOC
        Businesses.  In furtherance of the foregoing, TOC may enforce, in
        its own name and in the name and on behalf of THI, any of the
        rights of THI under Section 11 of the Restated Agreement, and, if
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        requested by TOC, THI shall take such actions, at its own
        expense, as TOC shall reasonably request in order that TOC shall
        have the full rights and benefits granted to it under this
        Section 3.
         
             4.   Captions.  The captions and headings to the various
        sections, paragraphs and exhibits of this Agreement are for
        convenience of reference only and shall not affect or control the
        meaning or interpretation of any of the provisions of this
        Agreement.

             5.   Integration.  This Agreement contains the entire
        understanding of the parties hereto with respect to the subject
        matter contained herein.

             6.   Notice of Communication.  Any notice or other
        communication shall be in writing and shall be personally
        delivered, or sent by overnight or second day courier or by first
        class mail, return receipt requested, to the party to whom such
        notice or other communication is to be given or made at such
        party's address set forth below, or to such other address as such
        party shall designate by written notice to the other party as
        follows:

             If to THI:

                  Thermo Instrument Systems Inc.
                  c/o Thermo Electron Corporation
                  81 Wyman Street
                  P.O. Box 9046
                  Waltham, MA  02445-9046
                  Attn: General Counsel

             If to TOC:

                  Thermo Optek Corporation
                  81 Wyman Street
                  P.O. Box 9046
                  Waltham, MA  02445-9046
                  Attn: General Counsel

        provided that any notice of change of address, and any notice or
        other communication given otherwise than as specified above shall
        be effective only upon receipt; and further that any presumption
        of receipt by the addressee shall be inoperable during the period
        of any interruption in Postal Service.

             7.   Governing Law; Assignment.  This Agreement is to be
        construed, interpreted, applied and governed in all respects in
        accordance with the laws of the Commonwealth of Massachusetts,
        without regard to its conflict of laws provisions, is to take
        effect as a sealed instrument, is binding upon and inures to the
        benefit of the parties hereto and their respect successors and
        assigns and may be canceled, modified or amended only by a
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        written instrument executed by THI and TOC.  No party hereto may
        assign its rights hereunder without prior written consent of the
        other party.
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             IN WITNESS WHEREOF, the parties hereto have executed this
        Agreement as of the date and year first above written.

                                 THERMO INSTRUMENT SYSTEMS INC.



                                 By:  Earl R. Lewis
                                    -------------------------------------
                                      Earl R. Lewis
                                      Executive Vice President and Chief
                                       Operating Officer


                                 THERMO OPTEK CORPORATION



                                 By:  Robert J. Rosenthal
                                    -------------------------------------
                                      Robert J. Rosenthal
                                      Senior Vice President