Exhibit 10.28



                                                     April 28, 2000


Mr. Robert Parlman
515 Spaulding Farm Road
Greenville, SC  29615

Dear Bob,

         Supplementing  the  terms  of your  Employment  Agreement  with  Sybron
Chemicals Inc. (the "Company"), this will confirm that, in the event there shall
be a Change in Control (as  hereinafter  defined) and thereafter your employment
with the Company terminates Without Cause (as hereinafter defined), you shall be
entitled to the following benefits:

         (a) If your employment terminates prior to the first anniversary of the
date of the  Change  in  Control,  you shall be  entitled,  in lieu of any other
severance  pay, to a lump sum payment,  payable  within 30 days of the date your
employment terminates, equal to the sum of the following:

                  (i)      two times your base salary in effect on the Change in
Control date; and

                  (ii) your Target Bonus (as defined in the Company's  Executive
Bonus Plan (the "Plan")) for the year in which your termination occurs, prorated
for the number of months of service  during that year prior to the  termination;
and

                  (iii)  your  full  Target  Bonus  for  each of the  two  years
following the year in which your termination occurs.

         (b) If your employment  terminates on or after the first anniversary of
the date of the Change in Control,  you shall be entitled,  in lieu of any other
severance  pay, to a lump sum payment,  payable  within 30 days of the date your
employment terminates, equal to the sum of the following:

                  (i)      one time your base salary in effect on the Change in
Control date; and

                  (ii) your Target Bonus for the year in which your  termination
occurs,  prorated for the number of months of service  during that year prior to
the termination; and

                                       -2-

                  (iii)    your full Target Bonus for the year following the
year in which your termination occurs.

         The value of each Target Bonus payable hereunder shall be determined in
accordance with the provisions of Section  7(g)(4) of the Plan, as amended.  The
number of shares of Company  Common  Stock  awarded for  partial  years shall be
determined  by prorating the Closing Price (as defined in the Plan) based on the
Closing Price of the Common Stock on December 31 immediately  preceding,  and on
December 31 immediately following, a date which is three years prior to the date
your employment terminates.

         Notwithstanding  anything  herein  to the  contrary,  in the  event the
aggregate  present  value,  determined in a manner  consistent  with  applicable
provisions of Section 280G of the Internal Revenue Code of 1986, as amended (the
"Code") and Treasury  Regulations  promulgated pursuant thereto, of the benefits
and/or  payments  provided  to you under the terms  hereof  that are  treated as
Parachute  Payments (as hereinafter  defined),  along with the aggregate present
value  (determined  in the same manner) of all other  payments  and/or  benefits
provided  to you by the Company  that are also  treated as  Parachute  Payments,
exceeds  three times your Base Amount (as  hereinafter  defined),  the  benefits
and/or payments to which you are otherwise entitled under the terms hereof shall
be reduced to the extent  necessary so that the  aggregate  present value of all
Parachute  Payments to which you are entitled  hereunder and any other agreement
or  arrangement  with the Company shall not exceed three times your Base Amount.
The reductions  required under this paragraph,  if any, shall be applied, to the
extent  possible,  to all payments  and/or  benefits to which you are  otherwise
entitled  under  this  Agreement  in  proportion  to the  Present  Value of such
payments  and/or  benefits,  and  otherwise in such manner as the Company  deems
appropriate  at its  discretion.  In the event you  receive  Parachute  Payments
having an aggregate present value in excess of three times your Base Amount, you
agree that you are not  entitled  to retain and shall  immediately  repay to the
Company,  in cash,  the excess of the  aggregate  present  value of all payments
and/or benefits which constitute  Parachute  Payments over three times your Base
Amount.  For  purposes  of this  paragraph  the  following  terms shall have the
meanings set forth below:

         "Parachute  Payment"  means  any  payment  to  you  in  the  nature  of
compensation  that constitutes a "parachute  payment" as that term is defined in
Code Section 280G(b)(2); and

         "Base  Amount"  means the amount which is  determined  to be your "base
amount" as that term is defined in Code Section 280G(b)(3).

         Termination  of your  employment  with the Company  Without Cause shall
mean (a) termination by the Company without Cause (as defined in your Employment
Agreement  with the  Company),  or (b)  termination  by you by reason of (i) the
Company's  failure to make any of the  payments,  or provide any of the material
benefits (or their equivalent),

                                       -3-

under the  terms of your  Employment  Agreement  with the  Company,  or (ii) any
material  adverse  change  in  your  position,  the  location  of  your  primary
workplace,  the scope of your duties and responsibilities,  or your compensation
and benefits.

         A  "Change  of  Control"  shall be  deemed  to have  occurred  upon the
earliest  to  occur  of the  following  events:  (a)  the  sale or  disposal  of
substantially  all of the  assets of the  Company,  or (b) the date any  entity,
person or group,  within the meaning of Section  13(d)(3) or Section 14(d)(2) of
the  Securities  Exchange  Act of 1934,  as  amended,  other than the Company or
Citigroup or any of their  subsidiaries,  any employee  benefit plan (or related
trust) sponsored or maintained by the Company or any of its subsidiaries, or any
other person or group in which the present  management of the Company shall have
an aggregate  equity  interest,  on a fully diluted basis,  of no less than 15%,
shall have become the beneficial owner of, or shall have obtained voting control
over,  more  than  fifty  percent  (50%) of the  outstanding  shares  of (i) the
Company's  Common Stock, or (ii) the Common Stock of the Company  resulting from
the merger or consolidation of the Company with or into any other entity.

         This letter amends and supersedes the letter  agreement  dated November
4, 1998 covering the same subject matter covered by this letter.

         If the above correctly reflects our  understanding,  please so indicate
by signing in the space provided below for such purpose.

                                         Sincerely,



                                         Richard M. Klein
                                         President and Chief Executive Officer

AGREED:

/s/ Robert Parlman
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Robert Parlman