Rule 424(b)(3)
                                                             File No. 33-38033

                             NALCO CHEMICAL COMPANY

                         COMMON STOCK ACQUIRED UNDER THE
                             NALCO CHEMICAL COMPANY
                             1990 STOCK OPTION PLAN

                           APPENDIX DATED MAY 12, 1997
                      TO PROSPECTUS DATED NOVEMBER 30, 1990


This Appendix  updates certain  information in the Prospectus dated November 30,
1990 (the "Prospectus")  relating to shares of Common Stock which may be offered
by the stockholders listed herein under the caption "Selling Stockholders" or by
their  transferees  (or by their donees or  pledgees).  The Company will furnish
without charge to participants additional copies of the Prospectus upon request.

                              SELLING STOCKHOLDERS

The following  table sets forth the name and position within the Company for the
last three  years of each  Selling  Stockholder,  the number of shares of Common
Stock of the Company  beneficially  owned by him on the date of this  Prospectus
and, the number of shares offered by the Prospectus.

                                                           Shares Offered
                                        Shares               By This
Name and Position                      Owned (1)(2)         Prospectus (2)
E. J. Mooney                            358,280               378,600
President and Chief Operating 
Officer from January, 1992 to
 March 1994; President as of
March, 1990; Chief Executive Officer 
as of April, 1994; and Chairman as of July,
1994.


(1)  Includes  314,334  shares which are subject to  outstanding  stock  options
     exercisable within sixty days of April 30, 1997.
(2)   Includes shares which may be acquired by exercise of stock options.



Additional Selling Stockholders will be identified by a subsequent appendix. One
or more of the Selling  Stockholders  may from time to time make gifts of any or
all of his shares as  collateral  for  loans.  In the event of such gift or of a
default under any such loan,  the donee may elect to sell donated  shares or the
lender may elect to sell shares held as collateral by means of the prospectus as
supplemented.