Exhibit 5





                                 June 24, 1994



Ionics, Incorporated
65 Grove Street
Watertown, MA  02172

    Re:  Registration Statement on Form S-8 relating to
         the Ionics, Incorporated 1979 Stock Option Plan


Gentlemen:

As General Counsel for Ionics, Incorporated, a Massachusetts
corporation (the "Company"), I am familiar with its corporate
affairs.  In particular, I have acted as counsel for the
Company in connection with the registration of 325,000 shares
of the Company's common stock, par value $1.00 per share (the
"Shares"), reserved for issuance under the Ionics, Incorporated
1979 Stock Option Plan (the "Plan"), pursuant to a Registration
Statement on Form S-8 (the "Registration Statement") under the
Securities Act of 1933, as amended and the conduct of certain
corporate proceedings relating thereto.

As such counsel, I have examined and am familiar with the
Registration Statement, certain corporate records of the
Company, including its Restated Articles of Organization, as
amended, its By-laws, minutes of meetings of its Board of
Directors and stockholders, and such other documents,
instruments and certificates of government officials as I have
deemed necessary as a basis for the opinions herein expressed.

In my examination described in the preceding paragraph, I have
assumed the genuineness of all signatures, the authenticity of
all documents submitted to me as originals, the conformity to
the corresponding originals of all documents submitted to me as
copies, the authenticity of the originals of such copies, and
the accuracy and completeness of all corporate records.

I have made such examination of Massachusetts law as I have
deemed relevant for purposes of this opinion, but have not made
any review of the laws of any other state or jurisdiction.
Accordingly, this opinion is limited to Massachusetts law.




/11
                              -2-





Based upon and subject to the foregoing, I am of the opinion
that the Shares to be issued by the Company from time to time
pursuant to the Plan will be duly authorized, validly issued,
fully paid and non-assessable.  Furthermore, the stock options
or performance units granted or to be granted from time to time
by the Company under the Plan are or will be, as the case may
be, legally authorized and issued options and performance units
for the purchase of Common Stock in accordance with their
terms.

I hereby consent to the filing of this opinion as an exhibit to
the Registration Statement and to the reference to me in Item
5, Interests of Named Experts and Counsel, in the Registration
Statement.  This opinion is being furnished to you solely for
the foregoing use and, other than in connection with such use,
is not to be disseminated, reproduced or published in any form,
used for any other purpose or relied upon by any other person
or entity without my prior written consent.

                                 Very truly yours,


                                 /s/Stephen Korn
                                 Stephen Korn
                                 General Counsel



/12