January 21, 2005


Via Fascimile (617-926-8691) and U.S. Mail

Stephen Korn, Esq.
Vice President and General Counsel
Ionics, Incorporated
65 Grove Street
Watertown, Massachusetts 02472-2882


Re:	Ionics, Incorporated
	Amendment No. 1 to Preliminary Schedule 14A
      filed January 14, 2005
	File No. 001-07211

Dear Mr. Korn:

      We have reviewed your response to our January 6, 2005 letter
and have the following comments.  Where indicated, we think you
should revise your document in response to these comments.  If you
disagree, we will consider your explanation as to why our comment
is
inapplicable or a revision is unnecessary.  Please be as detailed
as
necessary in your explanation.  In some of our comments, we may
ask
you to provide us with supplemental information so we may better
understand your disclosure.  After reviewing this information, we
may
or may not raise additional comments.

      Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your filing.
We look forward to working with you in these respects.  We welcome
any questions you may have about our comments or on any other
aspect
of our review.  Feel free to call us at the telephone numbers
listed
at the end of this letter.

Interests of Certain Persons in the Merger - Page 6
1. Please clarify whether any of the arrangements were created
since
the beginning of discussions about the merger.  Also, clarify
whether
presently anticipated actions will result in any payments under
the
severance agreements.

Ecolochem - Page 8
2. Clarify your disclosure to reconcile the 490,566 shares
mentioned
here with 19.2% mentioned on page 6.  Tell us the number of
parties
to the agreement and how you secured the voting agreement
consistent
with the proxy rules.  Also clarify who would vote the shares
absent
the voting agreement.

The Merger - Beginning on Page 18

3. Please expand your disclosure in response to comment 4 to
describe
why the board decided to engage two financial advisors (rather
than
one) and obtain two fairness opinions for this transaction
(particularly in light of the fact disclosed in connection with
comment 8 that the financial advisors did not provide independent
financial analyses, but instead collaborated).  Your revised
disclosure should clarify how a second opinion contributed to
management`s deliberations given that each advisor performed the
same
analysis.
4. Please expand your disclosure in response to the second
sentence
of comment 5 to clarify how the parties to the "arm`s length
negotiations" determined the price to offer.

Opinions of Ionics`s Financial Advisors - Beginning on Page 21

5. We note your response to our prior comment 6.  Supplementally
tell
us (i) how much compensation each financial advisor has received
from
GE and its affiliates within the last two years and (ii) why you
believe such information is not necessary for investors to
understand
your disclosure in context.

* * * * *

As appropriate, please amend your filing and respond to these
comments.  You may wish to provide us with marked copies of the
amendment to expedite our review.  Please furnish a cover letter
with
your amendment that keys your responses to our comments and
provides
any requested supplemental information.  Detailed cover letters
greatly facilitate our review.  Please understand that we may have
additional comments after reviewing your amendment and responses
to
our comments.

	Please contact Eduardo Aleman at (202) 824-5661 or me at
(202)
824-5697 with any questions.

Sincerely,


Russell Mancuso
Branch Chief

cc (via fax): Mark Burnett (617) 248-7100
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Stephen Korn, Esq.
Ionics, Incorporated
January 21, 2005
Page 1