Exhibit 4


                                    SECOND SUPPLEMENTAL INDENTURE dated as of
                           December 11, 2001 (this "Second Supplemental
                           Indenture"), to the Indenture dated as of June 15,
                           1992 (hereinafter the "Original Indenture"), as
                           amended by the First Supplemental Indenture dated as
                           of March 18, 1994 (the "First Supplemental
                           Indenture"; the Original Indenture, as amended by the
                           First Supplemental Indenture and the Second
                           Supplemental Indenture is herein called the
                           "Indenture") between Olin Corporation, a corporation
                           duly organized and existing under the laws of the
                           Commonwealth of Virginia (the "Company"), and
                           JPMorgan Chase Bank (f/k/a Chemical Bank), a
                           corporation duly organized and existing under the
                           laws of the State of New York, as trustee (the
                           "Trustee").

                  WHEREAS, the Company and the Trustee entered into the Original
Indenture providing for the creation, execution, authentication and delivery of
certain Debt Securities of the Company;

                  WHEREAS, Section 10.01(f) of the Indenture permits the
Company, when authorized by a resolution of the Board of Directors of the
Company, and the Trustee, from time to time and at any time, to enter into one
or more indentures supplemental to the Indenture for the purpose, of
establishing the form of Debt Securities, as provided in Section 2.01 of the
Indenture, providing for the issuance of any additional series of Debt
Securities as provided in Section 2.03 of the Indenture and to set forth the
terms thereof;

                 WHEREAS, the Company proposes in and by this Second
Supplemental Indenture to supplement and amend the Indenture in certain respects
to establish a series of Debt Securities issued pursuant to the Indenture
designated as the 9.125% Senior Notes due 2011 initially in aggregate principal
amount of $200,000,000 (the "Notes"). The Notes shall consist of the Notes and
any Additional Notes (as defined herein), which together shall constitute one
series of Debt Securities for purposes of the Indenture;

                  WHEREAS, the Company has requested that the Trustee execute
and deliver this Second Supplemental Indenture for the purposes set forth in
Section 10.01(f) of the Original Indenture as referred to above; and

                  WHEREAS, any and all other action necessary to constitute this
Second Supplemental Indenture a valid, binding and legal instrument of the
Company have been taken and performed by the Company, and the execution and
delivery of this Second Supplemental Indenture have in all respects been duly
authorized by the Company, and the Company, in the exercise of legal right and
power in it vested, executes this Second Supplemental Indenture.

                  NOW THEREFORE, the Company and the Trustee hereby agree that
the following sections of this Second Supplemental Indenture hereby supplements
and amends the Indenture with respect to that series of Debt Securities which
consists of the Notes as provided below:

                  SECTION 1. Definitions. (a) Capitalized terms used herein and
not defined herein have the meanings ascribed to such terms in the Indenture.

                  (b) Section 1.01 of Article One of the Original Indenture is
hereby supplemented, solely with respect to that series of Debt Securities which
consists of the Notes, to add the following definitions:

                  "Additional Notes" means Debt Securities designated as 9.125%
Senior Notes due 2011 issued from time to time after the Issue Date under the
terms of this Indenture (other than pursuant to Section 2.07, 2.08, 2.09, 3.02
or 10.04 of this Indenture).

                  "Code" means the Internal Revenue Code of 1986, as amended.

                  "Issue Date" means December 11, 2001.





                  SECTION 2. Creation of Series of Securities. Pursuant to
Section 2.03 of the Original Indenture, there is hereby created a new series of
Debt Securities designated as the "9.125% Senior Notes due 2011" in an unlimited
aggregate principal amount, but on the Issue Date, in an aggregate principal
amount of $200,000,000.

                           SECTION 3. Terms of the Notes. Pursuant to Section
         2.01 of Article Two of the Original Indenture the Notes shall be
         substantially in the form annexed hereto as Exhibit A. The terms and
         provisions contained in the form of the Notes annexed hereto as Exhibit
         A shall constitute, and are hereby expressly made, a part of this
         Indenture. The Company shall be entitled to issue Additional Notes
         under this Indenture which shall have identical terms as the Notes
         issued on the Issue Date, other than with respect to the date of
         issuance and issue price. The Notes issued on the Issue Date and any
         Additional Notes shall be treated as a single class for all purposes
         under this Indenture.

                           With respect to any Additional Notes, in addition to
         any other requirements set forth in the Original Indenture and the
         First Supplemental Indenture, the Company shall set forth in a
         resolution of the Board of Directors and an Officers' Certificate, a
         copy of each which shall be delivered to the Trustee, the following
         information:

                  (1) the aggregate principal amount of such Additional Notes to
                  be authenticated and delivered pursuant to this Indenture; and

                  (2) the issue price, the issue date and the CUSIP number of
                  such Additional Notes; provided, however, that no Additional
                  Notes may be issued at a price that would cause such
                  Additional Notes to have "original issue discount" within the
                  meaning of Section 1273 of the Code."

                  SECTION 4. The Second Supplemental Indenture. The Original
Indenture, as amended and supplemented by the First Supplemental Indenture, and
as amended and modified by this Second Supplemental Indenture, hereby is in all
respects ratified, confirmed and approved. This Second Supplemental Indenture
shall be construed in connection with and as part of the Original Indenture, as
amended and supplemented by the First Supplemental Indenture.

                  SECTION 5. Counterparts. This Second Supplemental Indenture
may be executed in any number of counterparts, each of which shall be an
original; but such counterparts shall together constitute but one and the same
instrument.

                  SECTION 6. Recitals. The recitals contained herein shall be
taken as the statements of the Company, and the Trustee assumes no
responsibility for their correctness. The Trustee makes no representation as to
the validity or sufficiency of this Second Supplemental Indenture.

                  SECTION 7. Effect of Headings. The Section headings herein are
for convenience only and shall not affect the construction hereof.

                  SECTION 8. Indenture and Debt Securities To Be Construed in
Accordance with the Laws of the State of New York. This Indenture and each Debt
Security shall be deemed to be a New York contract, and for all purposes shall
be construed in accordance with the laws of said state.

                  The Trustee hereby accepts the trusts in this Second
Supplemental Indenture declared and provided, upon the terms and conditions
hereinabove set forth.





                  IN WITNESS WHEREOF, OLIN CORPORATION has caused this Second
Supplemental Indenture to be duly signed by its Vice President duly authorized;
and JPMORGAN CHASE BANK has caused this Second Supplemental Indenture to be duly
signed by one of its Vice Presidents or Assistant Vice Presidents thereunto duly
authorized.

                               OLIN CORPORATION,



                               By  /s/ Janet M. Pierpont
                                  --------------------------------
                                  Name:  Janet M. Pierpont
                                  Title:  Vice President and Treasurer

                               JPMORGAN CHASE BANK,



                               By  /s/ Patrick Healy
                                   -------------------------------
                                   Name: Patrick Healy
                                   Title:  Vice President





No.                                                                    EXHIBIT A
$


                                                         [CUSIP No.           ]

                                 [FACE OF NOTE]
                          [INSERT APPROPRIATE LEGENDS]

                                OLIN CORPORATION
                           9.125% Senior Note due 2011

                  OLIN CORPORATION, a corporation duly organized and existing
under the laws of the Commonwealth of Virginia (herein referred to as the
"Company"), for value received, hereby promises to pay to CEDE & CO., or its
registered assigns, at the office or agency of the Company in the Borough of
Manhattan, The City of New York, the principal sum of $_______________
(________________) on December 15, 2011, in such coin or currency of the United
States of America as at the time of payment shall be legal tender for the
payment of public and private debts, and to pay interest, semiannually on June
15 and December 15 of each year (each, an "Interest Payment Date"), commencing
June 15, 2002, at a rate of 9.125% per annum, on said principal sum at said
office or agency, in like coin or currency, from the Interest Payment Date next
preceding the date of this Note to which interest has been paid, unless the date
hereof is a date to which interest has been paid, in which case from the date of
this Note, or unless no interest has been paid on this Note, in which case from
December 11, 2001, until payment of said principal sum has been made or duly
provided for; provided, however, that payment of interest may be made at the
option of the Company by check mailed to the address of the person entitled
thereto as such address shall appear on the Debt Security Register.
Notwithstanding the foregoing, if the Company shall default in the payment of
interest due on any Interest Payment Date, then this Note shall bear interest
from the next preceding Interest Payment Date, to which interest has been paid
or, if no interest has been paid on these Notes, from December 11, 2001. The
interest so payable on any Interest Payment Date, will, subject to certain
exceptions provided in the Indenture referred to on the reverse hereof, be paid
to the person in whose name this Note is registered at the close of business on
the June 1 or December 1 (whether or not a Business Day), as the case may be,
next preceding such Interest Payment Date. Interest will be computed on the
basis of a 360-day year of twelve 30-day months.

                  Reference is made to the further provisions of this Note set
forth on the reverse hereof. Such further provisions shall for all purposes have
the same effect as though fully set forth at this place.

                  This Note shall not be valid or become obligatory for any
purposes until the certificate of authentication hereon shall have been signed
by the Trustee under the Indenture referred to on the reverse hereof.





IN WITNESS WHEREOF, OLIN CORPORATION has caused this instrument to be signed by
facsimile by its duly authorized officers and has caused a facsimile of its
corporate seal to be affixed hereunto or imprinted hereon.

Dated:                             OLIN CORPORATION,

                                       By
                                           ---------------------------------
                                           Name :   Anthony W. Ruggiero
                                           Title:   Executive Vice
                                                      President and Chief
                                                      Financial Officer

                                       By
                                           ---------------------------------
                                           Name:   Janet M. Pierpont
                                           Title:  Vice President and
                                                     Treasurer





                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

This is one of the Debt Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                     JPMORGAN CHASE BANK, as Trustee,

                                       By

                                          ----------------------------------
                                          Authorized Officer





                                [REVERSE OF NOTE]

                                OLIN CORPORATION

                           9.125% Senior Note due 2011

                  This Note is one of a duly authorized issue of debentures,
notes, bonds or other evidences of indebtedness of the Company (the "Debt
Securities") of the series hereinafter specified, all issued or to be issued
under and pursuant to an indenture dated as of June 15, 1992 (the "Original
Indenture"), as amended and supplemented by the First Supplemental Indenture
dated as of March 18, 1994, and as amended and supplemented by the Second
Supplemental Indenture dated as of December 11, 2001 (the Original Indenture, as
amended by the First Supplemental Indenture and the Second Supplemental
Indenture is herein called the "Indenture"), duly executed and delivered by the
Company to JPMorgan Chase Bank (f/k/a Chemical Bank), as trustee (the
"Trustee"), to which Indenture and all indentures supplemental thereto reference
is hereby made for a description of the rights, limitations of rights,
obligations, duties and immunities thereunder of the Trustee, the Company and
the holders of the Debt Securities. Capitalized terms used herein and not
defined herein have the meanings ascribed thereto in the Indenture. The Debt
Securities may be issued in one or more series, which different series may be
issued in various aggregate principal amounts, may mature at different times,
may bear interest (if any) at different rates, may be subject to different
redemption provisions (if any), may be subject to different sinking, purchase or
analogous funds (if any), may be subject to different covenants and Events of
Default and may otherwise vary as in the Indenture provided. This Note is one of
a series of Debt Securities designated as the 9.125% Senior Notes due 2011 of
the Company (the "Notes"), initially in an aggregate principal amount of
$200,000,000 on the Issue Date. Terms used herein which are defined in the
Indenture shall have the respective meanings assigned thereto in the Indenture.

                  In case an Event of Default with respect to the Notes shall
have occurred and be continuing, the principal hereof may be declared, and upon
such declaration shall become, due and payable, in the manner, with the effect
and subject to the conditions provided in the Indenture.

                  The Indenture contains provisions permitting the Company and
the Trustee, with the consent of the Holders of not less than 66-2/3% in
aggregate principal amount of the Debt Securities at the time Outstanding of all
series to be affected (voting as one class), evidenced as in the Indenture
provided, to execute supplemental indentures adding any provisions to or
changing in any manner or eliminating any of the provisions of the Indenture or
of any supplemental indenture or modifying in any manner the rights of the
Holders of the Debt Securities of each such series; provided, however, that no
such supplemental indenture shall (i) extend the fixed maturity of any Debt
Securities, or reduce the principal amount thereof or any premium thereon or the
amount of any Sinking Fund Payment, or reduce the rate or extend the time of
payment of interest thereon, or reduce any premium payable upon redemption
thereof, without the consent of the Holder of each Debt Security so affected, or
(ii) reduce the aforesaid percentage of Debt Securities the consent of the
Holders of which is required for any such supplemental indenture, without the
consent of the Holders of each Debt Security so affected. It is also provided in
the Indenture that, with respect to certain defaults or Events of Default
regarding the Debt Securities of any series, prior to any declaration
accelerating the maturity of such Debt Securities, the Holders of a majority in
aggregate principal amount Outstanding of the Debt Securities of such series
(or, in the case of certain defaults or Events of Default, all the Debt
Securities) may on behalf of the Holders of all the Debt Securities of such
series (or all of the Debt Securities, as the case may be) waive any such past
default or Event of Default and its consequences. The preceding sentence shall
not, however, apply to a default in the payment of the principal of, premium, if
any, or interest, if any, on any of the Debt Securities. Any such consent or
waiver by the Holder of this Note (unless revoked as provided in the Indenture)
shall be conclusive and binding upon such Holder and upon all future Holders and
owners of this Note and any Notes which may be issued in exchange or
substitution herefor, irrespective of whether or not any notation thereof is
made upon this Note or such other Notes.

                  No reference herein to the Indenture and no provision of this
Note or of the Indenture shall alter or impair the obligation of the Company,
which is absolute and unconditional, to pay the principal of and any premium





and interest on this Note at the place, at the respective times, at the rate and
in the coin or currency herein prescribed.

                  The Notes are issuable in registered form without coupons in
denominations of $1,000 and any integral multiple of $1,000. At the office or
agency of the Company in the Borough of Manhattan, The City of New York, and in
the manner and subject to the limitations provided in the Indenture, but without
the payment of any service charge, Notes may be exchanged for a like aggregate
principal amount of Notes of other authorized denominations.

                  The Notes will be redeemable as a whole at any time or in part
from time to time, at the option of the Company, on at least 30 but not more
than 60 days prior notice (a "Redemption Date"), at a redemption price equal to
the greater of (i) 100% of the principal amount of this Note and (ii) the
present value of the Remaining Scheduled Payments on the Notes being redeemed on
the Redemption Date, discounted to the Redemption Date on a semiannual basis
(assuming a 360-day year consisting of twelve 30-day months) at the Treasury
Rate (as defined herein) plus 50 basis points, plus, in each case, accrued
interest on this Note to the Redemption Date (the "Redemption Price").

                  "Comparable Treasury Issue" means the United States Treasury
security selected by an Independent Investment Banker as having a maturity
comparable to the remaining term of this Note to be redeemed that would be
utilized, at the time of selection and in accordance with customary financial
practice, in pricing new issues of corporate debt securities of comparable
maturity to the remaining term of this Note. "Independent Investment Banker"
means Banc of America Securities LLC and/or Salomon Smith Barney Inc.

                  "Comparable Treasury Price" means, with respect to any
Redemption Date, (i) the average of Reference Treasury Dealer Quotations for
such Redemption Date, after excluding the highest and lowest such Reference
Treasury Dealer Quotations, or (ii) if the Trustee obtains fewer than three such
Reference Treasury Dealer Quotations, the average of all such quotations.

                  "Reference Treasury Dealer" means Banc of America Securities
LLC and Salomon Smith Barney Inc. and, at the Company's option, other primary
U.S. Government Securities dealers in New York City selected by the Company.

                  "Reference Treasury Dealer Quotations" means, with respect to
each Reference Treasury Dealer and any Redemption Date, the average, as
determined by the Trustee, of the bid and asked prices for the Comparable
Treasury Issue (expressed in each case as a percentage of its principal amount)
quoted in writing to the Trustee by such Reference Treasury Dealer at 5:00 p.m.,
New York City time, on the third Business Day preceding such Redemption Date.

                  "Remaining Scheduled Payments" means, with respect to this
Note, the remaining scheduled payments of the principal and interest thereon
that would be due after the related Redemption Date but for such redemption;
provided, however, that, if such Redemption Date is not an Interest Payment Date
with respect to this Note, the amount of the next succeeding scheduled interest
payment thereon will be reduced by the amount of interest accrued thereon to
such Redemption Date.

                  "Treasury Rate" means, with respect to any Redemption Date,
the rate per year equal to the semi-annual equivalent yield to maturity of the
Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue
(expresses as a percentage of its principal amount) equal to the Comparable
Treasury Price for such Redemption Date.

                  Unless the Company defaults in payment of the Redemption
Price, on and after the Redemption Date interest will cease to accrue on the
Notes or portions thereof called for redemption and those Notes will cease to be
outstanding.

                  Upon due presentment for registration of transfer of this Note
at the office or agency of the Company in the Borough of Manhattan, The City of
New York, a new Note or Notes of authorized denominations for an equal aggregate
principal amount will be issued to the transferee in exchange therefor, subject
to the





limitations provided in the Indenture, without charge except for any tax or
other governmental charge imposed in connection therewith.

                  The Company, the Trustee, any paying agent and any Debt
Security registrar may deem and treat the registered Holder hereof as the
absolute owner of this Note (whether or not this Note shall be overdue and
notwithstanding any notation of ownership or other writing hereon), for the
purpose of receiving payment hereof, or on account hereof, and for all other
purposes, and neither the Company nor the Trustee nor any paying agent nor any
Debt Security registrar shall be affected by any notice to the contrary. All
payments made to or upon the order of such registered Holder shall, to the
extent of the sum of sums paid, effectually satisfy and discharge liability for
moneys payable on this Note.

                  No recourse for the payment of the principal of, or premium,
if any, or interest on this Note, or for any claim based hereon or otherwise in
respect thereof, and no recourse under or upon any obligation, covenant or
agreement of the Company in the Indenture or any indenture supplemental thereto
or in any Note, or because of the creation of any indebtedness represented
thereby, shall be had against any incorporator, stockholder, officer or
director, as such, past, present or future, of the Company or of any successor
corporation, either directly or through the Company or any successor
corporation, whether by virtue of any constitution, statute or rule of law or by
the enforcement of any assessment or penalty or otherwise, all such liability
being, by the acceptance hereof and as part of the consideration for the issue
hereof, expressly waived and released.

                  This Debt Security shall be deemed to be a New York contract,
and for all purposes shall be construed in accordance with the laws of said
State.