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                                                                     Exhibit 3.5

                            Certificate of Amendment
                                       of
                          Certificate of Incorporation
                                       of
                                Clark USA, Inc.

                   -----------------------------------------

                   Adopted in accordance with the provisions
                   of Section 242 of the General Corporation
                          Law of the State of Delaware

                   -----------------------------------------


     I, Maura Clark, Executive Vice President of CLARK USA, INC., a corporation
organized and existing under the laws of the State of Delaware (the
"Corporation"), hereby certify as follows:

     FIRST:  That the Restated Certificate of Incorporation of the Corporation
was filed with the Secretary of State of the State of Delaware on the 28th day
of December, 1994 and that Certificates of Amendment thereto were filed with the
Secretary of State of the State of Delaware on the 23rd day of February, 1995,
the 3rd day of November, 1995 and the 1st day of October, 1997 (as so amended,
the "Certificate of Incorporation").

     SECOND:  That Article 4 of the Certificate of Incorporation of the
Corporation has been amended to read in its entirety as follows:

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     ARTICLE 4.  The total number of shares of capital stock which the
Corporation shall have the authority to issue 68,554,552 shares, consisting of
(a) 63,554,552 shares of common stock, par value $.0l per share, of which (i)
45,164,597 shares shall be designated "Common Stock," (ii) 3,389,955 shares
shall be designated "Class D Common Stock" (iii) 9,000,000 shares shall be
designated "Class E Common Stock," and (iv) 6,000,000 shares shall be designated
"Class F Common Stock," and (b) 5,000,000 shares of "Preferred Stock," par value
$.01 per share.

A.  Preferred Stock.

     1.  Issuance.  The Board of Directors is authorized, subject to limitations
prescribed by law, to provide for the issuance of shares of Preferred Stock in
one or more Classes, to establish the number of shares to be included in each
such Class, and to fix the designations, powers, preferences and rights of the
shares of each such Class, and any qualifications, limitations or restrictions
thereof.

B.  Common Stock.

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Common Stock shall be entitled to receive the
same dividends or distributions per share, whether payable in cash, in property
or in shares of capital stock, as may be declared and paid on the Class D Common
Stock, the Class E Common Stock and the Class F Common Stock, and the Board of
Directors may not declare or pay any dividend or distribution with respect to
the Common Stock unless the same dividend or distribution per share has been
declared or paid, as the case may be, with respect to the Class D Common Stock,
the Class E Common Stock and the Class F Common Stock; provided, that with
respect to dividends payable only in shares of common stock, each of the Common
Stock, the Class D Common Stock, the Class E Common Stock and the Class F Common
Stock shall receive an equivalent dividend per share payable in common stock of
the corresponding class.

     2.  Voting Rights.  At every annual or special meeting of stockholders of
the Corporation, every share of Common Stock shall entitle the holder thereof to
one vote, voting together with the holders of Class F Common Stock, in person or
by proxy, for each share of Common Stock standing in his or her name on the
books of the Corporation; provided that the holders of Common Stock shall have
no voting rights with respect to matters reserved (by law or by agreement with
the Corporation) solely for any other class of capital stock.

     3.  Liquidation, Dissolution or Winding Up.  In the event of any voluntary
or involuntary liquidation, dissolution or winding up of the affairs of the
Corporation (a "Liquidation"), after payment or provision for payment of the
debts and other liabilities of the

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Corporation and of the preferential amounts, if any, to which the holders of
Preferred Stock shall be entitled, the holders of all outstanding shares of
Common Stock shall be entitled to share ratably, on a share-for-share basis,
with the holders of Class D Common Stock, the Class E Common Stock and the Class
F Common Stock in the remaining assets of the Corporation.

     C.  Class D Common Stock

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Class D Common Stock shall be entitled to
receive the same dividends or distributions per share, whether payable in cash,
in property or in shares of capital stock, as may be declared and paid on the
Common Stock, the Class E Common Stock and the Class F Common Stock, and the
Board of Directors may not declare or pay any dividend or distribution with
respect to the Class D Common Stock unless the same dividend or distribution per
share has been declared or paid, as the case may be, with respect to the Common
Stock, the Class E Common Stock and the Class F Common Stock; provided, that
with respect to dividends payable only in shares of common stock, each of the
Common Stock, the Class D Common Stock, the Class E Common Stock and the Class F
Common Stock shall receive an equivalent dividend per share payable in common
stock of the corresponding class.

     2.  Voting Rights.  Holders of shares of Class D Common Stock shall not be
accorded any voting rights in respect thereof and such shares shall not be
deemed to be outstanding for purposes of determining the vote required on any
matter properly brought before the stockholders of the Corporation for a vote
thereon.

     3.  Conversion.  (a)  The Company shall have the right, at any time and
from time to time, to convert any or all of the shares of Class D Common Stock
into an equal number of shares of Common Stock.  The method of selection of such
shares shall be determined by the Board of Directors of the Company in its sole
discretion.

          (b) Following an initial public offering of Common Stock, any person
who is not an affiliate of Occidental Petroleum Corporation to whom shares of
Class D Common Stock have been directly or indirectly transferred by Occidental
Petroleum Corporation in an arm's-length transaction shall have the right, at
any time and from time to time, to convert any or all of such shares of Class D
Common Stock into an equal number of shares of Common Stock.

          (c) Following an initial public offering of Common Stock, any person
who is not an affiliate of Gulf Resources Corporation to whom shares of Class D
Common Stock have been directly or indirectly transferred by Gulf Resources
Corporation in an arm's-length transaction shall have the right, at any time and
from time to time, to convert any or all of such shares of Class D Common Stock
into an equal number of shares of Common Stock.

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     4.  Liquidation, Dissolution or Winding Up.  In the event of any voluntary
or involuntary liquidation, dissolution or winding up of the affairs of the
Corporation (a "Liquidation"), after payment or provision for payment of the
debts and other liabilities of the Corporation and of the preferential amounts,
if any, to which the holders of Preferred Stock shall be entitled, the holders
of all outstanding shares of Class D Common Stock shall be entitled to share
ratably on a share-for-share basis, with the holders of Common Stock, Class E
Common Stock and Class F Common Stock in the remaining assets of the
Corporation.

     5.  Anti-Dilution.  In the event the Company shall at any time (a) declare
a dividend on any shares of capital stock of the Company or any securities
issued in respect thereof, or in substitution therefor, in connection with any
stock split, dividend or combination, or any recapitalization, merger,
consolidation, exchange or other similar reorganization (a "Recapitalization"),
such dividend being payable in shares of capital stock of the Company, (b)
subdivide the outstanding capital stock of the Company, (c) combine the
outstanding capital stock of the Company into a smaller number of shares, or (d)
issue any shares of capital stock in a Recapitalization, the number of shares of
Class D Common Stock then outstanding shall be proportionately adjusted so that
the relative equity percentage ownership of the Company and the relative voting
power represented by each such share shall be preserved as nearly as
practicable.

D.  Class E Common Stock.

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Class E Common Stock shall be entitled to
receive the same dividends or distributions per share, whether payable in cash,
in property or in shares of capital stock, as may be declared and paid on the
Common Stock, Class D Common Stock and the Class F Common Stock, and the Board
of Directors may not declare or pay any dividend or distribution with respect to
the Class E Common Stock unless the same dividend or distribution per share has
been declared or paid, as the case may be, with respect to the Common Stock, the
Class D Common Stock and the Class F Common Stock; provided, that with respect
to dividends payable only in shares of common stock, each of the Common Stock,
the Class D Common Stock, the Class E Common Stock and the Class F Common Stock
shall receive an equivalent dividend per share payable in common stock of the
corresponding class.

     2.  Voting Rights.  Holders of shares of Class E Common Stock shall not be
accorded any voting rights in respect thereof and such shares shall not be
deemed to be outstanding for purposes of determining the vote required on any
matter properly brought before the stockholders of the Corporation for a vote
thereon.

     3.  Conversion.  Subject to compliance with any applicable laws related to
the acquisition of voting securities of the Corporation, the holder of any
shares of Class E Common

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Stock shall have the right, at any time and from time to time, to convert any or
all of such holder's shares of Class E Common Stock into an equal number of
shares of Common Stock; provided, that if as the result of any proposed
conversion by any holder of Class E Common Stock the total voting power of the
"ultimate parent entity" of such holder, as defined in the Hart-Scott-Rodino
Antitrust Improvements Act, as amended (the "HSR Act") would exceed any "filing
threshold", as defined in the HSR Act, then such proposed conversion shall not
be effective until all required filings under the HSR Act have been made and all
applicable waiting periods thereunder have expired or been terminated.

     4.  Anti-Dilution.  In the event the Corporation shall at any time (a)
declare a dividend on any shares of capital stock of the Corporation or any
securities issued in respect thereof, or in substitution therefor, such dividend
being payable in shares of capital stock of the Corporation, (b) subdivide the
outstanding capital stock of the Corporation, or (c) combine the outstanding
capital stock of the Corporation into a smaller number of shares, the provisions
relating to the conversion of shares of Class E Common Stock into Common Stock
shall be equitably and proportionately adjusted.

     5.  Liquidation, Dissolution or Winding Up.  In the event of any
Liquidation, after payment or provision for payment of the debts and other
liabilities of the Corporation and of the preferential amounts, if any, to which
the holders of Preferred Stock shall be entitled, the holders of all outstanding
shares of Class E Common Stock shall be entitled to share ratably, on a share-
for-share basis, with the holders of Common Stock, Class D Common Stock and
Class F Common Stock in the remaining assets of the Corporation.

D.  Class F Common Stock.

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Class F Common Stock shall be entitled to
receive the same dividends or distributions per share, whether payable in cash,
in property or in shares of capital stock, as may be declared and paid on the
Common Stock, the Class D Common Stock and the Class E Common Stock, and the
Board of Directors may not declare or pay any dividend or distribution with
respect to the Class F Common Stock unless the same dividend or distribution per
share has been declared or paid, as the case may be, with respect to the Common
Stock, the Class D Common Stock and the Class E Common Stock; provided, that
with respect to dividends payable only in shares of common stock, each of the
Common Stock, the Class D Common Stock, the Class E Common Stock and the Class F
Common Stock shall receive an equivalent dividend per share payable in common
stock of the corresponding class.

     2.  Voting Rights.  At every annual or special meeting of stockholders of
the Corporation, every share of Class F Common Stock shall entitle the holder
thereof to one vote

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(subject to adjustment as provided below), voting together with the holders of
Common Stock, on all matters submitted to a vote of the holders of Common Stock
or Class F Common Stock, in person or by proxy, in the same manner and with the
same effect as the holders of Common Stock; provided that the holders of Class F
Common Stock shall have no voting rights with respect to matters reserved (by
law or by agreement with the Corporation) solely for any other class of capital
stock; and provided further, that if the holders of the Class F Common Stock
would otherwise be entitled to cast votes representing, in the aggregate, more
than 19.9% of the total voting power of all classes of capital stock of the
Corporation entitled to vote, then the vote allotted to each share of Class F
Common Stock shall be proportionately reduced so that all outstanding shares of
Class F Common Stock shall be entitled to cast votes representing, in the
aggregate, 19.9% of the total voting power of all classes of capital stock of
the Corporation entitled to vote.

     3.  Conversion.  Any shares of Class F Common Stock that are owned
beneficially or of record by Occidental Petroleum Corporation and its affiliates
shall have no conversion rights.  Any holder of any shares of Class F Common
Stock other than Occidental Petroleum Corporation and its affiliates shall have
the right, at any time and from time to time, to convert any or all such other
holder's shares of Class F Common Stock into an equal number of shares of Common
Stock.

     4.  Antidilution.  In the event the Corporation shall at any time (a)
declare a dividend on any shares of capital stock of the Corporation or any
securities issued in respect thereof, or in substitution therefor, such dividend
being payable in shares of capital stock of the Corporation, (b) subdivide the
outstanding capital stock of the Corporation, or (c) combine the outstanding
capital stock of the Corporation into a smaller number of shares, the provisions
relating to the conversion of shares of Class F Common Stock into Common Stock
shall be equitably and proportionately adjusted.

     5.  Liquidation, Dissolution or Winding Up.  In the event of any
Liquidation, after payment or provision for payment of the debts and other
liabilities of the Corporation and of the preferential amounts, if any, to which
the holders of Preferred Stock shall be entitled, the holders of all outstanding
shares of Class F Common Stock shall be entitled to share ratably, on a share-
for-share basis, with the holders of Common Stock, Class D Common Stock and
Class E Common Stock in the remaining assets of the Corporation.

E.  Amendment of this Article.  The Corporation may not amend, alter, change or
repeal in any manner adverse to the holders of the Class D Common Stock, Class E
Common Stock or Class F Common Stock the rights or preferences of the holders of
the Class D Common Stock, Class E Common Stock or Class F Common Stock contained
in this Article 4 without the

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consent of the holders of 95% of the Class D Common Stock, Class E Common Stock
or the Class F Common Stock, as the case may be.

     THIRD:  That such amendment has been duly adopted in accordance with the
provisions of the General Corporation Law of the State of Delaware by the
written consent of the holders of a majority of all outstanding shares of each
class entitled to vote thereon in accordance with the provisions of Section 228
of the General Corporation Law.

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     IN WITNESS WHEREOF, the undersigned has signed this Certificate this 1st
day of October, 1997.

                                    CLARK USA, INC.

                                    By:     /s/  Maura J. Clark
                                       ------------------------
                                    Name:  Maura J. Clark
                                    Title: Executive Vice President &
                                           Chief Financial Officer



Attested By:


/s/  Katherine D. Knocke
--------------------------
Name:  Katherine D. Knocke
Title: Secretary

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