Document:

<PAGE>   1

                                                                   EXHIBIT 10.55

                                 SBL CORPORATION

                                  P.O. BOX 705

                             OKLAHOMA CITY, OK 73101

April 1, 2001

Mr. Jim Jones
LSB Industries, Inc.
P.O. Box 754
Oklahoma City, OK  73101

RE:    SBL Corporation Demand Note for $1,750,000 ("SBL Note")

This letter confirms the commitment of SBL Corporation to Prime Financial
Corporation. LSB Industries, Inc. and affiliates ("LSB") to forbear from
demanding payment of principal in excess of $300,000 under SBL Note until April
1, 2001, unless LSB receives cash proceeds in connection with either a) the sale
or other disposition of KAC Acquisition Corp. and/or Kestrel Aircraft, and/or b)
some other source that is not in LSB's projections for the year 2001.

I have also made this commitment to Ernst & Young in connection with Ernst &
Young's audit of LSB Industries, Inc. and ClimaChem, Inc. and the issuance of
the opinion of auditors to be issued in connection with the filing of LSB
Industries, Inc. and ClimaChem, Inc.'s Form 10-K for the year 2000.

Sincerely yours,

Jack E. Golsen
President<PAGE>   1
                                                                   EXHIBIT 10.56

VIA FACSIMILE: (303) 268-5251

December 22, 2000

Mr. David Taylor, President
ORICA USA Inc.
9781 South Meridian Boulevard
Englewood, Colorado 80112

         RE:      Letter of Intent

Dear David:

         This Letter of Intent is to confirm that ORICA USA Inc. ("ORICA")
intends to purchase certain assets of El Dorado Chemical Company ("EDC"), and
EDC intends to sell to ORICA certain fixed assets used to service customers of
EDC who purchase low density ammonium nitrate from EDC. The total purchase price
for the fixed assets is to be approximately $3.9 million. Inventory values are
to be negotiated. Such purchase is subject to definitive agreements to be signed
by the parties, which shall include, among other items, agreements for ORICA to
continue to service certain of EDC's customers with low density ammonium
nitrate, and EDC to supply to ORICA ammonium nitrate, and various regulatory and
corporate approvals.

         The parties intend to finalize a definitive agreement on or before
December 29, 2000.

                                                  By:
                                                     ---------------------------
                                                      El Dorado Chemical
Company
AGREED to:

------------------------------------
ORICA USA Inc.

<PAGE>   2

December 22, 2000

Jim Wewers, President
El Dorado Chemical Company
Box 1373
Oklahoma City, OK  73101

Dear Jim:

With respect to the Letter of Intent entered into by El Dorado Chemical Company
and Orica USA Inc. dated December 22, this will confirm our agreement that the
Letter of Intent;

         a) is non-binding, and;

         b) is subject to the approval of the Boards of Directors of both
companies, and;

         c) is subject to the parties developing and implementing a satisfactory
plan to transaction service to certain of EDC's customers, and;

         d) contemplates an effective date of December 29, 2000, which may be
different from the actual date of closing, and;

         e) and its terms and conditions are confidential and no public release
will be made of either the letter of intent or this transaction without the
consent of both parties.

Please signify your agreement by signing and returning one copy of this letter.

Yours truly,

ORICS USA Inc.

-----------------------------
David P. Taylor

Agreed to:
El Dorado Chemical Company

-------------------------------
James L. Wewers<PAGE>   1
                                                                   EXHIBIT 10.57

                            REAL ESTATE SALE CONTRACT

         THIS REAL ESTATE SALE CONTRACT (the "Agreement") is made and entered
into as of April 2, 2001 (the "Effective Date"), by and between Crystal City
Nitrogen Company, an Oklahoma corporation ("Seller"), and RIVER CEMENT COMPANY,
a Delaware corporation ("Purchaser").

                                    RECITALS:

         Seller represents that it is the owner in fee simple of certain land
and improvements in Jefferson County, Missouri shown generally on the Map
attached hereto and made a part hereof as Exhibit A, consisting of approximately
933 acres.

         Purchaser desires to buy and Seller desires to sell the property and
improvements.

         NOW, THEREFORE, in consideration of the Recitals (which are part of
this Agreement) and the terms, conditions and covenants contained herein, the
parties agree as follows:

                                   AGREEMENT:

         1. Agreement to Sell and Purchase. Seller agrees to sell to Purchaser
and Purchaser agrees to purchase form Seller the land shown on Exhibit A hereto
and improvements located thereon (the "Property") in accordance with and subject
to the terms and conditions hereof.

         2. Purchase Price. (a) The purchase price for the Property ("Purchase
Price") is Four Million Five Hundred Thousand Dollars ($4,500,000). The Purchase
Price is subject to credit and adjustment as hereinafter provided. The Purchase
Price shall be paid to Seller at Closing by wire transfer in immediately
available funds.

         (b) General real estate taxes and any special assessments on the
Property for all years prior to the year in which the sale and purchase is
closed shall be paid by Seller. General real estate taxes on the Property for
the year of closing based on the latest available assessment and the latest
available tax rate shall be prorated and adjusted as of the Closing Date on the
basis of thirty (30) days to the month, Seller to have the last day.

         (c) Seller shall pay all charges for fuel, electricity, water, sewer,
telephone and other utility charges used on or related to the Property up to the
Closing Date, without adjustment, and Purchaser shall pay all such charges
thereafter.

         (d) Within two (2) business days after the Effective Date, Purchaser
shall deposit Five Thousand Dollars ($5,000) with Hillsboro Title Company,
Highway 21 and Third Street, Hillsboro, Missouri 63050 ("Title Company"). Said
deposit, with accrued

<PAGE>   2

interest, is the "Earnest Deposit". Title Company shall deposit the Earnest
Deposit in an interest-bearing account and apply the Earnest Deposit in
accordance with this Agreement. The Earnest Deposit shall be credited to the
Purchase Price at Closing. If the sale of the Property is not closed by the date
fixed for Closing owing to breach of this Agreement by Purchaser, the Earnest
Deposit shall be forfeited by Purchaser as liquidated damages, and Seller shall
not be entitled to any other remedy at law or in equity. If the sale of the
Property is not closed by the date fixed for Closing for any other reason,
(including, without limitation, failure to meet the requirements of Section 4 or
the conditions of Section 5 hereof), the Earnest Deposit shall be returned to
Purchaser.

         3. Title and Survey. (a) The Property shall be sold and conveyed to
Purchaser free and clear of any and all liens, leases and encumbrances of any
kind and nature except the following ("Permitted Exceptions"): (i) current real
estate taxes not delinquent; and (ii) such easements and restrictions of record
an may be approved by Purchaser. The Permitted Exceptions shall not include (a)
rights or claims of parties in possession not shown by the public records; (b)
easements, or claims of easements, not shown by the public records; (c)
encroachments, overlaps, boundary line disputes or other mattes which would be
disclosed by an accurate survey or inspection of the Property; and (d) any lien,
or right to a lien, for services, labor, or material heretofore or hereafter
furnished, imposed by law and not shown by the public records.

         (b) As evidence of title, Purchaser shall at its expense promptly order
a commitment from Title Company for an ALTA Form B owner's policy of title
insurance ("Title Commitment") in which Title Company agrees to insure
Purchaser's good and marketable fee simple title in the Property in the full
amount of the Purchase Price for normal premiums, subject only to the Permitted
Exceptions and such easements and restrictions as may be approved by Purchaser.

         (c) Seller has provided Purchaser a copy of a survey prepared by the
Jefferson County Surveying Company ("Surveyor"). Purchaser shall engage the
Surveyor to provide a current and accurate property boundary and improvements
survey, prepared, sealed and certified by surveyor ("Survey"), locating the
out-boundaries of the land shown on Exhibit A, all improvements thereon, and all
matters constituting appurtenances or exceptions to title shown on the Title
Commitment and showing that said land constitutes not less than 933 acres. The
cost of the Survey shall be borne by Purchaser except in the case of a breach
hereof by Seller. The Survey, when accepted by Purchaser, shall conclusively
establish the legal description of the Property subject to this Agreement.

         (d) Within ten (10) days after Purchaser's actual receipt and
acceptance of both the Title Commitment and the Survey, Purchaser shall provide
to Seller a copy of the Title Commitment and the Survey and shall notify Seller
of any objections it has with respect to Seller's title to the Property
("Objections"). In the event (i) Seller shall fail to cure the Objections, if
any, on or prior to the Closing or (ii) further defects, liens, encumbrances,
adverse claims, restrictions, rights-of-way, easements or other matters relating
to Seller's title to the Property arise or are discovered after the effective
date of

<PAGE>   3

the Title Commitment and are not removed by Seller or approved by Purchaser on
or before the date of Closing, Purchaser shall have the right to cancel this
Agreement by giving written notice to Seller. In such event, the Earnest Deposit
shall be returned to Purchaser and this Agreement shall be null and void and of
no further force and effect.

         4. Closing and Conveyance of Title. (a) Subject to the terms of this
Agreement, the closing of the purchase of the Property shall take place ten (10)
days after the satisfaction or waiver of satisfaction of the conditions
contained in Sections 3 and 5, or sooner upon five (5) days prior written notice
by Purchaser to Seller of any accelerated closing date (the "closing" or
"Closing Date"). The Closing shall take place at 10 a.m. at the offices of the
Title Company or at such other time or place as the parties may agree upon in
writing.

         (b) At the Closing, Seller shall deliver the following to Purchaser:

                  (1) A recordable general warranty deed in form satisfactory to
Purchaser conveying to Purchase marketable and insurable fee simple title to the
Property, free and clear of all liens and encumbrances, subject only to the
Permitted Exceptions and such easements and restrictions an may be approved by
Purchaser.

                  (2) Possession of the Property, free of all leases, tenancies,
licensees and occupants, and any keys in Seller's possession to any part of the
Property, except for the nitric acid plant located on the Property, which is
subject to an option to purchase by Orica USA Inc. ("Orica").

                  (3) Such indicia of Seller's authority and related customary
documents and instruments an may be required by the Title Company or an may be
reasonable requested by Purchaser.

                  (4) Pursuant to the Real Property Tax Act of 1980, as amended,
an affidavit that Seller is not a foreign corporation under IRC Section 1445 and
stating Seller's United States taxpayer identification number.

                  (5) Affidavits as to rights of parties in possession and
mechanics' liens and claims as may be required by the Title Company in order to
issue to Purchaser the owner's policy of title insurance as specified in Section
6 (a).

                  (6) Closing Statement.

                  (7) Any such other documents and instruments as are necessary
to consummate the transaction contemplated by this Agreement.

                  (8) A copy of the agreement with Orica and the notice of
exercise of the option certified by Seller to be a true, correct and complete
copy.

         (c) At the Closing, Purchaser shall deliver the following to Seller:

<PAGE>   4

                  (1) The Purchaser Price as credited and adjusted in accordance
with this Agreement.

                  (2) Such indicia of Purchaser's authority and related
customary documents and instruments as may be required by the Title Company or
as may be reasonably requested by Seller.

                  (3) Any such other documents and instruments as are necessary
to consummate the transaction contemplated by this Agreement.

         5. Conditions. In addition to all other conditions to Purchase's
obligations hereunder, Purchaser's obligation to consummate the purchase
described in this Agreement shall be conditioned upon the occurrence or
fulfillment of each of the following conditions or events:

         (a) The receipt by Purchaser at Closing of an owner's policy (or
updated commitment therefore) of title insurance from Title Company insuring
good and marketable fee simple title to and ownership of the Property in
Purchaser in the amount of the Purchase Price on ALTA Form B with exceptions on
Schedule B thereof only for the Permitted Exceptions and such easements and
restrictions an may be approved by Purchaser.

         (b) The delivery to Purchaser at or prior to Closing of each of the
documents or instruments called for by this Agreement.

         (c) Within sixty-five (65) days after the Effective Date, Purchaser and
Purchaser's representative shall have made such inspections of the Property and
shall have conducted or obtained such examinations, tests, building inspections,
environmental assessments and other studies and reports of the Property as
Purchaser shall deem desirable, and the results of any such inspections,
examinations, tests, inspections, assessments, studies and reports shall be
satisfactory to Purchaser in Purchaser's sole discretion. Such examinations
include, but are not limited to (i) a Phase I Environmental Assessment under
ASTM Practice E 1527-00 and a Phase II Subsurface Environmental Investigation
and (ii) the drilling of test holes in such number and of such diameter and
depth as Purchaser may determine, at various points on the Property, to
determine the presence and estimated quantity of limestone underlying the
surface of the Property. Seller hereby grants permission to Purchaser and its
representatives to enter the Property for such purposes, and to make such
temporary roadways and to utilize such equipment as Purchaser may deem
necessary. Purchaser shall give Seller reasonable advance notice of such entry.
Purchaser shall have no obligation to repair any damage to the Property arising
out of any such entry or to reimburse Seller for any such damage.

         (d) Within sixty-five (65) days after the Effective Date, Purchaser
shall have received and accepted the Survey and Title Commitment.

<PAGE>   5

         (e) Within sixty-five (65) days after the Effective Date, Purchaser
shall have obtained all permits and approvals from all applicable governmental
or quasi-governmental entities necessary in Purchaser's opinion for the use and
occupancy of the Property for Purchaser's intended use.

         (f) Within sixty-five (65) days after the Effective Date, Purchaser
shall be satisfied with the zoning of the Property for Purchaser's use. If
requested by Purchaser, Seller shall cooperate with Purchaser in rezoning all or
part of the Property prior to Closing.

If any of the foregoing conditions are not fulfilled within the applicable time
period, and are not waived in writing by Purchaser, the Earnest Deposit shall be
returned to Purchaser and this Agreement shall be null and void and of no
further force or effect.

         6. Seller's Representations, Warranties and Covenants. Seller
represents, warrants and covenants to Purchaser as follows, which
representations and warranties shall inure to the benefit of Purchaser, its
successors and assigns and shall be considered made as of the date hereof and as
of the Closing Date:

         (a) Seller is the owner in fee simple of the Property. Seller is a
corporation duly organized and validly existing under the laws of the State of
Oklahoma and is qualified to do business in the State of Missouri, and has the
authority and capacity to enter into and perform this Agreement. Seller is not
bankrupt or insolvent.

         (b) Seller has not received notice, written or otherwise, from any
governmental agency, and is not aware of any pending governmental agency
notification, of any violations or alleged violations of law which affect the
Property and have not been cured; and Seller has not received any written notice
of any actions, proceedings or investigations which would affect the Property;
and Seller has not received notice of and is not aware of any pending or
threatened eminent domain action which would affect the Property.

         (c) There are, and as of Closing there shall be, no tenancies or
occupancies affecting the Property, and no service, supply, maintenance or
management contracts or agreements affecting the Property that have not been
disclosed to Purchaser in writing and cannot be cancelled by Purchaser
immediately without penalty.

         (d) There are, and as of Closing there shall be, no recorded or
unrecorded contracts and/or options to which Seller is a party pertaining to or
affecting title to or the sale of the Property, or any part thereof, other than
the right of Orica to remove certain nitric acid facilities, which removal shall
occur on or before October 31, 2002.

         (e) To the knowledge of Seller, the current uses of the Property
materially comply with all applicable laws, ordinances and regulations.

<PAGE>   6

         (f) To the knowledge of Seller, there are and have been no hazardous
waste or hazardous substances as defined under all applicable federal, state and
local environmental laws, including , but not limited to, hazardous waste as
defined in the Resource Conservation and Recovery Act of 1976, as amended, and
hazardous substances as defined in the Comprehensive Environmental Response,
Compensation and Liability Act, as amended, and all regulations thereunder and
there are no petroleum products, stored, released or disposed of on or from the
Property in violation of law or which would constitute an environmental of
safety hazard. To the knowledge of Seller, there are no underground storage
tanks on the Property.

         (g) To the knowledge of Seller, there is unrestricted roadway access
providing adequate ingress to and egress from the Property.

         (h) Seller has not entered into any agreement to cut or otherwise
remove timber from the Property. Prior to Closing, Seller shall not cut or
remove timber from the Property.

Seller shall indemnify and hold Purchase harmless from and against any claims,
liabilities, costs, demands, actions, injury, loss or damage (including
attorney's, expert witnesses' and consultants' fees and expenses) sustained by
reason of the breach of any of the representations and warranties herein
contained, including, without limiting, all environmental clean-up costs
therewith, or their being inaccurate as of the date hereof or as of the Closing
Date. Seller's warranties and representations, its obligation to indemnify
Purchaser, and Seller's liability for breach of any of its representations and
warranties hereunder shall survive closing for one (1) year and shall not be
merged into any deed or other document given at Closing.

         7. Casualty; Eminent Domain. (a) In the event of the damage or
destruction of all or any of the Property prior to Closing, Purchaser, at its
option, may either (i) terminate this Agreement by notice to Seller, whereupon
the earnest Deposit shall be returned to Purchaser and neither party shall have
any further obligations hereunder, or (ii) enforce this Agreement whereupon
Seller shall assign to Purchaser any insurance proceeds payable as a result of
such damage or destruction as such may relate to loss of any of the Property.

         (b) In the event that prior to Closing, any portion of the Property be
taken by eminent domain, or the subject of eminent domain proceedings threatened
or commenced, Seller shall promptly notify Purchaser thereof, and immediately
provide Purchaser with copies of any written communication from any condemning
authority. If any of said events shall occur then, in that event, Purchaser
shall have the option to terminate this Agreement by notice to Seller, whereupon
the Earnest Deposit shall be returned to Purchaser and neither party shall have
any further obligations hereunder. If any of said events shall be conveyed to
Purchaser at Closing; (ii) if the transfer to the condemning authority has not
taken place prior to Closing, the entire Property shall be conveyed to Purchaser
at Closing hereunder; (iii) if Seller has received payment for such condemnation
or taking prior to the Closing hereunder, the amount of such payment shall

<PAGE>   7

be a credit against the Purchase Price payable by Purchaser hereunder; and (iv)
if Seller has not received such payment at the time of closing, Seller shall
assign to Purchaser all claims and rights to or arising out of such taking,
including the right to conduct any litigation in respect of such condemnation.

         8. Brokers. Seller represents and warrants to Purchaser that Seller has
not engaged any agent or broker with respect to this transaction, and no person
is entitled to a broker's commission or fee as a result of the purchase and sale
of the Property. Purchaser represents and warrants to Seller that Purchase has
not engaged any agent or broker with respect to this transaction, and no person
is entitled to a broker's commission or fee as a result of the purchase and sale
of the Property. Each party shall indemnify and hold the other harmless from and
against any loss, cost and expense, including attorney's fees, which the other
shall suffer by reason of the breach of the indemnitor's foregoing
representation and warranty, which shall survive closing.

         9. Assignment of Agreement. Purchaser shall have the absolute right to
assign its rights under this Agreement. Upon Purchaser's assignment of the
Agreement, such assignee shall be deemed substituted for the named Purchaser,
and such assignee shall assume Purchaser's obligations hereunder, provided that
Purchaser shall not be released from its obligations hereunder.

         10. Maintenance of Property. Seller shall maintain the Property in
substantially the same condition existing on the date of this Agreement.

         11. Notice. Any and all notices required or permitted hereunder shall
be in writing and shall be deemed given upon receipt (which may be evidenced by
the return receipt in the event of registered or certified mail delivery) and
shall be delivered by (i) personal delivery; (ii) United States registered or
certified mail, return receipt requested; or (iii) overnight commercial package
courier or local delivery service, in all events prepaid and addressed, in the
case of Seller, to:

                  Tony M. Shelby
                  Vice President
                  Crystal City Nitrogen Company
                  16 South Pennsylvania Avenue
                  Oklahoma City, OK 73107

with a copy to:

                  David M. Shear
                  General Counsel
                  Crystal City Nitrogen Company
                  16 South Pennsylvania Avenue
                  Oklahoma City, OK 73107

<PAGE>   8

and addressed, in the case of Purchaser, to:

                  Bruce Keim
                  Vice President
                  River Cement Company
                  P.O. Box 1003
                  Festus, MO 63028-1003

with a copy to:

                  Kathleen T. Mueller, Esq.
                  Blackwell Sanders Peper Martin LLP
                  720 Olive Street, Suite 2400
                  St. Louis, MO 63101-2396

Each party hereto shall have the right to change its foregoing address for
notices by written notice to the other party to such effect.

         12. Miscellaneous Provisions.

         (a) Time is of the essence with respect to each and every provision of
this Agreement.

         (b) The captions in the various sections of this Agreement are inserted
only as a matter of convenience and for reference, and in no way define, limit
or describe the scope of this Agreement nor the intent of any provision hereof.

         (c) If any date for the occurrence of an event or act under this
Agreement falls on a Saturday or Sunday or legal holiday in the State of
Missouri, then the time for the occurrence of such event or act shall be
extended to the next succeeding business day.

         (d) This Agreement, together with its Exhibits, constitutes the entire
Agreement between the parties pertaining to the subject matter contained in this
Agreement. This Agreement may be amended only by a writing signed by both
Purchaser and Seller.

         (e) All of the terms and provisions of this Agreement shall be binding
upon and inure to the benefit of the parties hereto and their respective heirs,
personal representative, administrators, legal representatives, successors and
assigns.

         13. Nitric Acid Plant. Seller agrees that either Orica or Seller will
remove the nitric acid facilities from the Property by October 31, 2002. Seller
hereby agrees to indemnify, hold harmless and defend Purchaser from and against
any claims, liabilities, costs, demands, actions, injury, loss or damage
(including attorneys', expert witnesses' and consultants' fees and expenses)
arising out of the activities of Seller, Orica, and their respective employees,
agents, and contractors or arising out of the removal of the nitric acid

<PAGE>   9

facilities from the Property. Seller's obligations under this Section shall
survive Closing and shall not be merged into any deed or other document given at
Closing.

         IN WITNESS WHEREOF, Purchaser and Seller have executed this Agreement
as of the Effective Date.

                                          SELLER:

                                          CRYSTAL CITY NITROGEN COMPANY

                                          By:
                                             ----------------------------------
                                          Name:
                                               --------------------------------
                                          Title:
                                                -------------------------------

                                          Date:
                                               --------------------------------

<PAGE>   10

                                        PURCHASER:

                                        RIVER CEMENT COMPANY

                                          By:
                                             ----------------------------------
                                          Name:
                                               --------------------------------
                                          Title:
                                                -------------------------------

                                          Date:
                                               --------------------------------

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