<PAGE>




                              REVOLVING CREDIT AGREEMENT

                                     DATED AS OF

                                     JULY 7, 1997

                                        AMONG

                                   HACH COMPANY, A
                                 DELAWARE CORPORATION,

                                         AND

                               HACH EUROPE S.A./N.V., A
                             BELGIAN LIMITED LIABILITY COMPANY,
                            (COLLECTIVELY THE "BORROWER")
                                         AND

                                COLORADO NATIONAL BANK
                                     (THE "BANK")


<PAGE>


    THIS REVOLVING CREDIT AGREEMENT, dated as of July 7, 1997, is by and 
between HACH COMPANY,  a Delaware corporation, and HACH EUROPE S.A./N.V., a 
Belgian limited liability company (collectively, the "Borrower") and COLORADO 
NATIONAL BANK (the "Bank").

                                      ARTICLE I
                           DEFINITIONS AND ACCOUNTING TERMS

    Section 1.1.   DEFINED TERMS.  In addition to the terms defined elsewhere 
in this Agreement, the following terms shall have the following respective 
meanings (and such meanings shall be equally applicable to both the singular 
and plural form of the terms defined, as the context may require):

    "ADJUSTED EURODOLLAR RATE" means, for any Interest Rate Determination 
Date, the rate per annum obtained by dividing a) the London Interbank Offered 
Rate (expressed as a rate per annum and rounded upward to the nearest 1/16 of 
one percent) appearing on the Reuters system (as quoted by the Bank's 
standard administrative procedures) on such Interest Rate Determination Date 
for U.S. dollar deposits of amounts in same day funds comparable to the 
principal amount of the Eurodollar Loan for which the Adjusted Eurodollar 
Rate is then being determined with maturities comparable to the Interest 
Period for which such Adjusted Eurodollar Rate will apply by b) a percentage 
equal to 100% MINUS the actual rate of all reserve requirements (including, 
without limitation, any marginal, emergency, supplemental, special or other 
reserves) actually imposed on the Bank on such Interest Rate Determination 
Date.

    "ADVANCE" means an advance of funds under a Revolving Credit Loan. 

    "ADVERSE EVENT":  The occurrence of any event that could reasonably be 
expected to have a material adverse effect on the business, operations, 
property, assets or condition (financial or otherwise) of the Borrower and 
the Subsidiaries as a consolidated enterprise or on the ability of the 
Borrower or any other party obligated thereunder to perform its obligations 
under the Loan Documents.

    "AFFILIATE" shall include, any Person which directly or indirectly
controls, is controlled by, or is under common control with the Borrower.

    "AGREEMENT":  This Revolving Credit Agreement, as it may be amended,
modified, supplemented, restated or replaced from time to time.

    "BORROWER" means the entities described on the first page hereof 
collectively on a consolidated basis and singularly as to each of the 
entities constituting the Borrower. 

    "BORROWING DATE" means the date of funding of a Loan.

    "BUSINESS DAY" means (i) with respect to any Reference Rate Loan or any 
payment of the Nonuse Fee, any day except a Saturday, Sunday or other day on 
which commercial banks in Denver are authorized by law to close and (ii) with 
respect to any Eurodollar Loan, any day on which commercial banks are open 
for domestic and international business (including dealings in dollar 
deposits) in London and New York City.

<PAGE>

    "CAPITAL EXPENDITURES":  Any expenditures for fixed or capital assets
including assets financed under Capitalized Leases which are deemed "capital
expenditures under GAAP and should be shown in the "Capital Expenditures" entry
in the consolidated statements of cash flows.

    "CAPITALIZED LEASE":  Any lease which is or should be capitalized on the 
books of the lessee in accordance with GAAP.

    "CASH FLOW LEVERAGE RATIO" shall mean the ratio of Funded Debt compared 
to EBITDA for the previous 12 months.  Such ratio shall be measured on a 
consolidated basis as of the end of each fiscal quarter of the Borrower in 
accordance with GAAP.

    "CASH FLOW RATIO" shall mean the ratio of EBITDA divided by the sum of 
Interest Expense plus Mandatory Debt Reduction.  Such ratio shall be measured 
on consolidated basis as of the end of each fiscal quarter of the Borrower 
for the previous 12 months in accordance with GAAP.

    "CHANGE IN CONTROL":  The sale, transfer or disposition either 
beneficially or of record of outstanding voting common stock of Hach Company 
so that Kathryn Hach-Darrow, her descendants or their spouses and any trust 
or similar entity for the benefit of Kathryn Hach - Darrow, her descendants 
or their spouses shall beneficially own less than 40% of the outstanding 
voting common stock of Hach Company.

    "CODE":  The Internal Revenue Code of 1986, as amended, or any successor 
statute, together with regulations thereunder.

    "COMMITMENT":  The agreement of the Bank to make Loan to the Borrower 
subject to the terms and conditions of this Agreement.

    "COMPLIANCE CERTIFICATE"  The certificate required pursuant to Section 
7.1(d) hereof, substantially in the form of Exhibit D hereto.

    "CURRENT RATIO" shall mean as of the date of determination, the current 
assets divided by current liabilities of the Borrower excluding principal 
reduction of the Revolving Credit Loans required on the Revolving Credit 
Maturity Date, measured on a consolidated basis as of the end of each fiscal 
quarter of the Borrower in accordance with GAAP.

    "DEFAULT":  Any event which, with the giving of notice to the Borrower or 
lapse of time, or both, would constitute an Event of Default.

    "EBITDA" means, with respect to the Borrower on a consolidated basis in 
accordance with GAAP (net of minority interest and without duplication), for 
any period, the sum of (i) consolidated net income after taxes for such 
period, (ii) consolidated interest expense, (iii) federal, state and local 
income tax expense which is deducted from revenue in determining such 
consolidated net income, and 


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<PAGE>

(iv) depreciation and amortization less (v) to the extent reflected in net 
income (or loss), extraordinary gain (or plus any extraordinary loss) for 
such period.

    "ERISA":  The Employee Retirement Income Security Act of 1974, as 
amended, and any successor statute, together with regulations thereunder.

    "ERISA AFFILIATE":  Any trade or business (whether or not incorporated) 
that is a member of a group of which the Borrower is a member and which is 
treated as a single employer under Section 414 of the Code.

    "EURODOLLAR LOAN":  shall have the meaning set forth in Section 3.3(a) 
hereof.

    "EVENT OF DEFAULT":  Any event described in Section 9.1.

    "FIXED RATE":  shall have the meaning set forth in Section 3.3(a) hereof.

    "FUNDED DEBT" shall mean the total Indebtedness of the Borrower including 
Capitalized Lease Obligations determined on a consolidated basis in 
accordance with GAAP.

    "GAAP":  Generally accepted accounting principles consistently applied 
and maintained.  Whenever an accounting term is used herein which is not 
otherwise defined, it shall be interpreted in accordance with GAAP.

    "HACH COMPANY":  Hach Company, a Delaware corporation.

    "INDEBTEDNESS":  Without duplication, all indebtedness for borrowed money 
including the indebtedness created hereunder and the following (whether or 
not they should be classified as liabilities upon such balance sheet): (a) 
obligations secured by any mortgage, pledge, security interest, lien, charge 
or other encumbrance existing on property owned or acquired subject thereto, 
whether or not the obligation secured thereby shall have been assumed and 
whether or not the obligation secured is the obligation of the owner or 
another party; (b) any obligation on account of deposits or advances; (c) any 
obligation for the deferred purchase price of any property or services, 
except Trade Accounts Payable, (d) any obligation as lessee under any 
Capitalized Lease; (e) all guaranties, endorsements and other contingent 
obligations with respect to the indebtedness of others (excluding salary 
guaranties); (f) undertakings or agreements to reimburse or indemnify issuers 
of letters of credit; and (g) liabilities with respect to unfunded vested 
benefits under any retirement plan. For all purposes of this Agreement, the 
Indebtedness of any Person shall include the Indebtedness of any partnership 
or joint venture in which such Person is a general partner or a joint 
venturer.

    "INTEREST EXPENSE":  The expense of the Borrower for interest under the 
Revolving Credit Loans and any other Indebtedness of the Borrower, on a 
consolidated basis.

    "INTEREST PERIOD":  shall have the meaning set forth in Section 3.3(b) 
hereof.


                                    3
<PAGE>

    "INTEREST RATE DETERMINATION DATE" means each date for calculating the 
Adjusted Eurodollar Rate for purposes of determining the Fixed Rate with 
respect to an Interest Period.  The Interest Rate Determination Date shall be 
the first Business Day of the related Interest Period for a Eurodollar Loan.

    "INVESTMENT":  The acquisition, purchase, making or holding of any stock 
or other security, any loan, advance, contribution to capital, extension of 
credit (except for trade and customer accounts receivable for inventory sold 
or services rendered in the ordinary course of business and payable in 
accordance with customary trade terms), any acquisitions of real or personal 
property (other than real and personal property acquired in the ordinary 
course of business) and any purchase or commitment or option to purchase 
stock or other debt or equity securities of or any interest in another Person 
or any integral part of any business.

    "LIEN":  Any security interest, mortgage, pledge, lien, hypothecation, 
judgment lien or similar legal process, charge, encumbrance, title retention 
agreement or analogous instrument or device (including, without limitation, 
the interest of the lessors under Capitalized Leases and the interest of a 
vendor under any conditional sale or other title retention agreement).

    "LOAN DOCUMENTS":  This Agreement, the Note, and each other instrument, 
document, or other agreement executed and delivered by the Borrower in 
connection with this Agreement, the Loans or any collateral for the Loans.

    "LOANS":  The Revolving Credit Loans.

    "MANDATORY DEBT RETIREMENT" shall mean the mandatory debt reduction of 
the Borrower including mandatory reductions in the Revolving Credit Loans and 
Capitalized Lease Obligations determined on a consolidated basis in 
accordance with GAAP

    "NET WORTH" means as of the date of determination, the net worth or 
shareholders equity of the Borrower, determined on a consolidated basis in 
accordance with GAAP.

    "NOTE":  The Revolving Credit Note.

    "NOTICE OF BORROWING" means a notice substantially in the form of EXHIBIT 
B hereto delivered by the Company to the Bank with respect to each and every 
request for a Loan.


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    "NOTICE OF CONVERSION/CONTINUATION" means a notice, substantially in the 
form of EXHIBIT C attached hereto, delivered from time to time by the Company 
to the Bank pursuant to Section 3.3(c) hereof with respect to a proposed 
conversion or continuation of the applicable basis for determining the 
interest rate with respect to certain Loans.

    "PAYMENT DATE"  means (i) with respect to Reference Rate Loans, the first 
day of each month (ii) with respect Eurodollar Rate Loans having an Interest 
Rate Period of 90 days or less, the last day of the related Interest Rate 
Period; and (iii) with respect to Eurodollar Rate loans having an Interest 
Rate Period in excess of 90 days, 90 days from the Borrowing Date and each 
increment of 90 days during the Interest Rate Period and the last day of the 
related Interest Rate Period.

    "PBGC":  The Pension Benefit Guaranty Corporation, established pursuant 
to Subtitle A of Title IV of ERISA, and any successor thereto or to the 
functions thereof.

    "PERSON":  Any natural person, corporation, partnership, joint venture, 
firm, association, trust, unincorporated organization, government or 
governmental agency or political subdivision or any other entity, whether 
acting in an individual, fiduciary or other capacity.

    "PLAN":  An employee benefit plan or other plan, maintained for employees 
of the Borrower or of any ERISA Affiliate, and subject to Title IV of ERISA 
or Section 412 of the Code.

    "REFERENCE RATE":  The rate of interest from time to time publicly 
announced by the Bank as its "base" or "reference" rate. The Bank may lend to 
its customers at rates that are at, above or below the Reference Rate.  For 
purposes of determining any interest rate which is based on the Reference 
Rate, such interest rate shall change on the effective date of any change in 
the Reference Rate.

    "REFERENCE RATE LOAN":  shall have the meaning set forth in Section 3.2 
hereof.

    "REPORTABLE EVENT":  A reportable event as defined in Section 4043 of 
ERISA and the regulations issued under such Section, with respect to a Plan, 
excluding, however, such events as to which the PBGC by regulation has waived 
the requirement of Section 4043(a) of ERISA that it be notified within 30 
days of the occurrence of such event, provided that a failure to meet the 
minimum funding standard of Section 412 of the Code and Section 302 of ERISA 
shall be a reportable event regardless of the issuance of any such waivers in 
accordance with Section 412(d) of the Code.

    "REVOLVING CREDIT COMMITMENT":  The maximum unpaid principal amount of 
Revolving Credit Loans which may from time to time be outstanding hereunder, 
being the amounts set forth on Exhibit A hereto, and the agreement of the 
Bank to make Revolving Credit Loans to the Borrower subject to the terms and 
conditions of this Agreement.  

    "REVOLVING CREDIT LOANS":  The Loans described in Section 2.1.

    "REVOLVING CREDIT MATURITY DATE":  The date set forth on Exhibit A hereto 
being the date on which the Revolving Credit Loans shall be due and payable 
in full.


                                    5
<PAGE>


    "REVOLVING CREDIT NOTE":  The Revolving Credit Promissory Note of the 
Borrower of even date described in Section 2.3, as such promissory note may 
be amended, modified or supplemented from time to time, and such term shall 
include any substitutions for, or renewals of, such promissory note.

    "REVOLVING CREDIT RATE":  The rate of interest accruing on each Revolving 
Credit Loan prior to maturity or acceleration as set forth on Exhibit A 
hereto.

    "SUBSIDIARY":  Any Person of which or in which the Borrower or the other 
Subsidiaries own directly or indirectly fifty one percent (51%) or more of: 
(a) the combined voting power of all classes of stock having general voting 
power under ordinary circumstances to elect a majority of the board of 
directors of such Person, if it is a corporation, (b) the capital interest, 
profit interest and voting interest of such Person, if it is a partnership, 
joint venture, limited liability company or similar entity, or (c) the 
beneficial interest of such Person, if it is a trust, association or other 
unincorporated organization.

    "TRADE ACCOUNTS PAYABLE":  The trade accounts payable of any Person with 
a maturity of not greater than 90 days incurred in the ordinary course of 
such Person's business.

    Section 1.2.   ACCOUNTING TERMS AND CALCULATIONS.  Except as may be 
expressly provided to the contrary herein, all accounting terms used herein 
shall be interpreted and all accounting determinations hereunder (including, 
without limitation, determination of compliance with financial ratios and 
restrictions in Articles VIII and IX hereof) shall be made in accordance with 
GAAP consistently applied.  Any reference to "consolidated" financial terms 
shall be deemed to refer to those financial terms as applied to the Borrower 
and its Subsidiaries in accordance with GAAP.

    Section 1.3.   COMPUTATION OF TIME PERIODS.  In this Agreement, in the 
computation of a period of time from a specified date to a later specified 
date, unless otherwise stated the word "from" means "from and including" and 
the word "to" or "until" each means "to but excluding."

    Section 1.4.   OTHER DEFINITIONAL TERMS.  The words "hereof," "herein" 
and "hereunder" and words of similar import when used in this Agreement shall 
refer to this Agreement as a whole and not to any particular provision of 
this Agreement.  References to Sections, Exhibits, schedules and like 
references are to this Agreement unless otherwise expressly provided.


                                ARTICLE II
                              TERMS OF LENDING

    Section 2.1    THE REVOLVING CREDIT LOANS.  Subject to the terms and 
conditions hereof and in reliance upon the representations, warranties and 
covenants of the Borrower herein, the Bank agrees to make loans (each, a 
"Revolving Credit Loan" and, collectively, the "Revolving Credit Loans") to 
the Borrower from time to time from the date hereof until the Revolving 
Credit Maturity Date, during which period the Borrower shall repay and may 
reborrow in accordance with the provisions hereof in 


                                    6
<PAGE>



such amount as the Borrower shall request subject to the limitations of 
Section 2.2, provided, that the aggregate unpaid principal amount of all 
outstanding Revolving Credit Loans shall not exceed the Revolving Credit 
Commitment at any time.

    Section 2.2    BORROWING PROCEDURES FOR LOANS.  Any request by the 
Borrower for a Loan shall be made by delivery of a written Notice of 
Borrowing, or by telephone promptly confirmed by telecopy of the Notice of 
Borrowing no later than the next Business Day, and must be given so as to be 
received by the Bank not later than 10:00 a.m., Denver time, on the date of 
the requested Revolving Credit Loan.  Each request for a Loan shall include:  
(i) the Borrowing Date (which shall be a Business Day) and (ii) the amount of 
such Loan.  Unless the Bank determines that any provisions hereof have not 
been satisfied, the Bank will make the amount of the requested Loan available 
to the Borrower at the Bank's office in Boulder, Colorado, in immediately 
available funds on the date requested no later than 2:00 p.m. Denver time for 
Revolving Credit Loans.  Each requested Loan shall be in an amount not less 
than $500,000 and in minimum increments of $100,000.

    Section 2.3    THE REVOLVING CREDIT NOTES.  The Revolving Credit Loans 
shall be evidenced by the Revolving Credit Note, in the amount of the 
Revolving Credit Commitment originally in effect and dated as of the date of 
this Agreement.  The Revolving Credit Loans and the Revolving Credit Note 
shall mature and be payable on the Revolving Credit Maturity Date subject to 
mandatory prepayment requirements provided in the Loan Documents.  The Bank 
shall enter in its records the amount of each Advance comprising the 
Revolving Credit Loans, and such records shall be conclusive evidence of the 
subject matter thereof, absent manifest error.

    Section 2.4    USE OF PROCEEDS.  Proceeds of the Revolving Credit Loans 
shall be used by the Borrower to repurchase approximately 3,157,220 shares of 
the common stock $1.00 par value of Hach Company from Lawter International, 
Inc. (the "Stock Repurchase"), to fund the working capital requirements of 
the Borrower and for the general corporate purposes of the Borrower.

                                     ARTICLE III
                                  INTEREST AND FEES

    Section 3.1    INTEREST.

         (a)  REVOLVING CREDIT RATE.  The unpaid principal amount of each
    Revolving Credit Loan shall bear interest prior to maturity at a rate per
    annum equal to the Revolving Credit Rate as a Reference Rate Loan or a
    Eurodollar Loan.

         (b)  INTEREST AFTER MATURITY.  Effective five (5) business days after
    the Borrower receives written notice from the Bank of the occurrence of any
    Event of Default and the applicability of this Section 3.1(b) and for as
    long thereafter as any such Event of Default shall be continuing, the
    amount of the Loans not paid when due, whether at the date scheduled
    therefor or earlier upon acceleration, shall bear interest until paid in
    full at a rate per annum equal to five (5%) percent in excess of the
    applicable rate.


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    Section 3.2    INTEREST ON REFERENCE RATE LOANS.  Each Loan or any 
portion of the outstanding principal balance thereof (a "Reference Rate 
Loan"), which is not bearing interest at a Fixed Rate (as defined below) 
shall bear interest at a rate per annum (on the basis of a 360-day year for 
the actual number of days involved) equal to the Revolving Credit Rate for 
Reference Rate Loans in effect from time to time, as shown on Exhibit A 
hereto.

    Section 3.3    INTEREST ON EURODOLLAR LOANS.

         (a)  CALCULATION OF FIXED RATE.  Each Loan  or any portion of the
    outstanding principal balance thereof (a "EURODOLLAR LOAN"), which has been
    designated by the Borrower in a Notice of Borrowing or a Notice of
    Conversion/Continuation as a "Eurodollar Loan" in accordance with the terms
    hereof, shall bear interest from and including the first day of the
    applicable Interest Period to but excluding the last day of such Interest
    Period at a rate per annum (the "FIXED RATE") (on the basis of a 360-day
    year for the actual number of days involved), equal to the Revolving Credit
    Rate for Eurodollar Loans as determined by the Bank for each Interest
    Period, as shown on Exhibit A hereto.  Borrower shall be entitled to elect
    not more than ten (10) Eurodollar Loans at any time.
         
         (b)  SELECTION OF INTEREST PERIODS.  The Borrower shall select an
    interest period (each, an "INTEREST PERIOD") to be applicable to each
    Eurodollar Loan, pursuant to the applicable Notice of Borrowing or Notice
    of Conversion/Continuation, as the case may be, which Interest Period shall
    be, at the Borrower's option, a 30-, 60-, 90-, or 180-day period; PROVIDED,
    that all of the following shall be satisfied with respect thereto:

              (i)  the initial Interest Period for any Eurodollar Loan shall
         commence on the Borrowing Date in respect of such Loan, in the case of
         a Loan initially made as a Eurodollar Loan, in which event the Notice
         of Borrowing must be given at least two Business Days prior to the
         Borrowing Date and specify the Interest Period thereon or on the date
         specified in the applicable Notice of Conversion/Continuation, in the
         case of a Loan converted to a Eurodollar Loan;

              (ii) in the case of immediately successive Interest Periods
         applicable to a Eurodollar Loan continued as such pursuant to a Notice
         of Conversion/Continuation, each successive Interest Period shall
         commence on the day on which the next preceding Interest Period
         expires.  Notwithstanding the foregoing, if any Interest Period would
         otherwise end on a day which is not a Business Day, such Interest
         Period shall be extended to the next succeeding Business Day unless
         the result of such extension would be to carry such Interest Period
         into another calendar month, in which event such Interest Period shall
         end on the immediately preceding Business Day;

              (iii)     any Interest Period for a Eurodollar Loan that begins
         on the last Business Day of a calendar month (or on a day for which
         there is no numerically 


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<PAGE>


         corresponding day in the calendar month at the end of such 
         Interest Period) shall, subject to clause (ii) above, end
         on the last Business Day of a calendar month; and

              (iv) no Interest Period with respect to any portion of the
         Revolving Credit Loans shall extend beyond the Revolving Credit
         Maturity Date.

         (c)  CONVERSION OR CONTINUATION.

              (i)  Subject to the provisions of subparagraph (b) above and
         Section 3.4, the Borrower shall have the option (A) to convert at any
         time all or any part of its outstanding Loans or any portion thereof
         equal to $500,000 and integral multiples of $100,000 in excess of that
         amount, from Reference Rate Loans to Eurodollar Loans or from
         Eurodollar Loans to Reference Rate Loans or (B) upon the expiration of
         any Interest Period applicable to a Eurodollar Loan, to continue all
         or any portion of such Loan equal to $500,000 and integral multiples
         of $100,000 in excess of that amount, as a Eurodollar Loan; PROVIDED,
         HOWEVER, that a Eurodollar Loan may only be converted into a Reference
         Rate Loan on the expiration date of an Interest Period applicable
         thereto.

              (ii) The Borrower shall deliver a Notice of
         Conversion/Continuation to the Bank no later than 12:00 noon (Denver
         time) at least two Business Days in advance of the proposed
         conversion/continuation date in the case of a conversion to or from,
         or a continuation of, a Eurodollar Loan.  A Notice of
         Conversion/Continuation shall specify (A) the proposed
         conversion/continuation date (which shall be a Business Day), (B) the
         amount and type of the Loan, or portion thereof, to be
         converted/continued, (C) in the case of a conversion to, or a
         continuation of a Eurodollar Loan, the requested Interest Period, and
         (D) that no Event of Default has occurred and is continuing.  In lieu
         of delivering the above-described Notice of Conversion/Continuation,
         the Borrower may give the Bank telephonic notice by the required time
         of any proposed conversion/continuation under this subparagraph (d);
         PROVIDED that such notice shall be promptly confirmed in writing by
         delivery of a Notice of Conversion/Continuation to the Bank on or
         before the proposed conversion/continuation date.

              (iii)     The Bank shall not incur any liability to the Borrower
         in acting upon any telephonic or telecopy notice referred to above
         that the Bank believes in good faith to have been given by a duly
         authorized officer or other person authorized to act on behalf of the
         Borrower or for otherwise acting in good faith under this
         subparagraph (c), and upon conversion or continuation of the
         applicable basis for determining the interest rate with respect to any
         Loans in accordance with this Agreement pursuant to any such
         telephonic notice the Borrower shall have effected a conversion or
         continuation, as the case may be, hereunder.


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<PAGE>


              (iv) Except as otherwise provided in Section 3.4 hereof, a Notice
         of Conversion/Continuation for conversion to, or continuation of, a
         Eurodollar Loan (or telephonic notice in lieu thereof) shall be
         irrevocable on and after the related Interest Rate Determination Date,
         and the Borrower shall be bound to effect a conversion or continuation
         in accordance therewith.

    Section 3.4    SPECIAL PROVISIONS GOVERNING EURODOLLAR LOANS. 
Notwithstanding any other provision of this Agreement to the contrary, the 
following provisions shall govern with respect to Eurodollar Loans as to the 
matters covered:

         (a)  DETERMINATION OF ADJUSTED EURODOLLAR RATE.  As soon as
    practicable after 10:00 A.M. (Denver time) on each Interest Rate
    Determination Date, the Bank shall determine the Adjusted Eurodollar Rate
    that shall apply to the Eurodollar Loans for which an interest rate is then
    being determined for the applicable Interest Period and shall promptly give
    notice thereof (in writing or by telephone confirmed in writing) to the
    Borrower.

         (b)  NO MEANS FOR DETERMINING RATE.  In the event that the Bank shall
    have determined, on any Interest Rate Determination Date with respect to
    any Eurodollar Loans, that by reason of circumstances affecting the
    interbank Eurodollar market, adequate and fair means do not exist for
    ascertaining the interest rate applicable to such Loans on the basis
    provided for in the definition of Adjusted Eurodollar Rate, the Bank shall
    on such date give notice (by telecopy or by telephone confirmed in writing)
    to the Borrower of such determination, whereupon (i) no Loans may be made
    as, or converted to, Eurodollar Loans, until such time as the Bank notifies
    the Borrower that the circumstances giving rise to such notice no longer
    exist and (ii) any Notice of Borrowing or Notice of Conversion/Continuation
    given by the Borrower with respect to the Loans in respect of which such
    determination was made shall be deemed to be rescinded by the Borrower.

         (c)  CONTINUATION OF EURODOLLAR LOANS UNLAWFUL.  In the event that on
    any date the Bank reasonably determines after consultation with the
    Borrower that the making, maintaining or continuation of its Eurodollar
    Loans (i) has become unlawful as a result of compliance by the Bank in good
    faith with any law, treaty, governmental rule, regulation, guideline or
    order (or would conflict with any such treaty, governmental rule,
    regulation, guideline or order not having the force of law even though the
    failure to comply therewith would not be unlawful) or (ii) would cause the
    Bank material hardship, as a result of contingencies occurring after the
    date of this Agreement which materially and adversely affect the interbank
    Eurodollar market, or the position of the Bank in that market, then, and in
    any such event, the Bank shall give notice (by telecopy or by telephone
    confirmed in writing) to the Borrower of such determination (which notice
    shall set forth the reasons for the determination).  Thereafter (I) the
    obligation of the Bank to make Eurodollar Loans, or to convert Loans to
    Eurodollar Loans, shall be suspended until such time as the reasons for the
    suspension no longer exist, at which time the obligations of the Bank to
    make Eurodollar Loans shall be reinstated, (II) to the extent such
    determination by the Bank relates to a Eurodollar Loan then being requested
    by the 

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<PAGE>


    Borrower pursuant to a Notice of Borrowing or a Notice of 
    Conversion/Continuation, the Bank shall make such Loan as (or convert 
    such Loan to) a Reference Rate Loan,(III) the Bank's obligation to 
    maintain its outstanding Eurodollar Loans (the "AFFECTED LOANS"), shall 
    be terminated at the earlier to occur of the expiration of the Interest 
    Period then in effect with respect to the Affected Loans or when required 
    by law, and (IV) the Affected Loans shall automatically convert into 
    Reference Rate Loans on the date of such termination.  Notwithstanding 
    the foregoing, to the extent a determination by the Bank as described 
    above relates to a Eurodollar Loan then being requested by the Borrower 
    pursuant to a Notice of Borrowing or a Notice of Conversion/Continuation, 
    the Borrower shall have the option, subject to the provisions of 
    subparagraph (d) below, to rescind such Notice of Borrowing or Notice of 
    Conversion/Continuation by giving notice (by telecopy or by telephone 
    confirmed in writing) to the Bank of such rescission on the date on which 
    the Bank gives notice of its determination as described above.

         (d)  COMPENSATION OF BANK FOR LOSSES.  The Borrower shall compensate
    the Bank, upon written request by the Bank (which request shall set forth
    in reasonable detail the basis for requesting such amounts), for all
    reasonable actual losses, loss of yield, expenses and liabilities
    (including, without limitation, any interest paid by that Bank to lenders
    of funds borrowed by it to make or carry its Eurodollar Loan and any loss,
    expense or liability actually sustained by the Bank in connection with the
    liquidation or re-employment of such funds) which the Bank actually
    sustains: (i) if due to the fault of the Borrower, a borrowing of any
    Eurodollar Loan does not occur on a date specified therefor in a Notice of
    Borrowing or a telephonic request for conversion or continuation, (ii) if
    any prepayment or conversion of any of its Eurodollar Loans occurs on a
    date that is not the last day of an Interest Period applicable to that
    Loan, (iii) if any prepayment of any of its Eurodollar Loans is not made on
    any date specified in a notice of prepayment given by the Borrower, or
    (iv) as a consequence of any other failure by the Borrower in the repayment
    of its Eurodollar Loans when required by the terms of this Agreement.

         (e)  TRANSFER TO BRANCH BANKS.  The Bank may make, carry or transfer
    Eurodollar Loans at, to, or for the account of any of its branch offices or
    the office of an affiliate of the Bank.

         (f)  ACTUAL PURCHASE OF EURODOLLAR DEPOSITS.  Calculation of all
    amounts payable to the Bank under this Section 3.4 shall be made as though
    the Bank had actually funded each of its relevant Eurodollar Loans through
    the purchase of a Eurodollar deposit bearing interest at the rate obtained
    pursuant to clause (a) of the definition of Adjusted Eurodollar Rate in an
    amount equal to the amount of such Eurodollar Loan and having a maturity
    comparable to the relevant Interest Period; PROVIDED, HOWEVER, that the
    Bank may fund each of its Eurodollar Loans in any manner it sees fit and
    the foregoing assumptions shall be utilized only for the purposes of
    calculating amounts payable under this Section.  In no event, however,
    shall the adjustments in clause (b) of the definition of Adjusted
    Eurodollar Rate be applicable unless the Bank has actually funded the
    Eurodollar Loans through the purchase of a Eurodollar deposit.


                                    11
<PAGE>


         (g)  EURODOLLAR LOANS AFTER EVENT OF DEFAULT.  After the occurrence of
    and during the continuation of an Event of Default, (i) the Borrower may
    not elect to have a Loan be made or maintained as, or converted to, a
    Eurodollar Loan after the expiration of any Interest Period then in effect
    for that Loan and (ii) subject to the provisions of subparagraph (d) above,
    any Notice of Borrowing or Notice of Conversion/Continuation given by the
    Borrower with respect to a requested borrowing or conversion/continuation
    that has not yet occurred shall be deemed to be rescinded by the Borrower.

    Section 3.5    OTHER INTEREST RATES.  The parties may enter into interest 
rate protection agreements (swaps or caps) or provide for longer term 
interest periods and alternative payment dates upon such terms as the parties 
shall agree in writing.

    Section 3.6    FACILITY FEE.  The Borrower shall pay to the Bank a fee of 
$50,000 upon execution and delivery of this Agreement (the "Facility Fee"). 

    Section 3.7    NONUSE FEE.  The Borrower shall pay a nonuse fee (the 
"Nonuse Fee") in the amount set forth on Exhibit A calculated on the daily 
unused amount of the Revolving Credit Commitment, payable quarterly 
(calendar) in arrears within 30 days of invoice.

    Section 3.8    COMPUTATION.  Interest and Nonuse Fees shall be computed 
on the basis of actual days elapsed and a year of 360 days.

    Section 3.9    PAYMENT DATES.  Accrued interest under Section 3.1 (a) 
shall be payable on each Payment Date.  Accrued interest under Section 3.1(b) 
shall be payable on demand.

    Section 3.10   ADDITIONAL COSTS.  

         (a)  ADDITIONAL COSTS.  In the event that any change in applicable law
    or regulation or in the interpretation thereof by any governmental
    authority charged with the administration thereof subjects the Bank to any
    taxes whatsoever with respect to the basis of taxation of payments to the
    Bank of principal or interest payable on any Eurodollar Loan (except for
    changes in the rate of tax based on or measured by the net income of the
    Bank), and the result of the foregoing is to increase the cost to the Bank
    of making or maintaining any Eurodollar Loan by an amount which the Bank
    reasonably deems to be material, then the Borrower shall pay to the Bank 30
    days after written notice thereof from the Bank to the Borrower the
    additional amount or amounts necessary to compensate the Bank for such
    additional cost.

         (b)  CERTIFICATE, ETC.  The Bank shall promptly notify the Company
    upon becoming aware that the Company may be required to make any payment
    pursuant to this Section.  The Bank shall provide to the Borrower a
    certificate, signed by an officer of the Bank, setting forth the amount
    required to be paid by the Borrower to the Bank and the computations made
    by the Bank to determine such amount.


                                    12
<PAGE>


    Section 3.11   REASONABLE EFFORTS TO MITIGATE.  Bank agrees that as
promptly as practicable after it becomes aware of the occurrence of an event or
the existence of a condition that would cause it to be affected under Section
3.4 or Section 3.9, Bank will give notice thereof to the Borrower, and, to the
extent so requested by the Borrower and not inconsistent with applicable law,
the Bank's internal policies or sound banking practices, Bank shall use
reasonable efforts and take such actions as are reasonably appropriate if as a
result thereof the additional moneys which would otherwise be required to be
paid to Bank pursuant to such sections would be materially reduced, or the
illegality or other adverse circumstances which would otherwise require a
conversion of such Loans or result in the inability to make such Loans pursuant
to such sections would cease to exist, and in each case if, as determined by the
Bank in its sole discretion, taking such actions would not adversely affect such
Loans or Bank or otherwise be disadvantageous to Bank.

                                      ARTICLE IV
                   PAYMENTS, PREPAYMENTS, REDUCTION OR TERMINATION
                               OF THE CREDIT AND SETOFF

    Section 4.1    REPAYMENT.  Principal of the Loans, together with all
accrued and unpaid interest thereon, shall be due and payable as provided in
Section 2.3 regarding maturity of the Note and as provided in this Article IV.

    Section 4.2 MANDATORY PREPAYMENT.  The Borrower shall, without notice or
demand on the dates set forth on Exhibit A hereto, make mandatory principal
payments in such amounts as are necessary to reduce the aggregate outstanding
principal balance of the Revolving Credit Loans to be equal to or less than the
amount of the Revolving Credit Commitment as it reduces as shown on Exhibit A
hereto.  In the event an Advance causes the aggregate outstanding principal
balance of the Revolving Credit Loans to exceed the Revolving Credit Commitment,
such excess shall be payable upon receipt of written demand from the Bank.

    Section 4.3    OPTIONAL PREPAYMENT.  The Borrower may prepay the Loans, in
whole or in part, at any time.  Any such prepayment must be accompanied by
accrued and unpaid interest on the amount prepaid.  Any prepayment of Reference
Rate Loans shall be without penalty or premium.  A payment of Eurodollar Loans
prior to the last day of the Interest Period therefor shall require payment of
the amounts specified in Section 3.4(d).    

    Section 4.4    PREPAYMENT UPON FINANCIAL COVENANT NONCOMPLIANCE.  If the
Borrower shall at any time fail to comply with the financial covenants set forth
in Article III of Exhibit A, the Borrower shall, if applicable, immediately upon
demand of the Bank, prepay the principal balance of the Revolving Credit Loans
in the amount necessary to cause compliance with the financial covenants.

    Section 4.5    PAYMENTS.  Payments and prepayments of principal of, and
interest on, the Note and all fees, expenses and other obligations under the
Loan Documents shall be made without set-off or counterclaim in immediately
available funds not later than 2:00 p.m., Denver time, on the dates due 


                                    13
<PAGE>


at the office of the Bank in Boulder, Colorado.  Funds received after such 
time shall be deemed to have been received on the next Business Day and an 
additional day's interest shall be due provided that, the failure of the 
Borrower to make any such payment by such time shall not constitute a Default 
or Event of Default hereunder if such payment is received by the Bank by 5:00 
p.m. on such due date. Whenever any payment to be made hereunder or on the 
Note shall be stated to be due on a day which is not a Business Day, such 
payment shall be made on the next succeeding Business Day and such extension 
of time shall be included in the computation of any interest or fees.

                                      ARTICLE V
                                 CONDITIONS PRECEDENT

    Section 5.1    CONDITIONS OF INITIAL LOAN.  Unless a later date is
specified herein or otherwise agreed to by the Bank in writing, the obligation
of the Bank to make the initial Loan hereunder shall be subject to the
satisfaction of the conditions precedent. In this regard, as set forth in
Sections 5.1 and 5.2, the Bank shall have received all of the following and the
following shall have been completed, in form and substance satisfactory to the
Bank, each duly executed and certified or dated the date of the initial Loan or
such other date as is satisfactory to the Bank:

         (a)  The Note and the Loan Documents by a duly authorized officer 
    (or officers) of the Borrower as appropriate.

         (b)  A certified copy of the corporate resolution of the Borrower
    authorizing the execution, delivery and performance of the Loan Documents
    to which they are a party.

         (c)  An incumbency certificate showing the names and titles, and
    bearing the signatures of, the officers of the Borrower authorized to
    execute the Loan Documents and to request Loans hereunder, certified by the
    Secretary or an Assistant Secretary of the Borrower.

         (d)  A copy of the organizational documents of the Borrower with all
    amendments thereto. 

         (e)  A Certificate of Good Standing for the Borrower in the
    jurisdiction of its incorporation, certified by the appropriate
    governmental officials.

         (f)  An opinion of counsel to the Borrower, addressed to the Bank, in
    form and content acceptable to the Bank.

         (g)  Receipt by the Bank of current UCC searches for the Borrower
    disclosing no liens or security interests on the assets of the Borrower. 

         (h)  A Compliance Certificate giving effect to the proposed initial
    Advance of funds.


                                    14
<PAGE>


         (i)  Receipt by the Bank of such other approvals, opinions or
    documents as the Bank may reasonably request.

    Notwithstanding the foregoing, Hach Europe S.A./N.V. shall have until
August 7, 1997 within which to deliver the materials described in subparagraphs
(b), (c), (d), (e) and (f) above.

    Section 5.2    CONDITIONS PRECEDENT TO ALL LOANS.  The obligation of the
Bank to make any Loan hereunder (including the initial Loan but excluding a
continuation or conversion of a Eurodollar Rate Loan) shall be subject to the
satisfaction of the following conditions precedent (and the request for a Loan
shall be deemed a representation and warranty that the following are true and
correct):

         (a)  Before and after giving effect to such Loan, the representations
    and warranties contained in Article VI shall be true and correct, as though
    made on the date of such Loan, and Borrower shall have performed the
    affirmative covenants set forth in Article VII and not breached the
    negative covenants set forth in Article VIII as of the date of such Loan;

         (b)  Before and after giving effect to such Loan, no Default or Event
    of Default shall have occurred and be continuing;

         (c)  Before and after giving effect to such Loan, no Adverse Event
shall have    occurred with respect to the Borrower.


                                      ARTICLE VI
                            REPRESENTATIONS AND WARRANTIES

    To induce the Bank to enter into this Agreement, to grant the Commitment
and to make Loans hereunder, the Borrower represents and warrants to the Bank:

    Section 6.1    ORGANIZATION, STANDING, ETC..  Each of the entities
constituting the Borrower are corporations, limited partnerships or limited
liability companies, as appropriate duly organized  and validly existing and in
good standing under the laws of their respective jurisdiction organization and
have all requisite power and authority to carry on their respective businesses
as now conducted, to enter into the Loan Documents to which they are a party and
to perform its obligations under the Loan Documents.  The Borrower is duly
qualified and in good standing in each jurisdiction in which the failure to so
qualify might materially adversely affect the consolidated financial condition
or operations of the Borrower.

    Section 6.2    AUTHORIZATION AND VALIDITY.  The execution, delivery and
performance by the Borrower of the Loan Documents have been duly authorized by
all necessary entity action by the Borrower, and the Loan Documents constitute
the legal, valid and binding obligations of the Borrower, enforceable against
them in accordance with their respective terms, subject to limitations as to


                                    15
<PAGE>


enforceability which might result from bankruptcy, insolvency, moratorium and
other similar laws affecting creditors' rights generally and subject to
limitations on the availability of equitable remedies.

    Section 6.3    NO CONFLICTS NO DEFAULT.  The execution, delivery and
performance by the Borrower of the Loan Documents to which they are a party will
not (a) violate any provision of any law, statute, rule or regulation or any
order, writ, judgment, injunction, decree, determination or award of any court,
governmental agency or arbitrator presently in effect having applicability to
the Borrower except to the extent that the failure to comply therewith could
not, in the aggregate, have a material adverse effect on the business,
operations, property or financial or other condition of the Borrower taken as a
whole, or could not materially adversely effect the ability of the Borrower to
perform its obligations under this Agreement, (b) violate or contravene any
provisions of the organizational documents or by-laws of the Borrower, or (c)
result in a breach of or constitute a default under any indenture, loan or
credit agreement or any other agreement, lease or instrument to which the
Borrower is a party or by which such entity or any of such entity's properties
may be bound or result in the creation of any Lien on any asset of the Borrower.
The Borrower is not in default under or in violation of any such law, statute,
rule or regulation, order, writ, judgment, injunction, decree, determination or
award or any such indenture, loan or credit agreement or other agreement, lease
or instrument in any case in which the consequences of such default or violation
could constitute an Adverse Event.

    Section 6.4    GOVERNMENT CONSENT.  No order, consent, approval, license,
authorization or validation of, or filing, recording or registration with, or
exemption by, any governmental or public body or authority is required on the
part of the Borrower to authorize, or is required in connection with the
execution, delivery and performance of, or the legality, validity, binding
effect or enforceability of, the Loan Documents to which it is a party.

    Section 6.5    FINANCIAL STATEMENTS AND CONDITION.  The Borrower's audited
consolidated financial statements as of April 30, 1997, as heretofore furnished
to the Bank, have been prepared in accordance with GAAP on a consistent basis
and fairly present, in all material respects, the financial position of the
Borrower as at such dates and the results of their operations and cash flows for
the respective periods then ended.  As of the dates of such financial
statements, the Borrower has no material obligation, contingent liability,
liability for taxes or long-term lease obligation which is not reflected in such
financial statements or in the notes thereto.  Since April 30, 1997, no Adverse
Event has occurred except as set forth on Schedule 6.5.

    Section 6.6    LITIGATION AND CONTINGENT LIABILITIES.  Except as described
in Schedule 6.6, there are no actions, suits or proceedings pending or, to the
knowledge of the Borrower, threatened against or affecting the Borrower or any
of their properties before any court or arbitrator, or any governmental
department, board, agency or other instrumentality which, if determined
adversely to the Borrower, could constitute an Adverse Event.  Except as
described in Schedule 6.6(a), the Borrower has no contingent liabilities which
are material to the Borrower as a consolidated enterprise.


                                    16
<PAGE>


    Section 6.7    COMPLIANCE.  The Borrower is in compliance with all statutes
and governmental rules and regulations applicable to them for which the failure
to comply would have a material adverse effect on the Borrower.

    Section 6.8    ENVIRONMENTAL, HEALTH AND SAFETY LAWS.  There does not exist
any violation by the Borrower of any applicable federal, state or local law,
rule or regulation or order of any government, governmental department, board,
agency or other instrumentality relating to environmental, pollution, health or
safety matters which will or threatens to impose a material liability on the
Borrower or which would require a material expenditure by the Borrower to cure. 
The Borrower has not received any notice to the effect that any part of its
operations or properties is not in material compliance with any such law, rule,
regulation or order or notice that it or its property is the subject of any
governmental investigation evaluating whether any remedial action is needed to
respond to any release of any toxic or hazardous waste or substance into the
environment, the consequences of which non-compliance or remedial action could
constitute an Adverse Event.

    Section 6.9    ERISA.  Each Plan complies with all material applicable
requirements of ERISA and the Code and with all material applicable rulings and
regulations issued under the provisions of ERISA and the Code setting forth
those requirements.  No Reportable Event, other than a Reportable Event for
which the reporting requirements have been waived by regulations of the PBGC,
has occurred and is continuing with respect to any Plan.  All of the minimum
funding standards applicable to such Plans have been satisfied and there exists
no event or condition which would permit the institution of proceedings to
terminate any Plan under Section 4042 of ERISA.  The current value of the Plans'
benefits guaranteed under Title IV or ERISA does not exceed the current value of
the Plans' assets allocable to such benefits.

    Section 6.10   REGULATION U.  The Borrower is not engaged in the business
of extending credit for the purpose of purchasing or carrying margin stock (as
defined in Regulation U of the Board of Governors of the Federal Reserve System)
and no part of the proceeds of any Loan will be used for any purpose which would
violate any of the margin stock requirements of the Board of Governors of the
Federal Reserve System.

    Section 6.11   OWNERSHIP OF PROPERTY; LIENS.  The Borrower has good and
marketable title to its real properties and good and sufficient title to its
other properties, including all properties and assets referred to as owned by
the Borrower in the financial statements of the Borrower referred to in Section
6.5 (other than property disposed of since the date of such financial statement
in the ordinary course of business).  None of the properties, revenues or assets
of the Borrower is subject to a Lien, except for (a) Liens disclosed in the
financial statements referred to in Section 6.5, (b) Liens listed on Schedule
6.11, or (c) Liens allowed under Section 8.6.

    Section 6.12   TAXES.  The Borrower has filed all federal, state and local
tax returns required to be filed and has paid or made provision for the payment
of all material amounts of taxes due and payable pursuant to such returns and
pursuant to any assessments made against it or any of its property and all other
taxes, fees and other charges imposed on it or any of its property by any
governmental 


                                    17
<PAGE>


authority (other than taxes, fees or charges the amount or validity
of which is currently being contested in good faith by appropriate proceedings
and with respect to which reserves in accordance with GAAP have been provided on
the books of the Borrower).  No tax Liens have been filed and no material claims
are being asserted with respect to any such taxes, fees or charges.  The
charges, accruals and reserves on the books of the Borrower in respect of taxes
and other governmental charges are adequate.

    Section 6.13   TRADEMARKS, PATENTS.  The Borrower possesses or has the
right to use all of the patents, trademarks, trade names, service marks and
copyrights, and applications therefor, and all technology, know-how, processes,
methods and designs used in or necessary for the conduct of its business,
without known conflict with the rights of others.

    Section 6.14   INVESTMENT COMPANY ACT.  The Borrower is not an "investment
company" or a company "controlled" by an investment company within the meaning
of the Investment Company Act of 1940, as amended.

    Section 6.15   PUBLIC UTILITY HOLDING COMPANY ACT.  The Borrower is not a
"holding company" or a "subsidiary company" of a holding company or an
affiliate" of a holding company or of a subsidiary company of a holding company
within the meaning of the Public Utility Holding Company Act of 1935, as
amended.

    Section 6.16   SUBSIDIARIES.  Schedule 6.16 sets forth as of the date of
this Agreement a list of all Subsidiaries and the percentage ownership of each
class of equity ownership owned beneficially or of record by Hach Company or any
Subsidiary therein, and the jurisdiction of organization of each Subsidiary.

                                     ARTICLE VII
                                AFFIRMATIVE COVENANTS

    From the date of this Agreement and thereafter until the Commitment is
terminated or expires and the Loans and all other liabilities of the Borrower to
the Bank hereunder and under the Note has been paid in full, unless the Bank
shall otherwise expressly consent in writing, the Borrower will do all of the
following:

    Section 7.1    FINANCIAL STATEMENTS AND REPORTS.  Furnish to the Bank:

          (a)  As soon as available and in any event within 120 days after the 
    end of each fiscal year of the Borrower, the annual audit report of the 
    Borrower prepared on a consolidated basis and in conformity with GAAP, 
    consisting of at least statements of income, cash flows, and 
    stockholders' equity, and a consolidated balance sheet as at the end of 
    such year, setting forth in each case in comparative form corresponding 
    figures from the previous annual audit, certified without qualification 
    by independent certified public accountants of recognized standing 
    selected by the Borrower and acceptable to the Bank, together with any 
    management 


                                    18
<PAGE>


    letters, management reports or other supplementary comments or 
    reports to the Borrower or its board of directors furnished by such 
    accountants.

         (b)  Together with the audited financial statements required under
    Section 7.1(a), a statement by the accounting firm performing such audit
    stating that it has reviewed this Agreement and that in performing its
    examination nothing came to its attention that caused it to believe that
    any Default or Event of Default exists, or, if such Default or Event of
    Default exists, describing its nature.

         (c)  As soon as available and in any event within 45 days after the
    end of each fiscal quarter of each fiscal year, a copy of the unaudited
    financial statements of the Borrower prepared on a consolidated and
    consolidating basis in the same manner and format as the audit report
    referred to in Section 7.1(a), except for normal year end adjustments and
    the inclusion of footnotes signed by the Borrower's chief financial
    officer, consisting of at least consolidated statements of income, cash
    flows, and stockholders' equity for the Borrower for such quarter and for
    the period from the beginning of such fiscal year to the end of such
    quarter, and a consolidated balance sheet of the Borrower as at the end of
    such quarter.

         (d)  Together with the financial statements furnished by the Borrower
    under Sections 7.1(a) and 7.1(c), a statement in the form of Exhibit D
    hereto or other acceptable form signed by the chief financial officer of
    the Borrower demonstrating in reasonable detail compliance (or
    noncompliance, as the case may be) with each of the financial ratios and
    restrictions contained in Article VIII and Exhibit A and stating that as at
    the date of each such financial statement there did not exist any Default
    or Event of Default or, if such Default or Event of Default existed,
    specifying the nature and period of existence thereof and what action the
    Borrower proposes to take with respect thereto (a "Compliance
    Certificate").

         (e)  Within seven (7) days of becoming aware of any Default or Event
    of Default, a notice describing the nature thereof and the remedial action
    the Borrower proposes to take with respect thereto.

         (f)  Immediately upon becoming aware of the occurrence, with respect
    to any Plan, of any Reportable Event (other than a Reportable Event for
    which the reporting requirements have been waived by PBGC regulations) or
    any "prohibited transaction" (as defined in Section 4975 of the Code), a
    notice specifying the nature thereof and what action the Borrower proposes
    to take with respect thereto, and, when received, copies of any notice from
    PBGC of intention to terminate or have a trustee appointed for any Plan.

         (g)  Promptly upon the mailing or filing thereof, copies of all
    financial statements, reports, proxy statements and other items filed with
    the Securities Exchange Commission.

         (h)  Immediately upon becoming aware of the occurrence thereof, notice
    of the institution of any litigation, arbitration or governmental
    proceeding, or the rendering of a 


                                    19
<PAGE>



    judgment or decision in such litigation or proceeding, which could 
    constitute an Adverse Event, and the steps being taken by the Person(s) 
    affected by such proceeding.

         (i)  Immediately upon becoming aware of the occurrence thereof, notice
    of any violation as to any environmental matter by the Borrower and of the
    commencement of any judicial or administrative proceeding relating to
    health, safety or environmental matters (i) in which an adverse
    determination or result could result in the revocation of or have a
    material adverse effect on any operating permits, air emission permits,
    water discharge permits, hazardous waste permits or other permits held by
    the Borrower which are material to the operations of the Borrower or (ii)
    which will or threatens to impose a material liability on the Borrower to
    any Person or which will require a material expenditure by the Borrower to
    cure any alleged problem or violation.

         (j)  From time to time, such other information regarding the business,
    operation and financial condition of the Borrower as the Bank may
    reasonably request.

    Section 7.2    ENTITY EXISTENCE.  Subject to Section 8.1 in the instance of
a Subsidiary, maintain its entity existence in good standing under the laws of
its jurisdiction of organization and its qualification to transact business in
each jurisdiction in which the failure to so qualify might materially adversely
affect the consolidated financial condition or operations of the Borrower.

    Section 7.3    INSURANCE.  Maintain with financially sound and reputable
insurance companies such insurance as may be required by law and such other
insurance in such amounts and against such hazards as is customary in the case
of reputable corporations of similar sizes engaged in the same or similar
business and similarly situated.

    Section 7.4    PAYMENT OF TAXES AND CLAIMS.  File all tax returns and
reports which to the knowledge of the Borrower are required by law to be filed
by it and pay before they become delinquent all taxes, assessments and
governmental charges and levies imposed upon it or its property and all claims
or demands of any kind (including, without limitation, those of suppliers,
mechanics, carriers, warehouses, landlords and other like Persons) which, if
unpaid, would result in the creation of a Lien upon its property (other than
taxes, assessments and other governmental charges imposed by foreign
jurisdictions which in the aggregate are not material to the business, financial
conditions, or assets of the Borrower and its Subsidiaries on a consolidated
basis); provided that the foregoing items need not be paid if they are being
contested in good faith by appropriate proceedings, and as long as the
Borrower's title to its property is not materially adversely affected, its use
of such property in the ordinary course of its business is not materially
interfered with and adequate reserves with respect thereto have been set aside
on the Borrower's books in accordance with GAAP.

    Section 7.5    INSPECTION.  Permit any Person designated by the Bank to
visit and inspect any of its properties, corporate books and financial records,
to examine and to make copies of its books of accounts and other financial
records, and to discuss the affairs, finances and accounts of the Borrower with,
and to be advised as to the same by, its officers at such reasonable times and
intervals as the Bank 


                                    20
<PAGE>

may designate.  In this regard Borrower shall permit an audit of its books 
and records, semiannually on not less than 15 days prior written notice.  So 
long as no Event of Default exists, the expenses of the Bank for such visits, 
inspections and examinations shall be at the expense of the Bank, but any 
such visits, inspections, and examinations made while any Event of Default is 
continuing shall be at the expense of the Borrower.

    Section 7.6    MAINTENANCE OF PROPERTIES.  Maintain its properties used or
useful in the conduct of its business in good condition, repair and working
order (ordinary wear and tear excepted), and supplied with all necessary
equipment, and make all necessary repairs, renewals, replacements, betterments
and improvements thereto, all as may be necessary so that the business carried
on in connection therewith may be properly and advantageously conducted at all
times; provided, however that nothing in this section shall prevent the Borrower
or any of its Subsidiaries from discontinuing the operation and maintenance of
any of its properties if such discontinuance is, in the judgement of such
Borrower or Subsidiary, desirable in the conduct of its or their business and
which does not in the aggregate materially adversely affect the financial
condition, business or assets of the Borrower and its Subsidiaries on a
consolidated basis.

    Section 7.7    BOOKS AND RECORDS.  Keep adequate and proper records and
books of account in which full and correct entries will be made of its material
dealings, business and affairs.

    Section 7.8    COMPLIANCE.  Comply in all respects with all laws, rules,
regulations, orders,writs, judgments, injunctions, decrees or awards to which it
may be
subject the non-compliance with which could have a materially adverse effect on
the business, operations, financial conditions or properties of the Borrower or
on the ability of the Borrower to perform its obligations under this Agreement.

    Section 7.9    ERISA.  Maintain each Plan in compliance with all material
applicable requirements of ERISA and of the Code and with all material
applicable rulings and regulations issued under the provisions of ERISA and of
the Code.

    Section 7.10   ENVIRONMENTAL MATTERS.  Observe and comply with all laws,
rules, regulations and orders of any government or government agency relating to
health, safety, pollution, hazardous materials or other environmental matters to
the extent non-compliance could result in a Adverse Event.

    Section 7.11   FINANCIAL COVENANTS.  Comply with the financial covenants
described on Exhibit A hereto.

    Section 7.12   ACCREDITATION.  Maintain and comply with the terms of all
licenses, permits and accreditations necessary to conduct their businesses as
presently being conducted.  

    Section 7.13   FORM U-1.  Furnish to the Bank, upon its request, a
statement in conformity with the requirements of Federal Reserve Form U-1
referred to in Regulation U.


                                    21
<PAGE>


    Section 7.14   MANAGEMENT.  Advise the Bank in writing with respect to any
change in senior management (president, chief executive officer or chief
financial officer) within 30 days of such change.

                                     ARTICLE VIII
                                  NEGATIVE COVENANTS

    From the date of this Agreement and thereafter until the Commitment is
terminated or expires and the Loans and all other liabilities of the Borrower to
the Bank hereunder and under the Note have been paid in full, unless the Bank
shall otherwise expressly consent in writing, the Borrower will not do any of
the following:

    Section 8.1    MERGER.  Merge or consolidate with or merge into or with any
other corporation, or purchase or otherwise acquire all or substantially all of
the assets of any person or sell, transfer, lease or otherwise dispose of all or
any substantial part of its assets to any person, or permit any of its
subsidiaries to do so, except:

         (a)  the merger, consolidation or liquidation of any Subsidiary into
    the Borrower or with any other Subsidiary of the Borrower (the surviving 
    entity thereof also being a Subsidiary);

         (b)  the Borrower may merge with another entity provided Borrower is
    the surviving entity; or

         (c)  the merger, consolidation or liquidation into the Borrower or any
    Subsidiary, or the acquisition by the Borrower or any Subsidiary of all or
    substantially all the assets, of any other person other than Hach Company,
    but only if:

              (i)  such Person is engaged primarily in a business which is in
    substantially the same fields, related fields or supporting fields as
    the existing business of the Borrower or such Subsidiary, as the
    case may be; and

              (ii) any such merger or acquisition would not cause the Borrower
    to violate any other provision of this Agreement;

provided, however, that any such action of the nature referred to in this
Section 8.1 shall only be permitted if no Event of Default has occurred and is
continuing or would result therefrom.

    Section 8.2    SALE OF ASSETS.  Sell, transfer, lease or otherwise convey
all or any substantial part of its assets except for sales and leases of
equipment in the ordinary course of business which will not impair or impede the
conduct of the Borrower's business and except for sales or other transfers by a
Subsidiary to the Borrower or another wholly-owned Subsidiary.

    Section 8.3    PLAN DEFICIENCY.  Permit any condition to exist in
connection with any Plan which might constitute grounds for the PBGC to
institute proceedings to have such Plan terminated or 


                                    22
<PAGE>



a trustee appointed to administer such Plan, permit any Plan to terminate 
under any circumstances which would cause the lien provided for in Section 
4068 of ERISA to attach to any property, revenue or asset of the Borrower or 
any Subsidiary or permit the underfunded amount of Plan benefits guaranteed 
under Title IV of ERISA to exceed $250,000.

    Section 8.4    CHANGE IN NATURE OF BUSINESS.  Make any material change in
the nature of the business of the Borrower provided, however, that the Borrower
may expand its business through the application of its existing technologies to
additional fields such as the food and beverage field, and medical and clinical
fields.

    Section 8.5    INVESTMENTS.  Acquire for value, make, have or hold any
Investments, except:

         (a)  Investments in municipal bonds having an investment grade rating
    and investments in the types of securities outstanding on the date hereof
    and listed on Schedule 8.5;

         (b)  Travel, moving expense, entertainment and other similar advances
    to officers and employees in the ordinary course of business;

         (c)  Investments in readily marketable direct obligations of the
    United States of America having maturities of three years or less from the
    date of acquisition;

         (d)  Certificates of deposit or bankers' acceptances, each maturing
    within one year from the date of acquisition, issued by any commercial bank
    organized under the laws of the United States or any State thereof which
    has (i) combined capital, surplus and undivided profits of at least
    $100,000,000, and (ii) an investment grade credit rating with respect to
    its unsecured indebtedness from a nationally recognized rating service that
    is satisfactory to the Bank;

         (e)  Commercial paper maturing within 270 days from the date of
    issuance and given the highest rating by a nationally recognized rating
    service;

         (f)  Repurchase agreements relating to securities issued or guaranteed
    as to principal and interest by the United States of America;

         (g)  Extensions of credit in the nature of accounts receivable or
    notes receivable arising from the sale of goods and services in the
    ordinary course of business;

         (h)  Shares of stock, obligations or other securities received in
    settlement of claims arising in the ordinary course of business; and

         (i)  Investments in subsidiaries or entities engaged in a similar
    business to that of the Borrower provided, however, that any such
    investment shall only be permitted if no Event of Default has occurred and
    is continuing or would result therefrom. 


                                    23
<PAGE>

    
         (j)  Investments in the $1.00 par value common stock of Hach Company  
including approximately 3,157,220 shares owned by Lawter International, Inc.

         (k)  Investments in the voting or nonvoting common stock of Hach
Company for general corporate purposes.

    Section 8.6    INDEBTEDNESS.  Incur, create, issue, assume or suffer to
exist any Indebtedness, except:

         (a)  Indebtedness under this Agreement;

         (b)  Current liabilities, other than for borrowed money, incurred in
    the ordinary course of business;

         (c)  Indebtedness existing on the date of this Agreement and disclosed
    on Schedule 8.6 hereto;

         (d)  Indebtedness secured by Liens permitted under Section 8.7 hereof; 

         (e)  Indebtedness consisting of endorsements for collection, deposit
    or negotiation and warranties of products or services, in each case
    incurred in the ordinary course of business; 

         (f)  Indebtedness for Capitalized Leases in as permitted under 
    Section 8.10 hereof; and

         (g)  Intercompany indebtedness among Subsidiaries and the Borrower.

         (h)  Indebtedness of an entity acquired by the Borrower, at the time
    of acquisition, provided, however, that:

              (i) any such indebtedness shall only be permitted if no Event of
          Default has occurred and is continuing or would result therefrom;

              (ii) such entity is maintained as a separate corporate or other
          limited liability subsidiary; and 

              (iii) such indebtedness is nonrecourse to Borrower.

     Section 8.7    LIENS.  Create, incur, assume or suffer to exist any
Lien with respect to any property, revenues or assets now owned or
hereafter arising or acquired at any time, except:


                                    24
<PAGE>


         (a)  Deposits or pledges to secure payment of workers' compensation,
    unemployment insurance, old age pensions or other social security 
    obligations, in the ordinary course of business of the Borrower;

         (b)  Liens for taxes, fees, assessments and governmental charges not
    delinquent or to the extent that payments therefor shall not at the time be
    required to be made in accordance with the provisions of Section 7.4;

         (c)  Liens of carriers, warehousemen, mechanics and materialmen, and
    other like Liens arising in the ordinary course of business, for sums not
    due or to the extent that payment therefor shall not at the time be
    required to be made in accordance with the provisions of Section 7.4;

         (d)  Deposits to secure the performance of bids, trade contracts,
    leases, statutory obligations and other obligations of a like nature
    incurred in the ordinary course of business; and

         (e)  Liens incident to the acquisition of equipment pursuant to
    Capitalized Leases permitted under Section 8.10 hereof.

         (f)  Liens incurred in the ordinary course of business in connection
    with workmen's compensation, unemployment insurance or other forms of
    governmental insurance or benefits, or to secure the performance of
    tenders, statutory obligations, leases and contracts (other than for
    borrowed money) entered into in the ordinary course of business or to
    secure obligations on surety or appeal bonds.

    Section 8.8    CONTINGENT LIABILITIES.  Either: (i) endorse, guarantee,
contingently agree to purchase or to provide funds for the payment of, or
otherwise become contingently liable upon, any obligation of any other Person,
except by the endorsement of negotiable instruments for deposit or collection
(or similar transactions) in the ordinary course of business, or (ii) agree to
maintain the net worth or working capital of, or provide funds to satisfy any
other financial test applicable to, any other Person.

    Section 8.9    TRANSACTIONS WITH RELATED PARTIES.  Enter into or be a party
to any transaction or arrangement, including, without limitation, the purchase,
sale lease or exchange of property or the rendering of any service, with any
affiliated entity other than a wholly-owned Subsidiary, except in the ordinary
course of and pursuant to the reasonable requirements of the Borrower's or the
applicable Subsidiary's business and upon fair and reasonable terms to the
Borrower than would be obtained in a comparable arm's-length transaction with an
unaffiliated Person.

    Section 8.10  CAPITAL EXPENDITURES.  Make, incur or become liable for
Capital Expenditures in excess of the amount in any fiscal year of Borrower, as
set forth on Exhibit A hereto.


                                    25
<PAGE>


                                      ARTICLE IX
                            EVENTS OF DEFAULT AND REMEDIES

    Section 9.1    EVENTS OF DEFAULT.  The occurrence of any one or more of the
following events shall constitute an Event of Default:

         (a)  The Borrower shall fail to make when due, whether by acceleration
    or otherwise, any payment of principal required to be made to the Bank
    pursuant to the Loan Documents;

         (b)  The Borrower shall fail to pay any interest or fees or other 
    amounts owing hereunder within three (3) Business Days after the same 
    shall become due and payable whether at the Revolving Credit Maturity 
    Date or any accelerated date of maturity or at any other date fixed for 
    payment;

         (c)  Any representation or warranty made or deemed to have been made
    by or on behalf of the Borrower in the Loan Documents or on behalf of the
    Borrower in any certificate, statement, report or other writing furnished
    by or on behalf of the Borrower to the Bank pursuant to the Loan Documents
    shall prove to have been false or misleading in any material respect on the
    date as of which the facts set forth are stated or certified or deemed to
    have been stated or certified;
         
         (d)  The Borrower shall fail to comply with any agreement, covenant,
    condition, provision or term contained in the Loan Documents to which it is
    a party (and such failure shall not constitute an Event of Default under
    any of the other provisions of this Section 9.1) and such failure to comply
    shall continue for 30 calendar days after notice thereof to the Borrower by
    the Bank;

         (e)  The Borrower shall become insolvent or shall generally not pay
    its debts as they mature or shall apply for, shall consent to, or shall
    acquiesce in the appointment of a custodian, trustee or receiver of the
    Borrower or for a substantial part of the property thereof or, in the
    absence of such application, consent or acquiescence, a custodian, trustee
    or receiver shall be appointed for the Borrower or for a substantial part
    of the property thereof and shall not be discharged within 60 days;

         (f)  Any bankruptcy, reorganization, debt arrangement or other
    proceedings under any bankruptcy or insolvency law shall be instituted by
    or against the Borrower and, if instituted against the Borrower or a
    Subsidiary, shall have been consented to or acquiesced in by the Borrower
    or shall remain undismissed for 60 days, or an order for relief shall have
    been entered against the Borrower, or the Borrower shall take any corporate
    action to approve institution of, or acquiescence in, such a proceeding;

         (g)  Any dissolution or liquidation proceeding shall be instituted by
    or against the Borrower and, if instituted against the Borrower, shall be
    consented to or acquiesced in by the 
    


                                    26
<PAGE>


    Borrower or shall remain for 60 days undismissed, or the Borrower shall 
    take any corporate action to approve institution of, or acquiescence in, 
    such a proceeding;

         (h)  A judgment or judgments for the payment of money in excess of the
    sum of $250,000 in the aggregate shall be rendered against the Borrower and
    the Borrower shall not discharge the same or provide for its discharge in
    accordance with its terms, or procure a stay of execution thereof, prior to
    any execution on such judgments by such judgment creditor, within 30 days
    from the date of entry thereof, and within said period of 30 days, or such
    longer period during which execution of such judgment shall be stayed,
    appeal therefrom and cause the execution thereof to be stayed during such
    appeal;

         (i)  The institution by the Borrower or any ERISA Affiliate of steps
    to terminate any Plan if in order to effectuate such termination, the
    Borrower or any ERISA Affiliate would be required to make a contribution to
    such Plan, or would incur a liability or obligation to such Plan, in excess
    of $250,000, or the institution by the PBGC of steps to terminate any Plan;

         (j)  Any Indebtedness of the Borrower (other than Indebtedness under
    this Agreement) in excess $250,000 shall be accelerated, or the Borrower
    shall fail to pay any such Indebtedness when due or, in the case of such
    Indebtedness payable on demand, when demanded, or any event shall occur or
    condition shall exist and shall continue for more than the period of grace,
    if any, applicable thereto and shall have the effect of causing, or
    permitting (any required notice having been given and grace period having
    expired) the holder of any such Indebtedness or any trustee or other Person
    acting on behalf of such holder to cause, such Indebtedness to become due
    prior to its stated maturity or to realize upon any collateral given as
    security therefor; or

         (k)  The Borrower shall suffer or incur a Change of Control.

         (l)  The Borrower shall fail to give written notice as provided in
Section 7.1(e)     hereof.

    Section 9.2    REMEDIES.  If (a) any Event of Default described in Section
9.1(e) or (f) shall occur with respect to the Borrower or any Subsidiary, the
Commitment shall automatically terminate and the outstanding unpaid principal
balance of the Notes, the accrued interest thereon and all other obligations of
the Borrower to the Bank under the Loan Documents shall automatically become
immediately due and payable; or (b) any other Event of Default shall occur and
be continuing, then the Bank at its sole option may take any or all of the
following actions: (i) declare the Commitment terminated, whereupon the
Commitment shall terminate, (ii) declare the outstanding unpaid principal
balance of the Note, the accrued and unpaid interest thereon and all other
obligations of the Borrower to the Bank under the Loan Documents to be
immediately due and payable, whereupon the Note, all accrued and unpaid interest
thereon and all such obligations shall immediately become due and payable, in
each case without further demand or notice of any kind, all of which are hereby
expressly waived, anything in this Agreement or in the Note to the contrary
notwithstanding, (iii) exercise all other rights 



                                    27
<PAGE>


and remedies under any Loan Document other instrument, document or agreement 
between the Borrower and the Bank, and (iv) enforce all rights and remedies 
under any applicable law.

                                      ARTICLE X
                                    MISCELLANEOUS

    Section 10.1   WAIVER AND AMENDMENT.  No failure on the part of the Bank or
the holder of the Note to exercise and no delay in exercising any power or right
hereunder or under any other Loan Document shall operate as a waiver thereof;
nor shall any single or partial exercise of any power or right preclude any
other or further exercise thereof or the exercise of any other power or right. 
The remedies herein and in any other instrument, document or agreement delivered
or to be delivered to the Bank hereunder or in connection herewith are
cumulative and not exclusive of any remedies provided by law.  No notice to or
demand on the Borrower not required hereunder or under the Note shall in any
event entitle the Borrower to any other or further notice or demand in similar
or other circumstances or constitute a waiver of the right of the Bank or the
holder of the Note to any other or further action in any circumstances without
notice or demand.  No amendment, modification or waiver of any provision of this
Agreement or consent to any departure by the Borrower therefrom shall be
effective unless the same shall be in writing and signed by the Bank, and then
such amendment, modification, waiver or consent shall be effective only in the
specific instances and for the specific purpose for which given.

    Section 10.2   EXPENSES AND INDEMNITIES.  Whether or not any Loan is made
hereunder, the Borrower agrees to reimburse the Bank upon demand for all
reasonable expenses paid or incurred by the Bank (including filing and recording
costs and fees and expenses of outside legal counsel) in connection with the
preparation, review, execution, delivery, amendment, modification,
interpretation, collection and enforcement of the Loan Documents.  The Borrower
agrees to pay, and save the Bank harmless from all liability for, any stamp or
other taxes which may be payable with respect to the execution or delivery of
the Loan Documents.  The Borrower agrees to indemnify and hold the Bank harmless
from any loss or expense which may arise or be created by the acceptance of
telephonic, telecopy or other instructions for making Loans or disbursing the
proceeds thereof.  The obligations of the Borrower under this Section 10.2 shall
survive any termination of this Agreement.

    Section 10.3   NOTICES.  Except when telephonic notice is expressly
authorized by this Agreement, any notice or other communication to any party in
connection with this Agreement shall be in writing and shall be sent by manual
delivery, facsimile transmission, overnight courier or United States mail
(postage prepaid) addressed to such party at the address specified on the
signature page hereof, or at such other address as such party shall have
specified to the other party hereto in writing.  All periods of notice shall be
measured from the date of delivery thereof if manually delivered, from the first
Business Day after the date of sending if sent by facsimile or overnight
courier, or from four days after the date of mailing if mailed.

    Section 10.4   JOINT AND SEVERAL SUCCESSORS.  The obligations of the
Borrower hereunder and under the Note shall be the joint and several obligation
of each of the entities constituting the 


                                    28
<PAGE>


Borrower.  This Agreement shall be binding upon the Borrower and the Bank and 
their respective successors and assigns, and shall inure to the benefit of 
the Borrower and the Bank and the successors and assigns of the Bank.  The 
Borrower shall not assign its rights or duties hereunder without the written 
consent of the Bank.

    Section 10.5   PARTICIPATION AND INFORMATION.  The Bank may sell 
participation interests in any or all of the Loans and in all or any portion 
of the Commitment to any Person.  The Bank may furnish any information 
concerning the Borrower in the possession of the Bank from time to time to 
participants and prospective participants and may furnish information in 
response to credit inquiries consistent with general banking practice.  Bank 
agrees to hold any confidential information that it may receive from the 
Borrower pursuant to this Agreement or any other Loan Document in confidence, 
except for disclosure:  (a) to legal counsel and accountants for the Borrower 
or Bank; (b) to other counsel and accountants for the Borrower or Bank; (b) 
to other professional advisors to the Borrower or Bank, provided that the 
recipient has delivered to such Bank, as applicable, a written 
confidentiality agreement substantially similar to this Section; (c) to 
regulatory officials having jurisdiction over Bank; (d) as required by law or 
legal process or in connection with any legal proceeding to which Bank and 
the Borrower (or any Subsidiary of the Borrower) are adverse parties; and (e) 
to another financial institution in connection with a disposition or proposed 
disposition to that financial institution of all or part of Bank's interests 
hereunder or a participation interest provided that the recipient has 
delivered to such Bank, as applicable, a written confidentiality agreement 
substantially similar to this Section.  Bank further agrees that it will not 
use any such confidential information in any activity or for any purpose 
other than the administration of the credit facilities extended to the 
Borrower under this Agreement.  For purposes of the foregoing, "confidential 
information": shall mean any information respecting the Borrower or its 
Subsidiaries reasonably considered to be, is treated as, and is marked as, 
confidential by the Borrower, other than (i) information previously filed 
with any governmental agency and available to the public, (ii) information 
previously published in any public medium from a source other than, directly 
or indirectly, Bank, (iii) information already known by Bank or the other 
party in question other than as a result of a breach of this Agreement, and 
(iv) information previously disclosed by the Borrower or any Subsidiary to 
any Person not associated with the Borrower without a written confidentiality 
agreement substantially similar to this Section. Nothing in this Section 
shall be construed to create or give rise to any fiduciary duty on the part 
of the Bank to the Borrower or any Subsidiary.

    Section 10.6   SEVERABILITY.  Any provision of the Agreement which is 
prohibited or enforceability in any jurisdiction shall, as to such 
jurisdiction, be ineffective to the extent of such prohibition or 
unenforceability without invalidating the remaining provisions hereof or 
affecting the validity or enforceability of such provision in any other 
jurisdiction.

    Section 10.7   CAPTIONS.  The captions or headings herein and any table 
of contents hereto are for convenience only and in no way define, limit or 
describe the scope or intent of any provision of this Agreement.

    Section 10.8   ENTIRE AGREEMENT.  This Agreement and the Notes embody the 
entire agreement and understanding between the Borrower and the Bank with 
respect to the subject matter 


                                    29
<PAGE>


hereof and thereof.  This Agreement supersedes all prior agreements and 
understandings relating to the subject matter hereof.

    Section 10.9   COUNTERPARTS.  This Agreement may be executed in any number
of counterparts, all of which taken together shall constitute one and the same
instrument, and either of the parties hereto may execute this Agreement by
signing any such counterpart.

    Section 10.10  GOVERNING LAW.  THE VALIDITY, CONSTRUCTION AND 
ENFORCEABILITY OF THIS AGREEMENT AND THE NOTES SHALL BE GOVERNED BY THE 
INTERNAL LAWS OF THE STATE OF COLORADO, WITHOUT GIVING EFFECT TO CONFLICT OF 
LAWS PRINCIPLES THEREOF, BUT GIVING EFFECT TO FEDERAL LAWS OF THE UNITED 
STATES APPLICABLE TO NATIONAL BANKS.

    Section 10.11  CONSENT TO JURISDICTION.  AT THE OPTION OF THE BANK, THIS 
AGREEMENT AND THE NOTES MAY BE ENFORCED IN ANY FEDERAL COURT OR COLORADO 
STATE COURT SITTING IN DENVER, COLORADO; AND THE BORROWER CONSENTS TO THE 
JURISDICTION AND VENUE OF ANY SUCH COURT AND WAIVES ANY ARGUMENT THAT VENUE 
IN SUCH FORUMS IS NOT CONVENIENT.  IN THE EVENT THE BORROWER COMMENCES ANY 
ACTION IN ANOTHER JURISDICTION OR VENUE UNDER ANY TORT OR CONTRACT THEORY 
ARISING DIRECTLY OR INDIRECTLY FROM THE RELATIONSHIP CREATED BY THIS 
AGREEMENT, THE BANK AT ITS OPTION SHALL BE ENTITLED TO HAVE THE CASE 
TRANSFERRED TO ONE OF THE JURISDICTIONS AND VENUES ABOVE-DESCRIBED, OR IF 
SUCH TRANSFER CANNOT BE ACCOMPLISHED UNDER APPLICABLE LAW, TO HAVE SUCH CASE 
DISMISSED WITHOUT PREJUDICE.

    Section 10.12  WAIVER OF JURY TRIAL.  THE BORROWER WAIVES ANY RIGHT TO A 
TRIAL BY JURY IN ANY ACTION OR PROCEEDING TO ENFORCE OR DEFEND ANY RIGHTS (a) 
UNDER THIS AGREEMENT OR UNDER ANY AMENDMENT, INSTRUMENT, DOCUMENT OR 
AGREEMENT DELIVERED OR WHICH MAY IN THE FUTURE BE DELIVERED IN CONNECTION 
HEREWITH OR (b) ARISING FROM ANY BANKING RELATIONSHIP EXISTING IN CONNECTION 
WITH THIS AGREEMENT, AND AGREES THAT ANY SUCH ACTION OR PROCEEDING SHALL BE 
TRIED BEFORE A COURT AND NOT BEFORE A JURY.



                                    30
<PAGE>



    IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be 
executed as of the date first above.

                             BORROWER

                             HACH COMPANY, a Delaware corporation

                             By:        /s/ Bruce J. Hach
                                _______________________________
                                Bruce J. Hach, President

                             Hach Company
                             5600 Lindbergh Drive
                             Loveland, CO 80538
                             Attn:  Gary R. Dreher
                             Telephone:(970) 669-3050
                             Telecopy: (970) 962-6740

                             HACH EUROPE S.A./N.V., a Belgian limited liability
                             company

                             By:        /s/ Bruce J. Hach
                                _______________________________
                                Bruce J. Hach, Director and Administrator

                             Hach Company
                             5600 Lindbergh Drive
                             Loveland, CO 80538
                             Attn:  Gary Dreher
                             Telephone:(970) 669-3050
                             Telecopy: (970) 962-6740


                             BANK

                             COLORADO NATIONAL BANK

                             By:     /s/ Brian T. McKinney
                                _________________________________
                             Title:  Vice President
                                _________________________________

                             28th and Arapahoe 
                             Boulder, CO  80306
                             Attn:  Brian McKinney
                             Telephone:  (303) 444-8876
                             Telecopy:   (303) 444-1081

                                      31
<PAGE>
                                 TABLE OF CONTENTS
  
                                                                          Page

ARTICLE I
                           DEFINITIONS AND ACCOUNTING TERMS. . . . . . . .  1
    1.1. DEFINED TERMS . . . . . . . . . . . . . . . . . . . . . . . . . .  1
    1.2. ACCOUNTING TERMS AND CALCULATIONS . . . . . . . . . . . . . . . .  6
    1.3. COMPUTATION OF TIME PERIODS . . . . . . . . . . . . . . . . . . .  6
    1.4. OTHER DEFINITIONAL TERMS. . . . . . . . . . . . . . . . . . . . .  6

ARTICLE II
                                   TERMS OF LENDING. . . . . . . . . . . .  6
    2.1  THE REVOLVING CREDIT LOANS. . . . . . . . . . . . . . . . . . . .  6
    2.2  BORROWING PROCEDURES FOR LOANS. . . . . . . . . . . . . . . . . .  7
    2.3  THE REVOLVING CREDIT NOTES.   . . . . . . . . . . . . . . . . . .  7
    2.4  USE OF PROCEEDS . . . . . . . . . . . . . . . . . . . . . . . . .  7

ARTICLE III
                                  INTEREST AND FEES. . . . . . . . . . . .  7
    3.1  INTEREST. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
    3.2  INTEREST ON REFERENCE RATE LOANS. . . . . . . . . . . . . . . . .  8
    3.3  INTEREST ON EURODOLLAR LOANS. . . . . . . . . . . . . . . . . . .  8
    3.4  SPECIAL PROVISIONS GOVERNING EURODOLLAR LOANS . . . . . . . . . . 10
    3.5  OTHER INTEREST RATES. . . . . . . . . . . . . . . . . . . . . . . 12
    3.6  FACILITY FEE. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.7  NONUSE FEE. . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.8  COMPUTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.9  PAYMENT DATES . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    3.10 ADDITIONAL COSTS. . . . . . . . . . . . . . . . . . . . . . . . . 12

ARTICLE IV
                   PAYMENTS, PREPAYMENTS, REDUCTION OR TERMINATION
                               OF THE CREDIT AND SETOFF. . . . . . . . . . 13
    4.1  REPAYMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
    4.2  MANDATORY PREPAYMENT. . . . . . . . . . . . . . . . . . . . . . . 13
    4.3  OPTIONAL PREPAYMENT . . . . . . . . . . . . . . . . . . . . . . . 14
    4.4  PREPAYMENT UPON FINANCIAL COVENANT NONCOMPLIANCE. . . . . . . . . 14
    4.5  PAYMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

ARTICLE V
                                 CONDITIONS PRECEDENT. . . . . . . . . . . 14
    5.1  CONDITIONS OF INITIAL LOAN. . . . . . . . . . . . . . . . . . . . 14
    5.2  CONDITIONS PRECEDENT TO ALL LOANS . . . . . . . . . . . . . . . . 15

<PAGE>

ARTICLE VI
                            REPRESENTATIONS AND WARRANTIES . . . . . . . . 16
    6.1  ORGANIZATION, STANDING, ETC.. . . . . . . . . . . . . . . . . . . 16
    6.2  AUTHORIZATION AND VALIDITY. . . . . . . . . . . . . . . . . . . . 16
    6.3  NO CONFLICTS NO DEFAULT . . . . . . . . . . . . . . . . . . . . . 16
    6.4  GOVERNMENT CONSENT. . . . . . . . . . . . . . . . . . . . . . . . 16
    6.5  FINANCIAL STATEMENTS AND CONDITION. . . . . . . . . . . . . . . . 17
    6.6  LITIGATION AND CONTINGENT LIABILITIES . . . . . . . . . . . . . . 17
    6.7  COMPLIANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
    6.8  ENVIRONMENTAL, HEALTH AND SAFETY LAWS . . . . . . . . . . . . . . 17
    6.9  ERISA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
    6.10 REGULATION U. . . . . . . . . . . . . . . . . . . . . . . . . . . 18
    6.11 OWNERSHIP OF PROPERTY; LIENS. . . . . . . . . . . . . . . . . . . 18
    6.12 TAXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
    6.13 TRADEMARKS, PATENTS . . . . . . . . . . . . . . . . . . . . . . . 18
    6.14 INVESTMENT COMPANY ACT. . . . . . . . . . . . . . . . . . . . . . 18
    6.15 PUBLIC UTILITY HOLDING COMPANY ACT. . . . . . . . . . . . . . . . 18
    6.16 SUBSIDIARIES. . . . . . . . . . . . . . . . . . . . . . . . . . . 19

ARTICLE VII
                                AFFIRMATIVE COVENANTS. . . . . . . . . . . 19
    7.1  FINANCIAL STATEMENTS AND REPORTS. . . . . . . . . . . . . . . . . 19
    7.2  ENTITY EXISTENCE. . . . . . . . . . . . . . . . . . . . . . . . . 20
    7.3  INSURANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
    7.4  PAYMENT OF TAXES AND CLAIMS . . . . . . . . . . . . . . . . . . . 21
    7.5  INSPECTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
    7.6  MAINTENANCE OF PROPERTIES . . . . . . . . . . . . . . . . . . . . 21
    7.7  BOOKS AND RECORDS . . . . . . . . . . . . . . . . . . . . . . . . 22
    7.8  COMPLIANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    7.9  ERISA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    7.10 ENVIRONMENTAL MATTERS . . . . . . . . . . . . . . . . . . . . . . 22
    7.11 FINANCIAL COVENANTS . . . . . . . . . . . . . . . . . . . . . . . 22
    7.12 ACCREDITATION . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    7.13 FORM U-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    7.14 MANAGEMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

ARTICLE VIII
                                  NEGATIVE COVENANTS . . . . . . . . . . . 22
    8.1  MERGER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    8.2  SALE OF ASSETS. . . . . . . . . . . . . . . . . . . . . . . . . . 23
    8.3  PLAN DEFICIENCY . . . . . . . . . . . . . . . . . . . . . . . . . 23
    8.4  CHANGE IN NATURE OF BUSINESS. . . . . . . . . . . . . . . . . . . 23
    8.5  INVESTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
    8.6  INDEBTEDNESS. . . . . . . . . . . . . . . . . . . . . . . . . . . 24

                                       ii

<PAGE>

    8.7  LIENS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
    8.8  CONTINGENT LIABILITIES. . . . . . . . . . . . . . . . . . . . . . 26
    8.9  TRANSACTIONS WITH RELATED PARTIES . . . . . . . . . . . . . . . . 26
    8.10 CAPITAL EXPENDITURES. . . . . . . . . . . . . . . . . . . . . . . 26

ARTICLE IX
                            EVENTS OF DEFAULT AND REMEDIES . . . . . . . . 26
    9.1  EVENTS OF DEFAULT . . . . . . . . . . . . . . . . . . . . . . . . 26
    9.2  REMEDIES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

ARTICLE X
                                    MISCELLANEOUS. . . . . . . . . . . . . 28
    10.1 WAIVER AND AMENDMENT. . . . . . . . . . . . . . . . . . . . . . . 28
    10.2 EXPENSES AND INDEMNITIES. . . . . . . . . . . . . . . . . . . . . 29
    10.3 NOTICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
    10.4 JOINT AND SEVERAL SUCCESSORS. . . . . . . . . . . . . . . . . . . 29
    10.5 PARTICIPATION AND INFORMATION . . . . . . . . . . . . . . . . . . 29
    10.6 SEVERABILITY. . . . . . . . . . . . . . . . . . . . . . . . . . . 30
    10.7 CAPTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
    10.8 ENTIRE AGREEMENT. . . . . . . . . . . . . . . . . . . . . . . . . 30
    10.9 COUNTERPARTS. . . . . . . . . . . . . . . . . . . . . . . . . . . 30
    10.10 GOVERNING LAW. . . . . . . . . . . . . . . . . . . . . . . . . . 30
    10.11 CONSENT TO JURISDICTION. . . . . . . . . . . . . . . . . . . . . 30
    10.12 WAIVER OF JURY TRIAL . . . . . . . . . . . . . . . . . . . . . . 31











                                         iii

<PAGE>


                                       EXHIBITS

EXHIBIT                 CONTENTS

A                       Loan Terms

B                       Notice of Borrowing

C                       Notice of Conversion/Continuation

D                       Compliance Certificate


                                      SCHEDULES

SCHEDULE                CONTENTS

6.5                     Financial Statements (Section 6.5)

6.6                     Litigation (Section 6.6)

6.6(a)                  Contingent Liabilities (Section 6.6)

6.11                    Existing Liens (Section 6.11 and 8.9)

6.16                    Subsidiaries (Section 6.16)

8.5                     Investments (Section 8.5)

8.6                     Existing Indebtedness (Section 8.6)



                                     iv

<PAGE>
                                      EXHIBIT A

                              I.  REVOLVING CREDIT LOANS


1.  Revolving Credit Commitment   -    (i)  $40,000,000 to June 30, 2000;

                                       (ii) $32,500,000 from July 1, 2000 to
                                            June 30, 2001; and

                                       (iii) $22,500,000 from July 1, 2001
                                             to the Revolving Credit
                                             Maturity Date

2.  Revolving Credit Maturity Date          -    July 1, 2002 

3.  Revolving Credit Rate

    (a)  Reference Rate Loans          -    Reference Rate minus one percent
                                            (1%)

    (b)  Eurodollar Loans              -    If the Cash Flow Leverage Ratio
                                            determined as set forth in the most
                                            recent compliance certificate and
                                            financial statements delivered to
                                            the Bank pursuant to Section 7.1
                                            is:

                                       (i) greater than 2 to 1, then the
                                       Revolving Credit Rate shall be the
                                       Adjusted Eurodollar Rate plus one and
                                       three quarters percent (1.75%) per
                                       annum;

                                       (ii) greater than 1.75 to 1 but less
                                       than or equal to 2 to 1, then the
                                       Revolving Credit Rate shall be the
                                       Adjusted Eurodollar Rate plus one and
                                       one-half percent (1.5%) per annum;

                                       (iii) greater than 1 to 1 but less than
                                       or equal to 1.75 to 1, then the
                                       Revolving Credit Rate shall be the
                                       Adjusted Eurodollar Rate plus one
                                       percent (1%) per annum; or

                                  A-1
<PAGE>

                                       (iv) less than or equal to 1 to 1, then
                                       the Revolving Credit Rate shall be the
                                       Adjusted Eurodollar Rate plus sixty-five
                                       hundredths percent (.65%) per annum.  

    Changes in the Cash Flow Leverage Ratio shall not affect the rate stated
above for outstanding Eurodollar Loans until expiration of the applicable
Interest Period.


                               III. FINANCIAL COVENANTS


1.  Current Ratio (current assets compared to current liabilities excluding the
principal payment required on the Revolving Credit Loans on the Revolving Credit
Maturity Date) of not less than 2 to 1.

2.  Cash Flow Leverage Ratio (Funded Debt compared to EBITDA) of not more than
3 to 1.

3.  Cash Flow Ratio (EBITDA divided by the sum of Interest Expense and
Mandatory Debt  Reduction excluding the principal payment required on the
Revolving Credit Loans on the Revolving Credit Maturity Date) of not less
than 1.75 to 1.

4.  Net Worth of not less than $25,000,000.

5.  Capital Expenditures for any fiscal year shall not exceed $13,000,000.


                                    IV. NONUSE FEE

    During the term of the Revolving Credit Commitment, the Borrower shall pay
a nonuse fee determined as follows.  If the Cash Flow Leverage Ratio determined
as set forth in the most recent compliance certificate and financial statements
delivered to the Bank pursuant to Section 7.1 is:

    (i)  greater than 2 to 1, then the Borrower shall pay to the Bank a 
nonuse fee equal to the product of one-quarter percent (.25%) annualized 
multiplied by the daily amount of the unused portion of the Revolving Credit 
Commitment; or

    (ii) less than or equal to 2 to 1, the Borrower shall pay to the Bank a 
nonuse fee equal to the product of one-eighth percent (.125%) annualized 
multiplied by the daily amount of the unused portion of the Revolving Credit 
Commitment.
    
Such fees shall be calculated daily, billed quarterly (calendar) and payable
within 30 days after invoice.


                                     A-2