EXHIBIT 10.173
                                INVESTMENT LETTER
                                       AND
                  MEMORANDUM OF SUBSCRIPTION/PURCHASE AGREEMENT

                                February 25, 1999

Pollution Research and Control Corp.
506 Paula Avenue
Glendale, California 91201

Gentlemen:

     In  connection  with the  acquisition  by the  undersigned  of 25,000 units
consisting of 25,000 shares of common stock, no par value per share (the "Common
Stock") and 25,000 common stock purchase  warrants  ("Warrants")  exercisable at
$0.75 per share, at a combined per unit price of $0.75 (75% of the bid price per
share of Common  Stock as of February  25,  1999),  of  Pollution  Research  and
Control Corp. (the  "Company"),  in  consideration  for the sum of $18,750.00 in
cash, the undersigned  wishes to advise you of his  understanding  of, agreement
with and/or representation of, the following:

     These securities are not being registered under the Securities Act of 1933,
as amended (the "Act"), on the ground that this sale is exempt from registration
under  Paragraph 4(1) or Paragraph 4(2) of the Act and the Rules and Regulations
promulgated  thereunder  as not  involving  any public  offering.  The Company's
reliance on such  exemption is predicated in part on the  representation  of the
undersigned  that he is acquiring  such  securities  for  investment for his own
account,  with no present intention of dividing his participation with others or
reselling  or  otherwise  distributing  the  same.  These  securities  which the
undersigned is acquiring are "restricted  securities" as that term is defined in
Rule 144 of the General  Rules and  Regulations  under the Act. The  undersigned
acknowledges  that  he  understands  that  the  securities  covered  hereby  are
unregistered  and  must be  held  indefinitely,  unless  they  are  subsequently
registered under the Act or an exemption from such registration is available.

     The undersigned  agrees that any and all certificates,  which may be issued
representing the securities acquired hereunder,  shall contain substantially the
following legend, which the undersigned has read and understands:

     The shares  represented by this  certificate  have not been registered
     under the  Securities  Act of 1933 (the  "Act"),  and are  "restricted
     securities"  as the term is  defined  in Rule 144 under  the Act.  The
     shares  may not be offered  for sale,  sold or  otherwise  transferred
     except pursuant to an effective  registration statement under the Act,
     or pursuant  to an  exemption  from  registration  under the Act,  the
     availability of which is to be established to the  satisfaction of the
     Company.


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     The undersigned understands that the above legend on the certificates would
limit their value, including their value as collateral.

     The  undersigned  further  acknowledges  that he  understands  that, if the
securities  have  been  held for a period  of at least  one year and if Rule 144
adopted  under  the Act is  applicable  (there  being no  representation  by the
Company that this Rule will be applicable),  then he may make only routine sales
of the securities in limited  amounts in a specified  manner in accordance  with
the terms and conditions of the Rule. The undersigned further  acknowledges that
he  understands  that, if Rule 144 is  applicable  (no assurance of which can be
made),  he may sell the  securities  without  quantity  limitation  in sales not
involving a market maker or through  brokerage  transactions only if he has held
the securities for at least two years. In case the Rule is not  applicable,  any
sales  made by the  undersigned  may be made only  pursuant  to other  available
exemption  from  registration  under  the  Act,  or  an  effective  registration
statement.

     The undersigned further acknowledges that he is aware that only the Company
can  file  a  registration  statement  or  an  offering  statement  pursuant  to
Regulation  A under the Act and that the  Company  has no  obligation  to do so,
other than via the registration rights referred to in the following  paragraphs.
The undersigned also has been advised and acknowledges that he understands that,
in the event Rule 144 is not  available,  the  circumstances  under which he can
sell the  securities,  absent  registration or compliance with Regulation A, are
extremely limited.

     In the event,  during the period commencing on the date hereof and expiring
three years from the date hereof (February 25, 2002), the Company shall register
any private, primary or secondary offering of any debt or equity security issued
or to be issued by it pursuant to a registration  statement under the Securities
Act of 1933, as amended,  pursuant to which the common stock and the  securities
underlying  the common stock purchase  warrants can be  registered,  the Company
shall in each such event notify the  undersigned in writing not less than thirty
(30) days prior to filing such registration  statement with the Commission,  and
the  undersigned  will  have the  right to  register  all of the  aforementioned
securities  therewith by notifying  the Company in writing  within  fifteen (15)
days  of  receipt  of  the  Company's  notice,  requesting  registration  of the
securities and setting forth the intended method of distribution  and such other
data or information as the Company or its counsel reasonably shall require.  Any
registration  costs shall be borne by the Company,  except for sales commissions
and  related  fees  and/or   transfer  taxes  incurred  if  the  securities  are
subsequently sold.

     Warrants:  The  purchase  rights  evidenced  by the common  stock  purchase
warrants  may be  exercised  in whole or in part at any  time,  and from time to
time,  on or after  the  date  hereof  but  before  February  25,  2002,  by the
undersigned through the presentation and surrender of the warrant to the Company
at its principal  office or at the office of the Company's stock transfer agent,
if any, accompanied by a duly executed Notice of Exercise,  in the form attached
hereto as Exhibit A.

     Adjustments: Stock Dividends,  Reclassifications,  Merger and Anti-Dilution
Provisions.

     (a)  If the Company  increases  or  decreases  the number of its issued and
          outstanding  shares of Common Stock,  or changes in any way the rights
          and privileges of such shares,  by means of (i) the Common Stock, (ii)
          

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          a forward or reverse stock split or other subdivision of shares, (iii)
          a consolidation  or combination  involving its Common Stock, or (iv) a
          reclassification or recapitalization  involving its Common Stock, then
          the  Warrant  Exercise  Price in effect at the time of such action and
          the number os Shares  shall be  proportionately  adjusted  so that the
          numbers,  rights,  and privileges  relating to the Securities shall be
          increased, decreased or changed in like manner.

     (b)  If at any time or from time to time the Company  should  issue or sell
          any shares of Common  Stock,  including  shares held in the  Company's
          Treasury,  without consideration or for a per share consideration less
          that the Warrant  Exercise price of $0.75 per share,  then the Warrant
          Exercise  price of $0.75 shall be  adjusted  downward  accordingly  to
          equal the per share  consideration  received by the  Company  upon the
          issuance or sale of its Common Stock.

     The undersigned further  acknowledges and represents to the Company that he
is purchasing the securities for his own account and not as a trustee or nominee
for any other person or persons,  and that the funds or  consideration  invested
are his own. The undersigned further  acknowledges and represents that there are
no  existing  legal  restrictions  applicable  to him which would  preclude  his
acquisition of the securities for investment purposes, as described hereinabove.
The  undersigned  further  represents that he has no present plans to enter into
any contract,  undertaking,  agreement or arrangement for resale,  distribution,
subdivision or fractionalization of the securities purchased hereby.

     The undersigned further acknowledges that he understands that an investment
in the Company is extremely speculative and subject to a high degree of risk. In
this  connection,  the  undersigned  understands  that he may  lose  his  entire
investment in the Company.

     The undersigned further  acknowledges and represents to the Company that he
is able  to  bear  the  economic  risk of  losing  his  entire  investment.  The
undersigned  further  acknowledges  and warrants that his overall  commitment to
investments which are not readily marketable is not  disproportionate to his net
worth  and  his  investment  in the  securities  will  not  cause  such  overall
commitment to become excessive.  The undersigned  further represents that he has
adequate means of providing for his current needs and personal contingencies and
that he has no need for  liquidity  in  connection  with his  investment  in the
securities.  The undersigned further  acknowledges that he fully understands and
agrees  that  the  price  of  the  Company's  securities  acquired  by  him  was
arbitrarily  determined  without  regard  to any  value of the  securities.  The
undersigned understands, additionally, that the price of the securities bears no
relation  to the value of the  assets or net worth of the  Company  or any other
criteria of value.  The undersigned is aware that no independent  evaluation has
been made with respect to the value of the securities.  The undersigned  further
understands  and agrees that shares of the common stock of the Company have been
or may in the  future be issued to certain  other  persons  for a  consideration
which may be less than the price paid by him for the securities.

     The undersigned further  acknowledges and represents to the Company that he
is knowledgeable and experienced in venture capital  investments in general and,
in particular, with respect to  investments  similar in nature  to an investment

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in the Company.  The frequency of the undersigned's  prior investments in stocks
(including restricted stocks), in general, and in high technology companies,  in
particular, and other investments, of whatever kind, is as follows (check one in
each column):

                                Restricted      High Technology
                    Stocks        Stocks          Companies          Other
                    ------        ------          ---------          -----

Frequently               x                                x              x
                    ------       -------          ---------          ------
Occasionally        ______             x          _________          ______
                                 -------
Never               ______       _______          _________          ______

     The undersigned  further  acknowledges that he is capable of evaluating the
merits and risks of the Company.

     The  undersigned  further  acknowledges  that  he has  such  knowledge  and
experience  in financial  and business  matters that he is capable of evaluating
the merits and risks of an investment  in the Company;  that he has been advised
by the Company to consult with counsel  regarding this  investment;  and that he
has relied upon the advice of such counsel,  accountants or other consultants as
he deems  necessary with regard to tax aspects,  risks and other  considerations
involved in the  investment.  The  undersigned's  educational  and  occupational
background  which renders him capable of evaluating the merits and risks of this
investment as follows:


         29 years as broker & investment banker
         -----------------------------------------------------------------------


     The undersigned has made, or caused to be made, such  investigation  of the
Company,  its  management  and its  operations  as he  considers  necessary  and
appropriate to enable him to make an informed decision regarding his investment.

     Prior to making his  investment,  the  undersigned  was presented  with and
acted upon the  opportunity  to ask  questions  of and receive  answers from the
Company and its management  relating to the Company and to obtain any additional
information  necessary to verify the accuracy of the information  made available
to him,

     Prior to making  his  investment,  the  undersigned  made  arrangements  to
conduct such inspection as he deems necessary of the books, records,  contracts,
instruments and other data relating to the Company.

     Before acquiring these  securities,  the undersigned was presented with and
understood  the Company's  business  plan,  including,  among other things,  the
nature of the Company, financial reports and management.


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     The  undersigned  agrees that,  upon the delivery of  certificates  for his
shares,  the undersigned  will execute and deliver to and for the benefit of the
Company any instruments the Company may require to evidence that the purchase of
his shares is for investment purposes only.

     On the date the  undersigned  acquired the  securities,  he had a net worth
(exclusive of home, furnishings and personal automobile) of:

         ( )      Less than $500,000
         ( )      $500,000 - $1,000,000
         (x)      $1,000,000 - $3,000,000
         ( )      $3,000,000 - $5,000,000
         ( )      More than $5,000,000

     Liquid assets constituted the following percentage of the undersigned's net
worth, or his joint net worth with his spouse, on the date of acquisition of the
securities:

         ( )      Less than 1%
         ( )      1% - 10%
         ( )      10% - 20%
         (x)      20% - 50%
         ( )      More than 50%

     The undersigned's approximate net taxable income (after regular deductions)
in each of the two most recent calendar years was:

         (x)      Less than $100,000
         ( )      $100,000-$200,000
         ( )      $200,000-$500,000
         ( )      $500,000-$1,000,000
         ( )     More than $1,000,000

     The  undersigned's  approximate  net taxable  income in the current year is
expected to be:

         ( )      Less than $100,000
         (x)      $100,000-$200,000
         (x)      $200,000-$500,000
         ( )      $500,000-$1,000,000
         ( )      More than $1,000,000

     Based  upon  the  foregoing,   the  undersigned  hereby   acknowledges  and
understands the high risk and  speculative  nature of the shares of common stock
of the Company which he is acquiring and the nature of the management, financial
condition,  and all other  pertinent  factors  regarding  the  Company  and this
investment.  The undersigned  further  represents and warrants that he has fully
satisfied himself with respect to the nature of this investment. The undersigned
further warrants  an represents that he  has received  no assurances of any kind

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relative to, nor have there been any representations  made by the Company or any
of its principals or affiliates regarding,  any potential  appreciation in value
of the securities being acquired by him. The undersigned  hereby  represents and
warrants  that he has  sufficient  knowledge  and  experience  in  business  and
financial  matters to  evaluate  the merits and risks of an  investment  of this
type. The undersigned further represents and acknowledges that he has made other
investments   in  speculative   businesses   and  is  generally   familiar  with
"restricted"  securities and he is otherwise  knowledgeable  with respect to the
Company and its proposed  operations.  Based upon the foregoing  understandings,
the undersigned hereby reaffirms his acquisition of the securities  described in
this Investment Letter and Memorandum of Subscription/Purchase Agreement.

     The  foregoing   correctly   expresses  this  intent,   understanding   and
acknowledgements of the undersigned.



                                              /s/  William T. Richey
                                              ----------------------------------
                                              William T. Richey

Current Residence Address:   4960 Lakeshore Drive, Littleton, Co 80123
Current Residence Telephone Number:  303-794-7411
SS. No.  ###-##-####
Current Occupation and/or Business Position:  Stock Broker
Current Business Telephone Number:  303-629-5555
Current Name of Business with which Associated:  Rocky Mtn. Securities
Name of Person connected with Pollution Research
   And Control Corp., with whom conferred
   Concerning this investment:  Al Gosselin
Relationship, if any, with the above mentioned Co. Rep: None


Agreed  and  accepted  this 11th day of  March,  1999,  on  behalf of  Pollution
Research and Control Corporation.



/s/ Albert E. Gosselin, Jr.
---------------------------
Albert E. Gosselin, Jr., President and CEO

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                               NOTICE OF EXERCISE

To:  POLLUTION RESEARCH AND CONTROL CORP.

     The undersigned,  the holder of the attached  warrant,  hereby  irrevocably
elects to exercise the purchase  right  represented  by that warrant for, and to
purchase  under that  warrant,  ___________  shares of Common Stock of POLLUTION
RESEARCH AND CONTROL CORP.  and herewith  makes payment of and requests that the
certificates  for  those  shares  be issued  in the name of,  and  delivered  to
__________________________________________,        whose        address       is
__________________________________________  and if said  number of shares  shall
not  be  all  the  shares  now  purchasable  under  the  attached  warrant,  the
undersigned  hereby requests that a new certificate be registered in the name of
and delivered to the undersigned for the balance of the shares purchasable under
the attached warrant.

DATED:___________________

                                ------------------------------------------------
                                                   (signature)

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

                                Note: the above signature must correspond
                                with the name written upon the face of the
                                attached warrant certificate unless the warrant
                                has been properly and lawfully assigned.


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