Exhibit 10.18
                                                            Serial Number [0300]

                  Void after 5:00 p.m.,  Chicago  Time,  on May 31, 2001 (unless
extended as provided below)

                                                                               
                                                    Warrant to Purchase certain
                                                    Shares of Common Stock,
                                                    dated June 1, 1996.


                                 CERTIFICATE OF
                        WARRANT TO PURCHASE COMMON STOCK
                                       OF
                            CHEUNG LABORATORIES, INC.

This Is To Certify  That,  FOR CASH AND OTHER VALUE  RECEIVED,  NACE  RESOURCES,
INC., a Delaware corporation  ("NACE"),  its nominees,  or assigns (hereinafter,
the  "Holder(s)")  are entitled to purchase,  subject to the  provisions of this
Warrant (its  successors,  divisions or  additions),  from Cheung  Laboratories,
Inc., a corporation  duly organized,  in good standing within its domicile,  and
whose offices as of the date hereof are at 10220-1 Old Columbia Road,  Columbia,
MD 21046 (hereinafter, the "Company"),  restricted and legended shares of common
stock of the  Company  ("Common  Stock") at a purchase  price equal to Forty One
Cents  ($00.41 U.S.) per share in such amounts and at such times as are provided
herein.

The number of shares of Common  Stock to be received  upon the  exercise of this
Warrant  and the  price to be paid for a share of Common  Stock may be  adjusted
from time to time as hereinafter set forth.

Supplementing, notwithstanding, and in support of the foregoing, the Company and
the original Holder hereof  ("Nace"),  intend that the number of shares issuable
hereunder  shall  be  396,719,   which  represents  1.875%  of  the  issued  and
outstanding Common Stock. In the event the Company fails to redeem an additional
4,000,000 shares of the Common Stock from Gao Yu Wen on or before June 30, 1997,
the original  Holder hereof shall be entitled to a warrant on identical terms to
purchase an additional 75,000 shares.

The shares of Common Stock deliverable upon such exercise,  and as adjusted from
time to time, are  hereinafter  referred to as "Warrant  Stock" and the exercise
price for a share of Common  Stock in  effect at any time and as  adjusted  from
time to time is hereinafter sometimes referred to as the "Exercise Price".


                                      - 1 -









The term "Warrant" used above and throughout  this  Certificate  shall mean this
Warrant or successor  Warrants issued in exchange for it for any reason pursuant
to the terms and condition contained herein.

         (i) Exercise of Warrant.  Subject to the provisions of paragraphs 6 and
7 hereof,  this Warrant may be exercised in whole or in part at any time or from
time to time on or after  June 1, 1996 but not later  than  5:00  p.m.,  Chicago
Time,  on June  1,  2001 or if June  1,  2001  is a day on  which  U.S.  banking
institutions  are  authorized by law to close,  then on the next  succeeding day
which  shall not be such a day,  by  presentation  and  surrender  hereof to the
Company or at the office of its stock transfer agent, if any, with a copy of the
Purchase Form attached  hereto duly executed and  accompanied  by payment of the
Exercise  Price for the number of shares  specified in such form,  together with
all federal and state  taxes  applicable  upon such  exercise,  if any,  and the
Company shall  promptly issue and deliver stock  certificates  for the number of
shares purchased to the Holder hereof within two (2) business days in conformity
with  industry  practice.  The Company may  unilaterally  extend the time within
which this Warrant may be exercised but is not obligated to do so.

If this  Warrant  should be  exercised  in part  only or all or a portion  of it
renewed as provided for in paragraph 7 hereof or otherwise,  the Company  shall,
upon  surrender  of this  Warrant  for  cancellation,  execute and deliver a new
Warrant,  containing  terms and  conditions  identical to this Warrant except as
provided  for herein,  evidencing  the right of the  Holder(s)  to purchase  the
balance of the shares purchasable hereunder.

Upon receipt of this Warrant,  the executed Purchase Form and the Exercise Price
by the  Company  or,  if then  applicable,  by its  stock  transfer  agent,  the
Holder(s)  shall be deemed to be the holder(s) of record of the shares of Common
Stock issuable upon such exercise, notwithstanding that the stock transfer books
of the  Company  shall  then be closed or that  certificates  representing  such
shares of Common Stock shall not then be actually  delivered  to the  Holder(s),
their  agents or  designees.  The  Company  shall keep  detailed  records of the
disposition of this,  successor  Warrants,  and any Warrant issuable  hereunder,
each bearing a serial number, and shall make such records available to Holder(s)
or their agents upon request.

         (ii) Reservation of Shares.  The Company hereby represents and warrants
that at all times subsequent  hereto there shall be reserved for issuance and/or
delivery upon exercise of this Warrant such number of shares of its Common Stock
as shall be required for issuance or delivery  upon  exercise of this Warrant or
any Warrant issuable hereunder.

         (iii)    Fractional Shares.  No fractional shares or scrip representing
fractional shares shall be issued upon exercise of this Warrant. With respect to
any fraction of a share called for upon any exercises hereof,  the Company shall
pay to the Holder(s) an amount in cash

                                      - 2 -









equal to such fraction multiplied by the current market value of such fractional
share, determined as follows:

                  (a) If the  Common  Stock is listed on a  national  securities
exchange or  admitted  to unlisted  trading  privileges  on such  exchange,  the
current  value shall be the last reported sale price of the Common Stock on such
exchange on the last  business day prior to the date of exercise of this Warrant
or if no such sale is made on such day on such exchange; or

                  (b) If the  Common  Stock  is not so  listed  or  admitted  to
unlisted  trading  privileges,  the current  value shall be the mean of the last
reported bid and asked prices reported by the National Association of Securities
Dealers  Automated  Quotation  System  (or,  if not so quoted on NASDQ),  by the
National  Quotation  Bureau,  Inc.) on the last business day prior to the day of
the exercise of this Warrant; or

                  (c) If the  Common  Stock  is not so  listed  or  admitted  to
unlisted  trading  privileges and bid and asked prices are not so reported,  the
current  fair market  value shall be an amount,  not less than book value or the
last known price paid by a  purchaser  for said Common  Stock,  determined  in a
reasonable manner as may be prescribed by the Board of Directors of the Company.

         (iv)  Exchange,  Assignment  or Loss of Warrant.  Subject to applicable
securities laws and the terms of the legend set forth in paragraph 11(b) hereof,
this Warrant  certificate is fully exchangeable and (by definition)  assignable,
without expense, at the option of the Holder(s), upon presentation and surrender
hereof to the Company or at the office of its stock transfer  agent, if any, for
other Warrant  certificates of different  denominations  entitling the Holder(s)
hereof to purchase in the  aggregate  the same number of shares of Common  Stock
purchasable hereunder.

Any assignment  hereof shall be made by surrender of this Warrant to the Company
or at the office of its stock transfer agent,  if any, with a written,  executed
assignment,  instructions  and funds  sufficient  to pay  transfer tax (if any);
whereupon the Company shall,  without charge,  execute and deliver a new Warrant
certificate  in  the  name  of the  assignee(s)  named  in  such  instrument  of
assignment  and this  Warrant  certificate  shall  promptly be  cancelled.  This
Warrant may be divided upon presentation  hereof at the office of the Company or
at the  office of its stock  transfer  agent,  if any,  together  with a written
notice,  specifying the names and  denominations in which new Warrants are to be
issued,  and signed by the Holder hereof.  The terms "Warrant" and "Warrants" as
used herein include any Warrants  issued in  substitution  for or replacement of
this Warrant, or into which this Warrant may be divided or exchanged.


                                      - 3 -









Upon  receipt by the Company of evidence  reasonably  satisfactory  to it of the
loss,  theft,  destruction  or mutilation  of this Warrant,  and, in the case of
loss, theft or destruction, of reasonably satisfactory indemnification, and upon
surrender  and  cancellation  of this Warrant,  if  mutilated,  the Company will
execute and deliver a new Warrant of like tenure and date.  Any such new Warrant
executed and delivered shall constitute an additional  contractual obligation on
the part of the Company,  whether or not this Warrant so lost, stolen, destroyed
or mutilated shall be at any time enforceable by anyone.  Nevertheless,  neither
the  Company or the  Holder(s)  anticipate  that this  Warrant or any  successor
Warrant shall itself be registered  (rather that the underlying  shares shall be
registered),  the Company shall not impose unreasonable burdens on the Holder(s)
with respect to indemnification if same becomes necessary.

         (v) Rights of the Holders.  The Holder(s)  shall not, by virtue hereof,
be  entitled to any rights of a  shareholder  in the  Company,  either at law or
equity,  and the rights of the Holder(s)  are limited to those  expressed in the
Warrant and are not  enforceable  against  the Company  except to the extent set
forth herein,  PROVIDED  HOWEVER,  that the Company  shall,  in a timely manner,
provide  Holder(s)  with a copy of each and  every  press  release,  mailing  to
shareholders  and  periodic  filing  with  the  U.S.   Securities  and  Exchange
Commission  made by the Company,  and provided that the Company shall be, at all
times during the tenure of this Warrant or its  successors,  in compliance  with
all of its contractual obligations to Riker and its affiliates.

         (vi)     Adjustments to Exercise Price and Number of Shares.

                  (a) The  Company  shall not be  required to give effect to any
adjustment in the Exercise  Price unless and until the net effect of one or more
adjustments,  determined as above provided,  shall have required a change of the
Exercise  Price by at least one cent,  ($00.01 U.S.) but when the cumulative net
effect of more than one  adjustment so determined  shall be to change the actual
Exercise  Price by at least one cent,  such change in the  Exercise  Price shall
thereupon be given effect.

Notwithstanding  anything else in this  paragraph  which might be interpreted to
the contrary,  should at any time subsequent to the issuance of this Warrant but
during the tenure of this Warrant and any renewals or extensions as are provided
for  herein,  any  person  or  entity  shall be  issued  an  option  or  warrant
exercisable  to purchase stock of the Company or stock of the Company is sold to
such person or entity at a price per share less than the then relevant  Exercise
Price as determined as provided herein, an immediate  adjustment in the Exercise
Price for this Warrant (and  successor  Warrants to this Warrant) shall be made.
The effect of this  adjustment  shall be to make the  Exercise  Price under this
Warrant equal to the lesser  exercise,  option or sale price  referenced  above.
However,  this adjustment  shall not have the effect of increasing the number of
shares purchasable hereunder.  Rather it shall reduce the aggregate amount paid,
assuming full exercise of this Warrant, to an amount equal to the

                                      - 4 -









number of shares  otherwise then purchasable  hereunder  multiplied by the newly
adjusted Exercise Price pursuant to this adjustment.

                  (b) The 396,719 shares issuable hereunder shall be adjusted so
that  number of shares  issuable  hereunder  shall be equal,  at all times after
issuance of this Warrant,  to 1.875% of the total issued and outstanding  Common
Stock of the Company  until the Company  completes  its next public  offering of
securities.

                  (c)  Whenever  reference  is made in this  paragraph  6 to the
issue or sale of shares of Common Stock,  the term "Common Stock" shall mean the
Common  Stock of the Company of the class  authorized  as of the date hereof and
any other  classes of stock  ranking on a parity with or  convertible  into such
Common  Stock  providing,  as is  contemplated,  it is the  Common  Stock of the
Company  which  is to be  offered  and  sold  at the  next  public  offering  of
registered  Common Shares of the Company.  However,  as of the date of grant and
sale of this  Warrant  and subject to the  provisions  of  paragraph  10 hereof,
shares  issuable  upon  exercise  hereof shall  include only shares of the class
designated as Common Stock of the Company as of the date hereof.

         (vii) Renewal of Exercise Rights. If, while this Warrant or any portion
of it remains in effect,  Holder(s)  wish to extend their rights to exercise all
or a portion of this Warrant which would  otherwise  expire and be lost to them,
they may do so by paying to the Company, a sum equal to five percent (5%) of the
then  relevant  Exercise  Price  pertaining to that portion of the Warrant which
would  otherwise  expire (the  "Renewal  Fee") and the Company shall extend that
portion of the Warrant  for a further  period of five (5) years from the date of
receipt of the Renewal Fee but, in no case,  beyond 5:00 p.m.,  Chicago Time, on
June 1, 2006, and shall issue a new Warrant,  identical in every respect to this
Warrant,  except that such new  Warrant  shall  reflect the fact that  Holder(s)
shall have an  additional  five (5) years to exercise  their  rights to purchase
that portion of the Warrant  Stock for which they have paid a Renewal Fee.  This
provision extends to this Warrant and all successor Warrants issuable hereunder.

This  provision is included  partially to permit  Holder(s) to coordinate  their
exercise of this  Warrant and sale of Warrant  Stock so as to minimize the Costs
and  Expenses  and  time of the  Company's  management  in  complying  with  the
provisions  of this  Warrant.  Payment of the  Renewal  Fee will  confirm no new
rights  upon the  Holder(s)  except to extend and renew the time  period  during
which Holder(s) may exercise existing rights under this Warrant.

         (viii)  Officer's  Certificate.  Whenever the  Exercise  Price shall be
adjusted as required by the provisions of paragraph 6 hereof,  the Company shall
forthwith file in the custody of its Secretary or an Assistant  Secretary at its
principal  office,  and with its stock  transfer  agent,  if any,  an  officer's
certificate  showing the adjusted  Exercise Price  determined as herein provided
and setting forth in reasonable detail the facts requiring such adjustment.

                                      - 5 -









Each such officer's  certificate shall be made available at all reasonable times
for inspection by the Holder(s) and the Company shall, forthwith after each such
adjustment,  deliver a copy of such  certificate  to the  Holder(s)  and each of
them.  Unless  disputed in writing by the Holder hereof within thirty (30) days,
such certificate shall be conclusive as to the correctness of such adjustment.

         (ix) General Notices to Warrant Holders. So long as any portion of this
Warrant (or any successor  Warrant) shall be outstanding  and unexercised (a) if
the  Company  shall pay any  dividend or make any  distribution  upon the Common
Stock or (b) if the  Company  shall  offer to the  holders  of Common  Stock for
subscription  or  purchase by them any shares of stock of any class or any other
rights or (c) if any capital reorganization of the Company,  reclassification of
the capital stock of the Company, consolidation or merger of the Company with or
into another corporation, sale, lease or transfer of all or substantially all of
the  property  and assets of the  Company to  another  corporation  or engage in
voluntary or involuntary dissolution,  liquidation or winding up of the company,
then the Company shall cause to be delivered to the  Holder(s),  at least thirty
(30) days prior to the relevant date, a notice containing a brief description of
the  proposed  action and  stating the date of which a record is to be taken for
the purpose of such dividend,  distribution of rights, or such reclassification,
reorganization,   consolidation,   merger,   conveyance,   lease,   dissolution,
liquidation  or winding up is to take place and the date, if any, is to be fixed
as of which the holders of Common  Stock of record shall be entitled to exchange
their  shares  of  Common  Stock of  record  for  securities  or other  property
deliverable upon such reclassification,  reorganization,  consolidation, merger,
conveyance, dissolution, liquidation or winding up.

         (x)  Reclassification,   Reorganization  or  Merger.  In  case  of  any
reclassification,  capital  reorganization or other change of outstanding shares
of Common  Stock of the Company  (other than a change in par value,  or from par
value to no par  value,  or from no par value to par value) or as a result of an
issuance  of  Common  Stock by way of  dividend  or other  distribution  or of a
subdivision or  combination,  or in case of any  consolidation  or merger of the
Company with or into another  corporation (other than a merger with a subsidiary
in which  merger the Company is the  continuing  corporation  and which does not
result  in any  reclassification,  capital  reorganization  or other  change  of
outstanding  shares of Common Stock of the class  issuable upon exercise of this
Warrant)  or in case of any sale or  conveyance  to another  corporation  of the
property  of  the  Company  as an  entirety  or  substantially  as  an  entirety
(collectively,  a "Triggering  Event"), the Company shall use good faith efforts
to cause  effective  provision to be made so that the  Holder(s)  shall have the
right  thereafter  (and  shall  have  said  right  for the same  period  of time
remaining  on any  unexercised  portion of this  Warrant),  without  immediately
exercising this Warrant,  to purchase the kind and amount of shares of stock and
other  securities and property  receivable upon such  reclassification,  capital
reorganization or other change, consolidation, merger, sale or conveyance.


                                      - 6 -









Any such provision  shall include  provision for  adjustments  which shall be as
nearly equivalent as may be practicable to the adjustments  provided for in this
Warrant.  However, in the event that the Company,  using its good faith efforts,
is unable to negotiate with the acquiring  entity the assumption of the Warrants
as provided in the preceding  portion of this paragraph,  then and in such event
this Warrant shall terminate,  to the extent not previously exercised, as of the
record date for such  transaction  upon and only upon  payment of a  "Retirement
Fee" to the Holder(s) hereof.

This Retirement Fee shall consist of the same kind of property  (including cash,
if any) to be received by the Company's  stockholders pursuant to the Triggering
Event (and, at parity with holders of Common Stock,  treated in accordance  with
all the other terms and conditions,  including  timing and manner of payment for
the purchase)  and the Company  herein  agrees that said  Retirement  Fee may be
arrived at by private  negotiation  between the Company and the Holder(s) or may
be arbitrated in accordance with the provisions herein provided.

However,  the Company now and  specifically  agrees  that,  in the event of such
private negotiation, it shall accept an amount to be paid to the Holder(s) (as a
senior  obligation of the company in any such  transaction)  in  arbitration  or
negotiation which is not less than the lowest sum per Warrant which shall result
from application of any then applicable  Warrant  Valuation  Techniques (such as
the  Black-Scholes  Model)  which may be applied  to  publicly  traded  warrants
covering  publicly traded common stock, it being intended by the Company and the
Holder(s) that the Retirement Fee should reflect: (a) the difference between the
purchase and exercise price per share plus (b) a warrant premium factor commonly
determinable by the aforementioned models. Said Retirement Fee shall be a senior
obligation of the Company and shall be paid to Holder(s)  from first proceeds of
any sale or merger in cash unless otherwise  negotiated  between the Company and
Nace (the original Holder).

All subsequent  Holders shall agree,  by acceptance of assignment of any portion
of the Warrant covered by this certificate,  to be bound by this provision.  All
costs and expenses directly  attributable to the determination of the Retirement
Fee (including but not limited to the costs of outside appraisal(s)) shall be at
the expense of the Company.

The foregoing  provisions of this section 10 shall similarly apply to successive
reclassification,  consolidations,  mergers, sales, or conveyances. In the event
that in any such  capital  reorganization  or  reclassification,  consolidation,
merger, sale or conveyance, additional shares of Common Stock shall be issued in
exchange, conversion,  substitution or payment, in whole or in part, for or of a
security of the Company other than Common Stock, any such issue shall be treated
as an issue of Common Stock covered by the  provisions of paragraphs 3, 6, and 9
hereof,  with the amount of the  consideration  received  upon the issue thereof
being  determined by the Board of Directors of the Company in consultation  with
the  Company's  auditors,  such  determination  to be final and  binding  on the
Holder(s).


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         (xi)     Transfer to Comply with the Securities Act of 1933.

                           (a)      This   Warrant  or  the Warrant Stock or any
other security issued or issuable upon exercise of this Warrant may not be sold,
transferred  or otherwise  disposed of except to a person who, in the opinion of
counsel reasonably satisfactory to the Company, is a person to whom this Warrant
or such Warrant Stock may legally be transferred  pursuant to paragraph 4 hereof
without  registration and without the delivery of a current prospectus under the
Securities  Act with  respect  thereto;  and then only  against  receipt  by the
Company of an agreement  from such person to comply with the  provisions of this
paragraph 11 with respect to any resale or other disposition of such securities.

                           (b)      The  Company  may cause the following legend
to be set  forth on each  certificate  representing  Warrant  Stock or any other
security  issued or  issuable  upon  exercise of this  Warrant  not  theretofore
distributed to the public  pursuant to paragraphs  12, 13, or 14 hereof,  unless
counsel for the Company is of the opinion as to any such  certificate  that such
legend is unnecessary.


                           "The  securities  represented by this certificate may
not be offered for sale,  sold or otherwise  transferred  except  pursuant to an
effective  registration  statement under the Securities Act of 1933 (the "Act"),
or pursuant to an exemption from registration under the Act."

         (xii)  Demand  Registration.  If at any  time,  after  the next  public
offering of registered  Common Shares of the Company (as previously  covered and
defined herein) Nace shall decide to sell or otherwise  dispose of Warrant Stock
then owned or to be owned upon intended  exercise of this Warrant by Nace,  then
Nace and only  Nace may give  written  notice  to the  Company  of the  proposed
disposition,  specifying  the  number of shares of  Warrant  Stock to be sold or
disposed  of and  requesting  that the Company  prepare and file a  registration
statement under the Securities Act of 1933, as amended (the  "Securities  Act"),
covering such Warrant Stock.

The Company  shall within 10 days  thereafter  give written  notice to the other
Holders of  Warrants  or  Warrant  Stock of such  request  and each of the other
Holders shall have the option for a period of 30 days after receipt by it (them)
of  notice  from the  Company  to  include  its  (their)  Warrant  Stock in such
registration  statement.  The  Company  shall use its best  efforts  to cause an
appropriate registration statement (the "Registration  Statement") covering such
Warrant  Stock to be filed with the  Securities  and  Exchange  Commission  (the
"Commission")  and to become effective as soon as reasonably  practicable and to
remain  effective until the completion of the  distribution of the Warrant Stock
to be offered or sold; provided,  however, that not more than once in any twelve
month period the Company  shall have the right to postpone for a period of up to
60 days any demand made pursuant to this

                                      - 8 -









Warrant if the underwriters for such offering advise the Company in writing that
market conditions make such a postponement advisable to the Company.

The Holder(s) whose Warrant Stock is (are) included in a Registration  Statement
is (are) hereinafter referred to as the "Selling Shareholder(s)".

Each notice  delivered by a Selling  Shareholder(s)  to the Company  pursuant to
this  paragraph 12 shall  specify the Warrant  Stock  intended to be offered and
sold by such Selling Shareholder(s), express such Selling Shareholder(s) present
intent to offer such Common Shares for distribution, and contain the undertaking
of such Selling  Shareholder(s)  to provide all information and materials and to
take all action as may be required in order to permit the Company to comply with
all applicable requirements of the Securities Act, and any rules and regulations
promulgated thereunder, and to obtain acceleration of the effective date of such
Registration Statement.

The  Company  shall  not be  obligated  to file  more  than  three  Registration
Statements  pursuant  to the  foregoing  provisions  of this  paragraph  12. The
Company  shall bear all of the Costs and  Expenses  (as  hereinafter  defined in
paragraph 20 hereof) of the first such registration.  The Selling Shareholder(s)
shall bear the costs and expenses of all further registrations  pursuant to this
paragraph 12. A demand for  registration  under this paragraph 12 will not count
as such until the Registration Statement has become effective.

         (xiii) Shelf Registration By Original Holder. At any time and from time
to time during the term of this Warrant or its  successors  (including  renewals
and  extensions  as provided  for herein)  Nace  Resources,  Inc.  and only Nace
Resources,  Inc.  (as the  original  Holder  hereof),  may demand (and  actually
expects) that the Company will file a Registration Statement with the Commission
for the registration of underlying shares issuable upon exercise of this Warrant
or any part  thereof,  whether or not said  Warrant  has,  in the  interim  been
assigned or re-assigned to other parties.

In this  event,  the  Company  shall pay all of the Costs and  Expenses  of said
Registration  for each such demand except that the Holder shall be  responsible,
if such  demand is made by the  Holder  during a period in which the  Company is
unable or unqualified to file a "short form" S-3 Statement (or its then relevant
equivalent) for paying all of the Costs and Expenses of said Registration  which
are  estimated to exceed costs for a similar  Registration  assuming the Company
had been, as of the date of the demand, a reporting  Company for three (3) years
and could file a "short form" statement.  In this case, the costs payable by the
Holder shall be determinable  by securities  counsel to the Company and both the
Company and the Holder are entitled to rely on such an estimate.

Once filed, the Company shall be obligated to continue this "shelf registration"
for the maximum time allowable under the then relevant regulations,  at its sole
expense.

                                      - 9 -










         (xiv)    Procedure  for  Demand  Registration.  In  connection with the
filing of a  Registration  Statement  pursuant to  paragraph  12 hereof,  and in
supplementation  and not in limitation of the  provisions  thereof,  the Company
shall:

                  (a) Notify the Selling  Shareholder(s) as to the filing of the
Registration Statement and of all amendments or supplements thereto filed thirty
(30) days prior to the effective date of said Registration Statement;

                  (b)  Notify the  Selling  Shareholder(s),  promptly  after the
Company  shall  receive  notice  thereof,  of the time  when  said  Registration
Statement became effective or when any amendment or supplement to any prospectus
forming a part of said Registration Statement has been filed;

(c) Notify the Selling  Shareholder(s)  promptly of any requestby the Commission
for the amending or supplementing of such  Registration  Statement or prospectus
or for additional information;

                  (d)  Prepare  and  promptly  file  with  the  Commission,  and
promptly notify the Selling  Shareholder(s)  of the filing of, and amendments or
supplements to such Registration  Statement or prospectus as may be necessary to
correct any  statements or omissions if, at any time when a prospectus  relating
to the Warrant Stock is required to be delivered  under the Securities  Act, any
event with respect to the Company  shall have  occurred as a result of which any
such  prospectus  or any other  prospectus  as then in effect  would  include an
untrue statement of a material fact or omit to state any material fact necessary
to make the statements therein not misleading; and, in prepare and file with the
Commission,  promptly  upon the Selling  Shareholder(s)'  written  request,  any
amendments or supplements to such Registration Statement or prospectus which may
be reasonably  necessary or advisable in connection with the distribution of the
Warrant Stock;

                  (e)   Prepare   promptly   upon   request   of   the   Selling
Shareholder(s) or any underwriters for the Selling Shareholder(s) such amendment
or amendments to such Registration Statement and such prospectus or prospectuses
as may be reasonably  necessary to permit  compliance  with the  requirements of
Section 10 (a) (3) of the Securities Act;

                  (f) Advise the Selling Shareholders promptly after the Company
shall  receive  notice or obtain  knowledge of the issuance of any stop order by
the Commission  suspending the effectiveness of any such Registration  Statement
or amendment  thereto or of the  initiation or threatening of any proceeding for
that  purpose,  and promptly use its best efforts to prevent the issuance of any
stop order or obtain its withdrawal promptly if such stop order would be issued;


                                     - 10 -









                  (g) Use its best  efforts  to  qualify  as soon as  reasonably
practicable  the Warrant Stock for sale under the securities or blue-sky laws of
such states and  jurisdictions  within the United  States as shall be reasonably
requested by the Selling Shareholder(s);  provided that the Company shall not be
required in  connection  therewith  or as a  condition  thereto to qualify to do
business,  to become  subject  to  taxation  or to file a consent  to service of
process generally in any of the aforesaid states or jurisdiction;

                  (h) Furnish the Selling Shareholder(s),  as soon as available,
copies of any Registration  Statement and each preliminary or final  prospectus,
or supplement or amendment required to be prepared pursuant thereto, all in such
quantities  as the  Selling  Shareholder(s)  may  from  time to time  reasonably
request, and;

                  (i) If requested by the Selling Shareholder(s),  enter into an
agreement with the underwriters of the Warrant Stock being registered containing
customary provisions and reflecting the foregoing.

         (xv)  Incidental  Registration.  Other than as covering in paragraph 13
hereof,  if at any time the Company  subsequent  to the next public  offering of
registered  Common  Shares  of  the  Company,  shall  propose  the  filing  of a
Registration  Statement on an appropriate  form under the Securities Act for the
registration  of  any  securities  of the  Company,  other  than a  registration
statement on Form S-4 or S-8 or any equivalent  form of  registration  statement
then in  effect,  then the  Company  shall  give the  Holder(s)  notice  of such
proposed  registration and shall include in any Registration  Statement relating
to such  securities  all or a portion of the  Warrant  Stock then owned or to be
owned by such  Holder(s),  which such Holder(s) shall request (such Holder(s) to
be  considered  "Selling  Shareholder(s)"),  by  notice  given  by such  Selling
Shareholder(s)  to the Company  within 15 business days after the giving of such
notice by the Company,  within 15 business  days after the giving of such notice
by the  Company,  to be so  included.  In the event of the  inclusion of Warrant
Stock  pursuant  to this  paragraph  15,  the  Company  shall bear the Costs and
Expenses of such registration; provided, however that the Selling Shareholder(s)
shall pay the fees and  disbursements  of their own counsel and,  pro-rata based
upon the number of shares of Warrant Stock  included  therein as these relate to
the total  number of Common  Shares to be offered or sold,  the  Securities  Act
registration  fees and underwriters  discounts and compensation  attributable to
the  inclusion of such Warrant  Stock;  and,  provided  further,  however,  that
amounts to which any person or entity  shall  become  entitled  pursuant to this
sentence  shall  not  include  amounts  which may  become  payable  pursuant  to
paragraphs  16 or 17 hereof.  Nothing in this  paragraph  15 shall  require  the
registration of Warrant Stock in a Registration Statement relating solely to (a)
securities to be issued by the Company in connection with the acquisition of the
stock or the assets of another  corporation,  or the merger or  consolidation of
any other corporation by or with the Company or any of its  subsidiaries,  or an
exchange  offer with any  corporation,  (b) securities to be offered to the then
existing  security  holders of the Company,  or (c)  securities to be offered to
employees of the Company. In the event the

                                     - 11 -









distribution  of securities of the Company  covered by a Registration  Statement
referred  to in this  paragraph  15 is to be  underwritten,  then the  Company's
obligation to include  Warrant Stock in such a Registration  Statement  shall be
subject, at the option of the Company, to the following further conditions:

                  (a)  The   distribution   for  the   account  of  the  Selling
Shareholders shall be underwritten by the same underwriters who are underwriting
the  distribution  of the  securities  for the account of the Company and/or any
other persons whose  securities are covered by such  Registration  Statement and
the Selling  Shareholder(s) shall enter into an agreement with such underwriters
containing customary provisions.

                  (b)  If  the  Selling   Shareholders   are   included  in  the
Registration  Statement and if the underwriting  agreement entered into with the
aforesaid  underwriters contains restrictions upon the sale of securities of the
Company,  other than the  securities  which are to be included  in the  proposed
distribution,  for a period not exceeding 90 days from the effective date of the
Registration Statement, then such restrictions shall be binding upon the Selling
Shareholder(s) with respect to any Warrant Stock not covered by the Registration
Statement and, if requested by the underwriter, the Selling Shareholder(s) shall
enter into a written agreement to that effect.

                  (c) If the  underwriters  shall state in writing that they are
unwilling to include any or all of the Selling  Shareholder(s)  Warrant Stock in
the proposed underwriting because such inclusion would materially interfere with
the  orderly  sale and  distribution  of the  securities  being  offered  by the
Company, then the number of the Selling  Shareholder(s)' shares of Warrant Stock
to be included shall be reduced pro rata on the basis of the number of shares of
Warrant   Stock   originally   requested   to  be  included   by  such   Selling
Shareholder(s),  or there  shall be no  inclusion  of the shares of the  Selling
Shareholder(s)  in the  Registration  Statement  not proposed  distribution,  in
accordance with such statement by the underwriters.

                  However,  if in such an event,  the Holder(s) hereof shall not
be able to include at least fifty percent (50%) of the Warrant Stock  originally
requested to be included,  then the Company  shall agree to pay all of the Costs
and Expenses of a Shelf Registration to be filed at a later date.

         (xvi)  Indemnification by the Company.  The Company shall indemnify and
hold  harmless  each Selling  Shareholder,  any  underwriter  (as defined in the
Securities  Act) for the  Selling  Shareholder,  and each  person,  if any,  who
controls the Selling  Shareholder or such underwriter  within the meaning of the
Securities Act (but, in the case of an underwriter or a controlling person, only
if such under writer or controlling  person indemnifies the persons mentioned in
paragraph  17(b)  hereof in the manner set forth  therein)  against  any losses,
claims,  damages  or  liabilities,  joint  or  several,  to  which  the  Selling
Shareholder or any such

                                     - 12 -









underwriter or controlling  person becomes subject,  under the Securities Act or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect  thereof) are caused by any untrue statement or alleged untrue statement
of any material fact contained in any  preliminary  prospectus (if used prior to
the  effective  date  of  the  Registration  Statement),  or  contained,  on the
effective date thereof,  in any  Registration  Statement under which the Selling
Shareholder(s)'  shares of Warrant Stock were  registered  under the  Securities
Act, the prospectus  contained therein,  or any amendment or supplement thereto,
arising out of or based upon the omission or alleged omission to state therein a
material fact required to be stated  therein or necessary to make the statements
therein not misleading; the Company shall reimburse the Selling Shareholder,  or
any such underwriter or controlling  person, in connection with investigating or
defending any such loss, claim, damage, liability or action; provided,  however,
that the Company  shall not be liable to any such person in any such case to the
extent that any such loss, claim,  damage,  liability or action arises out of or
is based upon any untrue  statement or alleged  untrue  statement or omission or
alleged  omission  made in  reliance  upon and in  conformity  with  information
furnished in writing to the Company by such person  expressly  for  inclusion in
any of the foregoing documents.

         (xvii) Indemnification by Selling Shareholders. Each individual Selling
Shareholder shall:

                  (a)  Furnish  to  the  Company  in  writing  all   information
concerning  it and  it's  holdings  of  securities  of the  Company  as shall be
required  in  connection  with the  preparation  and filing of any  Registration
Statement covering any Shares of Warrant Stock.

                  (b)  Indemnify  and hold  harmless  the  Company,  each of its
directors,  each of its officers who has signed a Registration  Statement,  each
person,  if any, who controls the Company  within the meaning of the  Securities
Act and any  underwriter  (as defined in the  Securities  Act) for the  Company,
against any losses,  claims,  damages or liabilities to which any such director,
officer,  controlling  person  or  underwriter  may  become  subject  under  the
Securities  Act or  otherwise,  insofar  as such  losses,  claims,  damages,  or
liabilities (or actions in respect  therefor) are caused by any untrue statement
of any material fact contained in any  preliminary  prospectus (if used prior to
the effective date of the Registration Statement) or contained, on the effective
date  thereof,   in  any   Registration   Statement   under  which  the  Selling
Shareholder's   securities  were  registered   under  the  Securities  Act,  the
prospectus contained therein, or any amendment or supplement thereto, or arising
out of or based upon the omission to state  therein a material  fact required to
be stated therein or necessary to make the statement therein not misleading;  in
each case to the extent,  but only to the extent,  that such untrue statement or
omission was made in reliance upon and in conformity with information  furnished
to the Company in writing by the Selling Shareholder  expressly for inclusion in
any of the foregoing documents,  and the Selling Shareholder shall reimburse the
Company and any such director,  officer,  controlling  person or underwriter for
any legal or other  expenses  reasonably  incurred  by the  Company  or any such
director, officer, controlling

                                     - 13 -









person or underwriter  in connection  with  investigating  or defending any such
loss, claim, damage, liability or action.

         (xviii)   Notification   by   Selling    Shareholders.    The   Selling
Shareholder(s) and each other person indemnified pursuant to paragraph 16 hereof
shall, in the event it receives notice of the commencement of any action against
it which is based upon an alleged act or omission which, if proven, would result
in the Company having to indemnify it pursuant to paragraph 16 hereof,  promptly
notify the Company,  in writing,  of the  commencement of such action and permit
the  Company,  if the Company so notifies the Selling  Shareholder(s)  within 10
days after receipt by the Company of notice of the  commencement  of the action,
to  participate  in and to  assume  the  defense  of such  action  with  counsel
reasonably  satisfactory to the Selling Shareholder(s) or such other indemnified
person,  as the case may be. The omission to notify the Company  promptly of the
commencement  of any such action shall not relieve the Company of any  liability
to indemnify the Selling Shareholder(s) or such other indemnified person, as the
case may be, under  paragraph  16 hereof,  except to the extent that the Company
shall suffer any loss by reason of such failure to give notice which it may have
pursuant to the rights conveyed to the Holders) in this Warrant.

         (xix) Notification by the Company to Selling Shareholders.  The Company
agrees that, in the event it receives  notice of the  commencement of any action
against it which is based  upon an alleged  act or  omission  which,  if proven,
would result in a Selling  Shareholder  having to indemnify the Company pursuant
to  paragraph  17(b)  hereof,  the  Company  will  promptly  notify the  Selling
Shareholder in writing of the commencement of such action and permit the Selling
Shareholder,  if the Selling  Shareholder so notifies the Company within 10 days
after receipt by the Selling  Shareholder of notice of the  commencement  of the
action,  to  participate  in and assume the defense of such action with  counsel
reasonably  satisfactory  to the  Company.  The  omission  to notify the Selling
Shareholder  promptly of the  commencement  of any such action shall not relieve
the Selling  Shareholder  of liability to indemnify the Company under  paragraph
17(b) hereof, except to the extent that the Selling Shareholder shall suffer any
loss by reason of such failure to give notice, and shall not relieve the Selling
Shareholder of any other  liabilities  which it may have under this or any other
agreement then in effect between the Company and the Selling Shareholder.

         (xx) Costs and Expenses. As used in this Warrant,  "Costs and Expenses"
shall  include  all  of the  costs  and  expenses  relating  to  the  respective
Registration  Statement(s) involved,  including but not limited to, registration
fees, filing and qualification  fees,  blue-sky  expenses,  printing and mailing
expenses, fees and expenses of Company's counsel and, if/when appropriate,  fees
and  expenses of counsel  designated  by the Selling  Shareholder(s)  (provided,
however, that no more than one such counsel for the Selling Shareholder(s) shall
be designated on any occasion).


                                     - 14 -









         (xxi)   Addresses.   All  notices,   certificates,   waiver  and  other
communications required or permitted to be given hereunder to any of the parties
by any other party shall be in writing and shall be delivered personally or sent
by next day delivery  service or registered or certified mail,  postage prepaid,
as follows:

                      (a)      If to the Company, addressed to:

                                       Cheung Laboratories, Inc.
                                       10220-I Old Columbia Road
                                       Columbia, MD 21046-1705
                                       Attention: Mr. John Mon, General Manager

                      (b)      If to a Holder,  addressed to the address of
                               each  such  Holder  as  shall,  from time to
                               time,  appear on the  records of the Company
                               or those of the Company's  transfer agent as
                               may be the case.

Any notice  delivered  personally or sent by next day delivery  service shall be
deemed to have been given on the date so delivered,  and any notice delivered by
registered  or certified  mail shall be deemed to have been given on the date it
is received.  Any party may change the address to which notices hereunder are to
be sent by  giving  written  notice  of such  change of  address  in the  manner
provided for giving notice.

         (xxii) Waiver.  No waiver by a Holder of any right  hereunder  shall be
effective  unless it is in writing  which  specifically  refers to the provision
hereof under which such right  arises,  and no such waiver  shall  operate or be
construed  as a  waiver  of any  subsequent  breach,  whether  of a  similar  or
dissimilar nature.

         (xxiii) Entire  Warrant.  This Warrant may be amended,  supplemented or
modified only by a written instrument executed by the Company and the Holder(s).
While separate executed letters proposing and/or accepting  amendment(s) sent to
the Company by the Holder(s) or to the Holder(s) by the Company  shall,  for the
purposes  of  this  paragraph  23,  constitute  a  valid  agreement  as  to  the
relationship  then created by and between the Company and the individual  Holder
in  question,  only Nace (as the original  Holder)  may, by  agreement  with the
Company,  bind all  subsequent  Holders to one single written  instrument  which
shall  serve to amend  the terms and  conditions  hereof,  and to which by their
acceptance  of an assignment  of any portion of this  Warrant,  they  implicitly
agree to be bound by.

         (xxiv)  Applicable  Law. This Warrant and the legal relations among the
parties  hereto  shall be  governed  by and  construed  in  accordance  with the
substantive laws of the State of Illinois applicable to contracts made and to be
performed  therein  without  giving effect to the principles of conflict of laws
thereof.


                                     - 15 -









         (xxv)  Appraisal  Rights.  In the  event  that the  Company's  board of
directors  has not  approved  and the Company has not  executed  the next public
offering of the Company's  Common Stock prior to the second  anniversary  of the
issuance of this Warrant,  a majority in interest of the Holder(s) may, in their
sole discretion and at any time thereafter, give notice to the Company that they
wish to avail  themselves of Appraisal Rights rather than force the Company into
filing a  Registration  Statement  against  its will by  demanding  registration
hereunder.

Should this event occur,  the Company and the  Holder(s)  shall meet together to
appraise  the value of the  Warrant(s)  and shall  proceed  to do so in the same
fashion  and  spirit as is  provided  for in the first  paragraph  of section 10
hereof in determining a Retirement  Fee to be paid the Holders upon  termination
of the Warrant(s).

         (xxvi) Binding Effect.  The provisions  contained in this Warrant shall
be binding  upon and inure to the  benefit of the  Company  and the  Holders and
their respective successors, permitted assigns, heirs and legal representatives.
Any person to whom all or a part of a Holder's rights and obligations  hereunder
are assigned shall fulfill such of the assigning Holder's obligations  hereunder
as have been  assigned,  and shall be entitled to all of the rights and benefits
hereunder to the extent that such person has assumed such Holder's  obligations.
The rights and powers of each  successive  Holder  hereunder are granted to such
Holder  as an owner  of  Warrants  or  Warrant  Stock  as the  case may be.  Any
subsequent  Holder whether becoming such by transfer,  assignment,  operation of
law or  otherwise,  shall have the same rights and powers which a Holder  owning
the same number of Warrants  and/or  Warrant Stock has  hereunder,  and shall be
entitled to  exercise  such  rights and powers  until such Holder or  subsequent
Holder no longer owns any Warrants or Warrant Stock.  Except as provided in this
paragraph  26, this  Warrant  does not  create,  and shall not be  construed  as
creating, any rights enforceable by any person not a Holder.

         (xxvii) Validity.  If any term,  provision,  covenant or restriction of
this Warrant is held by a court of competent jurisdiction to be invalid, void or
unenforceable,  the  Company  agrees  that such  term,  provision,  covenant  or
restriction  shall be  reformed  to the  extent  possible  consistent  with such
judicial holding to reflect the intent of the Company and the original Holder as
stated  herein  and  the  remainder  of the  terms,  provisions,  covenants  and
restrictions  of this Warrant shall remain in full force and effect and shall in
no way be  affected,  impaired  or  invalidated.  It is  hereby  stipulated  and
declared to be the  intention  of the Company that it would have  executed  this
Warrant  including the remaining terms,  provisions,  covenants and restrictions
without including any of such provision of term which may be hereafter  declared
invalid, void or unenforceable.



This Warrant (Serial Number:  0300) is granted and sold on this 1st day of June,
1996.

                                     - 16 -










                                             Cheung Laboratories, Inc.



                                             By:______________________________
                                                 Augustine Cheung, President


                                     - 17 -









                                  PURCHASE FORM

                                                               Dated: __________

Cheung Laboratories, Inc.
10220-1 Old Columbia Road
Columbia, MD  21046-1705

Attention: Mr. John Mon, General Manager


Attached herewith is Cheung Laboratories,  Inc.'s Common Stock Purchase Warrant,
Serial Number:  __________,  giving the Holder the right to purchase  __________
shares.

I/We  hereby  notify  you that  I/we are  exercising  my/our  right to  purchase
__________  shares  and have  enclosed  herewith  my/our  check in the amount of
$__________,  representing  the  aggregate  exercise  price of said  shares.  If
transfer  taxes  (federal or state) are  applicable  to this  transaction,  I/we
understand that you will be billing me/us for said taxes,  which I/we agree will
be  promptly  remitted  to you  within  ten  (10)  days  of  my/our  receipt  of
notification.

I/We hereby  state that the shares being  purchased  are to be held by me/us for
investment purposes and not with a view to sale, except pursuant to an effective
registration statement or an exemption therefrom.

Please cancel the enclosed Warrant and, if applicable,  send me/us a Warrant, in
partial  substitution  on identical  terms,  for the remaining  shares not being
purchased pursuant to this notification.



Yours very truly,


Holder of Warrant, Serial Number __________

_______________________
_______________________
_______________________
_______________________
                                     - 18 -