THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
OCTOBER,  1892. 
PEPSIN  ASSAY. 
By  M.  B.  Manwaring. 
To  obtain  reliable  results,  the  conditions  herein  specified,  how- 
ever unimportant  some  of  them  may  appear,  must  be  carefully 
observed  when  testing  the  proteolytic  power  of  pepsins. 
Prepare  an  excessive  quantity  of  acidulated  water,  containing 
0-2  per  cent,  absolute  hydrochloric  acid  (HC1),  thus : 
Hydrochloric  acid,  U.  S.  P.  .  '  48  min.  or  3  cc. 
Distilled  water  sufficient  to  make  16  fl.  oz.  or  473  cc. 
For  every  1,000  grains  of  albumen  required  provide  217  fresh 
eggs.  Put  the  eggs  in  boiling  water  and  boil  for  fifteen  minutes, 
then  cool  them  with  cold  water.  Separate  the  whites  by  the  aid  of 
a  perfectly  clean  and  bright  spatula  (preferably  of  bone),  and  if 
necessary  wash  away  any  adhering  yolk  and  dry  the  coagulated 
albumen  with  a  clean  towel.  Press  the  whites  through  a  30-mesh 
hair  sieve ;  avoid  if  possible  using  a  brass  sieve. 
The  acidulated  water  and  the  coagulated  albumen  being  ready, 
as  also  a  water-bath  at  a  temperature  of  105 0  F. 
Weigh  exactly,  pepsin,   y2  gr. 
Weigh  with  approximate  accuracy  coagulated  albumen,  .  .  1250  gr. 
Measure  acidulated  water,   27  fl.  oz. 
Carefully  transfer  the  pepsin  to  a  wide  mouth  bottle  or  flask  of 
about  2)/2  pints  capacity,  adding  a  little  of  the  measured  portion 
of  acidulated  water.  If  the  pepsin  is  in  scale  form,  and  the  day  is 
damp,  so  that  the  pepsin  is  inclined  to  become  sticky,  it  should  be 
(505) 
