Mar.  Joint.  Pharm.  \ 
Feb.  1, 1872.  j 
New  Method  for  Preparing  Pepsin. 
57 
teresting  to  determine  if  chloride  of  sodium  would  aid  the  action  of 
pepsin  on  albumen  and  accelerate  its  solution. 
A  very  small  quantity  of  salt,  a  quantity  that  does  not  exceed  much 
that  of  the  purified  pepsin,  does  not  interfere  with,  on  the  contrary 
benefits  the  pepsin  in  its  action  ;  but  a  larger  quantity,  although  very 
small  in  itself,  retards  the  solvent  power. 
While  half  a  grain  of  pure  pepsin  in  2  oz.  of  acidulated  water  dis- 
solved 200  grains  of  coag.  alb.  perfectly,  a  great  deal  of  albumen  was 
left  undissolved  in  the  same  time  when  5  grs.  of  salt  were  added  to 
it,  while  by  10  grains  of  salt  a  portion'  of  the  albumen  was  not  dis- 
solved after  three  days. 
Stability  of  Pepsin. — As  watery  solutions  of  pepsin  decompose 
very  soon,  particularly  in  warm  weather,  it  was  of  interest  to  deter- 
mine the  stability  of  acidulated  solutions  ;  accordingly  solutions  con- 
taining one  grain  of  purified  pepsin  to  the  fluidounce  of  water,  and 
respectively  2,  4,  6,  8  and  10  drops  of  hydrochloric  acid  were  set 
aside,  a  portion  of  each  in  well-corked  vials  and  another  portion  in 
vials  only  tied  up  with  paper.  The  solutions  containing  2  drops  of 
acid  became  mouldy  after  the  first  and  second  week,  while  in  the  vials, 
with  4  drops  of  acid,  I  noticed  mould  after  five  weeks.  The  other  solu- 
tions kept  entirely  clear,  and  when  examined,  after  6  months,  they 
did  not  have  any  bad  odor,  but  had  lost  their  digestive  power  almost 
entirely  ;  albumen,  put  into  several  of  the  solutions,  was  hardly  acted 
upon,  and  chloride  of  sodium  did  not  produce  the  characteristic  pre- 
cipitate. 
To  20  grs.  of  purified  pepsin,  swelled  in  2  ounces  of  water,  were 
added  10  drops  of  hydrochloric  acid,  which  dissolved  the  pepsin  fully 
and  formed  a  liquid  of  a  slight  yellowish  color,  and  the  consistence 
of  the  officinal  mucilage  of  gum  arabic.  Put  aside  in  a  beaker-glass, 
tied  up  with  blotting  paper,  it  evaporated  slowly,  and  was,  after  6 
weeks,  dried  out  to  a  transparent  gum  which  felt  sticky  to  the  touch. 
Examined  after  several  months,  it  dissolved  readily  in  water,  form- 
ing a  clear  solution  of  sour  reaction  and  taste,  which  had  no  bad 
odor,  but  acidulated  and  diluted  to  the  strength  usually  employed  in 
my  experiments,  did  not  act  on  coagulated  albumen,  and  chloride  of 
sodium  gave  no  precipitate.  The  pepsin  was  therefore  totally  de- 
stroyed or  at  least  made  inactive. 
Anxious  to  learn  whether  liquid  pepsin,  which  had  been  put  aside 
^ight  months  before  for  experiments'  sake,  had  retained  its  digestive 
