AK$ktm£M'}    New  Method  for  Preparing  Pepsin.  51 
allow  the  mucus  to  settle.  To  the  clarified  liquid  the  same  bulk  of  a 
saturated  solution  of  sodium  chloride  is  added,  and  the  whole  thor- 
oughly mixed.  After  several  hours  the  pepsin,  which  by  the  addi- 
tion of  chloride  of  sodium  has  separated  from  its  solution,  is  found 
floating  on  the  surface,  from  whence  it  is  removed  with  a  spoon  and 
put  upon  cotton  cloth  to  drain ;  finally  it  is  submitted  to  strong  pres- 
sure, to  free  it  as  much  as  possible  from  the  salt  solution. 
The  pepsin,  when  taken  from  the  press  and  allowed  to  become  air 
dry,  is  a  very  tough  substance,  and  presents,  according  to  thickness,  a 
different  appearance,  resembling  in  thin  sheets  parchment  paper,  and 
in  thick  layers  sole  leather ;  its  color  varies  from  a  dim  straw  yellow 
to  a  brownish  yellow.  Besides  a  little  mucus  it  contains  a  small  quan- 
tity of  phosphate  of  lime  and  chloride  of  sodium,  which,  however,  do 
not  interfere  with  its  digestive  properties,  as  they  are  found  also  in 
normal  gastric  juice. 
Saccharated  Pepsin.  To  work  it  into  Saccharated  Pepsin  (Am. 
Journ.  of  Pharm.  January  1871)  the  damp  pepsin,  as  it  is  taken  from 
the  press,  is  triturated  with  a  weighed  quantity  of  sugar  of  milk  to  a 
fine  powder,  which,  when  having  become  air  dry,  is  weighed  again, 
the  quantity  of  milk-sugar  subtracted  and  so  the  amount  of  pepsin 
found.  The  strength  of  this  dry  Pepsin  is  now  ascertained  by  find- 
ing how  much  coagulated  albumen  it  will  dissolve  at  a  temperature  of 
100°  F.  in  five  or  six  hours,  and  after  this  sufficient  milk  sugar  is  ad- 
ded to  result  in  a  preparation  of  which  ten  grains  will  dissolve  one 
hundred  and  twenty  grains  of  coagulated  albumen,  and  this  prepara- 
tion I  have  called  Saccharated  Pepsin. 
Purification  of  Pepsin.  Anxious  to  get  the  pepsin  in  its  purest 
state,  if  possible,  chemically  pure,  I  tried  different  methods,  but  have 
not  succeeded  as  yet.  In  order  to  get  a  purer  article  I  re-dissolve 
the  pepsin,  as  obtained  after  expression,  in  acidulated  water,  filter  the 
solution  through  paper,  and  precipitate  again  with  a  solution  of  sodium  I 
chloride  ;  the  precipitate,  after  draining  and  pressing,  is  now  free  of 
phosphate  of  lime  and  mucus,  but  contains  yet  salt.  In  the  freshly 
precipitated  state  the  pepsin  is  very  readily  soluble  in  water  and  can- 
not therefore  be  freed  from  adhering  salt  by  washing. 
By  allowing  the  pressed  sheet  of  Pepsin  to  get  perfectly  air  dry — 
whereby  it  becomes  coated  with  a  white  film  and  small  crystals  of 
chloride  of  sodium — and  by  immersing  it  then  in  pure  water  for  a 
short  time,  the  greater  part  of  sodium  chloride  can  be  extracted,  but 
