Am.  Jour.  Pharm.  ) 
April,  1921.  ) 
Studies  on  Pepsin. 
2.S7 
rated  zinc  sulphate,  ammonium  sulphate,  picric  acid  solutions),  and 
protoproteoses  (by  saturated  sodium  chloride  solution,  potassium 
ferrocyanide  in  acetic  acid  solution). 
Results. — Altogether,  nine  purified  products  were  prepared. 
Including  the  basic  pepsin  material,  the  various  proteolytic  strengths 
of  the  enzyme  which  were  examined  ranged  from  i  :  2000  to 
1.  140,000  (U.  S.  P.  IX).  The  results  in  every  case,  based  on 
duplicate  determinations  and,  because  of  possible  variation  in  the 
U.  S.  P.  pepsin  assay,  these  estimations  were  carried  out  in  tripli- 
cate by  two  different  observers. 
The  purification  of  pepsin  is  accompanied  by  a  general  decrease 
in  the  total  mineral  matter.  This  ranges  from  an  ash  content  of 
nearly  5.5  per  cent,  in  the  case  of  the  basic  (1  :  2000)  product 
down  to  about  2  per  cent,  with  the  highest  proteolytic  strengths 
obtained.  The  phosphoric  acid  content,  also,  shows  a  gradual  de- 
crease so  that  the  value  at  1  : 40,000  is  less  than  one-third  that  of 
the  basic  material.  Both  the  calcium  oxide  and  total  sulphur  values 
fluctuate  in  the  different  strengths,  but  both  show  an  increase  in 
the  purified  as  compared  with  the  unpurified  samples.  It  is  a  sig- 
nificant fact  that  the  chlorides,  which  are  present  to  the  extent  of 
1. 1 9  per  cent,  (as  NaCl)  in  the  1  :2000  sample,  practically  dis- 
appear as  a  result  of  purification. 
Probably  the  most  important  data  are  furnished  by  the  various 
nitrogen  factors,  particularly  the  nitrogen  in  amino  acid  condition. 
Confirming  more  elaborately  the  results  found  by  other  investi- 
gators, there  is  found  to  be  almost  a  uniform  decrease  in  a-amino 
acid  nitrogen  so  that  in  the  sample  testing  1  : 40,000  only  0.61  is 
found.  Corroborating  these  results,  it  will  be  noted  that  there 
are  steady  increases  in  both  the  coagulable  protein  nitrogen  and 
that  existing  as  proteoses,  while  the  peptone  nitrogen  like  that  of 
the  amino  acids  shows  a  decrease.  The  values  for  total  nitrogen 
showed  decided  variations  among  the  different  samples  with  no 
significant  change  as  the  purification  increases. 
All  of  the  different  strengths  of  the  pepsin  examined  show 
levorotation  in  very  nearly  the  same  degree,  so  that  this  factor  is 
apparently  unaltered  as  a  result  of  purification.  With  the  excep- 
tion of  the  strongest  sample  obtained  ( 1  : 40,000)  a  slight  amounts 
of  hydrochloric  acid  was  used  in  the  preparation  of  the  other 
strengths  of  the  pepsin.    As  a  consequence,  2  per  cent,  aqueous 
