A  August  ?92irm' }     Scientific  and  Technical  Abstracts.  565 
1-10  of  its  volume  of  3  per  cent,  silver  nitrate  solution  is  added. 
After  a  few  minutes'  ebullition  there  will  be  a  black  paste-like  scum 
of  fatty  acids  come  to  the  surface,  if  cottonseed  oil  is  present.  This 
reaction  is  due  to  reduction  of  the  nitrate  and  does  not  take  place 
with  the  fatty  acids  of  pure  olive  oil.  With  this  method  1  per  cent, 
of  cottonseed  oil  in  the  olive  oil  can  be  detected.  Perfumery  and  Ess. 
Oil  Record. 
The  Use  of  Edestin  in  Determining  the  Proteolytic 
Activity  of  Pepsin. — The  United  States  Pharmacopoeia  method  is 
the  only  official  one  in  the  United  States  for  the  assay  of  pepsin. 
This  method  is  not  proving  satisfactory.  Edestin,  the  protein  of 
hempseed,  has  been  used  to  supply  the  protein  in  clinical  methods 
worked  out  by  others  for  the  determination  of  proteolytic  activity, 
and  since  it  is  easily  and  cheaply  prepared  the  author  considers  that 
it  may  advantageously  be  used  in  the  assay  of  commercial  pepsin. 
Edestin  is  prepared  by  extracting  nearly  fat-free  hempseed 
meal  with  5  per  cent,  sodium  chloride  solution  at  65 °.  The  edestin, 
which  separates  on  cooling  the  filtered  extract,  is  recrystallized  from 
the  same  medium.  The  nitrogen  content  of  the  washed  and  air-dried 
edestin  is  carefully  determined,  and  this  multiplied  by  5.35  is  adopted 
as  giving  the  percentage  of  edestin  in  the  preparation.  From  this 
the  amount  of  preparation  to  supply  a  given  amount  of  edestin  is  cal- 
culated. 
For  the  assay  a  1  per  cent,  solution  of  edestin  in  0.1  N  hydro- 
chloric acid  is  placed  in  test  tubes  arranged  in  a  constant  temperature 
bath  at  37.5 0  in  increments  of  0.25  cc,  beginning  with  0.25  cc.  in  tube 
1.  Tubes  4,  5  and  6  receive  1  cc.  To  the  edestin  solution  is  added 
0.1  N  hydrochloric  acid  in  decrements  of  0.25  cc,  beginning  with 
0.75  cc.  in  tube  1,  thus  adjusting  the  volume  in  each  tube  to  1  cc. 
One  cc.  of  10  per  cent,  sodium  chloride  solution  is  added  to  each 
tube  to  precipitate  the  protein.  This  is  followed  by  the  addition  of 
1  cc.  of  1  per  cent,  solution  of  the  pepsin  to  be  tested  in  0.05  N  hydro- 
chloric acid.  The  time  from  the  beginning  of  the  addition  of  pepsin 
until  the  protein  is  completely  liquefied  is  noted.  If  the  volume  of 
subtrate  is  represented  by  s,  and  the  time  of  digestion  by  t,  then  t/s 
is  nearly  constant.  It  is  better  to  adopt  the  mean  t/s  for  all  tubes  as 
the  constant.  The  comparison  of  the  proteolytic  activity  of  differ- 
ent pepsins  resolves  itself  into  a  comparison  of  the  constants  thus  ob- 
tained.— /.  Biol.  Chem.,  46  (1921)  :  119;  through  Journ.  Frank.  Inst. 
