42         Recent  Literature  Relating  to  Pharmacy.     {  *■  j^uarVjoos.111' 
quent  distillation,  even  if  the  safety-bulb  is  used  and  an  amalgam  is 
formed  on  the  block-tin  tubes,  which  causes  some  of  the  ammonia 
to  be  retained.  Mooers'  figures  show  a  loss  in  some  cases  of  over 
I  5  per  cent.  He  found  it  impracticable  to  bring  the  tubes  into  a 
satisfactory  condition  and  replaced  them  with  Jena-glass  tubes  which, 
after  a  year's  use,  have  shown  excellent  results.  He  regards  these 
glass  tubes  as  cheaper  and  better  than  block-tin.  Block-tin  tubes 
can  be  used  safely  with  the  Gunning  modification. 
Mooers  also  finds  a  source  of  error  in  following  the  official 
A.O.A..C.  method  for  nitrates.  He  advises  that  the  sample  of  fertil- 
izer, in  which  nitrates  are  to  be  determined,  should  be  mixed  with 
I  or  2  c.c.  of  water,  and  the  mixed  acids  (sulphuric  and  salicylic) 
not  added  until  ten  minutes  later.  H.  L. 
ASSAY  OF  COMMERCIAL  PEPSINS. 
A  new  method  for  the  assay  of  commercial  pepsins  was  given  in 
the  October  "  Bulletin  of  the  Pathological  and  Bacteriological  Lab- 
oratory ot  the  Delaware  State  Board  of  Health."  It  is  essentially 
the  U.S. P.  method,  excepting  that  the  acid  albumen  produced  by 
the  hydrochloric  acid  in  the  pepsin  mixture  is  precipitated  by  mak- 
ing slightly  alkaline  with  sodium  carbonate,  leaving  only  the  digested 
substances,  albumoses  and  peptone  in  solution. 
The  number  of  parts  of  egg  albumen,  which  I  part  of  the  pepsin 
will  convert  into  albumoses  and  peptone,  is  ascertained  by  compar- 
ing the  nitrogen  determination  of  prepared  egg  albumen  with  the 
digested  product  by  the  Kjeldahl  method.  The  author's  reason  for 
using  this  method  is  that  he  does  not  consider  a  freshly  coagulated 
and  granulated  egg  albumen  U.S. P.  digested,  when  it  is  dissolved, 
but  only  when  it  is  converted  into  those  products  which  are  absorbed 
into  the  system  without  further  change,  namely :  albumoses  and 
peptone,  products  of  proteolytic  action  and  not  acid  albumens.  He 
further  states  that  there  is  nothing  uniform  about  the  strengths  of 
pepsins,  either  from  different  firms  or  the  same  firm.  Appended 
are  a  few  results  obtained  by  this  method  of  assay  upon  four  of  the 
best-known  brands  of  pepsin,  marked  I  :  3000  : 
Pepsin  A  1  :  560 
Pepsin  B   1  :  1052 
Pepsin  C  1  :  1209 
Pepsin  D  .  .  .  1  :  1253 
W.  S.  Weakley. 
