Am.  Jour.  Pharui.  1 
March,  1892.  / 
Analysis  of  Peptones. 
157 
dryness,  dried  over  phosphoric  anhydride  for  8  hours  and  weighed. 
This  operation  is  difficult  as  the  residue  is  very  hygroscopic,  and 
M.  Denaeyer  prefers  to  estimate  the  extractives  approximately  by 
difference. 
The  alcoholic  precipitate  is  treated  with  warm  water  and  filtered 
from  albumin,  which  can  be  weighed  in  a  tared  filter.  The  solu- 
tion is  then  divided  into  three  portions. 
(d)  Of  these,  one  is  treated  with  excess  of  solution  of  phospho- 
tungstic  acid. 
This  throws  down  albumose,  gelatin  and  peptone.  The  precipi- 
tate is  thrown  on  a  tared  Schleicher's  filter,  washed  with  dilute 
hydrochloric  acid,  dried  and  weighed.  It  is  then  burnt,  and  the 
proteids  found  by  difference. 
(e)  Another  portion  of  the  aqueous  solution  of  the  alcoholic 
precipitate  is  treated  with  ammonium  sulphate  as  in  process  (J?). 
The  weight  of  the  precipitate,  after  deducting  the  sulphate,  gives 
albumose  and  gelatin. 
(f)  The  third  portion  is  accurately  neutralized  and  treated  with 
excess  of  saturated  solution  of  mercuric  chloride.  This  throws 
down  albumose  and  peptone,  but  not  gelatin.  The  precipitate  is 
rejected.  The  filtrate  is  treated  as  before  with  ammonium  sulphate, 
and  the  weightlof  gelatin  insoluble  in  alcohol  determined.1 
True  peptone  is  now,  of  course,  found  by  difference. 
This  scheme  for  the  analysis  of  peptones  is  certainly  the  best 
that  has  hitherfo  been  devised,  but  it  is  liable  to  objection  in  one  or 
two  respects.  The  process  which  we  have  adopted,  and  in  which 
that  of  Stutzer  is  incorporated,  appears  to  us  simpler  and  more 
satisfactory. 
(6)  A.  Denaeyer.  (Jour.  Pharm.  Anvers,  November,  1891,. 
Analyst,  December,  1891.)2  This  is  an  admirable  process  for  a 
simple  assay  of  genuine  commercial  peptones.  10  cc.  of  aqueous 
peptone,  containing  about  2  grams  of  dry  matter,  are  treated 
with  100  cc.  of  strong  alcohol.  After  standing  for  24  hours  the 
precipitate  is  washed  with  alcohol,  dried  and  weighed.  The  alco- 
holic solution  is  also  dried  at  105 0  C.  and  weighed.    M.  Denaeyer 
1  In  a  subsequent  note  M.  Denaeyer  recommends  the  removal  of  excess  of 
mercury  by  H2S,  and  points  out  that  the  phospho-tungstic  treatment  may  be 
avoided. 
2  Our  paper  was  written  before  this  note  appeared. 
