Am.  Jour.  Pharm.  \ 
March,  1892.  J 
Analysis  of  Peptones. 
159 
(ft)  Albumose  and  gelatin. — 25  cc.  of  stock  aqueous  solution  are 
evaporated  to  a  few  cc,  treated  with  saturated  solution  of  ammonium 
sulphate,  raised  to  nearly  ioo°  and  quickly  cooled  with  centrifugal 
agitation.  The  ppt.  is  thrown  on  a  tared  filter,  washed  with 
ammonium  sulphate,  dried  and  weighed.  In  the  ppt.  the  excess  of 
ammonium  sulphate  is  afterwards  estimated  gravimetrically  by 
barium  chloride  and  deducted. 
(c)  Albumose. — 50  cc.  of  stock  aqueous  solution  are  raised  to 
near  ioo°  C.  and  are  then  treated  with  30  cc.  of  Stutzer's  reagent. 
The  ppt.  is  washed  in  a  filter  with  hot  water,  and  the  nitrogen  con- 
tained  in  it  estimated  by  the  Kjeldahl  method.  30  cc.  H2S04  and 
a  globule  of  mercury  give  good  results. 
(d)  Gelatin. — It  is  evident  that  from  the  results  of  the  two  last 
operations  both  gelatin  and  peptone  may  be  found  by  difference, 
and  our  experiments  convince  us  that  a  satisfactory  assay  may  be 
obtained  in  this  way.  But  a  direct  estimation  of  gelatin  may  be 
made  as  follows  :  The  filtrate  from  the  copper  ppt.  is  concentrated 
to  a  few  cc.  in  a  beaker  previously  weighed  with  a  glass  rod ;  satu- 
rated solution  of  ammonium  sulphate  is  then  added,  the  mixture 
raised  nearly  to  the  boiling  point,  and  then  quickly  cooled  with 
centrifugal  agitation.  As  M.  Denaeyer  has  shown,  the  gelatin  now 
separates  and  adheres  to  the  sides  and  bottom  of  the  leaker, 
particularly  if  touched  from  time  to  time  with  the  rod.  The  gelatin 
may  now  be  once  washed  rapidly  with  the  ice-cold  water,  dried  and 
weighed,  and  the  ammonium  sulphate  retained  in  it  estimated  and 
deducted  as  before. 
(3)  With  regard  to  the  alcoholic  extract  which  we  have  described 
as  the  stock  alcoholic  solution,  we  confirm  M.  Denaeyer's  statement 
that  the  dried  extract  is  too  hygroscopic  to  permit  any  accurate 
inference  to  be  drawn  from  its  weight.  It  is  better  to  adopt  the 
following  method,  which  is  in  substantial  agreement  with  that 
recommended  by  M.  Denaeyer.  The  stock  alcoholic  solution  is 
made  up  to  a  definite  volume,  say  to  500  cc.  This  is  divided  into 
fractions  for  separate  treatment. 
(a)  Gelatin  soluble  in  alcohol. — One  fraction,  say  one-fifth,  is 
evaporated  to  dryness,  taken  up  with  warm  water  and  treated  with 
ammonium  sulphate  in  the  manner  already  described. 
(b)  Urea,  etc. — Another  fraction,  one-tenth,  may  be  evaporated 
to  dryness  and  treated  with  sodium  hypobromite.    But  evidently 
