154 
Analysis  of  Peptones. 
f  Am.  Jour.  Pharm. 
t      March,  1892. 
value.  Our  knowledge  of  these  compounds  has  of  late  been 
considerably  extended,  and  various  methods  for  their  quantitative 
estimation  have  been  devised.  We  have  no  new  reagent  to 
suggest ;  but  after  careful  trial  of  all  the  processes  at  present  in  use, 
we  have  found  that  by  a  combination  of  several  of  them  the  analysis 
may  be  simplified. 
The  substances  to  be  determined  may,  for  analytical  purposes,  be 
classified  as  follows : 
(1)  Water;  ash;  total  nitrogen. 
(2)  Matters  extracted  by  absolute  alcohol.  Definite  compounds 
for  the  most  part ;  some  nitrogenous,  some  non-nitrogenous.  It 
has  been  shown  by  M.  Denaeyer  (v.  infra)  that  one  variety  of 
gelatin  present  in  peptones  is  soluble  in  alcohol. 
(3)  Albumins : — coagulated  and  rendered  permanently  insoluble 
by  heat  or  by  strong  alcohol. 
(4)  Albumoses: — not  coagulated  by  heat.  Soluble  in  water. 
Precipitated  by  alcohol,  cupric  hydrate,  phospho-tungstic  acid, 
mercuric  chloride  and  ammonium  sulphate. 
(5)  Peptones: — not  coagulated  by  heat.  Soluble  in  water.  Pre- 
cipitated by  alcohol,  phospho-tungstic  acid  and  mercuric  chloride, 
but  not  by  cupric  hydrate  or  ammonium  sulphate. 
(6)  Gelatins  : — partly  soluble  in  alcohol.  Precipitated  entirely  and 
in  all  forms  by  phospho-tungstic  acid  and  ammonium  sulphate. 
Not  precipitated  by  cupric  hydrate  or  mercuric  chloride. 
It  is  well  known  that  the  nitrogen  in  proteids  varies  from  14-4 
per  cent,  in  chondrin  to  over  18  per  cent,  in  gelatin.  (Beilstein,  iii, 
1292-4.)  Following  previous  workers,  we  have  assumed  15-8  per 
cent,  of  nitrogen,  which  gives  as  the  factor  to  be  applied  to  the 
nitrogen  6-33.  More  exact  knowledge  is  required  before  separate 
factors  for  each  of  the  nitrogen  determinations  can  safely  be 
adopted. 
The  following  is  an  abstract  of  the  analytical  methods  described 
in  recent  researches  from  which  our  modified  process  has  been 
derived  : — 
(1)  A.  Stutzer.  {Ber.  13,  251.  Ch.  Soc.  Absts.,  1880,  676.  Cent, 
f.  allg.  Gesund.  Pflege,  1882,  179.  Ch.  Soc.  Absts.  1882,  1239. 
Analyst  x.  57.)  Meat  preparations  are  digested  with  pepsin  in  the 
usual  manner.  In  the  undissolved  residue  nitrogen  is  determined 
by  soda-lime.    The  fluid  is  then  agitated  with  cupric  hydrate, 
