Am.  Jour.  Pbarm.  1 
March,  1892.  J 
Analysis  of  Peptones. 
155 
suspended  in  weak  glycerin,  which,  if  the  fluid  be  not  too  acid, 
throws  down  albumose.  The  separation  appears  to  be  complete, 
and  the  liquid  filters  well.  In  the  cupric  precipitate  nitrogen  is 
determined  by  soda-lime.  The  cupric  mixture  can  be  prepared  as 
follows : — 
100  grams  of  crystallized  cupric  sulphate  are  dissolved  in  5 
litres  of  water  and  2  5  grams  of  glycerin  added.  The  solution 
is  then  made  alkaline  with  caustic  soda,  and  filtered.  The  precipi- 
tate is  well  mixed  with  a  large  excess  of  water  containing  5  grams 
of  glycerin  per  litre.  All  traces  of  alkali  are  now  completely 
removed  by  decantation,  and,  if  necessary,  by  filtration,  the  same 
glycerin  solution  being  used- throughout.  The  precipitate  is  then 
made  up  to  I  litre  with  water  containing  10  per  cent,  of  glycerin. 
The  thin  emulsion  then  contains  nearly  40  grammes  per  litre  of 
cupric  hydrate,  and  can  easily  be  transferred  by  a  pipette.  It  may 
conveniently  be  described  as  Stutzer's  reagent. 
(2)  Kiihne  and  Chittenden.  {ZeiL  Biol.,  xxii,  409,  423.  Amer. 
Jour.  Phar.  1886,  p.  568.)  The  substance  previously  known  as 
peptone  was  found  to  contain  bodies  of  two  kinds,  one  of  which 
(albumose)  can  be  precipitated  and  washed  by  a  saturated  solution 
of  ammonium  sulphate,  while  the  other  (peptone)  remains  in  solu- 
tion. The  filtrate  is  concentrated  until  crystals  of  ammonium  sul- 
phate separate  and  the  remaining  sulphate  is  then  removed  by 
barium  carbonate  and  hydrate,  the  excess  of  barium  being  carefully 
precipitated  by  sulphuric  acid.  Methods  for  the  estimation  of 
albumose  and  peptone  are  described.  They  involve  the  use  of 
phospho-tungstic  acid. 
The  paper  contains  much  valuable  matter  in  regard  to  the  nature, 
composition  and  reactions  of  peptones. 
(3)  Kbnig  and  Kisch.  (Zeit.  Analy.  Chetn.,  xxviii,  191.  Amer. 
Jour.  Phar.,  1889,  525).  The  peptonic  fluid  is  boiled  and  filtered. 
In  the  residue  nitrogen  is  determined  by  the  Kjeldahl  process,  and 
this  multiplied  by  6-25  gives  albumen. 
The  filtrate  is  divided  into  two  portions.  In  one,  albumose  only 
— as  it  was  then  thought — is  thrown  down  and  washed  by  ammo- 
nium sulphate,  as  in  the  method  of  Kiihne  and  Chittenden,  but  the 
precipitate  is  treated  differently. 
It  is  weighed,  and  the  ammonium  sulphate  in  it  is  afterwards 
estimated  volumetrically  by  barium  chloride  and  deducted,  the 
