80 
Peptone. 
/  Am.  Jour.  Pliarm. 
(      Feb.,  1881. 
warmed  in  the  acid  solution,  provided  the  acid  is  not  present  in  too 
small  quantity,  and  has  acted  thoroughly  (this  is  best  effected  by 
warming);  saturation  with  sodium  chloride  to  the  extent  of  4  per  cent, 
gives  a  precipitate,  which  completely  disappears  on  heating.  The 
same  takes  place  if  more  salt  is  added.  When  16  per  cent,  of  salt  has 
been  exceeded,  complete  solution  only  occurs  when  the  peptone  solu- 
tion is  somewhat  dilute.  Peptone  is  precipitated  from  the  feebly  acid 
or  alkaline  solution  by  neutralization ;  if,  however,  too  much  acid  or 
alkali  has  been  used  for  solution,  sufficient  salt  may  be  formed  to 
hinder  precipitation.  Strong  nitric  acid  gives  a  precipitate,  which 
vanishes  on  heating,  before  the  yellow  coloration  appears,  and  returns 
on  cooling.  Silver  nitrate  added  to  a  solution  of  peptone  which  is 
cooling,  and  therefore  is  becoming  cloudy,  increases  the  cloudiness. 
The  precipitate  disappears  almost  entirely  on  cooling ;  a  slight  opal- 
escence, due  to  sodium  chloride,  alone  remaining.  The  precipitate  pro- 
duced by  silver  nitrate  is  soluble  in  acetic  acid 
Absolute  alcohol  precipitates  peptone  in  neutral,  but  not  in  acid  or 
alkaline  solution.  Potassium  ferrocyanide  and  acetic  acid  give  a 
voluminous  precipitate,  soluble  on  heating. 
Basic  lead  acetate,  with  ammonia,  tannic  and  phosphomolybdic 
acids,  give  precipitates  which  are  not  soluble  on  heating. 
The  precipitate  yielded  by  Milloii's  reagent  dissolves  with  a  red 
color,  if  only  small  quantities  of  the  mercury  solution  are  used.  More 
of  the  reagent  gives  a  red  precipitate,  permanent  on  heating ;  cupric 
sulphate,  ferric  acetate,  ferric  sulphate,  lead  acetate  and  basic  lead 
acetate  do  not  precipitate  the  peptone  solution,  unless  sodium  chloride 
or  potassic  acetate  is  present. 
The  author  then  proceeds  to  say  that  from  these  reactions  no  albu- 
min can  be  present.  Peptones  from  fibrin  or  albumin  or  other  sources 
resemble  one  another  in  all  their  chemical  properties.  All  are 
Isevorotatory,  but  there  is  some  difference  in  the  degree  of  rotation, 
albumin  peptone  having  the  least,  and  casein  peptone  the  greatest^ 
effect  on  polarized  light. 
No  elementary  analysis  was  made  by  the  author.  The  question 
whether  peptone  is  isomeric  with  albumin,  or  differs  from  it  by  one  or 
more  molecules  of  water,  is  then  raised,  and  the  experiments  of 
Huizinga  and  others  on  the  subject  criticized  at  great  length.  With, 
the  view  of  showing  that  these  observers  did  not  use  a  pure  material,, 
Meissner's  peptones  are  examined  with  the  same  conclusion. — Joui\ 
Chem,  Soc,  Dec.  1880,  from  Pfluger^s  Archiv. 
