AmsJe°Ptr;i?92arm-}        Peptone  Salts  from  Glutin.  479 
are  mixtures  of  compounds  representing  different  degrees  of  pep- 
tonization ;  this  has  been  confirmed  by  subjecting  the  alcoholic 
solutions  to  fractional  precipitation  with  ether,  and  subsequent  frac- 
tional crystallization  of  some  of  the  precipitates  from  alcohol.  The 
salts  thus  obtained  contain  a  varying  percentage  of  acid,  their  solu- 
bility in  alcohol  decreasing  with  the  decrease  in  the  proportion  of 
acid.    A  much  more  satisfactory  separation  is  obtained  by  subject- 
ing an  aqueous  solution  of  the  salts  to  dialysis,  for  although  they  have 
not  been  obtained  crystalline  (probably  owing  to  their  hygroscopic 
nature),  they,  nevertheless,  pass  through  the  dialyser,  and  must  be 
regarded  as  crystalloids.    In  this  manner,  a  salt  containing  10-56 
per  cent,  of  acid  was  separated  into  two  portions,  that  passing 
through  the  dialyser  containing  14-19  per  cent,  of  acid,  and  the 
residue  only  5-79,  the  latter  being  insoluble  in  absolute  alcohol. 
The  percentage  of  carbon  and  hydrogen,  calculated  on  free  peptone, 
remains  fairly  constant,  except  in  so  far  as  the  salts  passing  through 
the  dialyser  are  concerned  ;  the  decrease  in  this  case  is  due  to  the 
fact  that  in  evaporating  the  large  volume  of  solution  obtained,  a 
quantity  of  alcohol  is  split  off.    It  was  found  that  only  those  salts 
containing  10  per  cent,  of  acid  and  upward  are  soluble  in  absolute 
alcohol,  and  those  fractions  which  are  only  just  dissolved  are  much 
less  soluble  in  propyl  alcohol,  and  insoluble  in  amyl  alcohol  ;  the 
salts  containing  less  than  10  per  cent,  are  all  readily  soluble  in 
methyl  alcohol,  and  these  also  dissolve  in  alcoholic  solution  of  the 
salts  containing  more  acid. 
The  same  separation  may  be  brought  about  by  treating  the  alco- 
holic solution  of  the  salt  with  mercuric  chloride;  two  mercuro- 
chlorides  are  thus  obtained,  one  of  which  separates  out  at  once, 
and  the  second  on  the  addition  of  ether ;  these  correspond  to  the 
insoluble  and  soluble  hydrochlorides,  and  may,  like  the  mercuro- 
chlorides  of  the  free  peptones,  be  employed  for  therapeutical  pur- 
poses. 
If  glutin  be  warmed  with  a  weaker  acid  than  that  first  mentioned, 
a  salt  may  be  obtained  which  dissolves  in  methyl  alcohol,  but  is 
insoluble  in  ethyl  alcohol,  and  contains  6-85  per  cent,  of  hydro- 
chloric acid.  It  closely  resembles  the  salts  already  described,  and 
may,  like  them,  be  separated  into  fractions  containing  different  per- 
centages of  acid,  that  containing  the  highest  percentage  bein^ 
somewhat  soluble  in  ethyl  alcohol.    By  the  action  of  pepsin  on 
