Am'uctuTi8?9.arm }    Examination  of  Commercial  Peptones.  525 
respectively.  The  quantity  of  iodine  absorbed  by  the  solution  after 
various  times  and  under  various  conditions  is  given  in  the  form  of  a 
table.  Neglecting  the  complications  due  to  the  action  of  sulphurous 
anhydride  on  thiosulphuric  acid,  it  seems  that  the  decomposition  of 
the  latter  begins  immediately,  and  increases  with  the  time  and  with 
the  proportion  of  hydrochloric  acid. 
The  action  of  sulphurous  acid  on  sodium  thiosulphate  in  various 
proportions  is  always  exothermic,  although  the  development  of  heat  is 
but  slight,  and  it  would  seem  that  there  is  a  division  of  the  base 
between  the  two  acids,  and  interaction  between  those  portions  of  the 
acids  which  remain  free.  When  the  two  liquids  are  mixed,  they 
become  yellow  and  sulphur  is  precipitated,  especially  if  the  thiosulphate 
is  in  excess.  If,  on  the  other  hand,  sulphurous  acid  is  in  excess,  only 
traces  of  sulphur  separate,  and  these  gradually  redissolve.  The 
quantities  of  iodine  absorbed  by  the  liquid  indicate  that  decomposition 
is  not  complete,  but  is  limited  by  the  formation  of  thionic  acids, 
The  latter  reaction  also  remains  incomplete  in  consequence  of  the 
dissociating  action  of  the  water,  and  it  follows  that  when  equilibrium 
is  established,  the  liquid  has  a  very  complex  constitution,  and  contains 
thiosulphuric  acid,  sulphurous  acid,  sulphur,  and  thionic  acids,  the 
base  being  divided  between  thiosulphuric  and  sulphurous  acids. 
EXAMINATION  OF  COMMERCIAL  PEPTONES.1 
By  J.  Koxig  AND  W.  KlSCH. 
The  methods  hitherto  in  use  for  estimating  the  soluble  and  non- 
coagulable  proteids  (the  albuminoses  and  peptones)  are  far  from  satis- 
factory. The  precipitation  of  the  albuminoses  by  ferric  acetate,  with 
subsequent  precipitation  of  the  peptones  by  sodium  phosphotungstate, 
yields  very  discordant  results.  The  authors  adopt  the  method  of  Kuhne 
and  Chittenden  (Am.  Jour.  Phar.,  1886,  p.  563),  precipitation  of  the 
albuminoses  with  a  saturated  solution  of  ammonium  sulphate,  and  in 
another  portion  the  precipitation  of  both  albuminose  and  peptone  by 
sodium  phosphotungstate,  and  estimation  of  the  peptone  from  the 
difference.  From  5  to  20  grams  of  substance  (according  to  the  propor- 
tion of  water  it  contains)  is  taken.  The  insoluble  matter  and  coagu- 
lable  albumin  are  separated  by  nitration  and  by  boiling,  and  their 
lZeit.  anal.  Churn.,  xxviii,  182-201  ;  reprinted  from  Jour.  Chem.  Soc,  August, 
1889,  p.  803. 
