AmNoZ'S&arm'}      Sodium  Thiosulphate  and  Acids.  583 
BEHAVIOR  OF  SODIUM  THIOSULPHATE  WITH 
ACIDS.1 
By  W.  Vaubel. 
The  author  having  noticed  that  by  the  decomposition  of  this  salt 
by  acids,  small  quantities  of  hydrogen  sulphide  were  sometimes 
formed,  has  carefully  studied  its  behavior  towards  acids.  With 
formic,  acetic,  succinic,  citric,  hydrobromic,  hydriodic,  hydrofluoric, 
nitric,  sulphurous,  dithionic,  phosphoric,  and  very  dilute  sulphuric 
acids,  the  amount  of  sulphurous  anhydride  and  sulphur  obtained 
always  agrees  with  that  required  for  the  equation  ]Sra2S203-(-2AcOH 
=2AcONa-j-H20-f  S02  +  S.  But  with  stronger  sulphuric  acid  this 
is  not  the  case.  In  a  series  of  experiments  where  10  mols.  of  sul- 
phuric acid  of  various  degrees  of  concentration  were  employed  to  1 
mol.  of  sodium  thiosulphate,  and  the  reaction  completed  in  the  cold, 
the  sulphurous  anhydride  evolved  varied  from  74  per  cent,  of  the 
theoretical  with  acid  of  20  per  cent,  to  92  per  cent,  with  acid  of  90 
per  cent.,  the  precipitated  sulphur  more  nearly  approached  the  the- 
oretical quantities.  But  with  100  per  cent,  sulphuric  acid,  the  per- 
centage of  sulphurous  anhydride  fell  to  45*4  per  cent.,  that  of  precipi- 
tated sulphur  to  915  per  cent.,  whilst  much  less  than  the  theoretical 
quantity  of  sulphuric  acid  was  neutralized.  In  the  last-named  reac- 
tion the  evolution  of  hydrogen  sulphide  was  very  noticeable.  With 
more  dilute  acid,  it  was  often  detected,  but  was  estimated  with  the 
sulphurous  anhydride. 
When  these  experiments  were  repeated  with  10  per  cent.,  20  per 
cent.,  and  40  per  cent,  hydrochloric  acid,  the  sulphurous  anhydride 
varied  between  82-88  per  cent,  of  the  theoretical,  that  of  precipitated 
sulphur  between  86  and  97  per  cent.,  whilst  quantities  of  sulphuric 
acid  corresponding  with  6  to  8'5  per  cent,  sulphur  were  always 
formed. 
Geuther  showed  that  when  a  solution  of  sodium  thiosulphate  is 
treated  with  silver  oxide,  silver  sulphide  is  formed,  and  the  author 
finds  that  the  quantities  so  formed  correspond  exactly  with  those 
required  for  the  equation  Ag20+Na2S203=AgoS-|-Na/S04.  Orlowski 
has  shown  (J.  Buss.  Chem.  Soc,  1883  [i],  32)  that  those  elements 
precipitated  by  hydrogen  sulphide  in  acid  solutions  are  also  under 
like  conditions  precipitated  as  sulphides  by  sodium  thiosulphate. 
1  Berichte,  xxii.,  1686-1694;  reprinted  from  Jour.  Chem.  Soc,  1889,  p.  943.  See 
also  this  Journal,  page  524. 
