A%i°rir;i87h9arm'}        Sulphocarbonate  of  Potassium.  1 8 1 
by  an  equal  number  of  atoms  of  sulphur  ;  the  formula  for  sulphocar- 
bonate of  potassium  is  therefore  K2CS3. 
On  passing  carbonic  acid  gas  into  an  aqueous  or  alcoholic  solution  of 
potassa,  carbonate  and  finally  bicarbonate  of  potassium  is  formed.  A  pre- 
cisely analogous  reaction  is  obtained  if  an  aqueous  solution  of  monosul- 
phide  of  potassium  isacted  upon  by  carbon  bisulphide  ;  K2S  +  CS2  Welds 
K2CS3.  Carbon  bisulphide  is  insoluble  in  water,  and  its  solubility  in  this 
menstruum  is  not  materially  increased  by  the  presence  of  a  polysulphuret 
or  of  the  officinal  sulphuret  of  potassium.  The  preparation  of  sulpho- 
carbonate involves,  therefore,  the  previous  formation  of  potassium  mono- 
sulphide,  and  this  is  most  conveniently  obtained  by  passing  sulphuretted 
hydrogen  gas  into  a  solution  of  caustic  potassa  as  long  as  the  gas  is 
absorbed,  and  afterwards  adding  an  equal  bulk  of  the  same  alkaline 
solution.  In  its  purest  state  it  yields  on  evaporation  colorless  prisms 
of  the  hydrated  sulphide,  which  are  deliquescent  on  exposure,  dissolve 
readily  in  alcohol  and  water,  and  in  contact  with  the  air  become  oxid- 
ized. The  solution  in  water  obtained  in  the  manner  indicated  is,  there- 
fore, best  preserved  in  well  filled  bottles,  or  it  is  at  once  agitated  with 
carbon  bisulphide,  as  long  as  the  latter  is  dissolved.  The  combination 
is  effected  in  a  stoppered  bottle  at  a  temperature  of  30°C.  (86°F.)  ;  as 
the  carbon  bisulphide  dissolves,  the  liquid  acquires  a  yellow,  brown- 
veliow  or  red-brown  color,  according  to  the  concentration  and  purity 
of  the  solution.  On  careful  evaporation  at  the  temperature  indicated 
and  subsequent  cooling,  yellow  crystals  of  the  hydrate  are  obtained, 
which  at  a  somewhat  higher  temperature  part  with  their  water  and 
leave  the  anhydrous  compound.  Potassium  sulphocarbonate  is  very  deli- 
quescent, freely  soluble  in  water,  sparingly  soluble  in  alcohol,  and  has 
a  cooling,  afterwards  pungent  and  peppery,  and  finally  somewhat  sul- 
phurous taste. 
The  sparing  solubility  in  alcohol  of  potassium  sulphocarbonate,  and 
the  free  solubility  in  the  same  liquid  of  potassium  monosulphide,  sug- 
gests the  preparation  of  the  former  from  an  alcoholic  solution  of  the 
latter.  On  adding  to  such  a  concentrated  solution  carbon  bisulphide  as 
long  as  this  is  taken  up,  the  liquid  will  gradually  separate  into  two  or 
three  layers,  the  lowest  of  which  is  a  syrupy  solution  of  the  compound 
desired.  But  for  the  purposes  for  which  potassium  sulphocarbonate  is 
employed,  it  is  obtained  sufficiently  pure  by  the  process  described 
before. 
