306       PREPARATION  OF  SULPHOCYANIDE  OF  POTASSIUM. 
THE  PREPARATION  OF  SULPHOCYANIDE  OF  POTASSIUM, 
By  James  F.  Babcock,  Boston. 
The  usual  process  for  the  preparation  of  this  salt,  as  given  by 
Fresenius,  is  as  follows  : 
"  Mix  together  46  parts  anhydrous  ferrocyanide  of  potassium, 
17  parts  of  carbonate  of  potassa,  and  32  parts  of  sulphur;  intro- 
duce the  mixture  into  an  iron  pan  provided  with  a  lid,  and  fuse 
over  a  gentle  fire.  Maintain  the  same  temperature  until  the 
swelling  of  the  mass  which  ensues  at  first  has  completely  sub- 
sided, and  given  place  to  a  state  of  tranquil  and  clear  fusion  ; 
increase  the  temperature  now  towards  the  end  of  the  operation, 
to  faint  redness,  in  order  to  decompose  the  hyposulphite  of  po- 
tassa which  has  been  formed  in  the  process.  Remove  the  half- 
refrigerated  and  still  soft  mass  from  the  pan,  crush  it,  and  boil 
repeatedly  with  alcohol  of  from  80  to  90  per  cent. 
"  Upon  cooling,  part  of  the  sulphocyanide  of  potassium  will 
separate  in  colorless  crystals  ;  to  obtain  the  remainder,  distil  the 
alcohol  from  the  mother  liquor." — Fresenim'  Qual.  Analysis, 
6th  ed.  p.  57. 
Those  who  have  attempted  this  process  may  have  been  dis- 
appointed in  not  obtaining  so  large  an  amount  of  sulphocyanide 
as  they  were  led  to  expect.  The  process  is,  when  best  con- 
ducted, far  from  economical. 
The  management  of  the  heat  is  difficult,  as  well  as  the  exclu- 
sion of  the  air  ;  and  the  subsequent  boiling  "  repeatedly  with  al- 
cohol of  from  80  to  90  per  cent."  is  of  course  expensive. 
Moreover,  the  slimy  mass  left  after  the  solution  has  been 
made  retards,  and  in  some  cases  almost  totally  prevents  the  fil- 
tration of  the  liquid,  while  it  has  been  the  writer's  experience  to 
find  it  extremely  difficult  by  this  process  to  get  rid  entirely  of 
the  sulphide  of  potassium  formed,  the  presence  of  which  unfits 
the  sulphocyanide  for  the  ordinary  uses  to  which  it  is  applied. 
Repeated  failures  by  this  and  other  methods  in  use,  as  the  "  bi- 
sulphide of  carbon  and  ammonia  process,"  (London  Pharm. 
Jburn.,  Vol.  VII.  No.  4,)  which  is  certainly  disagreeable,  and 
not  entirely  free  from  the  objections  mentioned  above;  and  the 
want  of  a  process  really  economical  led  to  experiments,  the  re- 
