236 
ON  FUSED  CYANIDE  OF  POTASSIUM. 
tassiura  to  form  four  at.  cyanate  of  potash  and  eight  at.  carbonic 
oxide: 
8  at.  C02  and  4  at.  KCy,  form 
4  at.  KO+CyO  and  8  at.  CO. 
Of  the  25  at.  KCy  there  remain  21  at.;  and  to  the  five  at. 
KO-f-CyO  four  more  are  added,  making  21  at.,  KCy  and  nine 
at.  KO-|-CyQ,  which  stand  in  the  relation  to  each  other  of  seven 
to  three.  The  oxygen  of  the  air  may  also  exert  a  partial  oxi- 
dizing agency  on  the  cyanide.  Besides  the  products  already 
mentioned,  when  the  carbonate  of  potash  or  ferrocyanide  of  po- 
tassium is  not  thoroughly  dry,  ammonia  is  also  formed  and 
being  evolved  on  fusing,  is  detected  by  its  odor. 
The  mixture  must  be  added  to  the  crucible  by  small  quantities 
at  the  time,  to  allow  of  its  being  covered  by  the  fused  portion, 
as  all  which  adheres  to  the  sides  of  the  crucible  above  this  does 
not  form  a  pure  product.  It  is  necessary  to  take  care  that  no 
particles  of  iron  remain  floating  in  the  mass  previous  to  pouring 
it  out. 
Eight  parts  of  prussiate  of  potash  and  three  parts  of  carbonate 
of  potash  should  produce  more  than  seven  parts,  but  the  yield 
is  never  so  high  as  this?  in  consequence  of  a  portion  adhering  to 
the  crucible.  To  avoid  wasting  this,  the  crucible  is  well  washed 
with  cold  water,  filtered  as  quickly  as  possible,  and  the  solution 
used  to  form  other  metallic  cyanides,  as  cyanide  of  zinc,  by  ad- 
ding to  it  a  solution  of  sulphate  of  zinc,  &c.  It  is  seldom,  how- 
ever, that  a  solution  of  cyanide  of  potassium  obtained  in  this 
manner  is  free  from  iron  ;  as  the  particles  of  this  metal  in  the 
crucible  abstract,  during  the  digestion  with  water,  a  portion  of 
the  cyanogen  from  the  cyanide  of  potassium,  and  form  with  an- 
other portion  of  the  latter  ferrocyanide  of  potassium  ;  the  libe- 
rated potassium,  by  decomposing  water  and  eliminating  hydrogen, 
forming  potash  : 
3  at.  KCy  1  at.  Fe,  and  1  at.  HO,  form 
1  at.  2KCy+FeCy,  1  at.  KO,  and  1  at.  H. 
Properties. — The  preparation  just  described  forms  solid  white 
lumps  of  a  crystalline  fracture,  odorless,  but  possessing  a  strong 
alkaline  taste  like  bitter  almonds.  In  the  air  it  deliquesces, 
evolving  prussic  acid  and  carbonate  of  ammonia,  whilst  carbonate 
