PERROCYANIDE  OP  POTASSIUM. 
233 
tion  of  Professor  Fresenius,  instituted  a  number  of  experiments 
on  the  "melts"  obtained  from  several  factories,  and  the  beha- 
vior of  these  various  ingredients  in  the  presence  of  water.  These 
experiments  have  fully  confirmed  the  opinion  that  the  fresh  and 
still  warm  "  melt  "  does  not  contain  any  ferrocyanide,  and  that 
this  salt  is  formed  only  by  the  action  of  water  or  moist  air  upon 
the  melt. 
Melt  from  the  Buxiveiler  factory  (Bas  Rhin.) — Apparently 
produced  at  a  very  high  temperature ;  very  hard,  fracture  pre- 
senting small  crystals  of  sulphuret  of  iron. 
1.  Alcohol  dissolved  out  sulphocyanide  and  much  cyanide  of 
potassium,  with  a  little  caustic  potash. 
2.  The  residue,  after  perfect  exhaustion  with  alcohol,  was 
then  treated  with  cold  water ;  the  first  portion  of  liquid  contained 
much  cyanide  of  potassium,  sulphuret  of  potassium,  and  carbon- 
ate of  potash,  sulphuret  of  copper  dissolved  in  cyanide  of  potas- 
sium, and  minute  traces  of  ferrocyanide  of  potassium.  The 
second  portion  of  liquid  contained  the  same  substances,  the  pro- 
portion of  ferrocyanide  being  greater.  The  residue  consisted  of 
carbon,  sulphuret  of  iron,  metallic  iron,  and  carburet  of  iron. 
3.  A  portion  of  the  melt  was  digested  for  twenty-four  hours 
with  water,  air  being  excluded.  The  solution  obtained  contained 
besides  cyanide  of  potassium  a  tolerably  large  quantity  of  ferro- 
cyanide. 
4.  A  portion  of  the  moistened  melt  was  exposed  to  a  stream 
of  carbonic  acid  in  a  closed  apparatus,  and  the  evolved  gas  passed 
through  an  acidulated  solution  of  silver.  In  this  way,  sulphuret 
and  cyanide  of  silver  were  precipitated,  which  proves  that  the 
melt  contained  cyanide  of  potassium,  for  carbonic  acid  does  not 
disengage  hydrocyanic  acid  from  solutions  either  of  sulphocya- 
nide or  ferrocyanide  of  potassium. 
5.  A  portion  of  the  melt  was  treated  with  water  in  a  flask  at 
a  temperatue  of  about  122°  Fahr.  A  very  small  evolution  of 
ammonia  was  observed,  and  the  solution  contained  a  large  quan- 
tity of  ferrocyanide,  together  with  some  cyanide  of  potassium. 
6.  Another  portion  was  boiled  for  some  time  with  water  in  a 
retort.  The  evolution  of  ammonia  was  considerable,  and  the 
solution  contained  a  great  quantity  of  ferrocyanide  of  potassium. 
7.  A  portion  of  the  melt  was  digested  with  water  in  a  small 
gas  generator  at  212°  F.,  and  the  gas  evolved  passed  first  through 
