434 
PREPARATION  OP  METALLIC  COBALT. 
the  chloride  of  purpureocobalt ;  any  commercial  oxide  answer- 
ing, even  in  the  presence  of  arsenic,  nickel,  iron,  and  other  im- 
purities. 
A  perfectly  pure  chloride  of  cobalt  is  easily  prepared  from 
this  salt  by  heating  it  in  a  porcelain  crucible  until  vapors  of  am- 
monia and  chloride  of  ammonium  cease  to  be  driven  off.  The 
pure  anhydrous  chloride  of  cobalt  thus  obtained  is  characterized 
by  beauty  of  color,  forming  pale  blue  talcose  scales. 
To  obtain  the  metal  in  a  state  of  sponge,  it  is  merely  neces- 
sary to  reduce  the  chloride  by  means  of  hydrogen.  In  order 
to  fuse  the  metal,  it  is  an  indispensable  precaution,  to  preserve 
its  purity,  that  it  be  effected  by  means  of  the  lime  crucibles  as 
employed  by  M.  Sainte-Claire  Deville.  In  connection  with 
these  crucibles,  he  uses  a  lamp  of  peculiar  construction,  in 
which  the  vapor  of  any  liquid  hydrocarbon,  as  oil  of  turpentine, 
is  completely  consumed  by  means  of  an  artificial  blast  of  air. 
By  means  of  this  instrument  the  fusion  of  felspar  can  be  ac- 
complished with  facility.  It  has  been  found  that  the  platinum 
metals  fused  in  these  crucibles,  present  properties  very  different 
from  those  hraretofore  attributed  to  them,  the  lime  serving  to 
deprive  them  of  osmium  and  silicon. 
As  much  carbon  becomes  mixed  with  cobalt  in  the  ordinary 
method  of  fusion,  one  of  its  characters,  that  of  malleability,  be- 
comes entirely  destroyed  ;  and  a  piece  of  the  metal  thus  pre- 
pared, when  placed  before  the  oxyhydrogen  blowpipe,  upon  a 
brick,  in  which  a  groove  had  been  cut  for  the  purpose  of  obtain- 
ing it  in  the  form  of  a  bar,  merely  assumed  an  intumescent 
state,  without  exhibiting  any  tendency  to  enter  the  incision. 
Since  this,  M.  Debray  has  found  that  pure  molybdenum  com- 
pletely withstands  the  temperature  at  which  platinum,  &c.  be- 
come liquid;  and  that  its  melting-point,  in  a  crucible  of  carbon 
before  the  oxyhydrogen  blowpipe,  is  at  a  temperature  at  which 
rhodium  fuses.  He  further  states,  however,  that  the  fused  mass 
was  contaminated  with  from  4  to  5  per  cent,  of  carbon. — Lond. 
Chem.  Gf-az.,  June  15,  1859,  from  Proc.  Charleston  Nat.  Hist. 
Soc. 
