158 
ON  A  NEW  COBALT  COLOR. 
sulphuret  of  ammonia  almost  immediately  causes  the  formation  of 
black  sulphuret  of  cobalt.  The  action  of  acids  on  this  substance 
gives  rise  to  a  disengagement  of  suffocating  vapors.  Calcined  in 
a  sealed  tube,  it  changes  its  tint,  which  passes  to  an  orange-yel- 
low. At  the  same  time  it  becomes  fused,  and  water  is  disengaged, 
together  with  the  red  fumes  of  hyponitric  acid,  and  the  white  va- 
pors of  nitric  acid.  The  residuum  obtained  is  composed  of  sesqui- 
oxide  of  cobalt  and  nitrate  of  potash. 
By  operating  in  a  current  of  nitrogen  or  dry  carbonic  acid,  there 
are  obtained  in  addition  all  the  products  of  binoxide  of  nitrogen. 
Lastly,  under  the  same  circumstances,  but  employing  the  elevated 
temperature  of  a  bright  charcoal  fire  to  effect  the  decomposition 
of  this  substance,  there  is  obtained,  after  the  removal  of  carbonic 
acid  by  means  of  potash,  and  binoxide  of  nitrogen  by  sulphate  of 
protoxide  of  iron,  a  gaseous  residuum,  presenting  the  characteris- 
tics of  nitrogen. 
Analysis  gave  the  following  formula  for  the  constitution  of  this 
new  color,  Az2  08>  Cb  O,  K  0,  J  H  0. 
It  is  therefore  necessary,  as  well  on  account  of  the  presence 
of  water,  as  the  formation  of  sesquioxide  of  cobalt  by  calcination, 
to  double  the  above  formula,  which  thus  becomes  2  (Az2,  08,  Cb 
0,  KO)  H  O  in  equivalents. 
Ear  sume,  it  thus  appears  that  this  salt  must  be  considered  as  a 
combination  of  nitric  and  nitrous  acids  united  to  potash,  water,  and 
protoxide  of  cobalt.  This  is,  at  least,  the  most  simple  description 
of  it,  resulting  from  an  examination  of  its  mode  of  production,  &c. 
On  account  of  the  great  beauty  of  its  color,  and  its  capability 
of  resisting  the  ordinary  agents  of  oxidation  and  sulphuration,  M. 
St.  Evie  is  of  opinion  that  this  color  may  be  successfully  employ- 
ed in  painting.  Experiments  which  have  been  made  on  this  point 
during  the  last  twelve  months,  the  particulars  of  which  are  in  the 
hands  of  M.  Chevreul,  tend  to  show  that  it  may  be  employed,  with- 
out undergoing  any  change,  both  in  oil  and  water  painting.  Seve- 
ral artists  have  used  it,  and  it  is  very  probable  that  the  color 
will  prove  an  addition  to  the  fine  arts. — Annals  of  Pharmacy, 
Dec.  1852. 
