THE  OPERATIVE  CHEMIST.
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common  antimony,  22  pounds  1  of  sub  carbonate  of  potasse,
and  20  gallons  of  water  in  an  iron  pot,  filtering  the  liquor
while  hot  into  earthen  pans,  and  letting  it  cool  slowly  for
24  hours;  the  Kermes  mineral  is  deposited  in  form  of  a
deep  purple-  brown  velvetty  powder.
The  supernatant  liquor,  on  the  addition  of  any  acid
yields  an  orange  sediment  called  golden  sulphur  of  antimony ¬
  ;  which  the  calico  printers  use  as  a  yellow  colour.  The
supernatant  liquor  is  evaporated  and  crystallized,  the  crys
tals  dissolved  in  water,  the  solution  thickened  with  paste  or
gum,  and  thus  printed  ;  the  cloth  is  then  dried,  and  passed
through  a  very  weak  acid  liquor,  which  separates  the
golden  sulphur,  and  fixes  it  on  the  cloth.
REGULUS  OF  COBALT.
Called  by  the  theoretical  chemists  simply,  cobalt,  which  is
properly  the  name  of  the  ore  from  which  this  metal  is  extracted. ¬

Regulus  of  cobalt  is  not  smelted,  but  the  ores  are  treated
for  the  oxide  of  that  metal,  which  is  a  rich  blue  colour.
Zaffre.
Zaffre  is  prepared  from  the  ores  of  cobalt  that  contain
sulphur  and  arsenic,  and  which  are  roasted  3  or  5  Cwt.  at  a
time,  in  a  reverberatory  furnace,  with  chambers  attached  to
receive  the  arsenic.  The  ore  generally  loses  rather  more
than  1/3ra  of  its  weight,  so  that  a  Cwt.  yields  about  68  pounds
of  zaffre,  or  zafflor.
The  ores  that  contain  much  nickel  are  not  fit  for  the  preparation ¬
  of  zaffre,  as  the  oxide  of  nickel  would  injure  the
beauty  of  the  blue  colour,  or  smalts;  for  the  making  of
which,  zaffre  is  manufactured.
Inferior  kinds  of  zaffre  are  made  by  mixing  this  oxide,
previously  stamped  and  sifted  to  a  fine  powder,  along  with
calcined  flints,  or  quartz,  also  ground  in  various  proportions, ¬
  according  to  the  use  for  which  it  is  intended,  moistening ¬
  the  whole  with  water,  and  packing  it  tight  in  casks,
where  it  hardens  to  a  stone.
A  very  fine  zaffre,  or  China  blue,  is  obtained  from  the
arsenical  and  grey  cobalt  ore,  found  in  Cornwall,  by  boiling
the  powdered  ore  in  nitric  acid,  which  converts  the  arsenic
into  arsenical  acid,  and  unites  it  with  the  different  metals
contained  in  the  ore.  The  solution  being  diluted  with  a
large  quantity  ot  water,  purified  pearl-ash  water  is  then
added  in  small  portions  to  the  diluted  solution,  and  on  the