ON ARTIFICIAL BLUE COPPER. 
217 
moved from the fire and allowed to cool and the lid taken 
off, when, if the right time has been hit, a portion of the 
sulphur will be found sublimed, and this should then be 
furthered by gentle heat. If the mass does not possess a 
dark blue, but still a black colour, it must be mixed with 
more sulphur and chloride of ammonium, and heated as 
above, constantly taking care, however, that the tempera- 
ture is not too high ; it is on that account advisable to add 
from time to time fresh portions of powdered chloride of 
ammonium. The indigo-blue or dark-black powder thus 
obtained is now finely ground, and washed with a sufficient 
quantity of water to remove all chloride of ammonium ; to 
get rid entirely of the sulphur, the well-washed powder is 
boiled with a strong solution of potash or soda until no more 
sulphur is removed. It is frequently requisite to wash the 
compound, which has been well exhausted with boiling 
ley, and to treat it with fresh ley. The mixture might also 
contain undecomposed oxide of copper, which could be re- 
moved by digestion with caustic ammonia, but not without 
occasioning some loss of sulphuret of copper. However, 
when the operation is well conducted, especially with re- 
peated additions of sulphur and chloride of ammonium, no 
such impurity will easily occur. The residuous mass is 
now well-washed with water, to remove all adherent pot- 
ash and soda. The sulphuret of copper so obtained forms 
an indigo-blue or blackish blue dull powder, which when 
burnished with a polishing steel assumes a beautiful steel- 
blue tint. Ground up with oil or varnish, it affords a beau- 
tiful violet-blue. It can be prepared equally well from 
metallic copper, or by mixing the dry monosulphuret of cop- 
per with sulphur and chloride of ammonium, and treating 
it as above directed. Carbonate of copper would answer 
equally well, as also the nitrate, but not the chloride. 
The compound described exhibits the same behaviour 
as the monosulphuret obtained by precipitating persalts of 
