66 Copper. 
duced to an oxyd. The question then will be to disco- 
ver the means of oxydating it in an economical manner, 
1st, I exposed the plates of copper to the gazeous ema- 
nations of the oxygenated muriatic acid in large glass re- 
ceivers, connected together in the manner of adopters, 
to which I fitted a retort from which the acid was disen- 
gaged. 
2d, I took a large earthen jar of Provence, well glazed, 
capable of containing two hundred (French) pints of wa- 
ter, buried it one half in a stratum of very warm dung in 
full decomposition, and having put some manganese in 
the bottom of it, and adapted to it a straight glass tube, 
which reached from the mouth to the bottom, I filled the 
jar with plates of copper slightly rolled, in order that they 
might not touch each other but in some points. I then 
made to pass into the bottom of the jar, by means of the 
tube, the necessary quantity of the muriatic acid, and 
immediately closed the upper aperture with a luted cov- 
ering. Two days after these plates were entirely crusted 
over with a greenish oxyd, which detached itself in dust 
and in scales : I separated of it two pounds ten ounces. 
This oxyd, less lively than that of the common verdigris, is 
soluble in vinegar : and this method may then be employed, 
with some advantage, to form the acetat of copper ; but it 
cannot supply the place of the acetous verdigris either 
in painting or dyeing. 
3d, I formed sulphat of copper by pouring, upon plates 
of copper brought to a red heat in a crucible, about a 
third in weight of pounded sulphur. This sulphur, ex- 
ceedingly friable, pulverised and exposed to a pretty vio- 
lent heat for four or five hours, left a grey powder, easily 
attacked by the acetous acid. That which I digested at 
a heat above a gentle temperature, gave, by evaporation, a 
considerable quantity of very blue and beautiful crystals 
of acetat of copper, and a stratum of true sulphat of cop- 
per of a pale blue and without crystals* 
