5(3 Copper • 
Observations on the Manufacture of the Acetite of Cop- 
per or Verdigris , Verdet , 
T! *e acetite of copper is one of the preparations of that 
metal most frequently used in the arts. It is not only one 
of the principal resources of painting, but upon many oc- 
casions is employed with great advantage in dying. Al- 
most all the oxyds of copper obtained by the action of sa- 
line substances have a blue colour, more or less inclining 
to green ; and almost all the neutral salts corrode the metal, 
and produce that oxyde which is called verdigris. It is 
sufficient to bring them into contact with the copper, or 
to immerse the metallic plates in a saline solution, and 
afterwards to expose them to the air to dry. 
Those acids which oxydate the copper by their decom- 
position, produce an effect like that of neutral salts. The 
oxyde is of a soft blueish-^reen colour ; their action is so 
speedy, that if the copper be exposed to the vapour of 
them for some minutes, its surface will be immediately 
oxy dated. The oxygenated muriatic acid produces that 
effect as well as the vapour of the nitric acid, and even 
those of the sulphuric acid. A phenomenon which can- 
not escape the eye of an observer, is, that the oxydes of 
copper obtained by fire, are very different from those pro- 
duced by the decomposition of acids on that metal. The 
colour of them is grey, instead of being green ; and when 
the calcination is continued a long time at a violent heat, 
they may be concentrated to a red oxyde of a blood co- 
lour. This phenomenon was observed by Kunckle in 
his Chemical Laboratory. 
Saline substances are not the only ones capable of oxy- 
dating copper green. All oils and fat matters produce 
the same effect. Even water, when left for a considera- 
ble time in copper vessels, causes an oxydation. But 
what will appear very extraordinary, is, that the greater 
part of these substances have no sensible effect upon cop- 
