65 
sticks, and cover them entirely, forming themselves into 
groups or dusters, which present on all sides perfect 
rhombs of a very lively dark blue colour,. Each cluster 
weighs from five to six pounds. These crystals, when 
broken, exhibit on their fracture a brilliant agreeable green,, 
inclining a little to blue. 
Three pounds of moist verdigris are necessary to make 
a pound of crystals. The indissolved residuum is re- 
jected as useless* Analysis, however, having proved to 
me that a great deal of copper in a metallic state, or weak- 
ly oxydated, still exists in it, I disposed boards in the 
form of a stage around the manufactory of C. Durand* 
and, forming strata of about two inches in thickness with 
these remains, I soon saw them covered with an efflor- 
escence of verdigris. I took care to moisten them from 
time to time with vinegar, to dissolve the verdigris as soon 
as a sufficiently strong efflorescence was formed, and they 
were again disposed in strata to proceed as before, in or- 
der that I might derive as much advantage from the resi- 
duum as I should find convenient. 
There are some manufactories of the crystals of 
Venus where the verdigris is prepared by means of vine- 
gar distilled according to the method followed at Greno- 
ble, which is well understood. All the operations tend to 
the same end, which is the solution of the copper in the 
acetous acid ; and the purity of the materials renders it 
certain that there will be no residuum or loss. But how- 
ever simple may be the process for manufacturing crys- 
tallized verdigris, the high price at which it is sold makes 
it much to be wished that it could still be rendered more 
so. I made some experiments for that purpose ; but at 
present I shall confine myself to a short view of my re- 
sults. We must set out from the principle, that the 
acetous acid does not attack copper in the state of a me- 
tal, and that it cannot effect a solution of it but when re- 
I 
