55 
Copper . 
Sulphat of copper has a very strong, styptic, somewhat 
acidulous, and excessively nauseous taste. It is soluble 
in about four times its weight of water. When dried at a 
heat not exceeding that of boiling water, it loses, accord- 
ing to Proust, about 36 per cent . which is mere water, 
after which the residue, which is a white pulverulent mass, 
is again soluble and crystallizable, as at first. But if it is 
calcined with a strong white heat, the acid itself is expel- 
led without undergoing decomposition, and at length there 
only remains black oxyd of copper, in the proportion of 
32 per cent, of the original crystallized salt. Hence 100 
parts of sulphat of copper consist, according to Proust, of 
Copper 25.6 1 forming 
Oxygen 6.4 5 black oxyd § w 
Sulphuric acid 32 
Water 36 
100 
BergmamPs analysis of this salt nearly agrees with that 
of Proust in the proportion of copper (26 per cent.) ; but 
of the other ingredients he reckons 28 of water, and 45 of 
acid. \_Rees\s Encyc. Art. Copper . 
Verdigris .— I know of no more authentic account than. 
ChaptaPs dissertation on the subject who has had more 
opportunities of information than any person else who has 
treated on this manufacture. I would premise, however, 
that I can see no reason why common blue vitriol preci- 
pitated by pearl ash, will not answer all the purposes of 
verdigris. They are both carbonals of copper. In the 
dying of hats, I am persuaded that much of the verdigris 
is wasted, and that blue vitriol would be an advantageous 
substitute; for blue vitriol and logwood give a blue, 
which though very fugitive on cotton, stands tolerably well 
when mixed with the black dye of the hatters* 
