198 M. Berzelius on the Comoinations of [Sept. 



from which their stock of verdigris had been obtained. I satis- 

 fied myself, therefore, with selecting for this examination the 

 greenest and the purest blue coloured specimens in my pos- 

 session. 



1. The Green Variety. — Dried in the state of powder, in the 

 open air, this variety left after calcination from 44 to 44-6 per 

 cent, of peroxide of copper. When previously dried in a tem- 

 perature of 140°, it left from 49 to 50 per cent. 100 parts of a 

 quantity dried in this manner, on being analyzed by hydrate of 

 barytes according to the process already detailed, yielded 83*33 

 parts of sulphate of barytes, and 49*86 parts of peroxide of cop- 

 per. This variety of verdigris, therefore, when dried in a tem- 

 perature of 140°, was composed of 



Peroxide of copper 49*86 containing oxygen 10*07 



Acetic acid 36*66 17*23 



Water, including loss 13*48 1 1*88 



The quantity here stated as water, comprehends also certain 

 foreign admixtures, which were in too minute a state of division 

 to admit of being separated without loss. The result demon- 

 strates pretty decisively, that the mass was a mechanical mix- 

 ture, in which the sub-salt soluble in water formed a principal 

 constituent. The property which the soluble sub-salt possesses 

 of giving off half its quantity of water when dried in a tempera- 

 ture of 140°, is an additional proof that it constitutes a chief 

 ingredient in this variety of verdigris, because the latter itself 

 loses about 10 p. c. of water when exposed to a similar degree 

 of heat. 



2. The Blue Variety. — I obtained a remarkably pure speci- 

 men of this variety, which, when examined under a magnifying 

 glass, was found to consist of an aggregation of very minute, 

 shining, crystalline scales. Its powder had an uncommonly 

 beautiful and pure pale blue colour, resembling that of the blue 

 carbonate of copper when pulverized. Dried in a temperature 

 of 68°, and analyzed by hydrate of barytes and by the precipi- 

 tation of metallic copper, in the manner already described, 100 

 parts of it yielded 



Atoms. 



Peroxide of copper . . 43*34 containing oxygen 8*74 1 



Acetic acid 27*45 12*90 1 



Water 29*21 27*97 6 



This result coincides with that of Phillips, and demonstrates 

 that the oxygen of the acetic acid is \\ times that of the base, 

 and that the oxygen of the water is thrice that of the base. 

 The blue species of verdigris, therefore, constitutes an indis- 

 putable exception to the empirical law. So long as we continue 

 unacquainted with any other varieties of this compound, it will 



