Acidity , Decompcjition of Water , and Phloglftoru j 2 5 
abundant, and deliquefeent cryftals formed. The fecond pe- 
riod is when the acid has been completely faturated, or per- 
haps fuperfatu rated, by repeated and alternate evaporation to 
drynefs, and re-diflolution in water, and then no cryftals but 
a green powder is formed. The third period is when, by a fur- 
ther evaporation of acid and increafe of heat, the green pow- 
der is changed into a brown or black calx. The complete fatu- 
ration of the green liquor feems then to be the caufe of the 
formation of the green powder on evaporation, inftead of deli- 
quefeent cryftals ; and the production of the brown calx may 
be fuppofed to be either the refult of a calcination of a part of 
the folution of copper which may have taken place in confe- 
quence of the great heat excited by the inflammation of the 
two airs j or to have been formed by the aCtion of the heated 
dephlogifticated air on the copper. 
In order to find the quantity of acid that was contained in 
the green liquor, I added, by flow degrees, to 100 grains of 
this liquor, a folution of mild fixed alkali, till no more preci- 
pitation took place, taking great care to ceafe adding alkali as 
foon as the copper ceafed to precipitate, to prevent a re-diffolu- 
tion of the precipitated metal. Upon examining how much of 
this alkaline folution was required to faturate a given quantity 
of oil of vitriol of the common fpecific gravity, viz. to water 
as 1844 to 1000, I found that the 100 grains of green liquor 
required for its precipitation as much alkali as would faturate 
2,837 grains of the above-mentioned acid of vitriol. And as 
the whole quantity of green liquor was 442 grains, its preci- 
pitation would require as much alkali as would be capable of 
faturating 12,54 grains of the concentrated vitriolic acid. 
This quantity of vitriolic acid is capable of faturating as 
much vegetable fixed alkali, as is contained in 22I grains of dry 
X x 2 nitre, 
