108 An ANALYSIS of 
produced a change in the litmus colour, or if any change was 
produced, it was only a vergency towards the red, which was 
{carcely perceptible ; and when the ftate of faturation was varied 
from this point, by an addition of 3 grains of the largely di- 
luted vitriolic acid, or by an equivalent quantity of the alkaline 
folution, the tint of the colour was remarkably changed to- 
wards the red or towards the blue. Suppofing therefore the 
above ftate of faturation exact, and I believe it to be the moft 
exact that could be depended on, the quantity of largely diluted 
vitriolic acid, employed in faturating the foflil alkali of the 
water, was gr. 163.4; for the whole quantity added was 
gr. 400, and the falt of tartar of the gr. 84.5, of the dilute fo- 
lution had required gr. 236.6 for its faturation. It follows, 
therefore, from the effays ] had made, of the power of this di- 
luted acid in faturating the pure or caultic foffil alkali, that the 
unfaturated quantity of this alkali, contained in the gr. 10,000 
of the water, was gr. 0.952, which is equal to gr. 1.587 of the 
_ fame alkali combined with air and evaporated to drynefs, or 
gr. 4.409 of the fame in a cryftalized ftate. 
Tue reafon for boiling thefe waters, with the quantities of 
acid which | had added to them, in thefe laft experiments, is 
fufficiently obvious. The abundance of acid was meant to in- 
fure the complete faturation of the whole of the alkali, and fe- 
paration of it from the filiceous earth; and the boiling pro- 
moted the fame purpofe, both by means of the heat which was 
‘applied, and alfo by bringing the acid and alkaline particles 
the nearer to one another, while the water evaporated. 
A pousT may however pofibly arife in the minds of fome 
of my readers, whether this boiling of the water might not be 
attended with the diflipation of fome part of the fuperfluous 
acid, which was not neutralized by the alkali of the water ; and 
if any part of the acid was diffipated, the conclufions concerning ~ 
the quantity of the alkali would be neceflarily erroneous. 
To 
