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- 

 fcarcely 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 mod: 

 exact that could be depended on, the quantity of largely diluted 

 vitriolic acid, employed in faturating the foffil alkali of the 

 water, was gr. 163.4 ; for the whole quantity added was 

 gr. 400, and the fait 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 elfays I had made, of the power of this di- 

 luted acid in faturating the pure or cauftic foflil 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. 



The reafon for boiling thefe waters, with the quantities of 

 acid which I 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 filieeous 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 doubt may however pombly 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 dimpated, the conclufions concerning 

 the quantity of the alkali would be neceHarily erroneous. 



To 



