x°6 An ANALTSIS of 



place, be deducted from the gr. 91.68, and thus we have 

 gr. 88.18, as the quantity of the diluted vitriolic acid which 

 was employed folely in faturating the alkali of the water. But 

 from the eflays I had made of the power of this diluted acid in 

 faturating alkalis, it is evident that this quantity of it was fuf- 

 ficient for faturating gr. 0.5 14 of the pure or cauftic foffil alkali, 

 or gr. 0.857 °f that which is faturated with air and evaporated 

 to drynefs, or about gr. 2.38 of that which is faturated with 

 air and in form of tranfparent cryftals. 



The next ftep was to make a fimilar experiment to determine 

 the proportion of alkali in the Geyzer water 5 but here I found 

 it necefTary to change a little the mode of afcertaining the point 

 of faturation. 



The water of Geyzer, by means of the fulphureous gas, 

 which it contained in greater quantity than the other, and per- 

 haps alfo by means of fome of the other ingredients which it 

 contained, and which gave it a light yellowifh colour, pro- 

 duced fuch a change in the colour of litmus, that it could not 

 be employed, as in the laft experiment, by mixing it with the 

 acidulated water and boiling them together ; the purple of the 

 litmus was changed to an orange, which could not be made to 

 return to blue or purple, although I added a quantity of alkali, 

 which rendered the liquor very evidently alkaline, when it was 

 examined by other trials. I therefore had recourfe to the com- 

 mon method, which I had formerly praclifed in many other 

 experiments of a fimilar nature, I mean the ufe of linen rags, 

 or bits of cambric, which had been tinged with an in'fufion of 

 litmus. A little bit of thefe, when touched with a liquor that 

 is in the fmalleft degree acid or alkaline, has its colour changed 

 from the purple to red or blue. This method is, next after the 

 one employed in the laft experiment, the moft nice that 1 know ; 

 provided that, in having recourfe to it, we remember what was 

 remarked in the former experiment, that the litmus colour is 

 affecled by acids in general much more eafily than by alkalis ', 



and 



