86 CHEMICAL AN A ITS IS 



I afterwards fubjected fome other whinftones to the fame 

 kind of precedes, and in each fpecies found foda. The nitric 

 and muriatic acids alfo diflblve a certain quantity of the alkali 

 contained in thefe fubftances ; but their action is weaker than 

 that of the fulphuric acid. 



By the experiments now defcribed, there were feparated from 

 ioo parts of each of the whins, between five and fix parts of 

 fulphate of foda, which may be equal to two or three parts of 

 pure foda. But as thefe two or three parts, when added to the 

 fum of the earths and iron, did not account for the lofs of 6 or 

 7 per cent, always obferved in my analyfes, I was fatisfied that 

 the whole of the alkali was not obtained by the procefTes which 

 were followed ; even although, in that with the whin from the 

 Water of Leith, it had been expofed, in very fine powder, to the 

 action of the fulphuric acid, at a boiling heat, for more than eigh- 

 teen hours. It appeared necefTary, therefore, to try other methods j 

 and after fome confederation it occurred to me, that if the pow- 

 dered whins could be expofed, while red hot, to the vapours of the 

 fulphuric acid, alfo in a red hot flate, its power in feparating 

 the whole of the alkali from the earthy bafes of thefe fubftances, 

 would probably be greatly increafed in fo high a temperature. 

 I fucceeded in applying a red heat both to the powdered ftone, 

 and to the acid at the fame time, by the following means. 



Some of the bafalt of StafFa being mixed, in very fine pow- 

 der, with three parts of fulphuric acid, the mixture was evapo- » 

 rated flowly to drynefs in a fand bath. The dry mafs was then 

 * heated gradually to rednefs, and kept in the fire for one hour. 

 It was next powdered, and boiled in water j and the water being 

 filtered, was treated with carbonate of ammonia, which threw 

 down a fmall quantity of a brownifh precipitate. After fepara- 

 ting this precipitate by filtration, the liquor was evaporated to 

 drynefs, and the fulphate of foda, which was left, was purified 



in 



