A Chemical Andyfis of Three Species of^VhinJlone, and Ttoi of Lava. 413 



By the experiments now defcribed, there were ftparated from lOO 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 annly^es, I 

 was fatisfied that the whole of the alkali was not obtained by the proceffes which were 

 followed; even although, in that with the whin from the Water of Leirh, it had been ex- 

 pofed, in very fine powder, to the aftion of the fulphuric acid, at a boiling heat, for more 

 than eighteen hours. It appeared neceflary, therefore, to try other methods ; and after 

 fome confideration it occurred to me, that if the powdered whins could be expofed, while 

 red hot, to the vapours of the fulphuric acid, alfo in a red hot ftate, its power in fepa- 

 rating the whole of the alkali from the earthy bafes of thefe fubftanccs, would probably be 

 greatly increafed in fo high a a temperature. I fucceeded in applying a red heat both to 

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



Some of the bafalt of StafFa being mixed, in very fine powder, with, three parts of ful- 

 phuric acid, the mixture Was evaporated 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 pow- 

 dered, and boiled in Water ; and the water being filtered, was treated with carbonate of 

 ammonia, which threw down a fmall quantity of a brownifti precipitate. After feparating 

 this precipitate by filtration, the liquor was evaporated to drynefs, and the fulphate of foda, 

 which was left, was purified in the manner already defcribed, and heated red hot. It 

 amounted to y parts for every 100 parts of the bafalt employed. 



In this experiment, the fulphuric acid was firft united to a part of the lime, of the argil,, 

 and of the iron, contained in the (lone ; and afterwards, when the mafs was expofed to a 

 red heat, the acid was driven off partly or wholly from thefe, and applied in red hot vapours 

 to every part of the powder ; by which its aftion appears to have been rendered much 

 more powerfuf, as 9 prr cent, of fulphate of foda was produced : and by the fame procefs,' 

 fo fimple and eafy to execute, I got from the reft of the fubftances, to be mentioned in 

 this paper, from 8 to 1 1 per cent, of fulphate of foda, although, when they were merely 

 boiled in the acid, the quantity of this fait never exceeded 5 or 6 per cent. 



As the proportion of acid and alkali in neutral falts has not been hitherto determined 

 with certainty, the quantity of foda in thefe whins cannot be exaftly known. But itls' 

 probable that 9 parts of fulphate of foda, dried by a red heat, do not contain lefs than J-j- 

 or 4 parts of pure alkali* ; which muft therefore- be confidered as the weight in 100 parts 

 of the bafalt of StafFa; and as 3^ or 4 parts of foda, when added to the fum of the earths 

 and iron, amount nearly to the 100 parts of the (l:)ne employed in the analyfis, this calcu- 

 lation may be reckoned very neat the truth. For the fame reafon I think it likely, that 

 the greater part, or the w,hole of the foda, was obtained from the bafalt by, tfee. nrocefs, 

 which has been laft defcribed. 



• This is nearly the proportion given by Mr. Kirwan, 



. It 



