A Oiemical Analyjis of Three Species of Whiriflone, and Two of Lava. 41 1- 



About a year ago I analyzed fpecimens of fome of the vphins in the neighbourhood of 

 ■Edinburgh, and found, that the fum of the earths and iron, feparated by the analyfes, 

 never amounted to more than 93 or g4 per cent.; fo that the lofs was always equal to that 

 juft mentioned. It was this circumftance which firft led me to fufpe£l that fome falinc 

 fubftance exifted in thefc ftoncs ; and their confiderable fulibility favoured the fufpicion. 



Soon after thefe analyfes were made, I obfcrved another circumftance, which amounted 

 to an abfolute proof of the whins containing fomething of a faline nature, in combination 

 with their earthy bafes. Moft of the artificial cryftallites, made by Sir James Hall, which 

 I had always an opportunity of examining, threw out on their furfaces, two or three weeks 

 after their formation, a white efflorefcence, which had a very fait tafte. It was in too 

 fmall a quantity to be colleded and examined ; but when waftied off, it was often formed a 

 fecond time. 



I was thus convinced of the exiftence of fome faline fubftance in thefe bodies, and made 

 different experiments with feveral of them, in order to feparate it, and afcertain its nature ; 

 and foon found that it was foda. 



I {hall next defcribe fome of the methods by which this alkali was moft eafily feparated 

 from the earthy parts of the whins. 



Experiments to obtain the Soda, and determine its ^tantity. 



Having broken fome of the bafalt of Staffa to fmall fragments, I weighed 400 grains, 

 and ground the whole with water to an extremely fine powder, in a Wedgwood mortar. 

 The powder, and the water with which it had been ground, were then put into a fmall 

 retort, and mixed with about 1200 grains of fulphuric acid, which I had carefully diftilled 

 for this operation. I placed the retort in the fand bath of a fmall furnace which I ufe for 

 analyfes, adapted a receiver, raifed the fire till the acid began to diftil flowly, and carried 

 on the diftillation to drynefs. Water was then poured into the retort, and boiled, the 

 mixture thrown on a filter, and the undiflblved refiduum fufEciently waftied. This refi- 

 duum was next treated a fecond time with a frefti portion of fulphuric acid ; and after- 

 wards boiled with water, filtered and vi'aftied, exactly in the fame manner as before. The 

 undiflblved part of the ftone was now almoft white. 



The filtered folutions being mixed together, were evaporated to drynefs ; and the faline 

 mafs which remained was heated red hot for one hour in a clean and new JrlefTian crucible. 

 When cold the mafs was of a brick red colour. Having powdered it well, I boiled it in 

 water, poured the whole on a filter, and waftied the reddlfti matter carefully. This fil- 

 tered liquor, in which all the foda, feparated from the bafalt by the fulphuric acid, was 

 diflblved in the ftate of fulphate of foda, could contain only a fmall quantity of earthy 

 matter ; for the greater part of the fulphate of argil, and of iron, formed by the firft part 

 of the procefs, muft have been decompofed by the red heat, to which the mafs was after- 

 wards expofed. Accordingly, the folution being treated with carbonate of ammonia, only 

 a fmall quantity of a precipitate was thrown down, which ^yas carefully feparated. The 



3 G 2 IblutioB 



