So CHEMICAL ANALTSIS 



proper wafliing, being dried, and heated red hot a quarter of an 

 hour, weighed 43 grains, and was perfectly white. To learn whe- 

 ther this filex was free from every other earth, I mixed a part of 

 it with four parts of carbonate of foda, and melted the mixture 

 in a filver crucible. Water, being poured on the melted mafs, 

 diflblved it entirely into a liquor filicum, which was diluted 

 largely, and faturated exactly with an acid. No precipitate ap- 

 peared, even after fix or eight days ; therefore thefe 43 grains 

 were pure filex. 



,5. The folution, No. 4. (from which the filex had been fepa- 

 rated), was of a light greenifh colour. Cauftic ammonia, when 

 poured into it, threw down a brownifh precipitate. Having 

 carefully feparated this precipitate, and warned it on a filter, I 

 dropt into the remaining folution, which was now colourlefs 

 and tranfparent, a fmall quantity of fulphuric acid, in order to 

 detect barytes or ftrontian. No precipitate was formed. The 

 folution was then evaporated to a fmall quantity, and treat- 

 ed with carbonate of ammonia, by which a fecond portion of 

 carbonate of lime was obtained. Its weight, after being heated 

 red hot, was 97 grains. 



6. The brownifh precipitates, thrown down from the folu- 

 tions No. 2. and 5. by cauftic ammonia, had the appearance of 

 argil mixed with iron. To feparate the argil, thefe precipitates 

 were mixed together, and boiled, while flill moift, in a folution 

 of cauftic potafh, in a filver crucible. A part was difTolved ; 

 but a fpongy matter remained, of a darker brown colour than 

 at firft, which was collected on a filter. 



7. Into the cauftic-alkaline folution I poured fulphuric acid, 

 till flightly in excefs, and neutralifed it again by carbonate of 

 foda. The argil was precipitated ; which being fufficiently 

 wafhed, was redifTolved in diluted fulphuric acid. This folu- 

 tion was then mixed with fome acetite of potafh, and gave, by 

 jfucceflive evaporations, fmall regular cryftals of alum. At laft 



it 



