5o CHEMICAL AN ALTS IS 



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

 hour, weighed 43 grains, and was perfe<5lly 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 lilicum, which was diluted 

 largely, and faturated exadlly 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. Cauflic ammonia, when 

 poured into it, threw down a brownifli precipitate. Having 

 carefully feparated this precipitate, and wafhed 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 

 dete(5l 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 Ume was obtained. Its weight, after being heated 

 red hot, was 97 grains. 



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

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

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

 were mixed together, and boiled, while flili moifl, in a folution 

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

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

 At firfl, which was colle6ted on a filter. 



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

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

 foda. The argil was precipitated; which being fuflSciently 

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

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

 jfuccefTive evaporations, fmall regular cryflals of alum. At lafl 



it 



