2 5 6 ANALYSIS of a BLACK SAND 



6. When evaporated to drynefs, and rediflolved in water, a 

 ■white powder remained, which proved to be filica, and which* 

 after being heated to rednefs, weighed one grain. 



7. The watery folution being fuperfaturated with pota£h > 

 and boiled for a few minutes, was thrown upon a filter, to fe- 

 parate a reddifh-brown matter, which had been precipitated. 

 The clear liquid which pafled through The filter, was mixed 

 with a folution of fal ammoniac. A foft white matter flowly 

 fubfided. It was alumina, and, after being heated to rednefs^ 

 weighed half a grain. 



8. The brown-coloured matter which had been precipitated 

 by the potafh, when dried upon the fteam-bath, weighed 20.2 

 grains. It diffolved with erTervefcence in muriatic acid. The 

 folution had the appearance of the yolk of an egg. When 

 boiled for fome time, and then diluted with water, it became 

 white, and let fall a curdy precipitate, which weighed, when 

 dry, 4.6 grains, and poneued the properties of oxide of tita- 

 nium. 



9. The refidual liquor being mixed with an excefs of ammo- 

 nia, let fall a brown matter, which, after being dried, drench- 

 ed in oil, and heated to rednefs, weighed 6 grains. It was 

 ftrongly attracted by the magnet, but was of too light a colour 

 to be pure oxide of iron. I therefore difiolved it in muriatic 

 acid, and placed it on the fand-bath, in a porcelain capfule. 

 When very much concentrated by evaporation, fmall white 

 needles began to make their appearance in it. The addition of 

 hot-water made them difappear ; but they were again form- 

 ed when the liquor became fufficiently concentrated. Thefe 

 cryftals, when feparated, weighed 1.3 grains, and proved, on 

 examination, to be white oxide of arfenic. During the folution 



of 



