Analysis of a Black Sandjrom the River T e, 99 



fine, and does not exceed one- fourth of the mixture at 

 most. Its colour is iron-black. It is in very small angu- 

 lar grains, commonly pretty sharp-edged, and sometimes 

 having the shape of imperfect octahedrons. The surface is 

 rough; the lustre is feebly glimmering and metallic; the 

 fracture, from the smallness of the grains, could not be 

 accurately ascertained, but it seemed to be conchoidal, 

 Opake, semi-hard, brittle, easily rciduced to powder. Pow- 

 der has a grayish -black colour ; powerfully attracted by the 

 magnet ; specific gravity 4*765. 



1. As acids were not found to act upon this mineral, 100 

 grains of it were reduced to a fine powder, mixed with 

 twice its weight of carbonate of potash, and exposed for 

 two hours to a red heat in a porcelain crucible. The mass, 

 being softened in water, was digested in muriatic acid. By 

 repeating this process twice, the whole was dissolved in 

 muriatic acid, except a brownish-white matter, which 

 being dried in the open air weighed 19|- grains. 



2. The muriatic acid solution, which had a deep yellow- 

 ish-brown colour, was concentrated almost to dryness, and 

 then diluted with water. It assumed a milky appearance; 

 but nothing was precipitated. Being boiled for some time, 

 and then set aside, a curdy-like matter fell. It was of a 

 i)]ilk-wliite colour, weighed, when dry, seven grains, and 

 possessed the properties of oxide of titanium. 



3. The residual liquid being supersaturated with am- 

 monia^ a dark reddish-brown matter precipitated, which 

 being separated by the filter, dried, drenched in oil, and 

 heated to redness, assumed the appearance of a black mat- 

 ter, strongly attracted by the magnet. It weighed 93*7 

 grains, and was oxide of iron* 



4. The 19'5 grains of residual powder, being mixed with 

 four times its weight of carbonate of soda, and exposed for 

 two hours to a red heat, in a platinum crucible, and after- 

 wards heated with muriatic acid, was all dissolved, except 

 about a grain of blackish matter, which was set aside. 



.*). The muriatic solution being concentrated by evapo- 

 ration, a little white matter was separated. It weighed 

 one-fourth of a grain, and possessed the characters of oxide 

 of titanium. 



6. When evaporated to dryness, and redissolved in water, 

 a white powder remained, which proved to be silica, and 

 which, after being heated to redness, weighed one grain. 



7- The watery solution being supersaturated with potash, 

 Aud boiled for a few minutes, was thrown upon a filter, to 



G 2 ^ separate 



