Id Analysis of Iron Ores, &c. 



employed very pure nitrate of ammonia, instead of the mu- 

 riate. Thus be obtained two percent. (0*3 grains) of a mix- 

 ture of silcx and alumine. 



He next saturated the liquor with pure nitric acid, added 

 a little in excess, and boiled it for a quarter of an hour, in 

 order to dissipate entirely the carbonic acid. 



To a portion of the liquor thus prepared he added a few- 

 drops of the solution of nitrate of mercury at a minimum : 

 but instead of yielding a red colour, as is usual with chrome, 

 they threw down a white precipitate, which at first he took 

 for muriate of mercury, but it afterwards appeared to be 

 phosphate of mercury. — Instructed by this trial, he added to 

 the remainder of the liquor limewater, which, when the 

 aeid was saturated, produced a rloceulent precipitate. This 

 had a slight tint of yellow, which changed to a green on 

 drying, a circumstance that indicated some foreign matter 

 in the phosphate of lime. 



Anxious to discover the cause of this colour, he made the 

 precipitate red-hot in a silver crucible ; but the green tint, 

 instead of disappearing, became more intense. He then 

 fused a little with borax by the blowpipe, and the fine eme- 

 rald green colour which the salt assumed, confirmed his first 

 suspicion of the existence of chrome in the scoriae from the 

 refining furnace. 



The remaining precipitate, being treated with nitric acid, 

 did not entirely dissolve ; a portion being left of a very deep 

 green colour, which was nothing but oxide of chrome mix- 

 ed with a little silex, the particles of which being brought 

 together and hardened by the heat had lost the capacity of 

 being soluble. 



The solution was colourless ; and oxalate of ammonia 

 threw down from it a granulous precipitate, which, when 

 washed and dried, weighed two decig. (three grains), and 

 was true oxalate of lime. 



The liquor from which the oxalate of lime was thus pre- 

 cipitated, being evaporated to dryness, and the residuum 

 ned, yielded an acid, which had all the properties of 

 the phosphoric. 



The first liquor, to which the limewater had been added 



to 



