}85 TURQUOIS STON£. 



together, precipitate of pot-ash was poured on, which formed 

 a precipitate of a fine deep blue, of which the weight, after 

 calcination, was found to be one part and a half. It was red 

 oxide of iron. Care must be taken to heat the liquor, in 

 order to separate the precipitate entirely. 



The supernatant Hquor held'in solution the acid phosphate 



of lime, which was shewn by the phosphorus it afforded, when 



treated with charcoal. 



A trace of ma"'- !• — This oxide of iron was heated again with a little pure 



jauese, - pot-ash. When the whole was in fusion, the matter assumed 



a deep green colour, and when the cold mass was afterwards 



dissolved in water, it gave the same colour to the fluid. Upon 



adding a small quantity of muriatic acid, it became of a fine 



rose colour. This experiment was repeated on a number of 



turquoises, and the phsenomenon always took place ; which 



evidently shows the presence of a very small quantity of 



magnesia. 



— and manga- K. — Being desirous of ascertaining whether the turquois 



'^^*^' contained phosphate of magnesia, as the experiments of Four- 



croy and Vauquelin upon bones, lead to suspect, I treated 



this substance according to the method indicated by those 



chemists, in the 47th volume of iha J nnalei- de Chymie. It was 



found that 100 parts of the turquois contained two parts of the 



phosphate of magnesia. 



Component Frc^m the preceding experiments, it folldws that 100 parts 



parts. of turquois contain 



Phosphate of lime SO 



Instead of 82, found In experiment E. 

 Deducting the quantity of phosphate of 

 magnesia, before mentioned .... 



Carbonate of lime 8 



Phosphate of iron 2 



of magnesia 2 



of manganese, minute quantity 



Alumine 1 



Water and loss 6 



^ 100 



Whether all the Though I obtained similar products in the examination of 

 turquoises be , ° . . i i • t i i .i xi u 



of the same na- several turquoises, it cannot yet be decided whether tney be 



ture as those indentical. The turquoises used in my experiment are per- 

 hcre examined fectly 



