On the Chemical Constitution of Childrenite. 119 



copper pyriteSj it is no easy matter to detach a sufficient quan- 

 tity of them in a tolerable state of purity. 



In the first analysis, the mineral in the state of powder having 

 been exposed to heat, was fused with carbonate of soda and treated 

 hke a silicate. The precipitate throwTi do-mi by ammonia was 

 exhausted several times with boiling potash, and then digested 

 with hydrosulphate of ammonia to extract the whole of the phos- 

 phoric acid. After supersaturation with hydrochloric acid, the 

 phosphate of alumina was precipitated from the potash solution 

 by means of ammonia, the remainder of the phosphoric acid in 

 the filtrate was next ascertained; the precipitate, after exposure 

 to a red heat, was dissolved in acid, and the phosphoric acid was 

 precipitated with chloride of magnesium. 



1*229 grm., when thus treated, gave — 



Silica 3-82 



Phosphoric acid 28-2 i 29-36 



Alumina 18-06 18-77 



Protoxide of iron .... 29-58 30-75 



Protoxide of manganese . . 5-89 6-12 



Oxide of copper 0-65 066 



Loss by exposure to heat . . 16-35 17*00 



102-59 102-66 



In a second analysis, 0-454 grm. was first exposed to a red 

 heat, whereby the loss of weight amounted to 0-074. 



2*804 grms. were next digested in hydrochloric acid, and left 

 a residue of 0-113. The solution, after evaporation in the water- 

 bath, was treated with ammonia and sulphuret of ammonium, 

 the residue chssolved in acid, the solution oxidized, precipitated 

 with ammonia, and the precipitate, after exposure to a red heat, 

 was analysed by fusing it with silica and carbonate of soda. 



After deducting the residue, the results obtained from this 

 analysis, the materials for which were purer than those employed 

 on the former one as given above, were — 



Oxygen. 



Phosphoric acid 28*92 16*20 



Alumina 14-44 6-74 



Protoxide of iron .... 30-68 6-8n 

 Protoxide of manganese . . 9-07 2-03 > 8-89 



Magnesia 0-14 O-I4J 



Water 1698 15-09 



100*23 



The quantities of oxygen are here in the ratio of 2*4 :1 : 1*32 :2*24. 

 If instead we assume the ratio to be 2*5: 1:1-32: 2-5 = 15 : 6:8:15, 

 and this we are the more justified in doing from the impossibility 



