730 



GEOLUGY AND MINING INDUSTRY OF LEADVJLLE. 



mony and arsenic, which exist only in small quantities in the ores. This accretion 

 contains tin, 5.6 per cent.; antimony, 2.7 per cent.; and arsenic, 5 per cent. 



The behavior of this accretion with reagents is noteworthy : treated by weak 

 nitric acid the metallic grains arid sulphides, as well as the excess of the oxide of lead, 

 are dissolved and the yellowish compound is left untouched. This residue, treated by 

 strong nitric acid, yields arseuite of lead, which dissolves in the state of arseuiate. The 

 residue, which is still yellow, is decomposed by sulphide of ammonium, which dissolves 

 tin. The residue, treated by weak nitric acid, in order to dissolve the sulphide of lead 

 formed, leaves behind a yellow powder, which proves to be autiuiouiate of lead. The 

 separations in this instance are so remarkable that the relative proportions of arseuite, 

 autiuiouiate, and stanuato of lead forming the yellow compound could in this way be 

 roughly estimated. 



ANALYSIS XLIII. PECULIAR ACCRETION. 



Discussion. The rational report may be expressed under the simple form : 



Metallic grains ....... ................................................ 24. 4.">7:'.4 



Metallic sulphides .................................................... 111. 



Oxide of lead compounds ............................................. 5(i.41.">li<l 



Loss.. .................................................. 0.00067 



Total 100.00000 



The writer has found that silicic acid, alumina, and peroxide of iron were com- 

 bined with oxide of lead in the state of silicate, aluuiiuate, and ferrite; as for gold, it 

 is a well known fact that this metal is o.vidized bv oxide of tin and combines with it. 



