554 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



relative distribution of the two metals was brought about by surface waters, 

 and is therefore dependent on the relative solubility of the combinations of 

 the respective metals formed during alteration. 



Silver sulphate is probably more soluble than either the sulphate or the 

 carbonate of lead, but, as it is not known to occur as a mineral, it cannot 

 be assumed that silver necessarily passed through sulphate during its change 

 from sulphide to chloride. 



The chloride of silver is said to be insoluble in pure water at ordinary 

 temperatures, but Vogel 1 and Hahn 2 have shown it to be soluble to a cer- 

 tain extent in the alkaline chlorides. According to Stas, 3 it is, in a measure, 

 soluble in pure cold water, its solubility varying according to its physical 

 condition and the temperature. Its solubility is greatest when in the flaky 

 state, as precipitated in the cold from a sufficiently dilute solution of silver, 

 and diminishes as the flakes shrink. It is precipitated from the solution by 

 the addition of an alkaline chloride. Still further evidence of its solubility 

 is afforded by the occurrence of the mineral Huantajayit, discovered by Rai- 

 mondi in Peru, 4 which consists of 11 per cent. Ag Cl and 89 per cent. 

 NaCl. According to Sandberger, this is readily soluble in a little water, but 

 an excess of water produces a precipitation of the chloride of silver. It may 

 therefore be assumed that chloride of silver is soluble in surface waters 

 under certain conditions, but is veiy readily precipitated from its solution. 



Although the statements given above as to the relative solubilities of lead 

 and silver salts are not so definite as might be wished, the fact of the rela- 

 tively greater richness of galena over cerussite in these deposits seems so well 

 established as to justify inverse reasoning, namely, the deduction of an 

 argument in favor of the greater insolubility of the lead salts. It might be 

 assumed from Stas's experiments that freshly-formed chloride of silver 

 (flaky) would be more soluble than carbonate of lead, but that after the 

 lapse of sufficient time the latter might become more soluble than the chlo- 

 ride of silver, especially in water charged with carbonic acid. 



Outcrop deposits richer than those in depth. There is a fair foundation for the 

 generalization that in the deposits, as developed at the time of this investi- 

 gation, the ores were growing poorer in silver as exploration extended far- 



1 Wagner's Jahree-Ber. 1874, 22, p. 481. 3 Coinpt.-rend., 1870-73, p. 998. 



2 Trans. A. I. M. E., 1873-74, p. 99. Neues Jahrb. f. Mineralogie, 1874, p. 174. 



