3 o WILLIAM H. EMMONS 



admit of easy changes of valence, but which act upon hydrochloric 

 acid with the production of free chlorine. 



In mine waters chlorine is supplied as NaCl. 



16b. Fe 2 (S0 4 ) 3 + H 2 S0 4 + NaCl + Mn0 2 + Au. 



N/io N/io N/25 1 gm. 0.15 gm. 

 0.00505 gm. loss of gold by solution in 14 days (cold). 



Under the same conditions without manganese there was no 

 weighable loss (see experiment 16a). 



As used herein the normal solution contains 1 gm. -equivalent 

 of the solute in 1 liter of solution. A solution normal with respect 

 to chlorine contains 1 gm. of chlorine times 35.45, the molecular 

 weight of chlorine, in 1 liter of solution. 



In this experiment the concentration of CI (1,418 parts per 

 million) is not so great as has been observed in a few mine waters, 

 and not more than three times as great as Don determined in 

 waters from a number of Australasian mines. 1 



Manganese is abundant in many gold-bearing deposits; is 

 sparingly represented in some; and from a very large number it 

 has not been reported. The chief primary minerals are the car- 

 bonates (rhodochrosite and manganiferous calcite), the silicate 

 (rhodonite), amethystine quartz, and the less-abundant sulphide, 

 alabandite. Some rock-making minerals carry small amounts 

 of manganese. It readily forms sulphates, chlorides, etc., and is 

 dissolved by acid mine waters. Manganese changes its valence 

 more readily than other elements common in gold ores. 



Lead oxides. — -Lead oxide is said to facilitate the solution of 

 gold 2 when added to solutions of ferric sulphate and sodium chlo- 

 ride. Lead is both bivalent and quadrivalent and forms corre- 

 sponding oxides and hydroxides. These, however, are generally 

 not abundant in the oxidized zones of lead-bearing ore deposits, 

 because the lead carbonate and the sulphate are relatively insoluble 

 in water and usually are formed instead of the oxides. Lead is 

 reported in but one of the 29 analyses of waters from gold and 



1 Trans., XXVII, 654 (1897). 



2 Victor Lehner, Journal of the American Chemical Society, XXVI, No. 5, 552 

 (May, 1904). 



