MANGANESE IN GOLD DEPOSITS 23 



thousand feet below water level, would not exceed ioo° C, and in 

 the main are considerably lower. The general character and, 

 approximately, the concentration of the solutions are known and 

 the conditions are fairly constant. From the mass of chemical 

 data relating to the subject, the following experiments are par- 

 ticularly suggestive in connection with the present problem. 



1. Stokes 1 placed gold leaf in a solution containing 25 gm. 

 per liter of ferric sulphate, and, after heating to 200 C, found 

 that not a trace of gold had been deposited in the cold part of the 

 sealed tube in which the experiment was carried on. This experi- 

 ment does not confirm the statement frequently made that ferric 

 sulphate will dissolve gold. 



2. Don 2 exposed to air, gold and auriferous sulphide ores in 

 solutions containing from 1 to 20 gm. of ferric chloride and ferric 

 sulphate per liter of water; after several months no gold had been 

 dissolved. 



3. W. J. McCaughey, 3 upon boiling for several hours 50 c.c. 

 of HC1 (sp. gr. 1. 1 78) diluted to 125 c.c. with 250 mg. of gold, 

 found there was no loss of gold. 



4. In a bent tube Stokes 4 heated gold leaf for 16 hours at 200 

 C. in a solution composed of 85 gm. of cupric chloride and 133 

 c.c. of 20 per cent HC1 in a liter of water. The gold leaf was dis- 

 solved and redeposited in the upper portion of the tube. He writes 

 the reaction as follows : 



Au+3CuCl 2 ^AuCl 3 +3CuCl. 



5. Stokes 5 heated gold leaf to 200 C. in a closed tube con- 

 taining a solution of 25 gm. of ferric sulphate and 0.01 gm. of 

 NaCl. Gold was dissolved in 40 hours. 



6. Stokes 6 found that at 200 C. gold leaf was dissolved in a 

 mixture of 2 parts of 20 per cent solution of ferric chloride and 1 

 part of 20 per cent solution of HC1. 



1 Economic Geology, I, No. 7, 650 (July- Aug., 1906). 



2 Trans., XXVII, 598(1897). 



3 Journal of the American Chemical Society, XXXI, No. 12, 1263 (Dec, 1909). 

 Wp. cit., I, 649. 



5 Economic Geology, I, No. 7, 650 (July- Aug., 1906). 



6 Ibid., 650. 



