2 6 WILLIAM H. EMMONS 



14. FeCl 3 +HCl+Au. 



(a) no weighable loss. (34 days.) 



(b) no weighable loss. 



15. FeCl 3 +HCl+Mn0 2 +Au. 



(a) 0.01640 gm. loss. Area of plate, 383 sq. mm. (34 



days.) 

 (&) 0.01502 gm. loss. Area of plate, 348 sq. mm. 



In each experiment the volume of the solution was 50 c.c. 

 The solution was one-tenth normal with respect to ferric salt and 

 to acid. In experiments 13 and 15, 1 gm. of powdered manganese 

 dioxide was also added. The gold, assaying 999 fine, was rolled 

 to a thickness of about 0.002 inch, cut into pieces of about 350 sq. 

 mm. area; and one piece, weighing about 0.15 gm., was used in 

 each duplicate. 



To approximate natural waters more closely, a solution was 

 made one-tenth normal as to ferric sulphate and sulphuric acid, 

 and one twenty-fifth normal as to sodium chloride. Then 1 gm. 

 of powdered manganese dioxide was^added to 50 c.c. of the solution, 

 and the experiment was repeated. The time was 14 days. 



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

 No weighable loss. 



166. Fe 2 (S0 4 ) 3 -fH 2 S0 4 -f-NaCl+Mn0 2 -f-Au. 

 Loss of gold, 0.00505 gm. 



The loss is comparable to that found in experiment 15, allow- 

 ing for the shorter time and the greater dilution of the chloride. 



To determine whether the free acid or the ferric chloride is 

 the solvent, experiment 17 was made, in which 50 c.c. of one-tenth 

 normal HC1 was used with 1 gm. of powdered Mn0 2 . 



17. HCl+Mn0 2 +Au. 



Loss of Au, 0.01369 gm. Time, 14 days. 

 In experiment 18, sodium hydroxide was added to 50 c.c. of 

 one-tenth normal ferric chloride solution until the precipitate 

 formed barely redissolved on shaking, after which 1 gm. of pow- 

 dered Mn0 2 was added. 



18. FeCl 3 +Mn0 2 +Au. 



Loss of Au, 0.00062 gm. Time, 14 days. 



