128 



The Philippine Journal of Science 



1913 



consisted of 45 parts calcite, 45 parts manganese dioxide, 5 parts 

 ferrous sulphate, and 5 p£,rts ferric sulphate. 



Experiment No. 1. — Samples of this mixture were placed in 

 vessels with filter bottoms. Through these a solution, consisting 

 of about 10 per cent by weight of sulphuric acid and 10 per 

 cent sodium chloride in 80 per cent water, was allowed to leach 

 continuously, and the following analyses show the composition 

 of the filtrate after given periods of time. 



Table II. — Analyses of water showing composition after given periods. 



Constituent. 



Per cent, =» 



Per cent, b 



Per cent, e 



Chlorine (free) 



Chlorine (CD (combined) 



Sulphuric-acid radicle (SO4) 



Carbon dioxide (CO2) (combined) 



Carbon dioxide (CO2) (free) 



Iron (Fe) 



Manganese (Mn) 



Calcium (Ca) 



Sodium (Na) 



nil 

 1.55 

 0.4 

 0. 0004 



nil 

 little 



nil 

 0.13 

 0.92 



nil 

 1.89 

 0.733 

 0. 0004 



nil 

 0.034 

 0.124 

 0.067 

 1.18 



nil 

 1.3 

 4.27 

 nil 

 nil 

 0.24 

 little 

 0.105 

 0.95 



a Solution neutral to litmus after 48 hours. 



b Became neutral to litmus after 72 hours. An iron salt precipitated immediately after 

 passing the filter bed. Solution slightly acid. 

 Solution acid after 75 hours. 



After seventy-five hours the nitrate became decidedly acid and 

 contained a large amount of ferric chloride. At this stage it 

 was evident that the leaching solutions had formed channels in 

 the ore and were reacting only upon the walls of the channels. 



The results of Table II indicate that no free chlorine would be 

 formed in a vein so long as the oxidizing waters were neutral, 

 alkaline, or only slightly acid, and that free chlorine is formed 

 only when the solutions are decidedly acid and iron is absent. 

 When iron is present, ferric chloride is formed which acts as a 

 solvent of gold in the presence of manganese dioxide. Experi- 

 ments 14, 15, 16, and 17 in Emmons' paper 5 show that gold 

 is dissolved when hydrochloric acid and manganese dioxide or 

 ferric chloride and manganese dioxide are present. 



Experiment No. 2. — A sample of the ore mixture was placed 

 in a bottle with 0.5 gram of finely divided gold, 50 cubic centi- 

 meters of saturated sodium-chloride solution, and 400 cubic cen- 

 timeters of 10 per cent sulphuric acid and agitated for eight 



'Opus cit., 782. 



