572 ' Kenneth A. Miclde : 



same amount of oil, acid and water, agitated for ^ hour, 

 showed that the gas above the solution consisted of — 



1 p.c. (absorbed as CO^'). 



21 p.c. oxygen. 



78 p.c. nitrogen. 



Lead acetate paper showed a reaction for H'gS. 



With mixed magnetite and zinc blende, Mt. Garnet ore 

 (Queensland) HoS. could be smelt strongly. This v/^as the case 

 also with South Comstock (Tasmania) ore. Some zinc concen- 

 trates from Central Mine (Broken Hill) tailings obtained from 

 an acid float, and agitated in a similar solution to the other 

 tests, showed that the gas above the solution contained COg 

 2. "2 p.c, and oxygen 19.8 p.c. 



Collection and Analysis of Gases evolved from 

 Wetted Minerals. 



As it seemed apparent that some gas or gases were still re- 

 tained on minerals after being wetted with water, it was de- 

 cided to collect and analyse the gas. This was carried out in 

 the following manner : — The mineral being examined was 

 wetted with distilled water that had been freed from dis 

 solved gases by continued boiling, and was placed in a flask 

 provided with gas-tight connections and connected to a vacuum 

 pump. The flask was immersed in water, which could be 

 heated when required. The gas collected was trapped in 

 portion of the apparatus, and transferred to a gas burette 

 designed to hold and measure small quantities of gas accu- 

 rately. In the case of minerals, the samples selected were all 

 clean, unaltered and in most cases cystalline fragments, ground 

 to pass an 80 mesh sieve. This material was imimersed in air- 

 free water, freed from bubbles of air held mechanically, and 

 then put in the flask as stated above. As some of the minerals 

 floated on reducing the pressure, a small cloth filter was 

 stretched across the end of the joint connecting the capillary 

 tap to the flask. This helped very much in drawing off the 

 gas, as when the sulphides -expanded on heating they com- 

 pletely tilled the flask, and with the aid of the vacuum pump 

 the cloth acted as a filter, only allowing the gases to pa.ss. 



