THE RUSSELL PROCESS IN AUSTRALIA. 319 
mineral, was visible in this gossan ; so that the precious metal was 
probably disseminated through it in the form of minute grains of 
silver chloride, bromide, &e. 
The average composition of the raw ore treated in vats D to M 
was as follows :— 
(a) 
S/O aes eine ies ... 48-92 per cent. 
Ons. : ae oe ee UR Rae J 
CaO: -:,: ise sik Jas) hE. 3 
MeO ... Ses oe aa: ‘Gor ~ 4, 
Pb GOS ke 
Cu sil whee, 
Fe Igelig, ~,, 
Zn ae She au ne Sata ere 
y ||: re nde a save Atltes 63.5, 
Sb ee Nate ix ..< ‘trace 
) oti th sae ait A (EARN diate 
Percentage soluble in water, ‘31. 
The highly siliceous nature of this ore, combined with its low 
value in lead and copper, fully accounts for the failure of the 
blast-furnace which was erected at one time to treat the ore from 
the Wongabah lode. 
In the preliminary roasting with salt, the first action which 
takes place is the volatilisation of half of the sulphur in the 
pyrites, the vapour burning in contact with the hot air to sulphur 
dioxide. 
As the temperature rises, the various sulphides in the ore are 
oxidised more or less completely to sulphates, which in turn are 
gradually converted into oxides by volatilisation of the SO, The 
rapidity of this latter action varies greatly with the different 
metals ; the order in which the sulphates are decomposed being 
first, that of iron, then copper, silver, lead, and zine. In the 
presence of salt, however, chlorine is liberated by the interaction 
of the salt and sulphur trioxide, and the chlorine reacts upon the 
sulphates and oxides of silver and the other metals with the 
formation of corresponding chlorides. 
During the roast, much of the arsenic and antimony are 
volatilised, the rest remaining in the ore in the form of arsenates 
and antimonates. These salts of silver are found in the roasted 
ore as the result of the oxidation of proustite and pyrargyrite, and 
hence the importance of the question of their solubility in hypo- 
sulphite solutions. 
