THE RUSSELL PROCESS IN AUSTRALIA. ot 
Part II.—By Epwarp S. Srpson, B.E. 
Since the publication of Stetefeldt’s exhaustive treatise on hypo- 
sulphite leaching, very little can be said with reference to the 
chemical aspects of the Russell process that is not already con- 
tained therein. Since, however, more extensive experiments with 
this process have been made on the Rivertree ore than on any 
other in Australia, and since this ore differs considerably in com- 
position from the American ores quoted by Stetefeldt, it may be 
useful to record the analyses of this ore, made during a short visit 
to Rivertree in 1895, and follow through the various reactions 
which took place during its chloridising and leaching. 
In order to thoroughly understand these, it will be necessary 
first to explain the general principles upon which this process 
depends. These are, in brief :— 
1. Native silver chloride and certain oxidised silver minerals 
are soluble in a solution of sodium hyposulphite. 
2. Many unoxidised silver minerals, which are insoluble in 
the plain sodium salt, dissolve readily in a solution con- 
taining in addition cuprous hyposulphite. 
3. By roasting unoxidised silver minerals with salt, they are 
converted for the most part into silver chloride. 
4, Solutions of silver in hyposulphites are precipitated by 
sodium sulphides. 
The fact that oxidised silver compounds are soluble in solutions 
of sodium hyposulphite, was known and applied practically by Von 
Patera as far back as 1858. His process has been found to give 
excellent results in the case of surface ores, in which all the silver 
is in the form of haloid salts, and on many ores which have been 
subjected to a thorough chloridising roast. 
This solubility depends upon the fact that these compounds 
react with sodium hyposulphite, forming the corresponding salt of 
silver, which is insoluble in water, but dissolves readily when 
sufficient excess of the sodium salt is present to form a soluble 
double salt of the form Ag, 8, O,, 3 Na, 8, O,. 
Metallic silver, which is of frequent occurrence in surface ores, 
dissolves somewhat easily in sodium hyposulphite, but only in the 
presence of free oxygen, in proportion necessary for the oxidation 
of the metal. When already existing as one of the haloid salts, 
no free oxygen is necessary to its solution, which is on that 
account more rapid. Silver arsenate and antimonate are also 
soluble, and although these compounds probably do not occur in 
nature, yet the question of their solubility becomes a vital one in 
practical working as will be explained later on. Silver sulphide 
and sulpharsenate and other minerals of a like nature are entirely 
