THE RUSSELL PROCESS IN AUSTRALIA. 328 
The well known affinity of copper for sulphur, and the complete 
insolubility of silver sulphide in ordinary solution render it pos- 
sible to precipitate the silver in this form. The precipitant em- 
ployed is sodium sulphide, which first throws down any copper 
remaining in the liquors,.and then the silver ; no extra solution 
remaining at this point to redissolve the silver sulphide formed. 
The sodium sulphide is prepared by the action of sulphur on 
hot caustic soda. The latter is fed into an iron cylinder with 
sufficient water to cover it, and then heated to about 110° C. by 
blowing steam through it. Stick sulphur is then added in sufficient 
quantity to produce whichever of the many sulphides of soda with 
which it is deemed best to work. Russell recommended a mixture 
of the mono and bisulphides, to produce which 65 1b. of sulphur 
are needed for every 100 lb. of caustic soda. 
On adding the sulphur to the hot caustic, a very violent reaction 
takes place, the heat produced being sufficient to cause the evolu- 
tion of clouds of steam. Small quantities of sulphuretted hydrogen 
and sulphur dioxide are also formed, and can be recognised by 
their characteristic smell. These compounds are probably formed 
in accordance with the equation 
2NaHO + 2H,O + 68 = NaS + 3H.S + 2SO,. 
The concentrated solution thus produced at Rivertree was diluted 
and stored in sheet-iron tanks. Owing to its somewhat rapid 
oxidation, it should not, however, be kept for many weeks at a 
time, but fresh solution made from time to time as required. 
Ill. THE WASH-WATER. 
The benefit of a preliminary washing with water is twofold— 
First, to rid the ore of any remaining sodium salts, which would 
tend to choke up the hypo solution, so that it could not be used 
over again ; second, to increase the grade of the final sulphides 
by removing all soluble salts of iron, lead, &c., which would be 
precipitated by the sodium sulphide solution. 
The salts of sodium remaining in the ore after chloridising are 
all very soluble in cold water, and are totally removed by the 
wash-water, together with sulphates and chlorides of Mn, Zn, Cu, 
Fe, Al, Ca, and Mg. After sinking through the first layer of ore 
the water becomes—from solution of these salts—a more or less 
concentrated brine, which is capable of dissolving still other 
compounds, such as silver chloride, which are practically insoluble 
in pure water. The liquor, therefore, as it comes from the vats 
always contains suflicient silver to render it necessary to preserve 
it, and precipitate it with sodium sulphide, as in the case of the 
hyposulphite solutions. 
A sample of the wash-water liquor taken at Rivertree, after it 
had been flowing for two hours from the vats, gave a distinctly 
