THE RUSSELL PROCESS IN AUSTRALIA. B45) 
solution, and attacks the silver chloride, converting part of it into 
insoluble silver hyposulphite, there being presumably not sufficient 
hypo in solution to form the soluble double, salt of silver and 
sodium. In the presence of a very minute amount of free acid, 
this silver hyposulphite is rapidly converted into silver sulphide, 
which we have seen is insoluble in ordinary solution. That such 
a series of reactions would take place under these conditions has 
been amply proved by the researches of Mr. C. H. Bothamly, 
F.I.C., F.C.S., into the chemistry of photographic printing. I only 
regret that neither time nor opportunity were at my disposal to 
prosecute this inquiry at Rivertree ; but I hope that this paper 
may induce others, who are interested, to follow up this subject. 
IV. THE ORDINARY SOLUTION. 
This consists, as before stated, of a solution in water of sodium 
hyposulphite ; the strength adopted being 1} per cent. in the 
crystallised salt, Na,S.0,5H.O. It is capable of dissolving out 
most of the oxidised compounds of silver through the formation of 
the soluble double, hyposulphite of silver and sodium. 
AgCl dissolves very readily in either cold or warm ordinary 
solution, a fact long taken advantage of in photography ; but 
metallic silver and the arsenate and antimonate yield more readily 
to the attack of warm solution than cold; and, since this solution 
is very stable, it is advantageous always to heat it up to 45° or 50° 
centigrade before using. 
Since both the bromide and iodide of silver occur somewhat 
frequently in silver ores in Australia, notably at Broken 
Hill, the author made some experiments on the solubility of the 
artificially-prepared compounds in a standard ordinary solution, 
with the result that silver bromide was found to dissolve almost 
as quickly as silver chloride, the co-efficient of solution being prac- 
tically the same, viz., 0°3 of silver for one part of Na,S,O.,5H,O. 
Silver iodide dissolved more slowly than either the chloride or 
bromide, but finally gave a similar co-efficient, viz., 0:3Ag. 
When the roasted ores contain sulphates of lead, or calcium, or 
quicklime, a considerable amount of hypo may be used up in 
dissolving these compounds with the formation of the corresponding 
double salt. Owing, however, to the highly siliceous character of 
the Rivertree ore, it is probable that very little of the hypo was 
consumed in this way. 
V. THE EXTRA SOLUTION. 
Itis the rapid action of this solution on unoxidised silver minerals 
which gives to the Russell process its high value in the treatment 
of base silver ores. The greatest difference in effect between 
ordinary and extra solutions is seen in their action on metallic 
