88 Reviews— Die Sulfid-Silikatschmelzlisungen. 
The facts here set forth are of the greatest possible interest, both 
in their technical applications to furnace practice and in their 
bearing on theoretical petrology and the genesis of the sulphide 
ores. It is now generally accepted that silicate melts of whatever 
composition are completely miscible in all proportions, but with 
regard to the relations between fused silicates and sulphides the 
conditions are quite otherwise. Silicate and sulphide melts, as well 
as silicates and molten metals, possess only very limited mutual 
solubilities, and in the fused state must form systems of two liquid 
phases. This proposition is, in fact, self-evident, since it forms the 
foundation of all smelting processes. Pig-iron and slag separate in 
the blast-furnace, not because the molten iron is heavier than the 
slag, but because the two liquids are mutually insoluble at the 
furnace temperature, and the same applies to the separation of 
sulphide and slag in copper matte smelting. In both these processes. 
it is obviously desirable to have the cleanest possible separation of 
metal or sulphide and slag, and it is the investigation of the conditions 
most favourable to this clean separation that is the chief object 
of Professor Vogt’s researches. 
In the first place, it is evidently desirable that the slag should 
be as liquid as possible, partly in order that it can be drawn off 
easily and partly to facilitate the sinking of globules of sulphide, 
which might otherwise remain entangled in a viscous slag. This can 
be obtained partly by employment of a very high furnace 
temperature, which is undesirable from the point of view of fuel 
consumption and running costs. It is found, however, that the 
viscosity of the slag is very clearly a function of its chemical com- 
position, and especially of its silica percentage. This also has a 
very important bearing on the solubility of sulphide in slag; this. 
solubility varies inversely as the silica percentage, and directly as 
the temperature. Very basic slags at a high temperature cause the 
greatest losses of copperin matte-smelting, and this loss is apparently 
increased by the presence of much zinc. The practical problem is 
therefore to find the best working conditions, so that the two opposed 
factors may compensate each other. The loss of copper inevitable 
with a liquid basic slag in which the solubility is high has to be 
balanced against the loss of copper in a viscous acid slag with low 
solubility, but with a strong tendency to mechanical retention of 
sulphide. This is a nice example of the application of mineralogy 
and petrology to problems of the highest practical importance, a 
point of view which appears to be scarcely appreciated by British 
petrologists. 
Rather more than half of the smaller work here reviewed is devoted 
to a discussion of the nickeliferous sulphide segregations and their 
relation to the norites. This is presumably a summary of the 
forthcoming larger publication before mentioned. It is shown that 
nickeliferous sulphides have a strong tendency to occur along with 
rocks rich in rhombic pyroxenes, which are mainly magnesia-iron 
