USES OF PYRITE AND SULPHUR
Pyrite and sulphur are closely related in their most essential uses, and one material can in many cases be substituted for the other. The largest and most important use of these minerals is in the manufacture of sulphuric acid, which is an essential material required for a very wide variety of purposes, including the production of acid phosphate for fertilizer, the manufacture of modern high-power explosives, the refining of petroleum, pickling of iron and steel, and for a vast number of chemical industries. The competition between pyrite and sulphur for this purpose has gone through several stages. With the large-scale development of Italian deposits sulphur was largely used for acid manufacture. As the prices of sulphur were increased it became cheaper to use pyrite, which in many localities then displaced sulphur, for this purpose. With the rapid expansion of the American production, and particularly with the tremendous increase in the capacity of sulphuric acid plants for war purposes, sulphur has again been very largely used for the manufacture of acid. The prospects since the close of the war are that, due to the tremendous capacity of the sulphur mines of the United States, sulphur may continue to compete with pyrite in this use.
Probably the second most important use of these materials is in the manufacture of sulphite wood pulp. In Europe pyrite is largely used for this purpose, while in the United States and Canada sulphur is the principal material used. For every ton of sulphite pulp manufactured, under the best practice, about 250 pounds of sulphur is required. In the United States and Canada about 175,000 tons of sulphur is used annually for this purpose, representing about 50 per cent. of the total sulphur consumption of these countries. There are also a number of other important purposes where sulphur is used rather than pyrite, the most important of which are in the manufacture of agricultural sprays and insecticides, and in the hardening of rubber. Sulphur is a primary ingredient of black powder, and considerable quantities are still used for that purpose. While most of the explosives used in modern warfare require the use of sulphuric acid in their manufacture, they do not use sulphur in its elemental form. There are many other minor chemical uses.
Substitutes for Sulphur and Pyrite.
—Because of the large deposits of sulphur now available, and of the extent and wide distribution of pyrite deposits, and of the cheapness of both these materials, there are no adequate commercial substitutes for them. The increase of by-product acid, from the copper and zinc smelters and possibly the nickel smelters of Sudbury, might be considered as the most important factors in replacing pyrite and sulphur. As a general thing, the factors of cost and transportation are the governing ones rather than any present or probable scarcity of materials.