Special Applications of Sulphur

SULPHUR, SPECIAL APPLICATIONS OF. Sulphur is a convenient source of sulphur dioxide gas, which is the basis for the manufacture of sulphuric acid and sulphite pulp. In a number of industries sulphur plays an essential part and has no substitute. This is the case in the vulcanization of rubber, and for many agricultural and horticultural purposes, such as insecticides and fungicides, and for the making of lime-sulphur solutions. Among the properties of sulphur are fusibility, acid resistance, a number of physical forms, extremely low electrical con ductivity and general chemical resistance. There are few solvents for sulphur and it is not acted upon by water, but for certain purposes its inflammability is detrimental.

As an Impregnant.---All

forms of pulp and paper products can be impregnated with molten sulphur and the more absorbent types take up three or four times their dry weight. Pre-formed pulp and paper articles, when impregnated with sulphur become very strong, weather-resistant and converted into much denser and harder materials. Among the applications of such paper products are flat fibre 'boards so treated as to prevent warping and make them resistant to acid and other destructive agencies. Spool heads, advertising signs and many other articles of paper, fibre or pulp can be hardened and weather-proofed by means of sulphur impregnation.

Practically all species of wood may be impregnated with molten sulphur under proper conditions, the more resistant species re quiring the application of vacuum and pressure. The general procedure is very similar to that so widely used for the creosoting of wood, but the effect is quite different. With sulphur there is very little change in colour, but a marked increase in weight and a phenomenal hardening and strengthening effect. Pieces of soft wood with a high sulphur content appear almost as though petri fied. It converts a soft wood into a very hard and durable prod uct, comparing favourably with the heaviest and densest tropical woods. By the addition of various sulphur soluble dyes, attractive colours are imparted. Wood so treated is much less absorbent to moisture and withstands the action of acid and other destruc tive agencies. Tests made on wood structures in contact with the

ground indicate that sulphur acts as a preservative even though not in itself particularly toxic. Its toxicity toward wood-rot fungi may be increased by the addition of certain substances that are recognized preservatives and which have been found to be mis cible with molten sulphur. The applications for sulphur-treated wood are numerous and include floor blocks, especially where acids are used, fence posts, railway ties, etc. Stone and concrete are likewise subject to sulphur impregnation.

Textiles and fabrics may likewise be impregnated with sulphur and have the advantage of being readily formed or shaped before processing. Fabric coverings saturated with molten sulphur may be spirally wound on metal pipes or other objects in order to produce extremely dense, impervious coverings. These were under test in 1928 for the prevention of underground corrosion.

Sulphur Introfiers.

The term "introfier" has been applied to certain organic substances having a most peculiar effect on the penetrance of molten sulphur. They may be used to advantage in practically all the examples of sulphur impregnation heretofore described and are also valued in making certain sulphur composi tions. Some of the substances which not only increase the rate but the ultimate limit of penetrance of molten sulphur are naptha lene, its chlorinated and hydrogenated derivatives, anthracene, triphenyl phosphate and other compounds.

Other Special Uses.

In view of the fact that one of the problems of the steel industry is the removal of sulphur, it is interesting to note that it is deliberately added to steel for special purposes, notably for the making of screw stock. Likewise, in petroleum refining, sulphur-compounds present in many crude oils must be removed to make them fit for refining. But for some uses an oil containing sulphur is desirable. This is the case with metal-cutting oils, used largely by the metal-working industries for thread cutting, turret lathes and other machine work. Sulphur is incorporated with an animal or vegetable oil base and subse quently added in proper proportion to a petroleum oil.