Applications of Sulphur

Much sulphur is consumed in the manufacture of matches, being applied in the form of phosphorus sulphide as a constituent of the heads of common friction matches, whilst on the Continent the wooden splints have frequently been treated with sulphur to facilitate the passage of the flame from the head to the remainder of the match. Large quantities of sulphur are also required for the production of gunpowder and fireworks; for these purposes finely divided sulphur is necessary, but " flowers of sulphur " is not suitable on account of its liability to contain traces of sulphuric acid, due to atmospheric oxidation, which would render its use dangerous.

Applications of Sulphur, take place commonly in the powdered form or as " flowers of sulphur," to medicinal purposes, and also agriculturally as a dust or dressing to check fungoid diseases of certain plants, especially the vine. The toxic properties of sulphur have not been fully elucidated and are variously ascribed to reduction to hydrogen sulphide, oxidation to polythionic acids, or to the vapour of the element itself, produced by slow vaporisation. If adsorbed pentathionic acid be removed from sulphur by means of ammonia, the sulphur loses its toxicity but regains it if suspended in water and exposed to air.

The element has a definite fertilising action which is exerted in two ways: (1) It supplies sulphuric acid by bacterial oxidation, the presence of the acid increasing the availability of certain mineral constituents in the soil, such as alkalis, ferric oxide, alumina and phosphates. (2) It facilitates the work of the ammonia and nitrifying bacteria, thus placing larger supplies of nitrogen at the disposal of the plants. But although such action may be beneficial in some soils it is equally harmful in others, and sulphur should not be applied to a soil already acid.

Many important inorganic compounds of sulphur, such as carbon disulphide, sulphur chloride, phosphorus sulphide, vermilion and " Mosaic gold," are manufactured from their constituent elements, and considerable quantities of free sulphur are also used in the preparation of certain organic dyes, the colouring matter Primuline probably being the best known "sulphur dye," Methylene Blue and Thioindigo being other examples of this class of dyestuffs. The vulcanisation of rubber also calls for the Applications of Sulphur and sulphur compounds. For this purpose, one of the following methods is usually employed: (1) The rubber is mixed with powdered sulphur and heated to a temperature of 135° to 160° C.; in the presence of a suitable accelerator a considerably lower temperature may be employed. (2) The rubber is dipped into a solution of sulphur chloride in a suitable inert solvent such as carbon disulphide, or is exposed to the vapour of such a solution; this method is restricted to thin material or surface treatment. (3) The rubber, either dry or in solution, e.g. in benzene, is treated successively with sulphur dioxide and hydrogen sulphide. The product obtained by the first process may be soft or hard (ebonite) according to the proportion of sulphur going into combination. Various unsaturated oils, e.g. the so-called " drying oils," can be " vulcanised " by similar means so as to yield elastic solids possessing, however, very little tensile strength. By heating with sulphur in a somewhat similar manner tar can be rendered harder and therefore more useful for many purposes. Resinous condensation products of high melting-point and considerable hardness may be obtained by heating homologues or substituted derivatives of phenol with sulphur in the presence of a basic catalyst.

Sulphur has recently been described as a valuable agent for impregnating wood. The absorption of molten sulphur by the wood preserves and strengthens it and gives it acid-resisting properties.

Amongst other Applications of Sulphur may be mentioned the use of free sulphur in the manufacture of Ultramarine and the occasional conversion of the element into thiosulphates, sulphurous acid or sulphur dioxide and sulphuric acid.