British Kinematography (1952)

February, 1952 4l CHEMICAL SHORTAGES AND THE EFFICIENT USE OF PROCESSING SOLUTIONS Summary of a Symposium presented to a Joint Meeting of the British Kinematograph Society and the Royal Photographic Society on October 3, 1951 . L— A SURVEY OF SULPHUR RESOURCES D. H. O. John, BSc, A.R.I.C* SULPHUR and sulphur compounds are of the greatest importance in the manufacture of photographic chemicals, and our recent shortages are due to the shortage of sulphur. Elementary sulphur Italy and Sicily supplied the sulphur requirements of almost the whole world until the early years of this century, when largescale production of sulphur commenced in the United States. The total world production of elementary sulphur changed from 00% Italian produced sulphur in 1905 to 90% American produced in 1920. This rapid rise in American production of sulphur was largely due to the success of prolonged efforts to make the Frasch system of steam extraction of sulphur commercially workable. This made possible the extraction of the huge deposits in Louisiana and Texas which were previously unworkable. Although the U.S.A. no longer retains a monopoly of supplies of sulphur, it produced nearly five million tons last year by this method. Sulphur compounds The most important sulphur compound mined is iron pyrites, a sulphide of iron containing about 45% sulphur, which is found in many countries, particularly Spain, Japan and Norway. Two other important sources of sulphur compounds are spent oxide, a waste-product of the coal-gas industry, obtained by scrubbing the impurities out of crude coal-gas, and anhydrite (calcium sulphate). The uses made of these materials in this country show that our internal production is less than one-quarter of our needs, our dependence upon American sulphur increasing in the past twelve years from 23% to 62% of our total consumption. Production of other chemicals Of the various sulphur-containing products the most important is sulphuric acid. So essential has it become that it is difficult to find an industry of any magnitude in which it does not play an important part. During the past fifteen years there has been a marked trend in this country towards the use of elementary sulphur from America for the manufacture of sulphuric acid in place of pyrites from Spain. The embargo on American sulphur supplies, which was threatened a year ago, was therefore of the greatest significance to our sulphuric acid industry. Sulphuric acid is responsible for about 85% of our total consumption of sulphur and sulphur compounds, and the quantities of sulphur used for chemicals in which the photographer is more directly interested (sulphites, bisulphites and thiosulphates) seem trivial by comparison. However, indirectly sulphuric acid is important in the manufacture of photographic chemicals. Synthesis of Metol and Hydroquinone Since metol is the sulphate of an organic base, sulphuric acid is required in the last stage of its synthesis. It is, however, less obvious that this same acid is required at every stage but one in the synthesis (Fig. 1). It is either used as such, or some product made with its aid is used (dimethyl sulphate or hydrochloric acid). * Research Laboratories, May & Baker, Ltd.