Mineral Phosphates and Pure Fertilisers

Abstract

THE date of the patent taken out by Mr. Lawes, in 1842, for treating mineral phosphates with sulphuric acid, has proved the date of the commencement of a new industry which has now attained to vast proportions. At present the manufacture of superphosphates in Great Britain can hardly be short of 400,000 tons per annum, and the market value of the same cannot be under 2,400,000l. Competition naturally tends to develop improvements, and of late years several novel processes have been suggested for the better treatment of mineral phosphates. Dr. Morfit's book is mainly devoted to a description of these new methods, and more especially to a detailed account of the practical working of his own inventions. The object of all these processes is the preparation of “Pure Fertilisers.” The mineral phosphates at the disposal of the manufacturer contain 50-80 per cent, of tricalcic phosphate, the poorer minerals preponderating. In making ordinary superphosphate the whole mineral is treated with sulphuric acid, and the resulting superphosphate is of course rich or poor according to the quality of the mineral taken. But in making a “Pure Fertiliser” the aim is to separate the calcium phosphate from the original mineral and offer it for sale in a nearly pure state. The production of a pure phosphate is of course a more costly operation than the simple treatment of the powdered mineral with sulphuric acid, and we believe that these pure fertilisers will consequently not be able to compete with ordinary superphosphate, except in cases where, as in America, the manure has to be transported over great distances, and small bulk is therefore a desideratum. Their advantage over the comparatively poor superphosphate is much lessened by the fact, that the non-phosphatic matter in superphosphate is principally gypsum, which is itself a valuable manure. There is one class of mineral phosphates, however, which is wholly unsuited for the manufacture of superphosphate—we allude to the native phosphates of aluminium; the processes patented by Mr. P. Spence and Mr. J. Townsend for the extraction of the phosphoric acid are in this case most valuable.

Mineral Phosphates and Pure Fertilisers.

By Campbell Morfit (London: Trübner and Co.)