Introduction-Phosphorus and Phosphates

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Slag from Tapped Furnace Cooling i n Outside Pit

'I'HE AAlEKlCAN PHOSPHORUS INDUSTRY Christian H. Aall

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ELEMENTAL PHOSPHORUS AND PHOSPHORIC ACID IN THE FERTILlZER lNDUSTRY W . L . H i l l . . . . . . . . . . . . . . .

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SUPERPHOSPHATE ACIDULATION WITH MIXTURES OF SULFURIC AND PHOSPHORIC ACIDS E. J . F o x a n d W. L . H i l l .

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COMPOSITION AND PROPERTIES OF SUPERPHOSPHATE H. L. Marshall and W. L. Hill

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QUICK-CURING SUPERPHOSPHATE G. L. Bridger and Edwin C. Kapusta.

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Today, nearly three centuries after Brand's discovery of phosphorus, we stand in the middle of a great expansion of the phosphorus industry in this country. This expansion is not merely a result of the quickened pace of American industry as a whole, following the outbreak of the Korean conflict, but reflects more the continuation of a growth that has marked the phosphorus industry since i t came into its own in the early thirties. Until 1914, phosphoric acid made by the wet process, containing nearly all the components of both the rock and sulfuric acid, had to be purified b y a tedious and expensive process before it was suitable for use in foods and pharmaceuticals; i t also had to be concentrated before it could be used in production of most phosphates. It was thus no wonder manufacturers welcomed the electrothermal phosphorus process in which a pure concentrated acid could be obtained directly by oxidation of the volatilized element. Except for TVA's large scale experiments there are currently no outlets for the electrothermal acid as an acidulating agent in fertilizer manufacture. This field is completely pre-empted by sulfuric acid. However, dwindling supplies of natural sulfur and an increased demand for sulfuric acid for other purposes may ultimately make this acid too costly for use in fertilizers, especially for triple superphosphate. Coupled with this development is the trend toward higher freight rates favoring the manufacture of highly concentrated fertilizer over that of regular superphosphate. It may take pears to reach a breaking point, but if and when i t happens. important new markets will be opened for electrothermal phosphoric acid. CHRISTIAN H. AALL M y 1952

INDUSTRIAL AND ENGINEERING CHEMISTRY

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