CHAPTEK IV. 



HISTORICAL REVIEW OF SUPERPHOSPHATE MANUFACTURE. 



It can l)e safely asserted that the superphosphate indiistrv is the 

 issue of Lie big's theory. He was, in fact, one of the first to recom- 

 mend restoring to the soil, not only the nitrogen removed by crops, 

 but also the mineral matter, more especially phosphoric acid. For 

 this purpose he recommended the use of bone dust, and also of 

 phospho guanos. But having remarked that the phosphoric acid 

 of these substances only acted very slowly, he advised that they 

 should be treated by sulphuric acid so as to render the phosphoric 

 acid soluble, and immediately assimilable by plants. His method 

 was adopted, and yielded remarkable results, thus giving birth to 

 the superphosphate industry which spread rapidly in Germany,,, 

 Great Britain, and France.^ 



The Manufacture of Superphosphates from 1850 to 1870. — It 

 is interesting to follow^ the new industry in the dilferent phases of 

 its evolution. The theory of superphosphate manufacture is in 

 itself very simple. Eaw phosphates contain phosphoric acid, as 

 tribasic phosphate of lime, insoluble in water, and consequently 

 not assimilable by plants. The task of the manufacturer of super- 

 phosphate consists, therefore, essentially in converting the insoluble 

 phosphoric acid of raw phosphates into water soluble or citrate 

 soluble phosphoric acid. This is done by treating them with 

 sulphuric acid, which removes, as gypsum, two parts of the lime, 

 with which the phosphoric acid is combined, leaving one part of 

 the lime combined with the phosphoric acid, as the monobasic or 

 acid phosphate of lime soluble in water. The product so converted 

 is called superphosphate, i.e. superior phosphate. - 



^ The writer has no intention of dispRragin.s Liebig's claim to the treatment 

 of bones by acid ; but the treatment of coprolites and mineral phosphate by acid 

 was first suggested by the Rev, Mr. Henslow. Mr. Lawes was either present at 

 Mr. Henslow's lecture or read a reporc of it. and took out a patent for the pro- 

 cess and proceeded to interdict Mr. Purser for ( igging for coprolites on his (Mr. 

 Purser's) own land for the purposes of treating them by acid so as to dissdve 

 them. Long litigation ensued, afterwards settled amicably. Lawes established 

 a factory at Deptford and Purser at Miliwall. with the river Thames between 

 them. Purser's Miliwall factory was closed in the early nineties. Lawes' 

 manure factory is now at Barking. The mineral superphosphate industry is 

 a British-born industry, like sulphuric acid manufacture. — Tr. 



■^This etymology is hardly satisfactory. Super here is not an abbreviation 



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