The utilisation of basic slag

E. J. Russell
1920 Transactions of the Faraday Society  
The utilisation of basic slag in agriculture is one of those import,anb developments in agricultural science for which the credit is due in the first instance t o British investigators. The possibility of utilising basic slag was put t o practical test by the late John Wrightson a t Ferryhill and a t Downton in 1884 and 1885, and, in spite of some opposition on theoretical grounds by pther workers, a good case was made out. The first field experiments were carried out in the south of England, b
more » ... south of England, b u t the centre of interest soon shifted to the north, and the most striking tests were carried out a t Cockle Park, under t.he direction successively of Professor Somerville, Sir T. H. Middleton, and Professor Gilchrist. To these three more than any others we owe the great advances in knowledge of the use of basic slag. The standard experiments and t.he well known trials were all made with the Bessemer slag. If agriculturists could have been assured of a st'eady supply of, say, 300,000 or 400,000 tons per annum of high grade Bessemer slag containing some 20 per cent. of P,O" there would have been no need for this discussion; the problem would have been the purely academic one of working out the constitution of the effective constituents of the slag. The int,roduction of the basic open hearth process, however, has threatened the supersession of t,he Besseiner process, and agriculturists can no longer feel certain of receiving adequate supplies of slag of the type to which the old material beloGged. Three distinct substances are now used under the one name of basic slag :-(1) Bessemer slag, containing about 20 per cent. of P,O, (43.6 per cent. tricalcic phosphate). (2) Open hearth basic slag, 7 to 14 per cent. P,O, (15.4 to 31 per cent. tricalcic phosphate). (3) Open hearth basic slag, 7 t o 10 per cent'. P,Oj (15.4 t o 21.8 per cent. tricalcic phosphate), in the manufacture of which a considerable proportion of calcium fluoride has been used. The phosphorus of the first two types of slag is nearly all soluble (55 per cent. or more) in 2 per cent. citric acid under certain conventional coiiditions: t h a t of the third type is not-only 20 per cent. or less dissolving. It may be said a t once t h a t no important agricultural distinction between the first and second of these classes has been proved with czrtainty when the slags are used i n quantities containing equal amounts of phosphorus, and so far as present information goes, these slags are of equal value per unit of phosphorus to agriculturists. T h e are, of course, dkadvantages in low-grade materials, in t,hat large bulks have to bo handlrd, and therefore larger expenditure is
doi:10.1039/tf9201600263 fatcat:oby5ynoklrh6pdnm3evwgfgw6u