522 



Basic Slag Problems. 



[Sept., 



amounts of slag produced in Great Britain in the year ended 

 30th September, 1920, were : — 



AsF.,0.,. 



Under 5 per cent. 



5 and under 7 „ 



7 10 



10 „ 12 „ 



12 15 



Over 15 





As Phos2)hate. 



Quantity. 







Tons. 



Under 



11 percent. 



22,522 



11 and 



under 15J ,, 



118.011 



151 





302,34t; 



22 





90,928 



26| 





121,357 



Over 



33 



46,229 





Total 



701,393* 



It may be doubted whether the 22,500 tons of slag containing 

 less than 5 per cent, of P2O- ( = under 11 per cent, tricalcic 

 phosphate) would be worth grinding. The 118,000 tons of next 

 higher grade (11 to 15J^ per cent, tricalcic phosphate) may be 

 found to have more value than appears from their phosphate 

 content, but owing to high cost of transport and present 

 uncertain knowledge as to their value would not at present be as 

 eagerly sought by farmers as the higher grades. There remain, 

 therefore, some 560,000 tons of slag, containing more than 

 15 J per cent, phosphate of which only 46,000 tons is of the 

 basic Bessemer type (more than 38 per cent, phosphate). 



Before the War the steel makers produced, and the farmers 

 consumed, some 260,000 tons of high-grade slag; last year 

 46,000 tons only were produced, and apparently even this small 

 production cannot be relied upon in the future. 



The above table shows that, as regards units of phosphate, 

 the farmer is not placed on such a short ration as might at first 

 appear. The 260,000 tons of high-grade slag of pre-war days 

 contained 9,880,000 units of phosphate; the 560,000 tons of last 

 year's slag contained 13,400,000 units. Adding in the units 

 contained in the 140,000 tons of the lowest two grades the figure 

 becomes 15,200,000 units. 



The problem appears in a less favourable light, however, when 

 it is remembered that farmers before the War were not using 

 anything like as much slag as in the opinion of competent 

 authorities they might with advantage have used. Sir Thomas 

 Middleton estimated that no less than 890,000 tons per annum 

 might be used in the United Kingdom, equivalent to 33,820,000 

 units — some 2 J times the present output. 



* Excluding the production of four firms from whom no returns were received. 



