524 



Basic Slag Problems. 



[Sept., 



Composition of Composition of Hlag 



Rock Phosphate. Before Addition. After Addition. 



per cent. per cent. per cent. 



CaO 51-92 48-75 50-4 



P^O, 35-63 9-66 10-66 



Solubility 17-87 88*88 76*95 



Total Calcium Phosphate 77-82 21-05 23-23 



There is no indication of any suffici^t alteration in the 

 mineral phosphate to justify the process. 



(b) Use of iron ore containing more 'phosphorus or addition 

 of phosphates in the blast furnace, with the express purpose of 

 obtaining a more phosphatic pig iron and therefore a more 

 phosphatic slag. It is agreed that this would constitute a satis- 

 factory solution of the agriculturist's problem, but from the steel 

 maker's point of view it adds to the cost of production of the 

 steel, and therefore could be adopted only if the price of the slag 

 Avere sufficiently attractive. 



(c) The re-introduction of the two lowest grades of slag into 

 the blast furnace, whereby a more phosphatic pig iron would be 

 produced, which, again, would yield a higher phosphatic slag. 

 This course would not increase the total units of phosphate, but 

 would increase the proportion of higher to lower grades. 



(b) and (c) are still being investigated by the Committee. 



(8) The Agricultural Value of the Slags now obtainable. — 

 The Committee felt bound to consider the possibility that no 

 improvement may be practicable in the quantity or quality of 

 basic slag, and it has therefore initiated experiments to ascer- 

 tain the agricultural value of present-day slags in comparison with 

 the basic Bessemer slags. These experiments were put in hand 

 at the beginning of the enquiry. Mineral phosphates are 

 included in the trial in order to ascertain whether they could 

 justifiably be used in increasing the phosphatic content of the 

 slag. 



Fortunately, the Agricultural Education Association had 

 already begun a series of trials on arable and hay land, and 

 Dr. G. Scott Eobertson has carried out various hay tests and has 

 projected feeding trials. These trials give some, but not all, 

 of the information the Committee needs. Further experiments 

 have, therefore, been arranged at Eothamsted to elucidate the 

 following points : — 



1. Whether the soluble and insoluble open hearth slags 



differ in agricultural value ; if so, whether some method of 



evaluation can be devised better than the present citric acid 



test. 



