THE AMOUNT OF FREE LIME AND THE COMPOSITION 

 OF THE SOLUBLE PHOSPHATES IN BASIC SLAG. 



By C. G. T. MORISON, B.A. (Oxon.). 

 Rothanisted Experiment Station. 



Basic Slag owes its value as a source of pliosphoric acid to the fact 

 that it is essentially basic in its character, and can be used on land 

 where an acid manure of the character of superphosphate is not to be 

 recommended. 



As no figures were available on the subject it seemed interesting to 

 determine how much of the lime which it contains existed in the free 

 uncombined condition. It has been stated that in some cases this is as 

 much as 20 °/o- 



With a view to this determination four samples of freshly ground 

 slag were obtained direct from the makers through the kindness of the 

 Lawes Chemical Manure Company. 



An attempt was made to follow the method of Stone and Scheuch^ 

 for the estimation of lime in commercial quicklime. The method 

 consists in shaking a weighed quantity of the slag with a 10 "/o solution 

 of cane sugar, filtering and titrating the lime with standard acid. 

 However it was found that in the case of some of the slags this solution 

 was darkly coloured and quite impossible to titrate, and contained in 

 addition to the lime considerable quantities of iron. Further on 

 acidifying the solution there was a considerable evolution of hydrogen 

 sulphide. It was found that calcium sulphide dissolves to some extent 

 in the sugar solution, 100 c.c. dissolving "0174 gram of calcium. 



This method was then abandoned — as were also others depending 

 on the reaction of ammonium and sodium carbonates with the lime 

 present. In all of these the reaction was interfered with by the sulphides 

 present, and by the fact that some phosphoric acid compound was also 

 attacked. 



1 J. Amer. Gli. Soc. 1894, xvi. 721. 



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