1905.] 



Basic Slag. 



479 



purposes, and an explanation of the results obtained in the 

 experiment above referred to may possibly be found in the fact 

 that, although there was a wide difference in the total amount of 

 phosphoric acid present in the high- and low-grade slags used, 

 there might not have been so much difference in the actual 

 quantities soluble in a weak solution of citric acid. In order to 

 test this question further, experiments were started at two centres. 

 The slags used in these experiments were tested both for the 

 total amount of the phosphoric acid present and for the amount 

 soluble in a 2 per cent, solution of citric acid and gave the 

 following results : — 



High grade. Low grade. 

 Per cent. Per cent. 



Total phosphate of lime 37' 38 27-93 



Phosphate soluble in 2 per cent, citric acid 



solution ... ... ... ... ... 30*00 26*54 



Percentage passing through the standard 



sieve, 10,000 holes per square inch ... 71-6 72*0 



£ d. £ s. d. 

 Price per ton 226 I 15 o 



The analyses show that, although there was a difference of 

 about 10 per cent, in the total amount of the phosphate of lime 

 present in the two slags, there was only a difference of about 



per cent, in the amount soluble in a 2 per cent, solution of 

 citric acid. 



The returns from the two centres have up to the present been 

 somewhat contradictory, but the point is one of considerable 

 practical importance. 



The Irish Department in their Leaflet dealing with basic slag, 

 point out that there is nothing in the appearance of basic slag 

 which gives the slightest indication of the percentage of phos- 

 phate of lime it contains, and recommend that the farmer 

 should (1) stipulate when purchasing that he shall be sup- 

 plied with a high-class slag ; (2) insist on being furnished 

 with an invoice on which are clearly stated (a) the percentage 

 of phosphate of lime, (b) the fineness of grinding, and (V^the 

 percentage of phosphate of lime soluble in a 2 per cent, solution 

 of citric acid according to Wagner's method. There should be 

 no difficulty in procuring from any reliable manure merchant 

 basic slag which contains 40 per cent, of phosphate of lime 

 and so finely ground that at least 80 per cent, of it will pass 

 through a sieve having 10,000 holes per square inch, and in 



