151 



QUANTITY OP SLAG PER ACRE. 



If the soil is particularly deficient in phosphoric acid, one can use as high as from 

 . !MM) pounds of -la- to the acre, plowed in and supplemented with 200 pounds of 

 a-i<l phosphate in the hill or drill. 



If, on the contrary, the soil is naturally rich in phosphoric acid or has been made so 



by lar-e additions of .-lug for several consecutive years (1,000 or more pounds yearly) 



then it is necessary- only to replace from year to year the amount removed by the 



rn>j>. In surh ra.-es Maer.-ker >iates that one part of phosphoric acid in basic slag is 



table as an equal amount in acid phosphate. 



VALUATION OF PHOSPHORIC ACID IN BASIC SLAG. 

 By H. I). HASKINS. 



Thoma.- lia.-ir .-lai: is being used in Massachusetts and some of the other New England 

 \ten.-ively each yi-ar, and it is therefore highly desirable that more 

 Mctory methods of analyzing and valuing this product be worked out by the 

 association. 



At the la.- 1 ni'-eiin- ..i' the asso< -iatit.n the referee on phosphoric acid recommended 



thai the pho-phorir acid in Thomas basic slag be valued by the degree of fineness of 



the -I. i- along tin- -aim- lines as are employed in the case of ground bone, but the 



recommendation did not specify the diameter of the openings in the sieve used in the 



me. hani. al .-..paraiimi. If \alued by its fineness the diameter of the openings in the 



i fort hi.- pnrpo-i- i- obvioii>lv of great importance, a.- is shown by the follow- 



' ,vo samples of ,-hig \\ere analy/.ed mechanically by the use of 100-, 50-, 



an-! I 1 ", n . the latter having circular oj>enings one-fiftieth of an inch in 



<liam> 



( 'in,. , 'ininiint ami i nhn of phosphoric arid (intilable by using sieves of different 



mesh. 



An average of the two samples shows that 94.34 per cent of the slag passes a 25-mesh 



per rent paaeee a 50-mesh sieve, and only 70.15 per cent passes a 100-mesh 



I .....king at the matter from the point of valuation, we find that allowing 4 cents 



f..r the phosphoric arid in the line and 3 rents for the phosphoric acid in the coarse 



aluation of thr two samples of slag by use of the 25-mesh sieve 



would be $l:{.!;. by u-e of the f,o-mesh sieve $13.81, and by use of the 100-mesh sieve 



;.!!; a ditferenre of nearly $1 per ton in the extremes. 



The next .|ii.-tion to be considered is whether this method of valuing the phos- 

 phoric arid in baM. -lag is a safe one for us to adopt. During the month of August 

 the writer's attention was called to a product put forth in large quantities in northern 

 New York. The material was a waste product said to be largely apatite and quartz, 

 romin- from iron ..re u.-e.l in that locality. It was finely ground, 69.44 per cent passing 

 a lm-m,-h sieve, and contained 16.78 per cent of total phosphoric acid; the phos- 



