HISTORY OF THE AMERICAN MENHADEN. 495 



7. Methods of calculating costs of valuable ingredients of fertilizers.* 



The method referred to on page 235 consists in comparing different 

 fertilizers by the costs per pound of the valuable ingredients at the prices 

 at which the articles are sold. 



The way in which these computations are made here may be explained 

 as follows : 



Take first a simple case, a sulphate of ammonia containing 20 per cent. 

 of nitrogen, and sold at $100 per ton. Twenty per cent, is equivalent 

 to 400 pounds in a ton of 2,000 pounds. These 400 pounds of nitrogen 

 cost $100. One pound will therefore cost $100 h- 400 = 25 cents. 



Now, a more complicated case. Suppose a superphosphate to contain 

 valuable ingredients (and that, for convenience, we indicate the latter 

 by abbreviations), as below : 



Soluble phosphoric acid, (Sol.) 10 per cent.=200 pounds in ton, 



Insoluble phosphoric acid (Ins.) 2.5 per cent. = 50 " " '' 



:N^itrogen (N.) 3 per cent. = GO " " '' 



that it be sold at $40 per ton, and that the values of the ingredients are 

 in the ratios of Sol. 15, Ins. 6, and N. 25 cents per pound. The problem 

 will be to find a series of values in the ratios 15 : 6 : 25, which, multiplied 

 by the respective numbers of pounds of Sol., Ins., and N. in a ton, will 

 give three products, whose sum will be $40. The method employed here 

 for solving the problem is as follows : The assumed rate for Ins. was 6 

 cents, that for Sol., 15 cents, or 2^ times as much, and that for N. 25 

 cents, or 4i times as much. Multiply the number of pounds of Sol. in 

 a ton by 2^, and that of S". by 4i, and add the products to the number 

 of pounds of Ins., and the sum will be the number of pounds of Ins. 

 which would have the same value as the Sol., Ins., and N. actually present 

 taken together. Divide the whole cost by this sum and the quotient 

 will be the cost of one pound of Ins. This multiplied by 2^ will give 

 the cost of one pound of Sol., and by 4i will give the cost of one pound 

 of N. The calculations for the above case will be : 



Sol 200 pounds x 2^=500 pounds Ins. 



Ins 50 '< X 1 = 50 " " 



N 60 " X 4i=250 " " 



800 " " 



The price per ton, $40, divided by 800, gives 5 cents, the cost of one 

 pound of Ins. ; 5 x 2J=12^ cents cost, of one pound of Sol. ; and 5 X 

 41= 20f, cost of one pound of N. 



*From report of Connecticut Agricultural Experiment Station, 1876, W. O. Atwatcr, 

 director. 



