merchantable quality and are up to the standard of guarantee. Food ' or 

 We conclude to get our three essential components from a P1 * nts 

 variety of materials and proceed thus: 



199 



Now let us suppose that out of these same materials we 

 wish to make a fertilizer containing from I to 2 per cent, of 

 Nitrogen, 6 to 8 per cent, of phosphoric acid, and from 2 to 3 

 per cent, of potash. We have 7our ingredients that supply 

 Nitrogen, namely, Nitrate of Soda, sulphate of ammonia, 

 dried blood, and dissolved bone meal, and they supply it in 

 the three forms of nitric acid, ammonia, and organic Nitro- 

 gen. We want from 20 to 40 pounds of Nitrogen, 120 to 

 1 60 pounds of phosphoric acid, and from 40 to 60 pounds of 

 potash. In compounding our formula we will take the higher 

 number for Nitrogen (40 pounds), and will take the Ni- 

 trogen in about equal proportions; that is, 10 pounds of Ni- 

 trogen from each of the four nitrogenous constituents. We 

 begin with Nitrate of Soda, containing 15.65 pounds of Ni- 

 trogen in each 100 pounds of the Nitrate. Now, how many 

 pounds of Nitrate of Soda must we have to get 10 pounds of 

 Nitrogen? It is a very simple calculation; since in 100 

 pounds there are 15.65 pounds of Nitrogen there must be in 

 i pound of Nitrate of Soda the one-hundredth part of 15.65 

 pounds, or .1565 pounds of Nitrogen. Hence, we must have 

 about 64 pounds of Nitrate of Soda.* 



* io,ooo-=_. 1565=63.89-!- pounds. 



