40 FARM AND SCHOOL PROBLEMS. 



These materials represent only a few of those which are 

 available for the compounding of fertilizers, but for the im- 

 mediate matter in hand these will be sufficient for our purpose. 



For the purpose of illustrating the method of calculating a 

 formula we will assume that the farmer wants to use a fertilizer 

 containing about 2.85% ammonia, 10.5% phosphoric acid and 

 5% potash. With this percentage composition how many pounds 

 of ammonia, phosphoric acid and potash would a ton of the 

 mixed fertilizer contain? To answer this question it is only 

 necessary to multiply the number of pounds in one ton of 

 fertilizer by the percent of each essential ingredient, as follows : 



2,000 X .0235 = 57 Ibs. ammonia. 



2,000 X .1050 = 210 Ibs. phosphoric acid. 



2,000 X .0500 = 100 Ibs. potash. 



Having thus ascertained the number of pounds of the vari- 

 ous essential ingredients that one ton of fertilizer will contain 

 our problem now is to determine how much nitrate of soda, acid 

 phosphate and muriate of potash respectively will be required 

 to supply them ; assuming that we have decided to use these par- 

 ticular raw materials as carriers. This is done by dividing the 

 amount of any particular ingredient in the mixed fertilizer by 

 the percent of this same ingredient in the raw material from 

 which it is derived. Thus to find how many pounds of nitrate 

 of soda (containing ig% ammonia) would be required to 

 furnish 57 pounds of ammonia we would say 



57 H- 0.19 = 300 Ibs. nitrate of soda. 



Similarly for the other ingredients we find that 



210-7-0.14 = 1,500 Ibs. acid phosphate. 

 100^-0.50 = 200 Ibs. muriate of potash. 



Assembling our figures therefore into a systematic formula 

 we should have 



