EXPERIMENT STATION BULLETINS. 



393 



samples were collected and consequently are not included in the discus- 

 sion. Several sani])les of other grades were found and the average selling 

 price and unit cost of phosphoric acid in each is shown in the following 

 table : 



Unit Cost of Phosphoric Acid 



Grade F' 



10% 

 14% 

 16% 



Average 

 [Retail Price. 



$23 . 13 



25.58 

 » ' 26.61 



'' Unit Cost of 

 iPhosptioric Acid. 



$2.31 

 1.83 

 1.66 



It is readily seen that as the grade or percentage of available phosphoric 

 acid increases the cost per unit of plant-food decreases. 



Assuming that !i>l.GG represents the average unit cost, to the consumer, 

 of available phosphoric acid in 16% acid phosphate during the past year, 

 we can now determine the cost per unit of ammonia in the various grades 

 of ammoniated phosphate. This is done by multiplying the number of 

 units of phosphoric acid by the price per unit. This result is then sub- 

 tracted from the price per ton which gives the cost of the total amount of 

 ammonia. If now we divide this by the number of units of ammonia, we 

 obtain the cost of ammonia per unit in that particular lot of fertilizer. 

 As an example let us assume a 1-12-0 fertilizer selling at |34.12 per ton. 

 Multiply the number of units of phosphoric acid by the price per unit 

 (12X|1-66=|19.92) which represents the value of the available phos- 

 phoric acid. Now subtract this result from the selling price (|34.12 — 

 |19.92=|14.20) and the result will be the cost of one unit of ammonia. 

 The cost per unit of nitrogen is determined by dividing the unit cost of 

 ammonia by the factor 0.82 (.|14.20^0.82=-|17.32) . 



The unit cost of ammonia in the various grades of ammoniated phos- 

 phate sold in the State during the past year is shown in the following 

 table : 



Some objection might be raised to this method of arriving at the unit 

 cost of ammonia, especiall}^ in using the lowest phosphoric acid unit value 

 for determining the cost of the phosphoric acid in the mixtures. However, 

 the cost of manufacturing any of the various grades of ammoniated phos- 

 I)hate, exclusive of materials, should not be much greater than the cost of 

 making 16% acid phosphate for the process is practically the same, except 

 that in making ammoniated phosphate the ammonia-bearing material is 

 mixed with the rock phosphate before the sulfuric acid is added. What- 

 ever extra overhead expense is incurred therefor should rightly be charged 

 up to the ammonia. On the other hand if the ammonia-phosphate mixture 



