4 BULLETIN 798. U. S. DEPAKTMENT OF AGKICULTUKE. 



paid and which must be ground and bagged and transported, is one 

 of the fundamentals in the fertilizer industry. If a means were 

 devised by which farmers could buy practically tmdiluted plant food 

 and make up their own mixtures, an enormous saving would be 

 effected, and any method that would decrease the amount of inert 

 matter carried in fertilizers would be of great benefit to the agricul- 

 ture of the country. The quantity of filler used is only a minor 

 phase of this problem, but perhaps the part of it which is most easily 

 susceptible of improvement while the present general methods pre- 

 vail in the industry. 



SULPHURIC ACID AND ACID PHOSPHATE. 



Some of the fertilizer manufacturers produce their own sulphuric 

 acid, while others buy sulphuric acid. Of the 425 companies for 

 which this office secured returns, 68 were producers of sulphuric acid. 

 These firms ^ used the quantities of pyrites and sulphur shown in 

 Table II in the production of sulphuric acid for the periods to which 

 the schedule refers : 



Table II. — Materials used in the manufacture of sulphuric acid. 

 [2,000-pound tons.] 



Material. 



Pyrites.. 

 Sulphur. 



The proportion of sulphur used during the first six months 

 of 1918 was much greater than the corresponding proportion dur- 

 ing 1917. In pre-war times Spanish pyrites was practically the 

 only som"ce of sulphuric acid, as pure sulphur was too expensive 

 to be used in the manufacture of the acid, but owing to lack of 

 shipping facilities, caused by the war, it became very difficult to 

 obtain pyrites from Spain; on the other hand, the price of sul- 

 phuric acid advanced decidedly as a result of the demand for the 

 acid by manufacturers of munitions, so that it became profitable to 

 make the acid out of pure sulphur. Domestic and Canadian sources 

 of pyrites were utilized, but they were not sufficient to supply the 

 demand. In addition to sulphur and pyrites, a certain amount of 

 nitrate of soda is used in the manufacture of sulphuric acid, but 

 the schedules did not call for the uses to which nitrate of soda was 

 put, and there is no way of determining how much was used in con- 

 nection with the acid chambers and how much went into mixed fer- 

 tilizers. Beginning with July, 1918, the Nitrate Committee of the 



