UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 312 



Contribution from the Bureau of Soils 

 MILTON WHITNEY, Chief 



Jfc&**&*fU 



Washington, D. C. 



November 5, 1915 



PHOSPHATE ROCK AND METHODS PROPOSED FOR 

 ITS UTILIZATION AS A FERTILIZER. 



By William H. Waggaman and William H. Fry. 



CONTENTS. 



Introduction 1 



Phosphate deposits of the United States 3 



Forms in which phosphoric acid is applied to 



soils 8 



Processes for treating phosphate rock in the 



manufacture of phosphoric acid and phos- 



phatic fertilizers 8 



Processes for the production of phosphoric 



acid or soluble phosphates by combined 



heating and acid treatment 12 



Double decomposition by means of an alkali, 



an alkali salt, or alkaline earth 12 



Processes to be used in connection with the 



iron and steel industries 14 



Page. 



Processes in which the phosphorus or phos- 

 phoric acid is volatilized 15 



Processes dealing with the production of two 

 or more fertilizer elements 17 



Processes dealing with the production of avail- 

 able phosphates by electrolysis 18 



Processes for the enrichment of phosphates . . 19 



Mechanical treatment of phosphates 20 



Miscellaneous processes for the production of 

 available phosphates 20 



Appendix: Classified tabular list of patented 

 processes 21 



INTRODUCTION. 



The basis of nearly all mixed fertilizers is water-soluble or so-called 

 "available" phosphoric acid, which is produced by submitting bones, 

 a mineral phosphate (apatite or phosphorite), or some other phos- 

 phate-bearing substance to a treatment by which the constitution of 

 the original body is materially changed. 



Our supply of bones is entirely inadequate to meet the present 

 demands of the fertilizer industry, while apatite has proved objection- 

 able because of the difficulty and expense of mining the mineral and 

 on account of the quantity of fluorine which it contains. By far the 

 greater part of the phosphate fertilizer is derived from phosphorites 

 or amorphous phosphate rock, of which there arc enormous deposits 

 in the United States. 



For many years the importance of the phosphate industry has been 

 growing steadily. At present the conditions id Europe incident to 

 war have temporarily curtailed the output of phosphate rock, in this 

 country u-> well as abroad, but on the termination of hostilities the 



6819°— Bull. 312 — 15 1 



