UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No 1179 
Washington, D. C. 
December, 1923 
INVESTIGATIONS OF THE MANUFACTURE OF PHOSPHORIC ACID BY 
THE VOLATILIZATION PROCESS. 
By William H. Waggamax. Scientist in Investigation of Fertilizer Resources; Henry 
W. Easterwood. Chemist, and Thomas B. Turley, Operation Engineer , Investiga- 
tion of Fertilizer Resources, Bur, au of Soils. 
CONTENTS. 
Page. 
Introduction 
Principles involved in the volatilization 
process 
Advantages of the volatilization process.. 
Review of methods for -producing phosphorus 
and phosphoric acid by volatilization 
The use of the electric furnace in the vola- 
tilization of phosphoric acid 
Cottrell electrical precipitator 
Larger scale experiments 11 
Electric smelting of mine-run phosphates 13 
Theoretical heat balances 17 
10 
Page. 
The use of the fuel furnace in the volatilization 
of phosphoric acid 19 
Comparative cost of the thermal unit fur- 
nished by electric power and fuel 20 
Preliminary laboratory experiments 24 
The briquetting of mineral phosphates 27 
Effect of high temperatures on various 
briquetted mixtures 32 
Larger scale experiments 37 
Pre-ent furnace equipment and latest re- 
sults 39 
Discussion of experimental results 45 
Estimated cost of production 46 
Summary and conclusions 48 
INTRODUCTION. 
During the last decade there has been a distinct tendency toward 
higher specialization in American industries. The late war, with its 
demands for a greater output of practically all agricultural and 
manufactured products, further stimulated industrial effort, and now 
the high cost of labor, increased freight rates, and the keen competi- 
tion which has grown out of the postwar period has forced upon us 
the necessity of even greater efficiency in our industrial processes. 
While the American fertilizer industry up to the time of the 
European war had shown a rather steady, healthy growth, in some 
regards it had lagged considerably. This was due in part, no doubt, 
to the fact that it had always been an industry utilizing refuse and 
waste products generally regarded as unfit for other purposes, and 
partly to the fact that the American farmer had grown so accus- 
tomed to the use of relatively low analysis fertilizers that it was 
1 For complete treatise on the mining of phosphate rock and various methods of manufacturing phos- 
phoric acid and phosphates for fertilizer and other purposes the reader is referred to a book entitled 
••Phosphoric Acid, Phosphates, and Phosphatic Fertilizers," by Wm. H. Waggaman and Henry W. 
voou, which will appear shortly as a monograph of the American Chemical Society. 
mm 73 — 1 i 
