BULLETIN OF THE 
C 
No. 144 
Contribution from the Bureau of Soils, Milton Whitney, Chief. 
December 24, 1914. 
THE MANUFACTURE OF ACID PHOSPHATE. 
By Wm. H. Waggaman, Scientist in Fertilizer Investigations. 
INTRODUCTION. 
The acid-phosphate industry in the United States has grown to 
enormous proportions. In spite of the fact that numerous other 
forms of phosphatic fertilizer have been proposed or patented from 
time to time, and the application of raw ground-rock phosphates 
directly to the field has been recommended by some agronomists 
and agricultural chemists, the annual production of superphosphate 
continues to increase There is little doubt, therefore, that this 
material will continue to be the basis of- most of our commercial 
fertilizers. 
While the general procedure followed in making acid phosphate 
is a familiar one, many of those engaged in the production of this 
material have but little knowledge of the chemistry involved and are 
unfamiliar with numerous details of its manufacture, which are of 
great economic importance. 1 Competition has become so keen in 
the fertilizer industry during the last few years that in order to make 
a reasonable profit the manufacturer can no longer afford to carry on 
his business in the loose way formerly so prevalent, but must practice 
the most modern scientific methods and exercise the closest supervi- 
sion over every detail of his factory processes. It is believed that 
the preparation of this bulletin is justified by the information it will 
furnish the fertilizer manufacturers; but it is intended primarily to 
give the progressive farmer a clearer knowledge of that compound 
which is the basis of fertilizers, in order that he may more intelligently 
buy and handle his fertilizer and determine for himself its true 
value. Such knowledge, it is believed, should tend greatly to clarify 
prevailing ideas concerning the value of factory and of home-mixed 
fertilizers, and to throw light on the attendant question of inordinate 
profits alleged to be made by manufacturers. This paper describes 
1 Brogdon, J. S., Manufacture of Acid Phosphate. Amer. Fertilizer, 39 (5), pp. 25-29 (1913). 
Note.— Describes the manufacture of acid phosphate from phosphate rock, detailing the chemical and 
mechanical changes involved. Of interest to fertilizer manufacturers generally. 
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