2 BULLETIN 1179, U. S. DEPARTMENT OF AGRICULTURE. 
difficult for him to see that the same fertilizer value might be carried 
in very much smaller bulk, and that by using the more concentrated 
materials he could actually obtain the unit of plant food at a con- 
siderably lower cost, owing to the saving effected in storage, shipping, 
and handling charges. 
The gradual realization, however, that many of these low analysis 
materials, such as tankage, cottonseed meal, fish scrap, and the like, 
could be used much more profitably as stock feed than as ferti- 
lizer resulted in the manufacturers turning toward the higher grade 
materials and chemical compounds carrying nitrogen, phosphoric 
acid, and potash to make up the deficit caused by the withdrawal of 
the organic ammoniates for the feeding of animals. Many of the 
high-grade materials and chemical products useful in the manufacture 
of fertilizers are also essential in the production of munitions, and 
therefore this double demand during the war period probably did 
more than anything else toward initiating researches which will 
eventually establish the fertilizer industry on a sound chemical basis. 2 
Of the three main fertilizing ingredients, potash, nitrogen, and phos- 
phoric acid, the last mentioned is by far the most extensively used 
in American agriculture, and therefore the production of phosphates 
and fertilizers carrying phosphoric acid have received more attention 
than any other. It is true that an American potash industry was 
built up during the war, where none existed before, but our output 
of this fertilizer ingredient has now been very much curtailed by 
foreign competition 3 and unless we can perfect methods of recovering 
potash as a by-product of other industries the economic production 
of this material from A merican sources appears doubtful. 
The researches on methods of fixing atmospheric nitrogen which 
are being carried on in this department and the probable development 
of much cheaper hydroelectric power than is at present available will 
eventually establish large industries wherein synthetic nitrogen com- 
pounds will be manufactured as main products, but at present the 
mining and manufacturing of phosphates for agricultural purposes 
is the only branch of our immense fertilizer industry in which we are 
not dependent either upon foreign sources or upon the by-prcducts 
of other industries for the necessary supply of raw materials. 
In recent years p} r rolytic methods of producing phosphoric acid 
have been receiving a great deal of consideration, and rather exhaus- 
tive investigations have been conducted in this bureau with a view 
to establishing their commercial possibilities. From the data obtained 
and the progress so far made on this problem both in the bureau and 
by outside commercial interests it seems highly probable that this 
process will be employed in the near future to supplement, in part at 
least, the now almost universally applied method of making water- 
soluble phosphates by treating phosphate rock with sulphuric acid. 
PRINCIPLES INVOLVED IN THE VOLATILIZATION PROCESS. 
While the volatilization process for producing phosphoric acid has 
only recently assumed much prominence, the general scheme em- 
ployed is by no means a new one, it being based on the old method 
so long in use for the manufacture of elementary phosphorus. • 
2 Whitney, Milton. The Fertilizer Situation. Chem. and Met. Eng. 22, p. 1021 (1920). 
bourse, M. R. Potash in 1921. In Mineral Resources, U. S. Geological Survey, part 2, pp. 51-63 (1922). 
