[Reprinted from the Journal of Industrial and Engineering Ch 



Vol. 4. No. 9. September, 1912]. 



CALIFORNIA 



AbKIUULIU 

 LIBRARY 



UNIVERSI 



nistry, 



THE EFFECT OF IGNITION ON THE SOLUBILITY OF SOIL 

 PHOSPHATES. 



By CHAS. B. LIPMAN. 

 Received July 31, 1912. 



In common with other soil investigators, the writer 

 has taken occasion to point out recently the dangers 

 involved in applying data obtained with solution 

 cultures of plants to soil problems with the same 

 plants. Time and again results have been obtained 

 in solution cultures of both plants and bacteria which 

 when compared with tests of the same organisms on 

 soils, both sterile and unsterile, were found to be widely 

 divergent and discordant. I have also found the same 

 to be true regarding the purely chemical changes of 

 the same materials in minerals and in soils as brought 

 about by the laboratory treatment involved in their 

 quantitative determination. My remarks apply par- 

 ticularly to the quantitative determinations of phos- 

 phates in soil ; I employ for this paper the same title 

 that Fraps 1 used for his recently, to call attention to 

 the differences effected in the degree of solubility 

 of phosphates in phosphate minerals and in soils, 

 by ignition. In the work just cited, Fraps has shown 

 that the ignition of phosphate minerals, including 

 wavellite, dufrenite and variscite, for 10 minutes at 

 a low red heat increased about 10 times the solubility 

 of the phosphoric acid contained in them in fifth normal 

 nitric acid and rendered it almost completely soluble in 

 12 per cent, hydrochloric acid. From these results 

 he concludes that the method for determining phos- 

 phoric acid in soils as used by him is not suited to 

 distinguish between the organic and the inorganic 

 phosphorus in soils, since the inorganic phosphates 

 are made more soluble through ignition. 



We are not concerned in this paper with the latter 

 conclusion of Fraps as regards the distinction between 

 the organic and inorganic phosphorus of the soil. 

 Having frequently noted, however, in our analytical 

 work on soils that the very opposite effect to that 

 above quoted is accomplished by ignition of soils 

 before determining the phosphoric acid, it was deemed 

 desirable to make some systematic tests with reference 

 to the matter, and determine, if possible, the cause 



1 THIS JOURNAL, 3, 335. 



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