RECENT WORK IN AGRICUETURAE SCIENCE. 



CHEMISTRY. 



On the determination of the citric-acid soluble phosphoric acid in Thomas 

 slag, R. SoRiiE {ZtKcJir. A))gcir. Chem., 17 {1904), V- 393; al>s. in CItent. Ztg., ^'S {1904), 

 No. 33, Rcpcrt. Nu. 9, p. 116). — In studies of Kellner's method for this purpose (E. 

 S. R., 14, p. 834), the author found that (1) the phosphoric acid precipitate contained 

 as much silicic acid after separation of this sul)stance as without such separation; 

 (2) the error due to solu])ility of ammonium-magnesium phosphate in ammonium 

 citrate was as great as that due to the simultaneous separation of silicic acid; (3) 

 the lower results obtained by tins method are apparently due to the increased solu- 

 bility of the ammonium-magnesium phosphate precipitate, resulting from longer 

 action of the ammonium citrate on this precipitate which takes place in the method. 



On citrate-soluble phosphoric acid, P. M. Van Haarst {Chem. Weekhlad, 1 

 (1903), pp. m:-.?ll, 221-236, 234-239; ahs. in Chem. CentbL, 1904, I, No. 9, p. 694).— 

 The methods employed in studying Thomas slag are discussed and tests of a number 

 of them are reported. 



On the solubility of soil constituents, F. Mach {Chem. /Ag., 27 {1903), No. 77, 

 p. 941; ah><. in Centbl. Agr. Chem., 33 {1904), No. 5, p. 34S). —Te^ts of the solubility 

 in pure water, in water containing carbon dioxid, hydrated silicic acid, and sus- 

 pended humic acid, and in dilute citric acid, of sandstone, shell limestone, basalt, 

 feldspar, gray wacke, zeolites, and other substances are reported, 5 gm. of the pul- 

 verized material being treated for 6 to 8 weeks with 1 liter of the various solvents. 

 In the case of the sandstone, graywacke, and basalt, and especially shell Umestone, 

 the water containing carbon dioxid dissolved considerably more than pure water. 



The phosphate present was almost entirely dissolved in citric acid, but the water 

 containing carl>on dioxid dissolved less of this substance than pure water. An 

 appreciable amount was dissolved in water containing hydrated silicic acid and 

 humic acid. A larger proportion of calcium carbonate was dissolved in water con- 

 taining carbon dioxid than in pure water. Water containing silicic acid dissolved 

 twice as much of this substance as pure water; that containing humic acid 10 times 

 as much, and that containing citric acid 53 times as much. Magnesium carbonate 

 was dissolved in large proportion by all of the solvents. The author was led to make 

 these tests as a result of observation that many plants are able to make a compara- 

 tively vigorous growth in a soil composed of freshly ground stone. 



Water-soluble plant food of soils, H. Snyder {Science, n. ser., 19 {1904), No. 

 491, pp. 834, 835). — This is a study of the amounts of phosi)horic acid removed from 

 the soil by wheat at different stages of growth, the results showing that the wheat 

 plant removes from the soil more phosphbric acid than is dissolved by extrac- 

 tion with water for 15 days. The paper was presented at the St. Louis meeting of 

 the Society for the Promotion of Agricultural Science (E. S. R., 15, p. 543), and 

 contains a critical analysis of the data given in Bulletin 22 of the Bureau of Soils of 

 this Department. 



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