1917J SOILS FERTILIZERS. 21 



Studies on soils, I, F. E. Rice (Jovr. Phys. Chem., 20 (1916), No. S, pp. 

 214-227, flg. 1; abs. in Chem. Abs., 10 (1916), No. 11. p. 1568; Jour. Chem. Soc. 

 [London], 110 (1916), No. 64S, I, p. 360). — Laboratory experiments conducted at 

 the New York State College of Agriculture with a number of soils collected 

 from various parts of New York are reported. 



The results are taken to indicate that " when so-called ' acid ' soils are shaken 

 with salt solutions, part of the cation of the salt is adsorbed and an equivalent 

 (luantity of bases from the soil is given up to the solution. The extracts, thus 

 obtained, show gi*eater acidity than that of the salt solutions themselves. This 

 can be accounted for by the fact that one of the bases present is aluminum, 

 which does not securely hold its share of the acid, but through hydrolysis 

 hydrated aluminum oxid is formed along with equivalent quantities of free 

 acid. The former being slightly ionized, possibly in a colloidal condition, and 

 the latter more or less strongly ionized, the resultant solution is quite acid. 



" Acid soils rarely contain water-soluble acid ; but one case of mineral soil 

 and one of muck soil was found that did yield an acid to water. Basic soils (as 

 distinguished from 'acid' soils) gave up to salt solutions more base than is 

 adsorbed. But as they are also found to give up to water quantities of base 

 sufficient to produce solutions of alkaline reaction, this should not be considered 

 entirely a phenomenon of basic exchange, but of simple solution of the excess 

 of base." 



Studies on soil colloids, I, Flocculation of soil colloidal solutions, M. I. 

 WoLKOFF (Soil Sci., 1 (1916), No. 6, pp. 585-601, figs. 5).— Experiments con- 

 ducted at the Michigan Agricultural College to study the behavior of brick 

 yard clay, silt loam soil, muck, peaty muck, and kaolin with respect to different 

 electrolytes, in order better to understand the phenomenon of flocculation in the 

 soil, are reported. Sixty-seven acid, salt, and alkali solutions were used in 

 fifth-normal strength. 



It was found that " besides the fact that the flocculating efficiency of different 

 electrolytes with the same colloidal solution is different, the results show that 

 the efficiency of the same electrolyte with the solutions from different soils 

 varies considerably, depending largely upon the chemical composition of the 

 soils. Schulze's valency law does not hold true with the soil colloidal solu- 

 tions studied. Humic materials hinder the coagulating power of the electrolytes. 

 It takes a greater amoiint of electrolyte for a flocculation of a more concen- 

 trated soil colloidal solution than that for a less concentrated one. In the floc- 

 culation of the soil colloidal solutions by the electrolyte, the reaction obeys, 

 within the experimental error, the law of mass action." 



Bacterial numbers in soils at different depths and in different seasons of 

 the year, S. A. Waksman (Soil Sci., 1 (1916), No. 4, pp. 363-380, figs. 6).— A 

 brief review of the work of others bearing on the subject is followed by a 

 report of experiments conducted at Rutgers College on the bacterial numbers 

 in loam and clay loam soils. 



It was found that " the greatest number of bacteria were at a depth of 1 in. 

 in the soils that are under shade all the year round. Garden soil gave on the 

 average the largest numbers 4 in. from the surface. There was a regular 

 decrease in numbers of organisms from a depth of 1 in. . . . down to a depth of 

 30 in. The greatest decrease in numbers between any two consecutive depths 

 of sampling occurred between the first and the fourth, or the fourth and the 

 eighth inches. The meadow soil gave the largest bacterial counts at a depth of 

 1 in. of all the soils. . . . The forest soil, though showing a high carbon and 

 nitrogen content, gave the lowest bacterial counts. . . . 



" The numbers of bacteria in the soils studied were not governed either by 

 the moisture content of the different soils or the nitrogen and carbon contents. 



