SOILS FERTILTZERS. 219 



SOILS— FERTILIZERS. 



Electrochemical methods in soil investigations, F. K. Cameron {Tran.t. 

 Amer. EIrctrocfinu. Soc, J5 {100'.}), pp. .5,W-.')67 ; ah.^. in Chem. Ahs., .? {lf)09), 

 No. 21, pp. 2601, 2602).— It is stated that "the eheinistry and physics of the 

 soil as related to crop ijroduction is primarily a solution study, and, sjieaking 

 generally, the electrooheniical methods which have proved effective in studying 

 solutions elsewhere are all more or less applicahle to soil studies." 



The article discusses the application of the Wheatstone bridge in the determi- 

 nation of salt content, temi)erature, and moisture in soils, and in solution and 

 absorption studies; the electro-analysis of soils; and the use of the Ostwald 

 half-cell in the determination of the concentrations of dissolved material held 

 close to the soil grain surfaces. 



"One of the most useful instruments which has been devised for soil work 

 is a slide wire bridge, of a form which can be readily carried into the field for 

 observations there as well as in the laboratory. The essential feature of this 

 bridge is a circular wire so calibrated that the ratio of the bridge arms is read 

 directly, and by a si)ecial iittachment a slight turn of the wrist will enable one 

 to read resistances of 10 to 1<I(> ohms, from 1(K» to ].(KH) ohms, and from 1,0(X» to 

 lo.dUO ohm.s. The whole apparatus, with dry battery induction coil, telephone, 

 and other attachments, is conveniently packed in a small case measuring 8 by 

 7 by 7 in. and weighing approximately G lbs. In areas where there is an 

 accumulation of .soluble salts or 'alkali,' the amoiml of alkali in the soil can be 

 determined approximately by mixing so much distilled water with the soil as it 

 will take up without allowing any free water to flow from it — in other words, 

 saturating the soil — placing the saturated soil in a hard rubber cell of known 

 dimensions, fitted with parallel electrodes. These electrodes each form a part 

 of the cell and are then slipped between si)ring contact-cliiis on the bridge box 

 and the resistance read off, the temperature of the wet soil being taken at the 

 same time by means of a small thermometer. The saturation of the soil is 

 accomplished with great readiness and precision after a little practice, as well 

 as the estimation of the texture of the soil; with this data the salt content of 

 the soil can be readily read off from tables i)reviously i)repared." 



The Siime principle has not been .so successfully ai)i»lied in the determination 

 of moisture on account of tlie difficulty of securing good soil contact of the 

 electrodes. 



The physical properties of soils, K. Thnka (Die itlniKil-dliKchrn Eigcnschnf- 

 ten dcs Bodena. Prague, 1909, pp. 2Jf, figs. S). — This is a description and report 

 of tests of modifications of Kopecky's methcMls for determination of the volume 

 w-eight and porosity of soils. The object of these modifications was to obtain an 

 accurate, rapid, and easy method of determining the physical properties of the 

 soils in place. The special apparatus devi-sed is described and the importance 

 of determining these properties under natural conditions is discussed. 



The influence of lime on the movement of water in soils, E. Blanck 

 (Landir. Jahrb., 38 (1909), No. 5-6, pp. 715-758; abs. in Deut. Landiv. Pre.s.s-e, 

 36 {1909), No. 87, p. 93/ ; Chcm. Abs., 4 {1910), No. 1, pp. 73, 7//).— The investi- 

 gations on this subject were made with sandy loam soil to which lime was 

 added at the rate of 20 gm. per 1,000 gm. of soil. Glass pots containing 1,000 

 gm. of soil were used and the carbon dioxid content of the soil was determined 

 at intervals during the experiments. Studies of the effect of the lime on the 

 capillary rise of water, water capacity, and hygroscopicity of the soil were al.so 

 made. 



It was observed that the caustic lime applied to the soil was converted into 

 carbonate of lime to a depth of 6 cm., slowly in undisturbed soil but more 



