SOILS — FERTILIZERS. 519 



of the plowed soil. Such an application properly made would also double the 

 yield of clovei* in the near future; and, if the clover were then returned to 

 the soil either directly or in farm manure, the combined effect of the phos- 

 phorus and nitrogenous organic matter with a good rotation of crops would 

 soon double the yield of corn on most farms." 



An appendix contains a discussion of soil survey methods and of the general 

 principles of soil fertility and its maintenance. 



A geological and agronomical study of the oolitic deposits of the Depart- 

 ment of Yonne, C. Brioux (Ann. Inst. Nat. Agron., 2. ser., 10 {1911), Nos. 1, 

 pp. H9-2Ji2, flffs. 8; 2, pp. 21t3S19). — This article reports in detail the results 

 of a study of the physical and chemical characteristics, crop adaptations, and 

 fertilizer requirements of the soils derived from the geological formations of 

 the region. Statistics on the extent of production of the principal crops in 

 1850 and in 189S are also given and discussed with regard to the economic 

 factors which have influenced the acreage of the more important crops, par- 

 ticularly that of the grape. A bibliography of the literature of the subject is 

 added. 



The determination of colloids in cultivated soils, J. Konig, J. Hasen- 

 BAUMER, and C. Hassler {Landw. Vers, mat., 75 {1911), No. 5-6, pp. 377- 

 UI, fig- 1; a&s- m Cliem. Ahs., 6 {1912), No. 3, p. 1,02; Jour. Soc. Cliem. Indus., 

 31 {1912), No. 2, p. 83). — In continuation of previous investigations (E. S. R., 

 19, p. 718; 20, p. 713; 24, pp. 521, 522) the authors report tests of the colorimetric 

 method of determining soil colloids; determinations of colloids by absorption of 

 salts; determination of absorbed and adsorbed ions in soils when dried at 

 200° C, treated with steam, oxidized with hydrogen peroxid, and treated with a 

 strong, constant electric current ; and a study of the relation between yield and 

 the results of chemical and physical investigation of the soil. 



The general conclusions, bri^y stated, are that soils contain important 

 amounts of substances of a more or less colloidal character which can be deter- 

 mined by their absorptive power for certain coloring matters and mineral salts. 

 Methyl violet seems best adapted to colorimetric determination of colloids, and 

 in most cases three concentrations, namely, 1, 2. and 3 gm. per liter, will suffice. 

 The absorption of the coloring matter depends primarily upon the content of 

 colloidal clay substances in the soil. 



For determination of colloids by means of absorption of salts a fiftieth-normal 

 solution of dipotassium phosphate is recommended. In this case the potash 

 is absorbed mainly by the colloidal clay, and the phosphoric acid by the lime, 

 iron oxid, and especially alumina. The potash is loosely combined in soil 

 colloids and can be to a large extent or entirely set free by steaming, by oxi- 

 dation with hydrogen peroxid, and by the action of an electric current. The 

 phosphoric acid is combined in the form of insoluble calcium phosphate. It 

 is more firmly fixed by heating, and can not again be entirely set free even 

 by strong action of the electric current. 



The relation between the yield and the absorptive capacity for coloring mat- 

 ter and dipotassium phosphate was quite close for surface soil and subsoil of 

 the same soil type, but not for different kinds of soil. 



A new method proposed in this article for the determination of the easily 

 soluble matter in soils is treatment with a strong, constant electric current. 

 Advantage is taken in this method of the fact that when such a current is 

 passed through a wet soil between platinum electrodes the soil acts more or 

 less (depending upon the colloid content) as a semipermeable membrane, with 

 the result that a certain amount of electrolysis takes place with separation of 

 the soil constituents at the electrodes. The apparatus and method employed 

 are in brief as follows : 



