SOILS FERTILIZERS. 1119 



" Bodies which have boon hciitod aiid then cooled in a vticuuiii show high 

 absorptive power ; cousequeutly, absorption can not be loolied iipon solely as the 

 solution of a gas in moisture films upon the grains of the solid. 



" In general, nitrogen is absorbed by soils in greater quantity than oxygen. 

 This is especially interesting, since the absorption of oxygen and nitrogen from 

 air by water gives a higher ratio of oxygen to nitrogen in the solution than the 

 1:4 relation which exists in air. The similar high absorptive power of alumi- 

 num hydroxid, ferric hydroxid, and magnesium carbonate for nitrogen indicates 

 that this preference of soils for nitrogen is a real phenomenon, since these sub- 

 stances have no way of making their true absorptive power for oxygen by con- 

 verting it chemically to cai'bon dioxid, as a soil does, or to other oxids. 



" The absorption of carbon dioxid by soils is due in great measure to the 

 presence of hydrated oxids, such as ferric oxid, and humus. Kaolin, calcium 

 carbonate, and quartz also absorb cai'bon dioxid, but in comparatively small 

 amounts. 



" Soils, whether acid or alkaline, dry or wet, absorb ammonia from the atmos- 

 phere in appreciable amount. 



./I No one mathematical expression has been found to hold generally for the 

 d^tribution of a gas between the vapor phase and absorbing solid. The specific 

 attraction of solid and gas. the diffusion of gas into solid, the condensation of 

 gas to liquids, and consequent clogging of capillary channels where the forms 

 and arrangement of these minute spaces enter to determine the vapor pressure 

 of the liquid there enmeshed, all these factors complicate the observed relation 

 of mass of gas absorbed to mass of gas left in the vapor phase." 



The flocculation of turbid liquids by salts, A. D. Hall and C. G. T. Morison 

 (Joiti: Agr. .SV/., 2 (1007), lYo. 3, i)p. 2U-256, pi. i).— This article records studies 

 of the influence of calcium nitrate, sodium chlorid, barium chlorid, aluminum 

 sulphate, and other salts, as well as various acids of different strengths on the 

 flocculation of suspensions of i)urified, fine-ground kaolin. 



It was observed that " up to a certain point, flocculation, as measured by the 

 rapidity of settlement, is proportional to the amount of flocculating salt added. 

 Beyond that limit all solutions flocculate alike." The reaction between the floc- 

 culated material and the flocculating substance was found to be quantitative. 

 Apparently the process of flocculation was not " accompanied by any removal 

 of the salt from solution by the flocculated kaolin (adsorption or laking out), 

 nor by any selective absorption of base from the salt, so as to give rise to 

 acidity in the liquid after flocculation had taken place." 



A comparison of the flocculating powers of diffei'ent substances showed that 

 the free acids were the most active flocculating compounds and that aluminum 

 salts stand very close to the acids in this resi)ect. 



Experiments with fine-ground bauxite and limonite showed that neither of 

 these substances would assume the " natant " condition in pure water. 



The authors failed to find any satisfactory theory that embraces all of the 

 observed facts and they believe that " before any theory of flocculation can be 

 reached it is probably necessary to determine the conditions which nuist be sat- 

 isfied before a given substance will assume the 'natant' state." They suggest, 

 however, that the " natant condition is dependent on the presence of traces of 

 free alkali derived from the partial hydrolysis of the suspended material . . . 

 and that flocculation ensues when these are neuti-alized or driven back into 

 combination with the suspended solid." 



Note on the protective action of colloids on clay suspensions, G. Keppeleb 

 -and A. Spangenberg (Jour. Landw., 55 (1907), No. Ji, pp. 2.9.9, 300; al)s. in Chem. 

 ZcntbL, 190S, I, No. 3, pp. 285, 286).— Observations similar to those of Ficken- 

 dey (E. S. R., 18, p. GIO) are briefly reported. The author states that the con- 



