618 EXPERIMENT STATION RECORD. 



Steaming for five hours at five atmospheres pressure proved to be the best 

 method for the determination of available potash in soils. The phosphorus 

 in a soil appeared to be less available the greater the content of lime, magnesia, 

 iron oxid, and clay in the soil. It vras also affected by weathering and the kind 

 of crop. 



No fixed relations were established between the amounts of phosphoric acid, 

 nitrogen, and lime assimilated by plants and the amounts found to be easily 

 soluble by different methods. The electrolytic conductivity, and also steaming 

 for five hours at five atmospheres pressure before and after harvest, served to 

 indicate the decrease of plant food in soils resulting from plant growth. 



Distribution of certain constituents in the separates of loam soils, L. A. 

 Steinkoenig (Jour. Indus, and Engin. Chem., 6 (lOlJf), No. 7, pi). 516, 511). — 

 Experiments conducted with a view to finding the distribution of the commoner 

 elements in the finer separates of a series of ten loam soils are reported. 



In every separate examined the percentage of silica was greater than that 

 of any other oxid and decreased from the coarser to the finer particles. Zir- 

 conia usually followed the same variation. In all but two cases alumina was 

 second in order of abundance, and in most cases iron was third. The i>ercentages 

 of iron oxid. alumina, titanium, potash, and phosphoric acid usually increased 

 with the fineness of the particles. Lime, magnesia, and soda seemed to follow 

 no general rule. 



The influence of electrolytes on the coagulation of clay suspensions, G. 

 WiEGNEB (Landic. Vers. Stat., 84 {1914), No. S-4, pp. 283-299, figs. 5).— The 

 author in a discussion of the effect of sodium and calcium hydroxids on clay 

 suspensions explains their flocculating effects on electrical grounds. He points 

 out that the hydroxyl ions of the salts are more easily adsorbed on colloidal 

 surfaces than are the calcium or sodium ions, but that each has a certain 

 limited mechanical i)ower for being adsorbed. On being added to a negatively 

 charged clay suspension the negative hydroxyl ion is first adsorbed and the 

 electrical charge, and therefore the stability of the suspension, increased to a 

 certain limit at which the positively charged calcium or sodium is adsorbed, 

 thus neutralizing the negative charge of the suspension and causing precipita- 

 tion. That the calcium hydroxid causes precipitation at much lower concen- 

 trations is attributed to the higher valence of the calcium ion.^ 



The properties of red colored soils, E. Blanck and J. M. Dobrescu (Landw. 

 Vers. Stat., 84 (1914), No. 5-6, pp. 421-445; abs. in Jour. Chem. Soc. [London'], 

 106 (1914), No. 621, I, pp. 915, 916).— Chemical studies of a typical red 

 soil and a deep red-colored weathered soil from augite porphyry showed that 

 a difference existed in their composition which was due to the colloidal condi- 

 tion prevailing in the red soil and the absence of colloids in the augite porphyry. 

 Van Bemmelen's method for determining the colloidal content was found to be 

 inadequate, while on account of the structure of the soils the Rodewald- 

 Mitscherlich hygroscopicity method (E. S. R., 15, p. 847) was favored. 



See also a previous note (E. S. R., 29, p. 514). 



Acid mineral soils, G. Daikuhara (Bui. Imp. Cent. Agr. Expt. Sta. Japan, 

 2 {1914), .T '. /, pp. l-'iO, pi. 1). — Continuing preliminary studies by Kozai 

 (E. S. R., 21, p. 18) the author reports investigations on the nature and origin 

 of acidity in soils, the relation between various salt solutions and soil acidity, 

 the relation of soil acidity to heating and to size of soil particles, methods of 

 detecting and determining soil acidity, and the relation between soil acidity and 

 the lime factor. 



The author concludes from the results of these investigations that in mineral 

 soils acidity is due to absorption of aluminum and iron compounds by the soil 



