720 EXPERIMENT STATION RECORD. [Vol.38 



was too low for plant cultures in the sand and perhaps also in the loam-sand 

 mixture, but in the loam it appeared to be capable of supplying the plants with 

 sufficient water for growth under ordinary greenhouse conditions. 



Relation of carbon dioxid to soil reaction as measured by the hydrogen 

 electrode, D. R. Hoagland and L. T. Shabp (U. S. Dept. Ayr., Jour. Agr. Re- 

 search, 12 {1918), No. 3, pp. 139-1 Jt8). — In continuation of work at tlie Cali- 

 fornia Station, previously noted (E. S. R., 36, p. 117), the authors studied more 

 fully the question of the effect of carbon dioxid on soil reaction as determined 

 by the hydrogen electrode. 



The apparatus used was the same as that employed in the previous work. 

 "To provide a chamber for mixing the hydrogen and carbon dioxid a graduated 

 1,000-cc. cylinder, the base of which had been cut off, was immersed in a larger 

 cylinder filled with mercury. The upper end of the inner cylinder was tightly 

 stoppered and contained two capillary stopcocks for admission and outlet of 

 the gases. A definite quantity of purified hydrogen, electrolytically generated 

 was admitted to this cylinder through one stopcock. Through the other stop- 

 cock there was admitted from a gas burette a known quantity of pure carbon 

 dioxid. Roth gases were measured at atmospheric pressure. A sufficient time 

 was then allowed for the thorough diffusion of the gases, which was aided by 

 raising and lowering the inner cylinder. The reservoir of mixed gases was 

 then connected to the hydrogen-electrode chamber which contained the soil 

 suspension. Forty to 70 cc. of the gas mixture were forced into the space above 

 the soil suspension, adjusted to atmospheric pressure, and the hydrogen-electrode 

 cell was then closed. Equilibrium was hastened by the shaking method, and 

 the voltmeter readings were noted. This procedure was repeated with new 

 portions of the gas mixture until the voltmeter readings were constant to within 

 0.005 volt." 



The H-ion concentrations of soil suspensions were measured under various 

 partial pressures of carbon dioxid. It was found that " the H-ion concentration 

 of suspensions of acid soils was not markedly affected by increasing the content 

 of carbon dioxid up to 10 per cent. The H-ion concentration of slightly alka- 

 line soils was slightly increased by such treatments. A notable increase in 

 H-ion concentration was observed when soils containing alkali carbonates were 

 similarly treated." None of the carbon dioxid treatments produced an alkaline 

 reaction in suspensions of an acid soil, and when the original conditions were 

 restored there was no permanent change in soil reaction which could be at- 

 tributed to the carbon dioxid. The point of view that solutions in equilibrium 

 with acid soils contain H ion in excess of OH ion was confirmed. 



A short bibliography of the subject is given. 



[Partial sterilization of soil], E. J. Russell (Cowitry Life [London^, 42 

 {1911), Nos. 1092, p. 548; 1093, pp. 578, 579, figs. 6).— The history and general 

 principles of soil sterilization as a means of increasing productiveness are 

 briefly discussed, and methods in practical use in England, particularly by 

 tomato growers, are described. In one of the methods most successfully used 

 steam is blown from a boiler under a large tray 6 by 8 ft. placed on the soil, 

 and it rapidly penetrates and heats the soil to a depth of 8 or 9 in. 



The search for a suitable antiseptic soil sterilizer which will also be an effec- 

 tive insecticide is referred to. This is considered a great national need in 

 England, since so much grassland has to be plowed up, and " wireworms, leather- 

 jackets, and other pests appear in the young crops on the freshly broken land 

 and do considerable damage." 



Humification of compounds entering into the composition of vegetable 

 matter, A. G. Trusov {Selslc. Khoz. i Liesov., 252 {1916), Nov.-Dcc, pp. 26-^ 

 47), — This is a continuation of work previously noted (E. S. R., 38, p. 26), 



