1916] AGRICULTURAL CHEMISTRY — AGROTECHNY. 715 



a continued decomposition of earthy carbonates by alkaline soils under moist 

 contact conditions at normal temperatures. This decomposition is shown to be 

 very appreciable in the absence of any hydrated silicates." 



The reaction of soil and calcium carbonate thrown out of carbonated water 

 solution by agitation and suction and the effect of the period of contact of soil 

 and CaH2(C03)2 solution before evaporation was also studied. The data ob- 

 tained demonstrate that a great difference in time of contact in the laboratory 

 affects in some degree the extent of the reaction between the carbonate and the 

 soils. 



It is indicated that " MgCOs will satisfy a soil's requirement for lime, but that 

 the satisfying of a soil's requirement for lime by long continued contact with 

 CaCOa does not inhibit the excessive decomposition of adde<l MgCOs under 

 laboratory treatment. Not only is this true of normal calcareous soils, but it is 

 also true of soils which have been ignited with an excess of CaCOs." 



" The combined presence of calcium, sodium, and potassium carbonates is not 

 necessarily inhibitory of the decomposition of the precipitated carbonate of 

 magnesium." 



A procedure for the determination of the immediate lime requirement of 

 soils, in which a suitable sample of soil is evaporated with calcium carbonate 

 solution and the excess carbon dioxid then determined according to the pro- 

 cedure previously noted (E. S. R., 30, p. SOS), is described in detail, together 

 with the procedure for preparing the calcium carbonate stock solution and a 

 pressui'e container for the same. A convenient form of carbon dioxid generator 

 is also described. 



From a comparison of the proposed method with the procedure of Hutchinson 

 and MacLennan (E. S. R., 32, p. 609), it is indicated that "not only does the 

 Hutchinson-MacLennan method fail to produce the decompositions equivalent to 

 those effected by the Veitch [E. S. R., 14, p. 41S] or the proposed method, but 

 the carbonated water solvent depresses the reaction and gives less carbonate 

 decomposition than is effected by agitation with CaCOj in COa-free water for the 

 same period at room temperature." 



It is deemed that the conditions of the procedure described effect the com- 

 plete satisfying of the temporary lime requirement of soils, and it is intended 

 to supply a simple means which will permit the satisfying of the maximum im- 

 mediate lime requirement of acid silicates and silicic acid, the principal causes 

 of lime requirement in rock-derived soils. 



The relation between laboratory and field lime requirements and the occur- 

 rence of soil acidity in field and laboratory experiments are briefly described. 



A method for the determination of the immediate lime requirements of 

 soils, W. H. MacIntiee (Jour. Indus, and Engin. Chem., 7 (1915), No. 10, pp. 

 864-867, figs. 2). — The method described, together with the procedure for pre- 

 paring and standardizing the calcium carbonate solution, a pressure container 

 for the same, and a modified form of carbon dioxid generator are noted above. 



Lime and magnesia in New Zealand soils, B. C. Aston (Jour. Agr. {New 

 Zeal.], 12 (1916), No. 1, pp. 47-54). — Analy.ses of 3G6 samples of New Zealand 

 soil showing the calcium and magnesium oxid contents as extracted by hydro- 

 chloric acid and by 1 per cent citric acid are reported, the results of which in- 

 dicate that the lime content of these soils is relatively low. " When soils which 

 are known to be sterile owing to the excess of magnesia, when the magnesia is 

 present in quantities ten times as great as the lime, both weak and strong 

 solvents indicate that the magnesia is in excess. . . . 



" Soil which will grow^ forest, although showing a greater amount of mag- 

 nesia than lime by the hydrochloric-acid method, shows a greater amount of 

 lime than magnesia by the 1 per cent citric-acid method of extraction, whereas 



