AGRICULTURAL CHEMISTRY. 911 



conditions. For first jiait of this articl(> sec a lu-cvioiis note (E. S. K., 15, 



On the titrimetric determination of phosphoric acid by means of uranium, 

 F. Repiton {.Uoitit. tSci., .',. so:, 21 (1907), II, No. 791, pp. 7:13, 75//; abst. in 

 Chnn. ZcntbL, 1907, II, Xo. 26, p. 207S; Chcm. Zig., 32 (1908), No. 20, Rcpcrt., 

 p. i25).— This is a modification of the cochineal method of Malot. It is asserted 

 that the sharpness of the color reaction is greatly increased by using a cochineal 

 tincture preparetl as follows: Boil 4 gm. pulverized cochineal one hour with 100 

 cc. of water. rei)lace evaporated water, and boil again. After cooling add HO cc. 

 of alcohol, mix. and filter. To the solution to be tested add r. cc. of acetic acid 

 solution of sodium acetate, dilute to 100 cc, boil, add a few drops of cochineal 

 tincture, and titrate with uranium solution to a gray-green coloration. By this 

 method an instantaneous change of color is obtained. 



Chemical soil and fertilizer analysis, E. A. Mitscheklich {Fiihling's 

 handle. Ztg., 57 (1908), No. 1, pp. 7-i5).— This article reports further experi- 

 ence with methods referred to in a previous article (E. S. R., 18, p. 417). The 

 controlling considerations in the working out of these methods have been (1) 

 the need of accurate and uniform methods of examining fertilizers and soils, 

 and (2) the recognition of the fact that plant food must be in soluble form to 

 be assimilated by plants. 



Studies made of the factors controlling the solubility of plant food in the soil 

 with reference to the working out of an analytical method of determining 

 availability of the soil constituents are briefly summarized. On the basis of 

 the results thus obtained the author takes as a measure of the plant food 

 which becomes available during the period of growth the amounts of the plant 

 food constituents dissolved from the soil by 25 times its weight (on the dry 

 basis) of water saturated with cai-bon dioxid, digesting with constant agitation 

 for 11^ hours at 30° C. 



The results obtained by this method on different kinds of soils unfertilized 

 and receiving different amounts of fertilizing materials, as well as on a large 

 number of samples of Thomas slag, are reported. While the method as a rule 

 showed very distinctly the increase in plant food due to the addition of the 

 fertilizing materials, it did not in many cases show increases agreeing with the 

 amounts actually added. This is explained in some cases as due to chemical 

 changes brought about in the soil by the action of the added material, and 

 leads the author to conclude that soils vary to such an extent individually that 

 no general rule can be laid down with reference to their fertilizer requirements. 



The comparison of the carbon dioxid method of the author with the citric 

 acid method of Wagner on various samples of Thomas slag showed that as a 

 rule 8.9 per cent less of the total phosphoric acid was dissolved by the author's 

 method than by that of Wagner. The author, however, claims that these 

 results agreed more closely wnth the results of pot experiments than those ob- 

 tained by the citric acid method. 



The colorimetric determination of nitrogen in soils by the Nessler reagent, 

 Chouchak and I. Pouget (Bui. Hoc. Vliim. France, .). set:, 1 (1907), No. 2.'i, 

 pp. 1173-1180; abs. in Chcm. ZcntbL, 1908, I, No. 8, pp. 761, 762).— Adapta- 

 tions of the soda-lime and Kjeldahl methods to the determination of nitrogen 

 in soils by the Nessler reagent are described, and tests of the convenience and 

 accuracy of the adaptations are reported. 



In case of the soda-lime method 0.3 gm. of soil taken from a carefully selected 

 and finely ground sample of 20 gm. is mixed with 0.02 to 0.03 gm. of anhydrous 

 oxalic acid, and after mixture with soda-lime in the usual way is subjected 

 to combustion in a glass tube 8 to 10 nun. diameter and 20 to 30 cm. long. The 

 various precautions to be observed iu order to insure purity of reagents and 



