RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



Comparison of methods for the estimation of soil acidity, F. P. Veitch (Jour. 

 Amer. Chem. Soc, 26 (1904), No. 6, ]>p. 637-66$). — Comparative studies of the sodium 

 chlorid method devised by Hopkins, Pettit, and Knox (E. S. R., 14, p. Ill) and the 

 limewater method devised by the author (E. 8. R., 14, p. 418) are reported. From 

 the results obtained the author concludes that in the sodium chlorid method "there 

 is no setting free of appreciable quantities of hydrochloric acid, and that there is 

 practically no reaction between the organic matter and the salt solution, whereby 

 difficultly soluble organic acids are dissolved, but that the acidity of the nitrate (or 

 that acidity which is greater than would be given by water under the same condi- 

 tions) is due to the solution of alumina or some other acid-salt yielding base. It 

 appears that the hydrated neutral silicates or aluminates are quite strongly attacked 

 by the salt solution, resulting in the replacement of aluminum by sodium, or a break- 

 ing up of the compound, and the consequent formation of an acid solution of alumi- 

 num chlorid, the titration of which, with alkali, constitutes the apparent acidity as 

 determined by this method." 



He further concludes that the method can not be relied on for the determination of 

 the total apparent acidity of a soil, or to show the acidity injurious to sensitive crops. 

 "A soil limed in accordance with the results of the sodium chlorid method is never 

 alkaline unless indeed the lime requirement by this method is as great as the lime 

 requirement by the limewater method." 



It is plain that the limewater method "shows the maximum lime requirements 

 of soils — that is, it shows the amount of lime required under the most favorable con- 

 ditions of distribution to make them alkaline in reaction," and it is believed to be 

 "the wisest practice to apply lime in sufficient quantities to render the cultivated 

 soil slightly alkaline in reaction, and consequently to use a method which will indi- 

 cate this quantity." 



The limewater method as modified and improved is as follows: "To determine 

 the reaction of a soil: About 10 gm. of soil are treated with 100 cc. of distilled water 

 in a Jena flask and allowed to stand over night. Fifty cubic centimeters of the super- 

 natant liquid are carefully drawn off and boiled with a few drops of phenolphthalein 

 in a covered Jena beaker until the appearance of the pink color or to a volume of 

 about 5 cc. with no development of color. The pink color shows the soil to be alka- 

 line, while no color shows it to be acid or neutral. 



"To determine the degree of acidity: To three portions of soil, each consisting of 

 as many grams as the standard limewater contains milligrams of lime (CaO) per 

 cubic centimeter, add 50 to 60 cc. of distilled water and different amounts of standard 

 limewater. For example, to the first add 10 cc, to the second 20 cc, and to the 

 third 30 cc of limewater. Dry down at once on the steam bath, transfer to stop- 

 pered Jena flasks with 100 cc. of distilled water, allow to stand over night, with 

 occasional shaking, draw off 50 cc, place in a Jena beaker, add a few drops of 

 phenolphthalein solution, and boil until the appearance of the pink color; or, in 

 14 



