EXPERIMENT STATION BULLETINS. 819 



thereby is removed from the liquid phase. The Ca(0H)2 which is in 

 solution is that only which is due to hydrolysis of the calcium silicate 

 compound. When the silicic acid, however, is fully saturated or satisfied 

 with the Ca(0H)2 then the hydrate will remain in the solution and affect 

 the freezing point depression. In spite of this tremendous amount of 

 lime absorption or requirement by the silicic acid, a neutral reaction is 

 attained, according to the phenolphthalein and litmus paper indicators, 

 when only about one-hundredth of the amount required is added. 

 . That the hydrolisis of the soil minerals and the effect of the result- 

 ing products upon the phenolphthalein indicator play a large role in the 

 estimation of the lime requirement of soils by the A'eitch method seems 

 to have been recognized by Veitch himself, although he does not appear 

 to have attached any serious consequences to the matter. Veitch found 

 that the length of time the treated soil was allowed to stand had con- 

 siderable effect upon the lime requirements.- Wlien the solution was 

 allowed to go on from 48 to 72 hours the pink color with phenolphthalein 

 was developed with less added lime water than when the solution was 

 allowed to stand IG hours or less. Furtheromer, Veitch found that some 

 soils which were acid when allowed to stand 16 hours gave an alkaline 

 filtrate when permitted to stand 24 to 48 hours longer. 



Any one who has tried to test soil acidity with the litmus paper test 

 will doubtless have noticed that many soils, even those which show lime 

 requirement by the Veitch method, will turn the red litmus pink or 

 neutral on long standing, especially when the soil is treated with an ex- 

 cess of water. This phenomenon can safely be attributed to hydrolysis. 



Veitch's method calls for treating the soil with water and Ca(0H)2 

 and then drying down at once on a steam bath. Now it is a well known 

 fact that hydrolysis is appreciably increased by a rise in temperature. 



Even practical experience seems to indicate that the Veitch method 

 may not be showing the true maximum lime requirement of soils, and 

 consequently the proper amount of lime may not be applied to the soils 

 for the successful growth of crops. Thus, for instance, in a recent paper 

 by Ames and Schollenberger of the Ohio Experiment Station^ it is shown 

 that the soil of some of the experimental plots, which was limed a long 

 time ago, is now almost neutral or alkaline according to the Veitch 

 method, yet the growth of clover will be materially benefited by an appli- 

 cation of lime. In speaking of the possible usefulness of the various 

 methods for comparative purposes when difi'erent soil treatments have 

 been made, Ames and Schollenger make the following statement: "If 

 either the Hopkins or the Veitch test were used to obtain a figure for 

 the limed soil's requirement, the results would lead to erroneous con- 

 clusions, because the Veitch method indicates that the limed halves of 



all the plots are alkaline " Yet an application of lime to these plots 



will materially benefit the growth of clover. 



The behavior of the Veitch method towards this soil which was limed a 

 long time ago but with amounts which were evidently too small, since 

 the growth of clover will be enhanced with further applications, is in 

 perfect agreement with the theory of hydrolysis and the reactivity of the 

 hydrolyzed products upon the phenolphthalein indicator, as already set 

 forth. 



Thus far an attempt has been made to show that probably none of the 



(2) Jour. Am. Chem. Soc. 24 (1904), 637. 



(3) Jour. Ind. Eng. Chem. 8 (1916), 243. 



