472 



Transactions. 



disturbing effect would be created by a high percentage of humus, we took 

 a clay subsoil poor in organic matter. The conditions of the experiment 

 were as follows : A saturated solution of Ca(OH) 2 was carefully prepared 

 and kept in a stoppered bottle. In order to obviate the formation of 

 CaC0 3 by the action of atmospheric C0 2 the air was displaced by coal- 

 gas. Titration with standard acid gave the initial concentration as 1-7 

 grammes per litre. Ten grammes of soil was used in all the experiments, 



■§ 



■015/V -0I7N -0/9/V 



Initial r oncervbra£Lon, 



■021 N 



■023N -025 N 



Fig. 1. 



and the volume of solution was 300 c.c. in each case. After a preliminary 

 shaking the contents were allowed to digest for three hours, after which 

 5 c.c. to 20 c.c. of the supernatant liquid were pipetted off and titrated 

 with standard acid, phenol-phthalein being used as indicator. The end 

 point was in all cases quite distinct. The equilibrium concentration of 

 Ca(OH) 2 was then calculated, and the diminution in concentration so 

 deduced. 



Results : Several series were repeated, and very good agreement was 

 obtained. The following set of values may be taken as typical : — 



Table VI. — Absorption of Lime from Lime-water by Clay Subsoil. 



The derivation of the figure in the last column (4a) will be explained later. 



Graphical representation : From these values two curves may be drawn — 



(1) diminution in concentration of Ca(OH) 2 against initial concentration ; 



(2) loss in concentration against final concentration of dissolved substance. 

 Both these curves were found to be perfectly general in form, and it will 

 be noticed that the majority of the points lie on the curves. 



Evaluation of constant 4a : Examination of the curve in fig. 2 will 

 show that it is of the parabolic type. Now, the general equation for the 

 parabola is y 2 = 4a:r, where a is a constant. From this curve the values 



