082 STATE BOARD OF AGRICULTURE. 



Tlifi geiiernl subject of s()liil)ility of soils niider diilVroiil coiKlitioiiH 

 and treatmeuts is being investigated at this laboiatoiy from all different 

 angles. McCool and Millar are making a very detailed and compre- 

 hensive study on the salt content and solubility of virgin and cropped 

 soils, using the freezing point method as a means, and in addition the 

 carl»on dioxide produced is also being determined, while ^purway is 

 making acliemical analysis of the material that goes into solution in 

 treated and untreated soils upon long standing in contact with water. 



METHODS OF rROCEDURE. 



The rate and extent of solubility of soils were measured (1) in natural 

 or untreated soils, (2) in soils treated with salts and acids, and (3) in 

 treated and untreated soils at various moisture contents and at different 

 degrees of temperature. 



In order to secure a proper and accurate measurement of the rate 

 and extent of solubility the soils, both treated and untreated, were 

 washed until they had a freezing point depression very close to that 

 of distilled water. The advantage and necessity of this procedure are 

 obvious. If the soils were not washed their solution might already be 

 in equilibrium or saturated and consequently no definite and reliable data 

 could be obtained on their rate and extent of solubility. 



The natural soils were washed by placing a certain amount of soil, 

 either air-dried or fresh, upon a filter paper in a funnel and washed 

 by the bleaching process until practically all their free-soluble salts were 

 washed away as indicated by the freezing point depression. The wash- 

 ing was usually continued until the depression of the soil was reduced 

 to about .005 °C, which is equivalent to about 125 parts of solid matter 

 per million parts of liquid. The amount of water that was necessary 

 to pass through the soil to reduce its salt content to the above amount 

 varied with the soil but it usually ranged from 400 to 800 c.c. 



In the case of the treated soils about 50 grams of soil were mixed with 

 150 c.c. of N/10 salt solution or acid, and the mixture allowed to stand 

 for about 24 hours, with occasional shaking. It was then poured on 

 the filter paper in the funnel and the soil washed until its freezing point 

 depression was reduced to the desired point. 



After the soils were washed two procedures were usually followed : 

 In the one procedure a small amount of the washed soil was ])lace(l in a 

 glass freezing point tube and enough water was added to it to br-ing it 

 up to a medium thin mud or to a ratio of 1 of soil to .7 of water. The 

 soil was allowed to remain in the tube, care being taken to prevent loss 

 of water by keeping the tube stoppered, and the freezing point depression 

 of the soil was determined immediately and often thereafter as it was 

 deemed necessary. Usually the determination was made every day the 

 first four or five days and quite often tliereafter. Many of the experi- 

 ments were allowed to continue for four months. 



In the second procedure, the remaining waslied soil was allowed to 

 lose moisture on the filter paper undisturbed until it reached the optimum 

 moisture content and then it was placed in a glass tumbler, mixed thor- 

 oughly, weighed, and from time to time water was added to it to main- 

 tain its moisture at the optimum content. At the end of 10, 30 and 60 



