18 THE PHYSICAL ACTION OF LIME ON CLAY SOILS 



EFFECT OF TIME AND SALTS ON SOIL EXPANSIONS Continued 



We see from the above data that the contraction with the calcium 

 hydrate treatments is decidely less than with the limestone. There is not 

 much difference between the limestone and precipitated carbonate data 

 when small applications were employed. The limestone seemed to be 

 superior to the precipitated carbonate, however, when large applications 

 were used. There was less contraction with the soils to which precipitated 

 calcium sulfate had been added than with any of the others. In this 

 connection it should be noted that a smaller contraction than the check 

 does not necessarily imply a greater expansion. Anything causing an 

 abnormal solidification of the soil mass may be wrongly interpreted as 

 an expansion. In the case of the sodium carbonate pots we probably 

 have this action. The precipitated magnesium carbonate seems to exert 

 no particularly striking effect. 



EFFECT OF LIMING ON THE TOTAL RETENTIVE POWER 



The determinations were carried out in the following manner: A soil 

 of known moisture content was poured into a weighed Hilgard cup, in the 

 bottom of which was a filter paper. After tamping a definite number of 

 times the top portion was struck off with a straight-edge, and then the 

 cup and soil weighed. Knowing the moisture content of the soil, the 

 dry weight equivalent in the cup could be easily determined. The cup 

 was then set into water in a thermostat so that there would just be 

 capillary contact. After the soils had become thoroughly saturated (a 

 matter of several hours), the cups were set aside to drain, after which 

 they were wiped dry, and weighed. A calculation of the amount of 



