Feb. II. i9i8 Freezing-Point Method and Soil Solution 



385 



A similar experiment was performed on' the 5B soil, containing 16.7 per 

 cent of moisture. The results in this case were 0.156° depression for the 

 control and 0.218° for the sample treated with carbon dioxid. It is 

 evident from these data that the gas has a striking effect in increasing the 

 concentration of the soil solution. Here, again, it is interesting to 

 observe that the cropped and uncropped soils maintain the same general 

 relation to each other, even after the treatment described. Water 

 extractions made on the same soils showed that the total water-soluble 

 material was considerably increased by the carbon-dioxid treatment. 

 Calcium was particularly affected, but several other elements were also 

 made more soluble. 



EFFECT OF DRYING ON CONCENTRATION OF SOIL SOLUTION 



One of the important influences which may affect the chemical state 

 of the soil is that of drying. King (4) has shown that drying soils in the 

 oven causes a considerable increase in the quantity of water-soluble 

 material. Bouyoucos and McCool (2) have pointed out that the evidence 

 obtained by their freezing-point method tends to the same conclusion. 

 The writers have desired in the present research to apply this method to 

 the study of the influence of air-drying on the soils from the tanks. 

 Freezing-point depressions were first determined upon the moist soils, 

 and samples were then spread out in the laboratory and allowed to 

 become thoroughly air-dried. They were then mixed in a mortar with 

 suitable quantities of distilled water, allowed to remain in closed jars for 

 several hours, and the freezing points, as well as the percentages of 

 moisture again determined. The results are given in Table V. 



Table V. — Effect of drying on freezing-point depressions 



Soil No. 



lA. 

 iB. 

 4A. 

 4B. 

 5A. 

 5B. 

 8A. 

 8B. 

 9A. 



loA 

 loB 

 iiA 

 iiB 



Moisture. 



Per cent. 

 22. 7 

 20. I 



17. 6 



17. 2 



17-7 



16.7 



10. 6 



10. 8 



9.4 



9-5 

 14. I 

 13-4 



13- 5 



Freeziag-point depres- 

 sions. 



Orisrinal 

 soil. 



°C. 



O. 056 

 108 

 oq8 

 148 

 ,083 

 156 

 062 



135 

 057 

 087 

 066 



125 

 065 



After dry- 

 ing and 

 retnoisten- 

 ing.a 



0.050 

 . 191 

 .089 

 . 114 

 .068 

 . 100 

 .058 

 . 142 

 .083 

 . 126 

 .094 

 • 136 

 . 067 

 . 110 



o Calculated to same moisture content as original sample. 



