B. A. Keen 



405 



Table II. 

 Lowering of the Freezing-point of various types of Soil at different 



moisture contents. 



('LAV 



Percentage Observed Calculated 

 of lowering of lowering of 



moisture freezing-point freezing-point 



18 

 20 

 22 

 24 

 26 

 28 

 30 

 32 

 34 



14 

 18 

 22 

 26 

 30 

 34 

 38 



■922 

 •580 

 •307 

 •212 

 •127 

 ■082 

 •062 

 •042 

 •034 



Humus Loam 



■G242 

 ■3916 

 ■2078 

 ■1435 

 ■0859 

 ■0555 

 •0419 

 •0284 



1^200 

 ■760 

 •420 

 •245 

 -140 

 •089 

 •0585 



•7888 

 ■4995 

 ■2761 

 •1610 

 •0920 

 •0585 



Silt Loam 



Percentage Observed Calculated 



of lowering of lowering of 



moisture freezing-point freezing-point 



16 

 18 

 20 

 22 

 24 

 26 

 28 

 30 



7 

 9 

 11 

 13 

 15 

 17 

 19 

 21 



•860 

 •560 

 •350 

 •200 

 •095 

 •076 

 •071 

 •060 



Sandy Loam 



•688 



•448 



•280 



■160 



•076 



•0608 



•0568 



•390 

 ■220 

 •130 

 •087 

 •065 

 •040 

 •030 

 •025 



■2925 

 ■1650 

 ■0975 

 ■0642 

 •0487 

 •0300 

 ■0225 



Discussion of the Experimental Data. 



Taking the values for quartz sand (Table I) it is seen tkat very fair 

 agreement holds with equation (1) above, the freezing-point depression 

 being inversely proportional to the moisture content. This points to 

 the moisture in the sand obeying the same law as dilute solutions — the 

 freezing-point depression varying approximately as the concentration. 



With soils this relation does not hold, but is replaced by an approxi- 

 mate geometrical progression ratio. The question at once arises, is any 

 proportion of the soil moisture '"unfree," in the sense that it is not part 

 of the soil solution as understood in these experiments? 



If this were so the soil solution would become increasingly concen- 

 trated as the total moisture content decreased towards the value of this 

 unfree water. To repeat the example given by Bouyoucos in support 

 of this idea, a clay ^oil which renders 1-5 per cent, of water unfree, by 

 adsorption or chemical combination for instance, and which at 36 per 

 cent, and 18 per cent, of total moisture content gave depressions of 

 •03-1° C. and -955° C. respectively, would have available for the soil 



Journ. of Agrio. Sci. ix 27 



