EXPERIMENT STATION BULLETINS. 



581 



he would at once concliule that soil No, 19, for instance, contains 73 

 times more soluble salts than soil No. 13 at the arbitrary ratio of 5 of 

 soil to 1 of water. Such a conclusion, however, would be entirely er- 

 roneous. Although soil No. 19 may contain more soluble salts than soil 

 No. 13, but certainly not in the proportion indicated by the respective 

 depressions. This tremendous difference in the lowering of the freezing 

 point between the various soils is actually and mainly due to the different 

 power of the various soils for causing water to become inactive or un- 

 available and consequently "to the different amounts of free water acting 

 as a solvent of the soluble material. In table 9 there are shown 

 the relative amounts of water that some of the soils of the above list 

 caused to become inactive or unavailable. These results were obtained 

 by means of the dilatometer method (15). The principle of this method 

 is based upon the fact that when water freezies it expands. Knowing the 

 amount of expansion produced by a certain quantity of water, say one 

 gram, then the total amount of water frozen can be easily calculated. 

 The amount that is not frozen can be ascertained by difference. In the 

 case of soils the amount of frozen and unfrozen water was ascertained 

 as follows: To 25 grams of soil was added 5 c. c. of water. If all of 

 this 5 c. c. of water froze in the soil the amount of expansion produced 

 would be equal to that of 5 c. c. of water frozen alone. If only a frac- 

 tion of the 5 c. c. added froze, then the quantity that did not freeze was 

 ascertained by difference. In Table 9 the amount of the 5 c. e. of water 

 that did not freeze and consequently remained as inactive or unfree 

 and did not take part in dissolving the soluble material in the soil is ex- 

 pressed both in c. c. and in percentage. In the same table are repeated 

 the lowering of the freeziing point of the corresponding soils so that a 

 direct and convenient comparison can be made of the amount of water 

 that each soil caused to become inactive and the corresponding lowering 

 of the freezing point. It will be noticed that the amount of soil and 

 water employed is not the same in the two cases but the ratio is the 

 same. 



(15) Jour. Agr. Res., v. 8, No. 6, 1917. 



