GIO STATE BOARD OF AGRICULTURE. 



iio( remain constnnt but varies tremendously, and indeed increases 

 i^reatly with (lie decrease in moii^ture content, so that at a low water 

 content (he nia.unitude of (he concentration is very great. Further- 

 more, (he magiii (ude ol^ conceiH ration at a low moisture content is not 

 only not the same l(n- the various types of soil, but it is far greater in 

 those classes which would be expected to possess the greatest absorbtive 

 power. 



Hence, if either one or bodi of the above theories are correct, then 

 the foregoing results on the lowering of the freezing ])oint do not repre- 

 sent actual concentration of solution, but they are influenced by some 

 physical force. One of the physical factors which might produce such 

 results, it was thought, is the pressure wi(h which the water films are 

 held by the soil grains. It is well known, for example, that pressure 

 lowers the freezing point of water to the extent as shown by the data 

 in Table 5. 



Table 0. Effect of Pressure on the Frcezino Point of 

 Water. 



It was reasoned that at the low moisture content the pressure of the 

 water films would be greater than at the high moisture content and 

 consequently the lowering of the freezing point would be greater in the 

 former than in the latter. 



A critical theoretical examination of this hypothesis, however, has 

 failed to show that the pressure is the probable cause of the results 

 noted. Furthermore, all direct and indirect evidences point overwhelm- 

 ingly against it. ir^ome of the evidences against it may be mentioned 

 the following: (1). The rate of increase of the lowering of the freez- 

 ing point with the decease in moisture content, is practically the same 

 from the lowest to the highest moisture content. (2). The washed 

 quartz sand which would not be expected to contain a solution of high 

 concentration gives a depression of only .070°C at 1.5% moisture con- 

 tent or almost at the point of dryness, while clay, which would be ex- 

 pected to possess a very highly concentrated solution, gives a lowering 

 of the freezing point of .955°C at 18.80% moisture. The clay, at a 

 high moisture content where the pressure of the water films would be 

 reduced to minimum, gives a freezing-point depression many times 

 greater than that of the quartz sand at the point of dryness. (3). 

 The w^ater which is adsorbed or condensed on the surfaces of the soil 

 particles on account of the great pressure probably resulting from the 

 adhesive forces, is conceived to be removed from the liquid phase and 

 becomes solid like water of crystallization and probably takes no part 

 in the freezing, as will subsequently be discussed. 



