602 STATE BOARD OF AGRICULTURE. 



ployed to determine the iucrease in concentration, is produced mainly 

 by two factors, first by the amount of soluble material present, and sec- 

 ond by the degree of dissociation of this material. The last factor un- 

 doubtedly plays an appreciable role. 



SUMMARY. 



The work previously reported upon the freezing point method as a new 

 means of measuring the concentration of the soil solution directly in 

 the soil has been repeated with new or improved procedures, and greatly 

 extended. The general results of the second study have entirely con- 

 firmed those of the first. These results together with the new improve- 

 ments in the procedure may be summarized as follows : 



The new procedure consisted of placing a short column of soil in a 

 glass tube, inserting the bulb of a Beckmann thermometer into this 

 column of soil until it was completely covered. The tube containing the 

 soil and the thermometer was then placed directly in the cooling mix- 

 ture having a temperature between — 2° and — 3°C, and the soil allowed 

 to supercool to 1°C. The^ the thermometer was moved in the soil in 

 order to start solidification. The temperature was then allowed to rise 

 until it became constant. The thermometer was tapped and the reading 

 recorded. 



It was found again that it is extremely easy to determine the freezing- 

 point lowering of soils. The solidification can be started when the soil 

 mass is supercooled to only about 0.3°C and it is far easier to induce 

 solidification in soils than in pure solutions or soil water extracts. The 

 depression of the freezing point of soils can be measured from any maxi- 

 mum water content to a very low water content. Below this minimum 

 of moisture, solidification cannot be induced to take place, at least very 

 readily, and the results are not very reliable. The minimum water con- 

 tent seems to lie very close to the wilting coefficient of soils. 



The freezing-point lowering has been measured in over 58 soils at 

 two different moisture contents — very low and very high. These soils 

 included characteristic types of 10 different states, Rhode Island, Penn- 

 sylvania, Michigan, Kentucky, Florida, Texas, Wisconsin, Minnesota, 

 Washington, and California. The purp'ose of employing typical soils 

 from all these states was to ascertain the concentration of the soil solu- 

 tion by means of the freezing point method. The results obtained from 

 this study show (1) that the lowering of the freezing point of soils is 

 entirely different at the two moisture contents in all the different soils. 

 (2) The degree of the freezing-point lowering is quite small at the high 

 moisture content and varies rather appreciably in the different soils, 

 while at the low moisture content it is tremendously high and varies con- 

 siderably in the various soils. At the maximum percentage of water the 

 lowering of the freezing point varies from 0.010 °C in the case of some 

 sands to 0.075 °C in the case of some clay loams, and clays, while at the 

 minimum percentage of moisture it ranges from about 0.110° in some 

 sands to about 1.370°C in some of the loams and clays. The degree of 

 depression for heavy sandy loams, silts, clay loams, and clays tends to 



