EXPERIMENT STATION BULLETINS. 697 



fundamental principles governing the soil solution. In the following 

 pages, therefore, there are presented a complete description of the 

 method and the experimental data obtained. 



DESCRIPTION OF THE METHOD. 



The lowering of the freezing point of soils and consequently the 

 concentration of their solution were determined by the use of the Beck- 

 mann apparatus with certain modifications. The complete apparatus 

 employed is shown in Figure 1. A is the Beckmann thermometer. Its 

 whole scale is composed of only 5.860°C. Each degree is divided di- 

 rectly into 100 parts, and with the assistance of a pair of lenses, the 

 readings can be made to .001 °C. B is a glass tube 1 inch in diameter 

 and 9 inches long, and contains the soil. The thermometer passes 

 through a rubber stopper at the mouth of the tube and its bulb is in- 

 serted in the soil column until it is entirely covered. The tube B passes 

 through a rubber stopper into the wider glass tube, C, which is 1.5 

 inches in diameter and 6 inches long, and acts as an air jacket to pre- 

 vent rapid cooling or radiation from the soil by preventing it from 

 coming in intimate contact with the cooling mixture contained in the 

 battery jar, D. In order to reduce as much heat ratiation as possible 

 from the cooling mixture and thus keep its temperature more con- 

 stant, the battery jar is placed in a small wooden box and packed around 

 with excelsior. The wooden box, having a hole at the bottom, allowed 

 to drain into the pan, E, any water that might have fallen into it dur- 

 ing the operation of filling the battery jar with the ice and water. F 

 is a common thermometer which indicates the temperature of the cool- 

 ing bath. 



For performing a freezing point determination the following proced- 

 ure was always followed. The battery jar was filled with crushed ice. 

 To this ice was added some water and sufficient salt, usually Nad, 

 to produce a temperature of about — 4.5 °C. The Beckmann thermometer 

 was set so that the mercury thread would come to rest towards the 

 upper part of the scale when the bulb M^as held in the mixture of pure 

 ice and distilled water, and then calibrated with distilled water. The 

 freezing point of distilled water was taken as zero, and the lowering of the 

 freezing of soils was obtained by getting the difference between the freez- 

 ing point reading of the distilled water and that of the soil. The freez- 

 ing point reading of the soil was determined by placing about one inch 

 column of soil in the glass tube, and then inserting the bulb of the 

 thermometer into this column of soil until it was completely covered. 

 The tube containing the soil and the thermometer was placed into the 

 air jacket and allowed to cool in the cooling bath. The temperature 

 of the soil was allowed to fall until it was about 1°C lower than the 

 freezing point of the soil, i. e., supercooled. In order to start solidifi- 

 cation, the soil tube was held firmly with the left hand near its mouth, 

 and with the right hand, the thermometer was moved or rotated toward 

 and away from the operator, until the temperature began to rise. The 

 temperature was allowed to rise until it came to rest at a certain point 

 on the scale and remained at that point for some length of time. This 

 maximum temperature attained was considered as the proper freezing 



