EXPERIMENT STATION BULLETINS. 559 



to examine more critically the possible explanations for these results, 

 to present the new modifications made in the apparatus and procedure, 

 etc. 



Since the original experimental data, general conclusions and hypothe- 

 ses are confirmed and substantiated by the further researches presented 

 in the present bulletin, a large portion of the general discussion of the 

 former bulletin is here naturally repeated. Other material which was 

 deemed essential for an intelligent and convenient treatment of the 

 present paper, "*is also repeated. 



PRINCIPLE OF THE METHOD. 



The determination of the freezing-point lowering of soils and conse- 

 quently the concentration of their soil solution, is based upon the well 

 known principle that the freezing point of water is lowered by the 

 presence of soluble material and that the degree of the lowering is pro- 

 portional to the amount of soluble material present in the case of non- 

 electrolytes; and somewhat greater than proportional in the case of 

 electrolytes before infinite dilution is reached. From the freezing point 

 depression the concentration of a solution can be estimated. Since the 

 soil solution contains soluble material dissolved from the soil mass whicn 

 it bathes, its freezing point will be lowered according to its concentration. 



DESCRIPTION OP THE METHOD AND THE PROCEDURE. 



For determining the freezing point lowering of soils the Beckmann 

 apparatus was again employed but with many radical modifications. The 

 complete set of apparatus used is shown in Fig. 1. It is composed of a 

 Beckmann thermometer A, a glass tube B which contains the soil, a larger 

 glass tube C which acts as an air jacket, and the cooling bath D which 

 contains crushed ice and NaCl. The glass tube B is 1 inch in diameter 

 and 9 inches long, while glass tube C is 1.5 inches in diameter and 6 

 inches long. The cooling bath D which is different from that used in the 

 first investigation, consists of two earthen-ware jars one inside the 

 other. The outer jar is of 4-gallon capacity and the inner of 2-gallon 

 capacity. The space between the two jars is filled with asbestos. In 

 order to keep this asbestos dry the upper part is made water proof with 

 paraffin and thus prevents any water falling into the space between the 

 two jars. The top of the bath is covered with a board which contains 

 several holes for placing the tubes into the ice mixture. This form of 

 cooling bath proved more satisfactory than the Beckmann bath employed 

 in the first investigation. 



The temperature maintained in this bath varied with the depression 

 of the soil. For soils with high moisture content or with a very small 

 lowering of the freezing point the temperature was maintained at about 

 — 2°C. For soils with very low water content or with very high freezing- 

 point lowering, the temperature was usually kept at about — 3°C. 



For calibrating the thermometer or determining the freezing point of 



