836 STATE BOARD OF AGRICULTURE. 



freezing point depression of soils. Then 2 grams of soil were weighed 

 out on a cliomical balance and placed into the soil tube B and added to 

 it 10 c. c. of distilled water. The tliernionieter was inserted into the 

 tube and was so arranged that the bulb was close to the bottom of the 

 tube and entirely covered with the soil mixture. By holding the tube 

 with one hand and the thermometer with the other the soil mixture was 

 stirred for about a minute by gently moving the tliermometer. The tube 

 Ihen was placed directly into the cooling mixture contained in the vessel 

 F and by continuously stirring the soil mass witli a gentle move of the 

 Ihermometer, the tcm])erature fell very rapidly. The agitation was con- 

 tinued until the temperature reached the freezing point of water when 

 it was stopped and the soil was allowed to cool undisturbed until it was 

 supercooled to about 1.0° C. below the freezing point of water and then 

 the tube was placed in the air jacket C of the main cooling bath and the 

 soil mass again stirred. The soil generally commenced to solidify at 

 once and the temperature to rise very rapidly to the proper freezing 

 point. Before the final reading was taken, the soil mixture was 

 thoroughly mixed by moving the thermometer. The thermometer then 

 was set so its bulb stood in the center of the tube and did not touch the 

 walls, tapped with the finger a few times and then the final reading 

 recorded. The tube then was taken out of the air jacket, the thermometer 

 placed in the stand G, and a definite quantity of Ca(OH)o was added to 

 the soil. The thermometer was placed back into the soil, the mixture 

 stirred for about a minute, and the process of freezing was repeated as 

 before. The process of freezing, then adding Ca(OH)o to the soil, and 

 refreezing was continued until the maximum lime requirement of the 

 soil was attained, which was indicated by a change in the reading of the 

 thermometer and hence of the freezing point depression. 



In order to reduce the number of determinations made and thereby cut 

 down on the length of time, large quantities of Ca(0H)2 were first 

 added. The method which proved most convenient consisted of adding 

 to the soil first 5 c. c. of N/25 Ca(OH)o. If the depression of the soil 

 was still the same as before or less, then 5 c. c. more of Ca(0H)2 was 

 added. If the freezing point depression at the end of the third de- 

 termination was greater than that of the preceding that indicated that 

 the maximum lime requirement of the soil had been attained and sur- 

 passed, i. e., an excess of lime had been added. From the difference in 

 the depression between the second and third determination it could be 

 easily estimated what would be the approximate lime requirement, and 

 with this knowledge as a guide the exact quantity was determined in a 

 second sample of soil. Thus, for example, supposing that 2 grams of 

 soil plus 10 c. c. of water gave a depression of .010° C. Adding 5 c. c. of 

 N/25 Ca(0H)2 to the mixture the depression still remained at .010° C. 

 Adding 5 c. c. more of CaCOH), the depression changed to .012° C, or a 

 difference of .002° C. The lime requirement of this soil, therefore, lay 

 between 5 and 10 c. c. of Ca(0H)2; but does it lie nearer the 5 or 10 

 c. c? Information concerning this point could be obtained by knowing 

 the depression of 5 and 10 c. c. of N/25 Ca(OH)o diluted in 20 c. c. of 

 distilled water — the amount which had been added to the soil. Suppos- 

 ing the depression of 5 c. c. of N/25 Ca(OH)., in 20 c. c. of distilled 

 water was .020° C, and 10 c. c. in 20 c. c. of water was .035° C. From 

 these figures it could be readily judged that the true lime requirement 



