EXPERIMENT STATION BULLETINS. 837 



was closer to the 10 c. c. than to the 5 c. c. of Ca(OH)2 since the change 

 in the depression was only .002° C. A second sample of soil therefore, 

 was taken and instead of adding 5 c. c. of Ca(OH)o at first 8 c. c. were 

 added and then the additional amounts were added in portions of 1 c. c. 

 in order to obtain the accurate value. If a soil, however, in 2 gram 

 portion, required only 2 c. c. of Ca(0H)2 and were added to it at first 

 5 c. c, the depression in the second determination would be far greater 

 than that of the soil plus water alone. By applying the same principle 

 as above as to whether the true lime requirement lay closer to 2 or 5 

 c. c. the exact amount could be determined in a second sample of soil. 

 After one is accustomed to the method, however, he can estimate ac- 

 curately almost down to 0.5 c. c. without having to employ a second 

 sample of soil. 



From the above detailed description of the procedure of the method, 

 it might appear that the method is very complicated, tedious, and time- 

 consuming. Fortunately none of these objections is applicable to it. On 

 the contrary, the method is very simple, extrem.ely rapid, and quite 

 accurate. 



As to its simplicity, it must have already been seen from the descrip- 

 tion that there is practically no procedure in the method which requires 

 an unusual amount of skill or technique. Anyone who has never per- 

 foraied freezing point determinations might imagine that the method 

 is complicated but those who have made such studies will readily admit 

 the simplicity of operation of the method. 



Probably one of the most favorable virtues of this method is its 

 rapidity of execution. As it is now developed, the freezing point method 

 can determine the lime requirement of a soil from 10 to 15 minutes if 

 a duplication is not necessary. It has determined the lime requirement 

 of many soils in less than 10 minutes. This exceeding rapidity of execu- 

 tion lies in the fact that by bringing the tube containing the soil mix- 

 ture in dir-ect contact with the cooling mixture and keeping the soil 

 mixture stirred with the thermometer, the temperature falls very rapidly, 

 and the desired super-cooling is nttained in a very few minutes, — as 

 contrasted with the long time that it takes if the soil were cooled in the 

 air jacket. 



At this point the question may be raised as to the value and accuracy 

 of the method for determining the lime requirement of soils in such an 

 exceedingly short period of time, since the reaction between the Ca(0H)2 

 and the soil may not be completed in that short period. It must be 

 declared at once that this particular point was subjected to a thorough 

 examination, and the results obtained have led to the interesting con- 

 clusion that the reaction between the Ca(0H)2 and the soil, under the 

 condition in which the experiments are performed, is exceedingly rapid 

 if not almost instantaneous. Many experiments were performed wherein 

 the soils were treated with slightly larger amounts of lime than they 

 required, as determined during the short period of the operation, and 

 allowed to stand for 6 to 24 hours. At the end of these periods the 

 freezing point depression show^ed that the soils did not take up any more 

 lime. 



The remarkable rapidity of the completion of the reaction between the 

 soil and Ca(0H)2 is supported by other experiments which the writer 

 has performed; as well as the observations of other investigators. In 



