494 STATE BOARD OF AGRICULTURE. 



There are a large number of methods employed for specific heat 

 determination of solid materials, but they are all based upon the method 

 of mixtures. While numerous as are these methods, thev are all de- 

 fective; an error enters into all of them due to the loss of heat during 

 the operation. 



The method eni])loyed in the present study was devised in the course 

 of the investigation and was adopted in preference to a large number 

 of others that were tried. This method consists in wrapping a defi 

 nite weight of soil in a known weight of filter paper, tying the latter 

 with a very fine thread, then suspending it in a heater at a temperature 

 of about 97° C. After the soil remained in the heater for two or more 

 hours and had attained a constant temperature it was dropped at once 

 into the calorimeter and stirred vigorously until the maximum tem- 

 perature was indicated on the thermometer. This temperature was usual- 

 ly obtained in about one minute. The filter paper upon coming in con- 

 tact with the water would immediately break up and allow the soil 

 contained to mix with the water and thus give up its heat more rapidly 

 than if it had been enclosed in a water-tight vessel as has been done by 

 several investigators, Avhich process delays the reaching of the maximum 

 point on account of the poor heat transference of the soil material. 

 Both the free soil and the filter paper upon becoming wet increased 

 the temperature, but this increase was deducted from the final calcu- 

 lation by ascertaining it in a separate experiment wherein was used the 

 same amount of soil, filter paper, and water as in the regular determina- 

 tions and having them at about the same temperature (25° C.) The 

 temj)€rature increase due to wetting of the various dry soil powders 

 is considerable, as will be shown subsequently, and unless it is taken 

 into consideration in the final calculation of the results the latter will 

 be altogether too high, especially for certain soils. The size of particles 

 also iniluences the heat generation due to wetting, consequently in all 

 the different kinds of soils except the gravel, whose specific heat was 

 detennined, the same size of particles was used, i. e., those which could 

 pass thru a 40 sieve mesh. 



In the determination of the specific heat of the peat it was found 

 that this material would not settle to the bottom of the calorimeter 

 and consequently considerable heat would be lost before the cover of the 

 calorimeter was put on and the stirring process begun. To overcome 

 this difficulty and thereby eliminate the error, a piece of copper was 

 placed with the soil which would cause the soil to immediately fall 

 to the bottom of the calorimeter. The sj)ecific heat or water equivalent 

 of this copper piece being known would be deducted from the final 

 calculation of the results. In all these specific heat determinations the 

 temperature was taken by a Beckmann thermometer, and the specific 

 heat apparatus employed was of McCall's type. 



SPECIFIC HEAT OF SOILS BY EQUAL WEIGHTS. 



The following table represents the specific heat of the different types 

 of soil as determined by the above method, and the different individual 

 data necessary for the calculation of the same. The mechanical 

 analysis of these difl'erent types of soil is shown on table 18a. 



This table shows that the specific heat of the different types of soil 

 varies very little, that of the quartz sand is the lowest, followed in order 



