652 STATE BOARD OF AGRICULTURE. 



EFFECT OF SOLUBLE SALTS ON THE RISING AND LOWERING 



OF TEMPERATURE OF SOILS. 



OBJECT AND METHOD OF EXPERIMENTATION. 



Solutions possess many physical properties which have a very decided 

 influence on temperature. Solutions of jjreater densities possess a lower 

 freezing point, a higher boiling point, a lower vapor pressure, a higher 

 surface tension and a higher viscosity, than solutions of lower concen- 

 tration. xVll these properties vary with the composition of the solution 

 and influence the rising and lowering of temperature either directly or 

 indirectly. Soils, therefore, with diflerent densities of solution will have 

 different rising and lowering of temperature. Rising and lowering are 

 employed here as general terms and are intended to include the rate 

 of freezing, the degi'ee of the lowering of the freezing point, the rate of 

 thawing, the rate and degree of rising temperature, etc. 



In the literature of soil temperature no record is found on the effect 

 of soluble salts on the rising of soil temperature, but there is one work 

 reported on the other phase of this subject. This is by Ulrich,^^ and it 

 is on the influence of frosts on the temperature conditions of soils with 

 different salt content. He conducted the investigation by mixing fine 

 kaolin in cylinders with .05, 0.1 and 0.2 percent of Co(OH)o, NaCL. 

 NaNog, and some other salts and subjected the mixtures to temperatures 

 varying from to -10° C. The results show, in general, that the tem- 

 perature of freezing was lowered by the addition of salts, the greater 

 the amount of salt present the greater the lowering of temperature. 

 When the soil water froze the temperature of the soil rose at once to 

 0° C, remained for a time at this point and then gradually fell under 

 the influence of the low temperature. Certain salts, such as Ca (OH),, 

 CdClo, etc., retarded this fall of temperature, others such as KOH, etc., 

 hastened it. 



In order to ascertain more positively, if possible, to what extent the 

 cooling and warming of the soil is affected by the different soluble salts 

 and what kind of salts have the greatest influence in either respect, the 

 folowing experiments were undertaken. They consisted in placing 

 equal amounts of quartz sand in wooden boxes, 12 inches square and 2 

 inches high with bottoms and no top, and then placing this sand in the 

 boxes out doors on a stand to study either the lowering or rising of 

 temperature. The quartz sand in the different boxes was previously 

 thoroughly moistened with different solutions of various concentrations. 

 These densities varied from one-half to three times normal. Where 

 direct comparison was desired, either between the different concentra- 

 tions within the same salt or between different salts, the same amounts 

 of solution were added to equal weights of quartz sand. The study of 

 the rising of temperature was conducted during clear hot days in sum- 

 mer, and that of the lowering of temperature was carried on during 



» Forsch. a. d. G. a. Agrik. Phy. II : 218 - 229, 1897. 



