DIVISION OF SOILS. 133 



chemical inactivity, and prominence as a soil constituent. It was 

 found that the amount of the dissolved salt which is removed from 

 solution by the soil grains increases with the concentration of the 

 solution. A very important feature in this connection is that the 

 amount of adsorption is relatively very much greater for the dilute 

 solutions of concentrations found in Eastern soils. 



The nature of the dissolved salt was also found to have a consider- 

 able effect upon the amount of adsorption. For example, the solu- 

 tions of substances which have an alkaline reaction, such as caustic 

 soda or carbonate of soda, are adsorbed to a much greater extent 

 than neutral solutions, such as common salt. The magnitude of this 

 property is shown from the experimental fact that, when the soil is 

 saturated with a solution containing 400 pounds of carbonate of soda 

 per acre, 180 pounds of the sodium carbonate is adsorbed by the soil 

 grains, and it is not moved with the soil moisture so long as the con- 

 centration remains constant. 



This work is now being extended to include natural soils and the 

 common mineral constituents of commercial fertilizers. Investigation 

 is also being made to determine whether mixture of salts exerts any 

 mutual action on the amount of adsorption. 



CONDENSATION OP CARBON DIOXIDE ON SOIL GRAINS. 



The adsorption or condensation of carbon dioxide upon the surface 

 of fine quartz particles has also been investigated. The existence in 

 the soil of a relatively large amount of carbon dioxide has been known 

 for some time, and the present work leads to the belief that this is 

 very largely held in the soil by adsorption. Since the amount of 

 adsorption is proportional to the pressure of the carbon dioxide, it is 

 evident that the carbon dioxide can be largely removed from the soil 

 simply by loosening the soil so that the contained gas may escape. 

 The pressure of the carbon dioxide is then reduced and the gas 

 adsorbed will be liberated. This feature is of importance, since 

 recent investigations have led to the belief that the acidity of many 

 soils is due simply to the abnormally large amount of carbon dioxide 

 present in the soil. On the other hand, in some cases it is very 

 desirable that the carbon dioxide should not be liberated. For exam- 

 ple, in the Sevier Valley, Utah, the alkali exists very largely in the 

 form of bicarbonate of soda, which is much less harmful than the 

 sodium carbonate which would be formed if the carbon dioxide pres- 

 ent were allowed to escape freely. 



SOIL MOISTURE INVESTIGATIONS. 



The investigations on the capillary movement of water in dry and 

 moist soils, begun during a previous year, have been extended, and 

 the subject has been more fully developed. It has been found that 

 the extent of capillary action in the soil under held conditions is not 

 represented by the capillary rise of water in the air-dried soil, the 

 method which has heretofore been employed. A method has, how- 

 ever, been devised through which the extent of capillary action in 

 moist soils may be determined, and which it is believed is fairly repre- 

 sentative of field conditions. This method also permits investigation 

 of the rate at which water is supplied by capillary action through soil 

 columns of various heights, a subject which is of fundamental impor- 

 tance, since all plants are to some extent dependent upon the capillary 

 action for their water supply. 



