Jan. 7, 1918 Studies in Soil Reaction 23 



The samples of soil which have been treated witii excessive amounts of 

 calcium and magnesium carbonate show a greater concentration of OH 

 than H ions in solution. Dr. Mclntire informed the writer that the car- 

 bonates have long since disappeared in these soils. Obviously the new 

 compounds of calcium and magnesium, whatever they may be, give a 

 strong basic reaction. 



These results bear out very forcibly the contentions of Gillespie (7) and 

 Sharp and Hoagland {12) that there is a preponderance of H over OH ions 

 in the liquid phase of many soil suspensions. Whether the " true acidity " 

 as indicated from the results of Table I is developed from organic acids 

 or acid silicates can not be stated. In some of the sandy soils the organic 

 matter is quite low, yet indications lead to the conclusion that there is a 

 greater concentration of H ions than found in neutral solutions. With 

 the muck samples the organic -matter content is very high, being 90 per 

 cent or more, and most marked acidity is shown. 



H-ION CONCENTRATION OF SOIL FILM OR CAPILLARY WATER 



The question has often been raised, "Is the water held as a liquid film 

 around the soil particles of different reaction from that in the free state ? " 

 The difficulty encountered in securing any workable amount of the film 

 water has militated against any direct study of this question. Recently, 

 Morgan (9) has devised a workable modification of the "oil displacement " 

 method for obtaining the soil solution in an unaltered form. A study of 

 this water should throw much light on some of the obscure problems of 

 soils. One serious difficulty yet remains with the method, which is its 

 inability to get back all of water held as thin films around the soil grains. 

 However, a study of the reaction of that portion of the film water obtain- 

 able should give indications of value as to the conditions of the soil 

 solution. 



The Morgan apparatus, with a few unimportant modifications, has 

 been used in obtaining that portion of the capillary water displaced by 

 paraffin oil under high pressure. The oil used in this work was the 

 purest obtainable. As far as could be noticed, it gave a neutral reaction 

 with the hydrogen-electrode apparatus and by titrating against standard 

 alkali with methyl orange, methyl red, and phenolpthalein as indicators. 



Some of the soil samples used were taken directly from the filed; 

 others had been stored in the laboratory for a number of years. The 

 portion which passed a 2-mm. sieve was thoroughly mixed, and the water 

 content determined. Sufficient distilled water was added to bring the 

 moisture content up to about what is considered the optimum for that 

 soil. Water lost through evaporation was replaced at frequent intervals, 

 after which the soils were thoroughly packed in the cylinder and treated 

 with oil under high pressure. 



The results of this investigation are shown in Table II 



