24 THE PHYSICAL ACTION OF LIME ON CLAY SOILS 



STUDIES WITH PLAT SOILS 



An attempt was made to determine whether differences could be 

 observed between soils from limed and unlimed plats, using our methods 

 for estimating internal surface. Accurate samples of the surface and 

 subsoil were taken from plats 7007, 7008, 7207, 7208, 3611, 3612, 3613, 

 and 3614. The seven thousand plats received a moderate application of 

 CaO in the summer of 1915, while the three thousand plats were last 

 limed in the summer of 1910. The soils were examined according to the 

 total retentive power, dye adsorption, and oxidation methods. None of 

 the results were consistent with regard to the limed and unlimed plats, 

 with one exception, the oxidation results for the seven thousand plats. 



OXIDATION OF PHENOLPHTHALEIN BY LIME PLAT SOILS 



The above figures are averages of duplicate determinations, and the 

 probable error is less than one. W<- may conclude that several years time 

 are usually sufficient to virtually obliterate all physical differences 

 between limed and unlimed soils. 



DISCUSSION 



Six methods have been employed in the present investigation. \Vc 

 have observed that the total retentive power and penetration procedures 

 are not particularly valuable because of the hi^h probable error involved. 

 The oxidation method has not been used sufficiently as a means of esti- 

 mating internal surface to permit its appraisement at the present time. 

 Expansion, hygro-interstitial moisture, and dye adsorption seem to be 

 accurate and valuable methods. It appears to the writer that the dye 

 method has the brightest future of all, for it permits the determination 

 of tlie effect of substances in specific materials. 



CONCLUSIONS 



1. The penetration method is not a suitable procedure for estimating 

 internal surface. 



2. Small contraction exhibited by a salt treated soil does not neces- 

 sarily imply large expansion. 



3. Gypsum treated soils contracted less than any other lime treat- 

 ment. 



