318 STATE BOARD OF AGRICULTURE. 



iiration point was not yet attained at the high temperature at the end of 

 95 days. 



The solubihty product of the rocks and minerals at the ratio of 5 of water 

 to 1 of sohd, was greatly smaller than that at the ratio of 1 of water to 0.75 

 of solid, at room temperature. At the temperature of 53°C it was about 

 the same at both ratios. 



The results as a whole point to two outstanding conclusions: (1) that 

 the rocks and minerals employed, with few exceptions, do not show a definite 

 solubility as definite compounds do; and (2) the equilibrium attained in 

 solubility at the various moisture contents and temperatures is only ap- 

 parent and not real or absolute. 



A consideration of the nature and composition of the rocks and minerals 

 together with the type of their reaction with water, makes the above experi- 

 mental facts and conclusions appear reasonable and logical. 



The large increase in soluble content in the rocks and minerals at the 

 higher temperatures is probably largely the result of hydrolysis. 



All the rocks and minerals employed without a single exception reacted 

 alkaline, using phenolphthalein and red litmus paper as indicators. There 

 were few rocks and minerals which failed to show alkalinity with phenol- 

 phthalein but they turned red litmus blue very readily. 



The marked increasing effect of the higher temperatures on the solubility 

 of rocks and minerals goes to prove that the large increase in solubility ob- 

 tained in soils at similar high temperatures was not due wholly to the de- 

 composition of the organic matter content but also to the solubility and 

 hydrolysis of the mineral particles of the soils. 



Treating the rocks and minerals with salt solutions and then washing 

 them until free of soluble salts, had very little if any effect upon the rate 

 and extent of solubility, at ordinary temperature. 



Even when the salts were allowed to remain in contact with the rocks 

 and minerals for long time the solubility was very little if any increased, 

 at ordinary temperature. 



*Manuscript submitted for publication July, 1920. 



(1) Bouyoucos, G. J. Rate and Extent of Solubility of Soils under Different Treatments and Con- 

 ditions. Tech. Bui. 44, Mich. Agr. Expt. Sta., 1919. 



(2) Bouyoucos, G. J. and McCool, M. M. Further Studies on the Freezing Point Lowering of Soils. 

 Tech. Bui. 31. Mich. Agr. Expt. Sta., 1916. 



(3) Extensive bibliographs upon the solubility of rocks and minerals will be found in U. S. Bureau 

 of Soils, Bulletin No. 3 (1905), by Frank K. Cameron and James M. Bell; and in Soil Science of October, 

 1919 in an article by E. De Turk entitled "Potassium Bearing Minerals as a source of Potassium for Plant 

 Growth." 



(4) Bouyoucos, G. J. and Laudeman, W. A. The Freezing Point Method as a New Means of Study- 

 ing Velocity of Reaction Between Soil and Chemical Agents and Behavior of Equilibrium. Mich. 

 Expt. Station Technical Bulletin No. 37, 1917. 



