EXPERIMENT STATION BULLETINS. 311 



soils under the same conditions, and would go to indicate that the minerals 

 and rocks employed do not seem to have a definite eolubility, \vith few ex- 

 ceptions. If they do, their rate of solubility is so extremely slow at ordinary 

 temperatures that they may never attain complete equilibrium. 



Considering next table 16 which contains the results obtained at the tem- 

 perature of 53°C it becomes at once apparent that even at the high ratio of 

 liquid to solid the elevated temperature had a very pronounced influence on 

 the solubility product on all of the minerals and rocks with few exceptions. 

 By comparing these results with those in tables 11 and 12 it is readily seen 

 that the solubility product at the ratio of 1 to 5 is about as great as that at 

 the ratio of 1 to 0.75, at the corresponding dates. Evidently, therefore, 

 at the elevated temperature, the solubility product of the minerals and rocks 

 is not so dependent on the relative masses of solid to liquid, as it is at lower 

 temperature. This fact, however, does not mean that the various minerals 

 and rocks have a definite solubility. 



IDISeUlSSION OF !RE(S'UI/r:S 



The experimental results thus far presented have shown the following 

 main facts : 



(1) That the amount of readily soluble material in the unleached pow- 

 der of rocks and minerals is quite appreciable, especially in some rocks and 

 minerals. 



(2) At room temperature the quantity of additional solubility after the 

 initial solubility both in the unleached and leached rocks and minerals is 

 extremely small, even for a period of over one hundred days. 



(3) At the temperature of 53°C and also at the steam pressure of 26 

 pounds, the solubility of nearly all the rocks and minerals employed was 

 considerably increased, and in some rocks and minerals greatly more than 

 in others. 



(4) At room temperature the solubility of rocks and minerals was much 

 smaller at the ratio 1 of solid to 5 of liquid than at the ratio of 1 to 0.75. At 

 the temperature of 53°C, however, it was about the same at both ratios for 

 the same date. 



(5) The solution of all the rocks and minerals employed reacted alkaline. 



From these experimental facts two outstanding conclusions are very ap- 

 parent, namely (1) that the rocks and minerals employed, with few excep- 

 tions, do not show a definite solubility as definite chemical compounds do; 

 and (2) the equilibrium attained in solubility at the various moisture con- 

 tents and temperatures is only apparent and not real or absolute. 



A consideration of the nature and composition of the rocks and rock form- 

 ing minerals together with the type of their reaction with water, makes the 

 above experimental facts and conclusions appear reasonable and logical. 



The minerals which go to make the rocks are largely salts of a strong base 

 or bases: sodium, potassium, calcium, magnesium, ferrous, iron, manganese, 

 etc., combined with a weak inorganic acid : silicic, aluminic, alumino-silicic, 

 ferro-silicic, etc. It logically follows, therefore, that water not only dis- 

 solves them but also hydrates them and hydrolyzes them. Their alkaline 

 reaction is a strong proof that they are hydrolyzed. On account of their 

 complex composition, relatively difficult solubility, and their tendency to 

 hydrate and to hydrolyze with water, probably they should not be expected 

 to give a definite solubility or a true condition of chemical equilibrium. 



