EXPERIMENT STATION BULLETINS. 317 



At a lower moisture content the freezing point depression and consequent- 

 ly the concentration, is considerably .greater in most of the rocks and min- 

 erals. 



When the powdered rocks and minerals are leached with distilled water 

 the freezing point depression is greatly decreased in all of them, with few 

 exceptions. These results go to show that the material in the finely pow- 

 dered rocks and minerals which goes very readily into solution, is washed 

 away, and its place is not immediately taken by other soluble material, with 

 few exceptions. 



At room temperature the rate and extent of solubilitj^ of the rocks and 

 minerals both in the leached and unleached condition are very small after 

 the initial .solubility, even for a period of over 100 days. The increase is 

 only about 0.010° C or less at the end of 107 days. With few exceptions, the 

 leached rocks and minerals did not attain the same degree of freezing point 

 depression or concentration of solution, as existed before leaching. 



In few rocks and minerals, especially in shale and serpentine, there is a 

 tendency for the initial material in solution to go out of solution, or at least 

 the freezing point depression decreases with lapse of time. This is true 

 mainly at room temperature. 



At the temperature of 53° C for 95 days and at the steam pressure of 26 

 pounds for 8 hours, the rate and extent of solubility both in the leached and 

 unleached condition were greatly increased in all the rocks and minerals, 

 excepting the shale and kaolinite. Thus, at the temperature of 53° C and 

 in the unleached condition the depression of a biotite granite rose from 0.019° 

 to 0.083°, in pegmatite from 0.025° to 0.137°, in quartzite from 0.020° to 

 0.132 , in siliceous sandstone from 0.030° to 0.058C°. In the leached con- 

 dition it rose in amphibole from 0.010° to 0.124°, in chrj'solite from 0.005° 

 to 0.220°, in quartz from 0.007° to 0.357°, in serpentine from 0.020° to 0.340° 

 etc. 



Of all the results the most surprising and unexpected were those yielded 

 by the quartz and the quartzites at the higher temperatures. These ma- 

 terials gave the highest solubility product, with one or two exceptions. The 

 quartz gave a solubility of 0.357°, the three varieties of quartzite 0.113°, 

 0.132°, and 0.152° respectively. This is indeed a tremendous solubility 

 for these materials. They were, however, not absolutely pure but the ma- 

 terial in solution consisted almost entirely of silica. 



A very interesting and significant point in regard to the solubility of 

 many rocks and minerals and especially of the siliceous materials, is the 

 fact that the rate of solubility at the temperature of 53° was not most rapid 

 at the beginning but after a long time. This phenomenon would seem to 

 suggest the theory that the rocks and minerals required a certain length of 

 time under this temperature before they began to decompose or hydrolyze 

 rapidly. 



The materials whose solubility was not increased by the higher temper- 

 atures were shale and kaolinite. 



The initial depression of shale and of one variety of the ferrugineous sand- 

 stone, decreased even at the highest temperature. 



Although at room temperature the solubility of all the rocks and minerals 

 became practically stationary immediately, at the temperature of 53°C it 

 continued to go on, even at the end of 95 days without any apparent signs 

 of stopping, and in some of them it progressed with increased velocity. 



The material which goes into solution at the high temperature still per- 

 sists when the mass is cooled to -3°C indicating that equilibrium or the sat- 



