306 STATE BOARD OF AGRICULTURE. 



From an examination of the above data it becomes at once evident that 

 the temperature of 53°C had a very marked influence both on the rate and 

 extent of solubility of all the rocks and minerals, both leached and unleached, 

 with few exceptions. With the exception of shale, and kaolimite the rate 

 of solubility was considerably hastened and the extent greatly increased in 

 all of the rocks and minerals. In some of the rocks and minerals the amount 

 of material that went into solution at the end of 83 or 95 days is really tre- 

 mendous. Thus, in the unleached condition the depression of one of the 

 biotite granites rose from .019° to .083°, in pegmatite from .025° to .137°, in 

 quartzite from .020 to .132°, in sihceous sandstone from .030° to .058°. In 

 the leached condition the depression rose in amphibole from .010° to 0.124°, 

 in chrysohte from 0.005° to 0.220°, in quartz from 0.007 to 0.357°, in serpen- 

 tine from 0.020° to 0.340° etc. Expressing these depressions in parts per 

 million of solution, the amount of material that disolved was as high as 1650 

 p. p.m. in some of the unleached rocks and as high as 4962 p.p.m. in some of 

 the leached minerals. 



Of all these results the most surprising and unexpected are those yielded 

 by the quartz and the quartzites. These materials gave the highest solu- 

 bility obtained with one or two exceptions. The quartz gave a solubility 

 of 0.357° and the baraboo quartzite 0.278° at the end of 95 days, and two 

 other quartzites 0.113° and 0.132° respectively at the end of 83 days. When 

 it is considered that these materials are supposed to be composed almost 

 entirely of silica, which is believed to be very insoluble, their tremendous 

 solubility is certainly most surprising and unexpected. Of course, these 

 materials were impure, as indicated both by their rather darkish color when 

 finely ground, and by their alkaline reaction to phenolphthalein, but it is 

 hardly believeable that they contained more bases than some of the other 

 rocks and minerals which gave a considerably smaller solubility product. 

 Indeed analyses showed that this solubility product consisted almost entirely 

 of soluble silica which after the solution became supersaturated with it, was 

 precipitated as hydrated silica. Another interesting point about these sili- 

 ceous materials is that their rate of solubility is highest not at the beginning 

 but after a long time. It seems as though after a certain length of time in 

 contact with water and at the high temperature, they underwent decompo- 

 sition and allowed material to go into solution more rapidly. 



The high temperature did not increase the solubility of kaolinite and shale 

 and one of the ferrugineous sandstones. The initial depression of the freez- 

 ing point of the shale and of one of the ferrugineous sandstones not only did 

 increase at the high temperature but actually decreased. Thus, the de- 

 pression of the shale decreased from 0.65° at the second day to 0.045° at 

 the end of 83 days, while that of the ferrugineous sandstone diminished from 

 0.062° the third day to 0.042° at the end of 83 days. The shale, behaved, 

 as it will be recalled, similarly even at the room temperature. 



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

 minerals becomes stationary from the beginning, at the temperature of 

 53°C it continues to go on even at the end of 95 days, without any apparent 

 signs of stopping, and in some cases it progresses with an increased velocity. 

 These results go to emphasize two important facts: (1) that the solubility 

 of all the rocks and minerals, with few exceptions, is so slow after the initial 

 solubility that at room temperature it is hardly perceptible, and (2) that a 

 higher temperature tends to decompose or hydrolize them slowly but per- 

 ceptibly. 



Another very interesting point that is revealed by the solubility results 



