720 STUDIES FOR STUDENTS 



that the presence of the alkalies of lime and magnesia could be 

 recognized in a single drop of the filtrate from the liquid in 

 which the powdered minerals were digested. By digestion for 

 forty-eight hours in carbonated waters they obtained from horn- 

 blende, actinolite, epidote, chlorite, serpentine, feldspar, etc., a 

 quantity of lime, magnesia, oxide of iron, alumina, silica and 

 alkalies amounting to from 0.4 to i per cent, of the whole mass. 

 The lime, magnesia and alkalies were obtained in the form of 

 carbonates ; the iron, in the case of hornblende, epidote, etc., 

 passing from the state of carbonate to that of peroxide during 

 the evaporation of the solutions. Forty grains of finely pulverized 

 hornblende, digested for 48 hours in carbonated water at a 

 temperature of 60°, with repeated agitation yielded : silica 

 0.08 per cent.; oxide of iron 0.095 P^^ cent.; lime 0.13 per cent.; 

 and magnesia 0.095 P^^ cent, with traces of manganese. Com- 

 menting on these results Bischof remarks^ that " by repeating 

 this treatment 112 times with fresh carbonated water, a perfect 

 solution might be affected in 224 days." If now he says, "40 

 grains of hornblende unpowdered, in which, according to the 

 above assumption, the surface is only x-o-o¥"o"(F¥ ^^ ^^^ powdered, 

 were treated in the same way, and the water renewed every two 

 days, the time required for perfect solution would be somewhat 

 more than six million years." In considering these figures and 

 their practical bearing we must remember that while in nature 

 the quantity of water coming in contact with a crystal imbedded 

 in a rock during a given time is much less than that assumed 

 above, the mineral is undergoing a gradual splitting up, becoming 

 more and more porous, so that the process is gradually accel- 

 erated. 



Richard Miiller has also shown ^ that carbonic acid waters 

 will act even during so brief a period as seven weeks upon the 

 silicate minerals with such energy as to permit a quantitative 

 determination of the dissolved materials. The accompanying 



'Chemical and Physical Geology, Vol. I, p. 6i. 



' Untersuchen iiber die Einwirkung des kohlensaurehaltigen wasser auf einige 

 Mineralien und Gesteine. Tschermaks Min. Mittheilungen. 1877, p. 25. 



