THE MINERAL CONSTITUENTS OF THE SOIL, SOLUTION 35 



zeolites by Gonnard 1 and by Doroshevskii and Bardt, 2 and the 

 formation of apatite by Weinschenk. 3 Feldspars and zeolites are 

 common natural associations, it being generally conceded that 

 zeolites are alteration products of the feldspars through the 

 action of water; but Van Hise 4 has pointed out that under con- 

 ditions of weathering such as would obtain in the soil, the tend- 

 ency is for the zeolites to alter to feldspars. Wohler's classical 

 experiment of recrystallizing apophyllite from hot water 5 is 

 significant, for only the products of hydrolysis should be obtained 

 if there is an irreversible reaction between the mineral and 

 water. Lemberg found that leucite (KAlSi 2 O 6 ) when treated 

 with an aqueous solution containing 10 per cent, or more of 

 sodium chloride, was partially transformed to analcite 

 (NaAlSi 2 O 6 .wH 2 O), potassium chloride being formed at the 

 same time. The reverse reaction was also realized, that is, the 

 partial conversion of analcite to leucite by treatment with a 

 solution of potassium chloride, and similar transformations were 

 carried out with the feldspars. 6 L,emberg's experiments are of 

 especial value as they were carried out at ordinary as well as at 

 high temperatures. It appears probable, therefore, that the 

 hydrolysis of a silicate of the alkalis or alkaline earths is a revers- 

 ible reaction. It should be noted, however, that Kahlenberg and 

 Lincoln 7 have shown that probably, in very dilute solutions of 



*Note sur une observation de Fournet, concernant la production des 

 zeolites a froid, par F. Gonnard, Bull. Soc. min. France, 5, 267-269 (1882) ; 

 Jahrb. Min., 1884, I, Ref. 28. 



* Metathetical reactions with artificial zeolites, by A. Doroshevskii 

 and A. Bardt, Jour. Russ. Phys. Chem. Soc., 42, 435-42 (1910) ; Chem. 

 Zentr., 1910, II, 68. 



8 Beitrage zur Mineralsynthesis, von E. Weinschenk, Zeit. Kryst., 17, 

 489-504 (1890). 



4 U. S. Geol. Surv. Monograph, 47, A treatise on metamorphism, by 

 Charles R. Van Hise, 1904, p. 333. 



5 Jahresb. Fortschr. Chemie Liebig and Kopp, 1847-48, 1262; note. 



8 Ueber Silicatumwandlungen, von J. Lemberg, Zeit. deutsch. geol. 

 Ges., 28, 519-621 (1876) ; Inaug. diss. Dorpat, 1877; Bied. Centbl., 8, 567- 

 577 (1879). 



T Solutions of silicates of the alkalis, by L. Kahlenberg and A. T. 

 Lincoln, Jour. Phys. Chem., 2, 77-90 (1898). 



