174 LECTURES ON 



Way, after studying separately as far as possible the effect of each 

 ingredient of the soil without arriving at any satisfactory conclusion 

 as to the seat of this peculiar absorptive power, as a last resort inves- 

 tigated the relations of the silicates to saline solutions. Silicates con- 

 taining but one base he found ineffectual, and next had recourse to 

 compound silicates. He experimented then with feldspar, but found 

 that it was without action on solutions of ammonia salts, and hence 

 concluded that the powder of granitic rocks is not the agent of these 

 decompositions. His next step was a more successful one. He attempted 

 to imitate the compound silicates that may occur in the soil as products 

 of the weathering of rocks, such as most probably exist in all soils to 

 a greater or less degree. He artificially prepared silicates of alumina 

 with potash, soda, lime, and ammonia, respectively; and these he found 

 to possess the property of suffering decomposition in saline solutions, 

 with the mutual replacement (fixation) of isomorphous bases. 



But it was reserved for Eichhorn, in 1858, to set forth in a true 

 light the action of the double alumina-silicates. This experimenter, 

 in cognizance of the fact that Way' s artificial silicates contained water 

 as an essential ingredient, was led to make trials with natural compounds 

 of a similar character. He selected for this purpose the zeolites, chaba- 

 zite, and natrolite, whose composition is given among those minerals 

 from which soils originate in the table on page 150. The chabazite 

 he employed was essentially a silicate of alumina, lime, and water. 

 The fine powder of this mineral being agitated and digested for some 

 days with hydrochlorates (chlorids*) of potash, soda, dilute solutions 

 of ammonia, lime, &c, fixed in the solid and nearly insoluble form a 

 portion of the basic ingredient of these salts, while the acid was found 

 in the solution combined with a quantity of lime equivalent to the 

 absorbed base. In one experiment the powdered chabazite was 

 digested for ten days with a dilute solution containing a known 

 amount of pure common salt. The mineral was then found to have a 

 composition, compared with that it originally possessed, as follows : 



Composition of Chabazite. 



Silica 



Alumina 



Lime 



Potash 



Soda 



Water 



99-75 100.37 



Comparing the two statements, we see that nearly one -half the lime 

 of the original mineral is replaced by soda. A loss of water also has 

 occurred. The solution separated from the mineral contained nothing 

 but soda, lime, and chlorine, and the latter in precisely its original 

 quantity. 



8 In chemistry the hydrochlorate of an ozyd signifies the same as the chloride of a metal; thus 

 hydrochlorate of soda and chlorid or chloride of sodium mean the same thing. 



