348 Mow cuors feed. 



The precipitate he operated with, contained (water-free) 



in 100 parts: 



Silica 49.0 



Alumina 11.1 



Oxide of iron 21.9 



Lime 6.9 



Matrnesia 1.1 



Insoluble matters -with traces of alkalies, etc 10.0 



100.0 

 On digesting portions of this substance witli sohitions 

 of sulphates of soda, potash, magnesia, ammonia, for a 

 single hour, all tlie lime was displaced and replaced by- 

 potash — two-thirds of it by soda and nearly four-fifths of 

 it by magnesia and ammonia. 



Further investigations by Rautenberg {Henneherg^s 

 Jour, fur Landiotrthschaft, 1862, pp. 405-454), and 

 Knop ( Vs. St., VII, 57), which we have not space to re- 

 count fully, have demonstrated that of the bodies possible 

 to exist in the soil, those in the following list do not pos- 

 sess the power of decomposing sulphates and nitrates of 

 lime, potash, ammonia, etc., viz.: 



tlj f Quartz sand. "j 



S I Kaoliuite (purified kaolin.') i 



•S J Carbonate of lime (chalk.) I These liodies have no absorptive effect, either 



^ 1 Iluinus (decayed wood.) f separately or together. 



g I Hydrated oxide of iron. 1 



p5 (Hydrated alumina. I 



Hamate of lime, magnesia, and alumina. [Knop. 



Phosphate of alumina. 



Gelatinous silica. 



" dried in the air. 



These observers, together with Heiden [Jahresbericht 

 lUber Agricultvrchemie, 1864, p. 17), made experiments on ' 

 soils to which hydrated silicates of alumina, and soda, or 

 of lime, etc., were added, and found their absorptive 

 power thereby increased. 



Rautenberg and Ileiden also found an obvious relation 

 to subsist between the absorptive powers of a soil and cer- 

 tain of its ingredients. Rautenberg observed that the ab- 

 sorptive power of the nine soils he operated with was 

 closely connected with the quantity of alumina and oX' 



