io8 GEORGE F. KAY AND J. NEWTON PEARCE 



base-forming metals, like sodium, potassium, calcium, magnesium, 

 iron, and aluminium. These silicates are only very slightly soluble 

 in water. While the amount dissolved may be exceedingly slight, 

 it is nevertheless sufficient for the purposes here involved, if the 

 time allowed is sufficiently long. For a given rock material the 

 solubility, and hence the speed, of the weathering process increases 

 with increasing fineness of the particles. Hence the fineness of the 

 glacier flour renders it peculiarly suitable for rapid chemical 

 conversion. 



Like all salts of weak acids with strong bases, these silicates 

 when dissolved react chemically with water, that is, hydrolyze, 

 to form the free more or less ionized bases— ^the soluble hydroxides 

 of sodium and potassium, the less soluble hydroxides of calcium 

 and magnesium, the relatively insoluble hydroxide of iron, and 

 either the free un-ionized silicic acid or some simple silicates. These 

 simpler silicates continue to hydrolyze, if the reaction products 

 are removed. There results the liberation of still other bases and 

 in the end still simpler silicates, possibly kaolin, or even silica as 

 quartz or sand. 



If the reaction products are not removed by leaching, the dis- 

 solved materials soon attain a state of solution equilibrium. Under 

 these conditions the decomposition products of one rock material 

 may react with those of another to form more or less complex 

 silicates of a secondary origin. Let the saturated solution be 

 removed and fresh water added, the various solution equilibria are 

 disturbed and the solution processes begin again. 



The solution and subsequent hydrolysis of rock material, and the 

 chemical reactions involved.- — ^In the soil solution thus formed the 

 dissolved materials will at the proper concentrations react with 

 the carbon dioxide of the soil atmosphere to form the soluble, 

 easily hydrolyzable carbonates of sodium and potassium and the 

 slightly soluble carbonates of calcium and magnesium. These 

 slightly soluble carbonates crystallize out as calcareous concretions, 

 so frequently found in the clay subsoils. In the presence of an 

 excess of carbon dioxide these insoluble carbonates pass into the 

 soluble acid-carbonates and are leached away by the downward- 

 moving free-water to lower depths, where they are again deposited 

 in the form of concretions. 



