PRACTICAL APPLICATION. 23 



generally ascribed to adsorption on the surfaces of the particles, 

 although the improbability of such a state of things is apparent. If 

 the hydrolytic reactions as pointed out in this paper take place, with 

 the formation of hydrated films, it is no more remarkable that water 

 is held in this way by certain finely powdered minerals than by pre- 

 cipitates of alumina or silica which are prepared in the course of an 

 ordinary mineral analysis. 



Even the finest, whitest sedimentary clays often contain small 

 amounts of potash, and it has always been a question with what this 

 potash was to be considered as combined when the microscope showed 

 not the slightest trace of unkaolinized feldspar or other mineral 

 aggregates present. 



A most important problem that still awaits solution by industrial 

 chemistry is the unlocking of the potash which is held in enormous 

 quantities in the crystalline rocks. It is possible that by wet grinding 

 alone or with dilute solutions of certain electrolytes, or by wet grind- 

 ing and subsequent treatment with such solutions, the alkali can 

 be made at least partially available. There would seem to be no 

 doubt that analogous methods are at work in nature, in which the 

 geological and meteorological processes are continually unlocking the 

 plant foods from the rocks and storing them up to become slowly 

 available for vegetation and for man. 



SUMMARY. 



(1) The effect of wet grinding is to increase the binding power or 

 cementing value of rock powders, and there are indications that the 

 addition of small amounts of suitable electrolytes to the water will 

 still further increase the action. 



('2) When water comes in contact with most rock powders immediate 

 reactions take place, which are to a certain extent analogous to those 

 which take place with cement and powdered glass. 



(3) These reactions are shown by the alkalinity indicated by phe- 

 nolphthalein, but this alkalinity is to a great degree inhibited if the 

 solid particles are filtered out. 



(4) The microscope reveals an accumulation of amorphous material 

 of a gummy appearance largely associated with the surfaces of the 

 crystalline particles as the action of water proceeds. 



(5) Evidence is given to show that the basic ions set free associate 

 themselves to a certain degree with the solid particles, leading to a 

 concentration of the acid ions in the clear solution. 



(6) It is shown that the behavior of rock powders after being acted 

 on by water is similar to that of coagulated colloids artificially prepared 

 in the laboratoiy, and that the formation of colloids upon the surfaces 

 of the particles would account for the increased binding power under 



