62 REPOKT — 1901. 



mastic hydrate, as CuSo^, and have the surface tension zero. The coagula- 

 tion, or clearing of mastic solution by this salt solution, is explained in the 

 same way as with CuSOj. 



Turbid solutions of kaoline in glass cylinders of 100 X 10 cm. form a 

 series of horizontal layers separated by equal intervals. After two 

 months a great many flocks adhere on the shaded side of the glass. Under 

 the microscope the flocks show threads or tubes of a downward flowing 

 liquid, with spheroidal enlargements or contractions (Anschwellungen und 

 Eiuschniirungen). The sediment at the bottom of the glass cylinder has 

 the appearan.te of solidified liquid, containing deformed bubbles and 

 coherent foam-cells, smooth spheres of diameter 0-002 to 0-0004 mm., with 

 greater refraction than the surrounding substance. 



The particles of kaoline are covered by the action of the water with 

 an oily viscous fluid, probably silica hydrate, on the surface of which 

 another fluid is spread out. The periodical spreading combines the sus- 

 pended kaoline particles in larger flocks, which slowly sink to the ground 

 or are drawn by the vortices against the glass walls, where the particles 

 covered with oily fluid adhere. The oily silica hydrate forms spheres, 

 bubbles, or coherent foam-cells, and afterwards becomes solidified. 



Turbid solutions of tottit kaoline in test-tube solutions over CUSO4, 

 FeCl;,, CaCl.,, or Ca(H0)2 give foam flocks with thin walls in which 

 many little grains are distributed, or with thick foam-walls in which, 

 again, small chambers or cells with thin walls are enclosed. The flocks 

 of kaoline formed in the beginning by the viscous fluid adhere to the 

 glass wall. 



Also over solutions of sugar, solutions of kaoline form two thick 

 flock-layers. 



Turbid solutions of potash soap have shown flocks over chloroform, 

 sulphide of carbon, aqueous solution of sugar, CuSO^, HCl. 



Turbid solution of oleic acid has been flocked by solutions of HCl, 

 CUSO4, chloroform, sulphide of carbon, and sugar ; turbid solution of 

 China ink by solution of OUSO4 and HCl. 



The order of the flocking solution, determined by the velocity of the 

 clearing, changes with the concentration of the suspended particles. 



Electrolytes and insulators may be clearing substances. 



The flocks of mastic and kaoline, formed by artificial clearing by means 

 of the light, adhere to the shaded side of the glass-wall. 



The views of Barus, Hardy, and Spring on the clearing power of 

 diflFerent liquids, especially of the electrolytes, are not confirmed by my 

 experiments. It is not proved that the kation of the clearing electrolyte 

 is the clearing substance. 



The flocks of gum mastic in the turbid solution are formed by a thin 

 layer of mastic salt solution (mastixhaltiger Salzlosung), which is con- 

 nected to the surface of the mastic particles by molecular force. This 

 thin layer of mastic salt solution will develop no sensible electromotive 

 foi'ce in contact with the pure salt solution outside, and no movement of 

 the suspended particles with the thin layer by an electric current will be 

 possible. My theory explains the formation of the flocks and of the iso- 

 electric flocks of Hardy, which are not moved by the electric current. 

 The process of clearing is the same in all turbid solutions. All flocked 

 particles, or suspended particles united in flocks, are covered with a thin 

 . layer of solution, nearly isoelectric with the surrounding pure salt solu- 

 tion, and cannot be moved by electric forces. 



