172 

 ineli'ically, the liyflroxide having been first converted into chloride. 



From this table we deduce at once, that the volume of the dispersed 

 particles is considerably greater than would be expected, if these par- 

 ticles consisted of mol3'bdetium blue, resp. iron hydroxide only. The 

 specific gravity of the molybdenum blue used was found to be 3,1 

 at 12°, that of the iron hydroxide may be put equal to about 4. 

 The volume of .0511 g molybdenum blue in the solid state is there- 

 fore .017 c.c, and here we calculate for the dissolved particles 

 .036 c.c, more than the double value. For the iron hydroxide the 

 proportion is still greater, and even rises to about 4. These results 

 show conclusively that the colloid particles condense water mole- 

 cules around themselves or combine with them, and that the hydroxide 

 takes up more water than the molybdenum blue. Although if has 

 often been maintained that such dispersed particles would be composed 

 of colloid and water, it has, 1 think, never been so clearly demon- 

 strated by experiment. 



We may also proceed in a slightly different manner, and calculate 

 the density of the particles. Let us imagine a volume w of the liquid, 

 in which particles having the total volume v' and the density D 

 are floating; the total weight of the particles being consequently i;'Z). 

 Let further d' represent the density of the solution, and iy/' its weight. 

 Now, the volume of the "free" water, that is the water, which is 

 not combined with colloid particles, will be v — v' ; if its density be 

 called (/, then we have 



d'Z? = vd' — (y — v') d. 



1) — ~(d'-d) + d. 



V 



Therefore 



