﻿556 Douhle Refraction in Colloids. 



away in all directions ; in course of time the crystals collected 

 on the bottom of the dish. 



Silicic Acid. 



A thin film of colloidal silicic acid (cr= 1*0189, one month 

 dialysed) was spread out on a glass slide. Liquid was driven 

 away from the anode so that the surface of the slide dried 

 up. Although the wires were clean the transference did not 

 take place equally in all directions ; radial furrows ran out 

 from the electrode. At the cathode the acid was heaped up. 

 As in the case of gelatine small (O'Ol mm.) rhombohedral 

 crystals were found round the cathode. With 440 volts 

 feeble double refraction was to be seen in places round the 

 anode giving a displacement of 0*04 X. With loss of water 

 the acid fell into single pieces between cracks cutting every- 

 where at right angles. When a second slide was pressed on 

 the top of the first after the acid had dried up, the distance 

 apart was greater at the anode ; only water had moved to 

 the cathode. 



Iron Hydrate. 



Colloidal ferric hydrate was spread out on a glass slide. 

 Liquid was driven away from the cathode ; the jelly cracked 

 and show T ed with the compensator a displacement of 0'29 X. 

 Water collected at the anode ; here crystals could be seen. 

 The dried-up layer was thicker at the cathode than at the 

 anode ; water is moved to the anode and simultaneously 

 colloid to the cathode, i. e., in the opposite direction to 

 gelatine, silicic acid and albumen. 



Albumen. 



Filtered albumen on a glass slide showed round the anode 

 several concentric rings, the outer a zigzag or waved line. 

 Before the cathode a crescent of small rhombohedral crystals 

 could be seen. At the cathode the albumen was heaped up. 

 Next day a second slide pressed on top was nearly the same 

 distance apart at both ends. At the cathode the dry substance 

 was folded up and loose from the slide. 



Albumen coagulated in capillary tubes (prepared as above 

 described) became transparent and liquid at the cathode ; at 

 the anode, on the other hand, it shrank and the water ran 

 back along the sides of the tube. 



My sincere thanks are due to Professor Quincke for ever- 

 ready kindness and help during the course of the foregoing 

 investigations. 



