450 Dr. L. Bleekrode on the Electric Conductivity 



conductivity and other physical or chemical properties (mole- 

 cular weight, molecular volume, &c). The main proposition 

 of Hittorf's theory of electrolysis, according to which the 

 difficulty of exchange of the constituents is connected with 

 the resistance of electrolytes, derives no support at all from 

 my experiments. Hittorf always tried the compounds in 

 solution ; and for that very cause it must be hazardous to 

 deduce therefrom definite conclusions respecting their con- 

 ductivity. It has recently been proved by F. Kohlrausch, 

 Herwig, and others, that liquids which are bad conductors 

 become more conductive through mixture with other sub- 

 stances, even when these are themselves bad conductors. 

 Besides, we have in mercaptan, hyponitric acid, bisulphide of 

 carbon, the organ o-metallic radicals, &c. instances of compounds 

 which easily exchange their constituents with salts, acids, or 

 water, and yet behave to very powerful electromotive forces 

 as almost: insulating substances. 



A newer conception, based by Gr. Wiedemann, and after 

 him by F. Kohlrausch, upon their experiments, takes chiefly 

 into consideration the mechanical processes going on in elec- 

 trolysis, such as friction of the molecules against one another, 

 conveyance of the ions with different velocities, &c, points 

 which in other theories remain quite in the background. The 

 great resistance of liquids is then explained by the frequent 

 collisions between the constituents. The solvent gives oppor- 

 tunity for the molecules to move through comparatively great 

 distances before meeting one another and again combining. 

 It is therewith mentioned that not a single liquid is known 

 which at ordinary temperature is by itself a good conducting 

 electrolyte*. My experiments, however, point out liquid 

 ammonia and hydrocyanic acid as substances which are clearly 

 decomposed even by moderate galvanic currents. Although 

 there may be reasons for these assumptions f , and the rest of 

 the experiments point to the conclusion that liquids in general 

 are very bad conductors, while by the above assumption the 

 remarkable phenomenon of the diminution of the resistance by 

 mixing two compounds both of which are bad conductors, yet 

 I cannot reconcile therewith the fact that a salt when fused 

 is notwithstanding a good conductor — for instance, chloride 

 of silver. Here the melting-point is far below the temperature 



* Pogg. Ann. 1876, p. 253. 



t F. Kohlrausch, before he was informed of my experiments, expressed 

 the anticipation that liquid hydrochloric, hydrobromic, and hydriodic acids 

 would prove insulating (I. c. p. 278) ; I have found this fully confirmed 

 by experiment. On the other hand, he reckoned hydrocyanic aeid and 

 ammonia in solution among the worst conductors ; in the condensed state 

 they proved, in my experiments, to be very good conductors and electro- 

 lytes. This exceptional behaviour is very remarkable. 



