380 Dr. L. Bleekrode on the Electric Conductivity 



the acid was placed in a freezing-mixture, by which the 

 temperature was kept down to 0° C. at least. At the close 

 of the experiment no alteration could be perceived on the 

 surface of the platinum electrodes. On very strongly re- 

 frigerating the tube no effervescence could any longer be 

 observed, but instead an undulatory motion of the surface : 

 this phenomenon will be considered in a subsequent part of 

 this paper. The tube being now taken from the freezing- 

 mixture and exposed to the temperature of the air, the effer- 

 vescence soon reappeared at the electrodes. This shows 

 that the gas-evolution was only a consequence of the heating 

 of the electrodes by the discharges. No polarization was 

 afterwards manifested by the galvanometer ; nevertheless the 

 liquid may have been so far conducting that the current 

 passed through at the opening and closing of the circuit ; or 

 the resistance of the liquid may have been too great to permit 

 a polarization-current to produce a deflection. 



As the conductivity of these bodies when liquefied is quite 

 different from their conductivity when in the state of solution, 

 so is their chemical character very different. I have been 

 able to demonstrate this with respect to hydrochloric acid, by 

 placing in the condensation-tube, before closing the circuit, a 

 white strip of zinc and then condensing the gas, so that the 

 metal was completely immersed in the liquid. Only at the 

 end of seven weeks could small white spots of chloride of 

 zinc be here and there perceived on the strip ; everywhere 

 else the metallic appearance was pretty well preserved. After 

 nearly a year a slight white precipitate could be seen in the 

 tube. On opening the tube the strip of zinc, exposed to the 

 air, immediately became moist from the hygroscopic property 

 of the coating of chloride of zinc. On a strip of copper it 

 was not till after four months that a little white powder was 

 visible ; and subsequently a white precipitate gradually 

 formed in the tube, most probably of anhydrous protochloride 

 of copper *. In liquefied sulphuretted hydrogen a strip of 

 zinc was first distinctly attacked after fourteen days, with the 

 formation of a white precipitate (sulphide of zinc) at the 

 bottom of the tube. Wires of silver and copper were already, 

 before the condensation of the gaseous acid, coated with a 

 sulphide, which then protected them from further attack. 

 Accordingly the liquefied hydrogen acids exchange their 

 hydrogen with great difficulty for the metals with which, when 

 dissolved in water, they at once form metallic chlorides &c. It 



* For similar experiments by Gore with strips of lead, iron, and 

 magnesium, see Phil. Mag. [IV.] vol. xxix. p. 547, and Proc. Eoy. Soc. 

 vol. xvii. 



