216 



Prof. G. F. Fitzgerald. Clausius's Formula [Mar. 31, 



obtained on connecting the two mercury cups by a wire, the current 

 passing could be modified at will, and shown to exhibit all the 

 ordinary phenomena of moderately weak currents. 



After continued action with small resistance only in circuit, the 

 liquid in the funnel was found on analysis to contain no copper what- 

 ever, whilst that surrounding the copper plate, though colourless 

 before removal from the tube, speedily became blue on exposure to 

 air, and contained more or less considerable amounts of copper in 

 solution, obviously originally in the condition of cuprous oxide, Cu 2 0. 



Following up the ideas suggested by the above observations, we are 

 making a number of experiments with a variety of analogous com- 

 binations, in which atmospheric oxidation constitutes the essential 

 chemical action taking place ; by varying the nature of the aeration 

 plates, the metals dissolved, and the liquids employed (as also by 

 substituting other gases, e.g., chlorine, for air), a large number of 

 combinations are obviously obtainable. Some of those which we 

 have so far examined present points of considerable interest, the 

 oxidising action exerted under favourable conditions being strongly 

 marked, so much so that certain metals, e.g., mercury and silver, not 

 ordinarily prone to atmospheric oxidation, can under suitable condi- 

 tions be gradually oxidised and dissolved in appropriate liquids, just 

 as the copper is dissolved in the ammonia in the cell above described ; 

 these actions, moreover, being accompanied by the development of 

 currents of strength sufficient to cause measureable amounts of electro- 

 lytic decomposition outside the cell, e.g., in a silver voltameter. 



II. " Clausius's Formula for the Change of State from Liquid to 

 Gas applied to Messrs. Ramsay and Young's Observations 

 on Alcohol." By Geo. Fras. Fitzgerald, M.A., F.T.C.D., 

 F.R.S., Erasmus Smith's Professor of Natural and Experi- 

 mental Philosophy in the University of Dublin. Received 

 March 14, 1887. 



Clausius, in Wiedemann's ' Annalen,' vol. 14, 1881, pp. 279 — 290, 

 and 'Phil. Mag.,' vol. 12, 1881, p. 381, and vol. 13, 1882, p. 132, has 

 given an empirical formula for calculating the relation between the 

 volume, pressure, and temperature of a substance in both liquid and 

 gaseous states. The equation he gives is a continuous one for an 

 isothermal, and he determines the pressure at which evaporation takes 

 place by considering that the work done in the transformation from 

 liquid to gas at a constant pressure must be equal to what would be 

 done if the transformation took place along the continuous isothermal. 

 He requires, for convenience in applying this to actual cases, to calcu- 



