On the Action between Metals and Acids. 833 



a 2 

 If in addition -^ can be neglected compared with unity 



we have 



and 



b 2 



i = \nec a 2 lb 



i/ h =(l + 2keV)e- 2keY . 



The equation between the current and the opposing potential- 

 difference in this case therefore differs from the similar 

 equation for infinite parallel planes by the inclusion of the 

 factor (l + 2fo?V). 



LXXV1II. On the Action between Metals and Acids and 

 the Conditions under which Mercury causes Evolution of 

 Hydrogen. By S. W. J. Smith, M.A., D.Sc, Lecturer 

 on Physics, Imperial College of Science and Technology* . 



Contexts. 

 § 1. Introductory. 

 § 2. Electrolytic solution pressure. 



§ 3. A conception of the Interaction of Metals and Acids. 

 § 4. Symbolic expression of § 3. 

 § 5. Possible effect of Surface Tension. 

 $ 6. The problem for experiment. 



§ 7. Detrimental effect of Oxygen in the Surface-layer. 

 § 8. Possible methods of eliminating this effect. 

 § 9. Experimental realization. 

 § 10. Results. 



§ 11. Proof of Evolution of Hydrogen. 

 § 12. Secondary effects with Sulphuric Acid. 

 § 13. Effects of dilution of the Acids. 

 § 14. Possible effects at the Jet. 

 § 15. A kinetic representation of § 3. 

 § 16. Summary of conclusions. 



§ 1. JNTRODUCTORT. — Under ordinary conditions 

 metals like mercury, silver and copper are unable 

 to displace hydrogen from solutions of acids (dilute or con- 

 centrated) with appreciable and easily demonstrable evolution 

 of the gas. 



An attempt is here made to show how, in the case of 

 mercury, the fluidity of the metal at the ordinary temperatures 

 may be utilized to exhibit the cause of the inability and to 

 supply a method by which it may be overcome. 



The effects with hydrochloric and sulphuric acids only 

 have been examined, but there is no apparent reason why 



* Communicated by the Physical Society : read March 2Q, 1909. 



