256 On the Electrolysis of Gases. [June 20, 



sides of the plate, but with negative results. Chlorine seems a gaa 

 in which we might expect to find this effect, for as Dr. Schuster, 

 in his Report on Spectrum Analysis, says, the behaviour of its spec- 

 trum indicates that we have several spectra superposed. I have not, 

 however, been able to effect a separation of its spectra, the differences 

 I observed between the spectra on the two sides of the plate were 

 irregular, and due, I think, to impurities producing effects like those 

 observed when the discharge passes through a compound gas. How- 

 ever, as has been mentioned before, there is even in the case of gases 

 where distinct evidence of separation can be obtained, a region of 

 pressure within which the effects are irregular, and I ascribe my 

 failure to observe separation in the case of chlorine to my having 

 failed to get the relation between the intensity of the discharge and 

 the pressure so adjusted as to get outside this irregular region. The 

 cases, however, in which distinct differences between the spectra of 

 a simple gas occur at the two electrodes, seem to indicate that the 

 spectrum given by an element is influenced by the sign of the 

 electrical charge carried by its atoms. 



I have made some experiments to determine whether there was 

 any separation produced in a mixture of equal volumes of hydrogen 

 and chlorine kept in the dark, when a considerable difference of 

 potential though not sufficient to produce discharge was maintained 

 between the two electrodes. The parts of the tube adjacent to the 

 two electrodes could be shut off from each other by a tap, and the 

 amount of chlorine in the two sides was determined by absorbing it 

 by caustic potash. The mixture was at atmospheric pressure, and 

 the electrodes were maintained at a potential difference of about 

 1,200 volts by connecting them to a large battery of small storage 

 cells. The potential difference between the terminals was main- 

 tained for about 16 hours on three separate occasions, but on 

 analysing the vessels surrounding the two electrodes, the amount 

 of chlorine in the vessel adjacent to the negative electrode did not 

 differ from that in the vessel adjacent to the positive electrode by 

 more than 1 per cent., and this could be accounted for by errors of 

 experiments, as test experiments in which the mixture had not been 

 exposed to the electric field gave differences comparable with these. 

 We should conclude from the preceding experiments that the 

 molecules of a gas are not acted on by any appreciable translational 

 force tending to move them from one place to another, when they 

 are near to a body charged with electricity. To test this point 

 further, two large terminals were placed in bulbs which were con- 

 nected by a horizontal capillary tube, in which a drop of sulphuric 

 acid was placed ; a difference in the pressure of the gas would cause 

 the sulphuric acid to move, and the arrangement acts as a very 

 delicate pressure gauge. The bulbs and tube were filled with 



