276 M. G. Quincke on Electrolysis^ and the 



compartments of equal size by a tliin plate of mica parallel to 

 the smaller side of the prism. The two compartments commu- 

 nicated by a very small aperture of about 0*2 millim. diameter, 

 and were filled to a height of 42-5 millims. with concentrated 

 solution of pure sulphate of copper. The current of a Grovels 

 battery of 77 cells passed into one compartment and out of the 

 other by means of two copper plates coated on the back with 

 sealing-wax^ which were of the same size as the smaller sides of 

 the trough^ and were placed parallel to them. 



Thus the electrical current flowed within two cones with rect- 

 angular base, the summits of which touched one another at the 

 opening in the mica plate. The intensity of the current was so 

 much the greater the nearer the section of the conical conductor 

 formed by the solution was to the opening in the mica plate. 



In the course of the experiment the opening in the mica plate 

 increased to a section of about 3'9 square millims. ; and when 

 the copper electrodes were at a distance of 30 millims. from the 

 mica plate, •0611 grm. of copper were deposited in ten minutes. 

 On closing the circuit, gas-bubbles were given off abundantly 

 on both sides of the mica plate, and near the opening the tem- 

 perature of the liquid rose several degrees. From the increase in 

 volume also of the air-cavities in the mica it was e^ddent that 

 near the aperture the temperature was high, which also very 

 probably occasioned the enlargement of the opening. At the 

 large copper electrodes no evolution of gas was observed. 



It may be observed that this rise in the temperature of the 

 liquid, when it is unequally distributed, causes a difference of 

 specific gravity in the two chambers and by that means a cur- 

 rent through the opening of the mica plate from the other 

 chamber to the one in which the greater heating has taken place. 

 Of course this current of liquid then carries along with it the 

 small gas-bubbles. 



In order to determine the nature of the liberated bubbles of 

 gas, they were collected in inverted glass hemispheres of about 

 20 millims. diameter, in the top of which a platinized platinum 

 wire was fused. 'When the glass vessels containing the gas- 

 bubbles were placed near one another in a large vessel contain- 

 ing dilute sulphuric acid, and the platinum wires connected by 

 means of a delicate multiplier, the current did not correspond to 

 the current of a Grovels gas battery, as would have been the case 

 had the separated gas consisted of oxygen and hydrogen. More- 

 over when an electric spark v»-as passed through a mixture of the 

 two gases obtained as has been described, no explosion took 

 place. This, together with the fact that the gas-generation gra- 

 dually becomes weaker and weaker, plainly shows that the gases 

 liberated consisted of atmospheric air which, previously absorbed 



