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of Edinburgh y Session 1880 - 81 . 
an electrolytic cell, from which the air was removed by a mercury 
air-pump ; but I did not succeed in getting it absolutely free of air, 
because the lubricating grease of the stopcocks allowed some air to 
get in during the long time through which it was necessary to 
continue the experiments. 
Lately I have had better results with a cell hermetically sealed, 
containing acidulated water and a vacuum, filled of course with 
vapour of water. Three electrodes enter the cell; two of them 
platinum wires, the third a thin platinum wire, to which a 
spiral of palladium is fixed. Before closing the glass tube through 
which I had introduced the liquid, I removed the atmospheric air 
left in the cell by means of a water air-pump, and sent an electric 
current through the cell, so that oxygen was evolved at the two 
platinum wires, and all the hydrogen was occluded in the 
palladium. Then I closed the tube with the blow-pipe. The traces 
of oxygen remaining in the interior of the cell combined again 
slowly with the hydrogen of the palladium, and even if I evolved 
new quantities of electrolytic gases in the interior of the closed cell, 
they could be removed again by the electro-motive force of a 
Daniell’s cell, driving the oxygen to the platinum wires and the 
hydrogen to the palladium. On the contrary, I may charge the 
two platinum wires with hydrogen, if 1 connect them for a short 
time with the palladium wire. 
If the platinum wires be freed from all hydrogen, a feeble 
electro-motive force, of about 0*01 to 0*001 Daniell, gives only a 
very short deflection; then the galvanometer returns to zero. Bemov- 
ing the electro-motive force without breaking the circuit, I saw 
an opposite deflection, equal in magnitude to the former and of the 
same duration. I have measured the capacity of the two platinum 
surfaces considered as condensers. They behaved like two con- 
densers, the two electric strata of which were separated by an interval 
of a ten millionth part of a millimeter. This is a capacity smaller 
than that found by Kohlrausch ( T y.wo, woo mm * distance) and other 
observers. But I found that the capacity appeared to be much 
greater, if only a small quantity of hydrogen were carried by an 
electric current to the platinum. The same was the case if the wires 
were newly polarized with oxygen, but this latter modification 
vanished some hours after the battery had been taken away. In 
