390 EXPERIMENTAL INVESTIGATIONS. 



was no symptom of any effect produced by the missing equi- 

 valent of oxygen. 



9th. With a solution of caustic potash the coated point, 

 which was positive, gave a gas which contracted to 0*32 of its 

 volume, the residue being hydrogen ; the plate, which was 

 negative, gave off a mere trace of gas. 



loth. Two plates were used as the terminals of the secon- 

 dary coil in dilute sulphuric acid, instead of a plate and a point. 

 No gas was given off from either, though the experiment was 

 continued for several hours. 



nth. I could detect no difference in the solutions employed 

 before and after the experiment ; but as the sulphuric acid 

 might be expected to mask the effect of any oxygenated com- 

 pound which might result from the absorption of oxygen, 

 which took place in all these experiments, except those where 

 the strong solutions of sulphuric acid were employed, and as 

 pure distilled water would give no effect, I tried the effect of 

 the spark passed through aqueous vapour. Some distilled 

 water was boiled and placed under the receiver of an air- 

 pump, with a coated point and plate of platinum enclosed in 

 a tube filled with the liquid, and inverted; the point and plate 

 communicating respectively with the upper and under plate 

 of the receiver, and thence brought into metallic communica- 

 tion with the ends of the secondary coil. 



The receiver was then exhausted, and the vapour which 

 had formed at the top of the tube soon dilated sufficiently to 

 expose the point and plate ; the spark was then passed across 

 the vapour, and a permanent increase in volume of the vapour 

 was soon detected. The experiment was continued for a week, 

 the apparatus working five hours each day ; at the end of that 

 time much of the gas formed had bubbled out into the re- 

 ceiver, and on letting in the air the water rose in the tube until 

 a bubble of gas of 0*03 c. i. remained in the top ; this was 

 analysed, and proved to be pure hydrogen. 



On the interior of the tube near the platinum point was a 

 dark pulverulent deposit, far too minute in quantity for analysis, 

 but which had evidently proceeded from the platinum. 



The only possible mode in which I can account for this 

 experiment is, that this deposit consisted of an oxide or per- 



