Dr.W. C. Henry's Experiments on Gaseous Interference. 329 



access of fresh unaltered gas to elevate materially the tempera- 

 ture of the platina. In confirmation of this view I found that 

 caustic potassa, by absorbing the carbonic acid as fast as it 

 is formed, accelerates the acidification of carbonic oxide. 

 When the metallic superficies is so extensive (for instance, in 

 the powder of Liebig,) that a high temperature is quickly at- 

 tained by the metal in contact with the first portions of gas 

 that are consumed, it has been already shown that carbonic 

 oxide, like hydrogen, then unites with oxygen, with incan- 

 descence. Finally, it is well known that even mixtures of hy- 

 drogen and oxygen do not detonate on first admitting the 

 prepared plate. During the first minute the union is ge- 

 nerally very slow, and it only becomes explosive when the 

 temperature of the plate has been raised by its action upon 

 the gaseous mixture. 



2. Olcfiant Gas. — The olefiant gas which I employed had 

 been carefully washed with caustic potassa, and in the experi- 

 ments made over mercury, it had stood for many days in 

 contact with dry potassa fusa. It resulted from all my ex- 

 periments with platina in its various conditions, that the pro- 

 perty of interference is much less energetic in olefiant gas than 

 in carbonic oxide*. Of this I could not feel satisfied without 

 repeated examination, because the reverse is the result of 

 Dr. Faraday's experience, according to which olefiant gas inter- 

 feres when it constitutes ^^^gth of the entire mixture, and carbonic 

 oxide only when it amounts to g^th. I found, however, that in 

 a mixture of 3-00 cu. in. explosive mixture with '08 of olefiant, 

 in which the olefiant is about ^^yth of the whole, the plate 

 began to act visibly on first admission. In ten minutes there 

 remained 2*50, and in a quarter of an hour 2*00, when the 

 action became very rapid, the plate being so hot as to cause 

 the ascending water, in contact with it, to boil, and only 

 •25 cu. in. were left unconsumed. Even when the olefiant 

 amounted to y^th of the entire mixture there was manifest 

 action in the course of a quarter of an hour, and in two days 

 the water had covered the plate. 



Olefiant gas in much larger proportion, even when con- 

 stituting ^th or ird of the mixture, did not in the slightest de- 

 gree retard the action of the platina balls or sponge. Several 

 trials were made, in which the olefiant and explosive mixture 

 were mingled in equal pioportions. In all of these the ball 

 acted instantaneously, and ascended rapidly into the tube du- 

 ring one or two minutes, when its rise was suddenly checked. 

 Thus r02 cu. in. were reduced in the first minute to '90, and 

 became '82 after an hour's contact. The following day only '56 



• See also Mr. Graham's Experiments, Journal of Science, 1829, p. 356, 

 Third Series. Vol.9. No. 55. Nov. IS3G. 2Q 



