72 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



gas exploded. Here also the retarding- effect of the olefiant gas was very beautifully 

 illustrated. 



643. Plates prepared by alkali and acid (605.) produced corresponding effects, 



644. It is perfectly clear from these experiments, that olefiant gas, even in small 

 quantities, has a very remarkable influence in preventing the combination of oxygen 

 and hydrogen under these circumstances, and yet without at all injuring or affecting 

 the power of the platina. 



645. Another striking illustration of similar interference may be shown in carbonic 

 oxide, especially if contrasted with carbonic acid. A mixture of one volume oxygen 

 and hydrogen (638.) with four volumes of carbonic acid was affected at once by a 

 platina plate prepared with acid, &c. (605.), and in one hour and a quarter nearly all 

 the oxygen and hydrogen was gone. Mixtures containing less carbonic acid were still 

 more readily affected. 



646. But when carbonic oxide was substituted for the carbonic acid, not the 

 slightest effect of combination was produced ; and when the carbonic oxide was only 

 one eighth of the whole volume, no action occurred in forty and fifty hours. Yet the 

 plates had not lost their power ; for being taken out and put into pure oxygen and 

 hydrogen, they acted well and at once. 



647. Two volumes of carbonic oxide and one of oxygen were mingled with nine 

 volumes of oxygen and hydrogen (638.). This mixture was not affected by a plate 

 which had been made positive in acid, though it remained in it fifteen hours. But 

 when to the same volumes of carbonic oxide and oxygen were added thirty-three vo- 

 lumes of oxygen and hydrogen, the carbonic oxide being then only yVth part of the 

 whole, the plate acted, slowly at first, and at the end of forty-two minutes the gases 

 exploded. 



648. These experiments were extended to various gases and vapours, the general 

 results of which may be given as follow. Oxygen, hydrogen, nitrogen, and nitrous 

 oxide, when used to dilute the mixture of oxygen and hydrogen, did not prevent the 

 action of the plates even when they made up four fifths of the whole volume of gas 

 acted upon. Nor was the retardation so great in any case as might have been ex- 

 pected from the mere dilution of the oxygen and hydrogen, and the consequent me- 

 chanical obstruction to its contact with the platina. The order in which carbonic 

 acid and these substances seemed to stand was as follows, the first interfering least 

 with the action ; nitrous oxide, hydrogen, carbonic acid, nitrogen, oxygen : but it is 

 possible the plates were not equally well prepared in all, and that other circumstances 

 also were unequal ; consequently more numerous experiments would be required to 

 establish the order accurately. 



649. As to cases of retardation, the powers of olefiant gas and carbonic oxide have 

 been already described. Mixtures of oxygen and hydrogen, containing from -jVth to 

 jVth of sulphuretted hydrogen or phosphuretted hydrogen, seemed to show a little ac- 

 tion at first, but were not further affected by the prepared plates, though in contact 



