COMBINATION OF OXYGEN AND HYDROGEN BY SOLID BODIES. 63 



and would often produce explosion in the mixed gases ; but the strong sulphuric acid 

 was most certain and powerful. 



607. If borax, or a mixture of the carbonates of potash and soda, be fused on the 

 surface of a platina plate, and that plate be well washed in water, it will be found to 

 have acquired the power of combining oxygen and hydrogen, but only in a moderate 

 degree ; but if, after the fusion and washing, it be dipped in the hot sulphuric acid 

 (601.), it will become very active. 



608. Other metals than platina were then experimented with. Gold and palladium 

 exhibited the power either when made the positive pole of the voltaic battery (570.), 

 or when acted on by hot oil of vitriol (601.). When palladium is used, the action 

 of the battery or acid should be moderated, as that metal is soon acted upon. Silver 

 and copper could not be made to show any effect at common temperatures. 



609. There can remain no doubt that the property of inducing combination, which 

 can thus be conferred upon masses of platina and other metals by connecting them with 

 the poles of the battery, or by cleansing processes either of a mechanical or chemical 

 nature, is the same as that which was discovered by Dobereiner*, in 1823, to belong- in 

 so eminent a degree to spongy platina, and which was afterwards so well experimented 

 upon and illustrated by MM. Dulong and Thenard-)-, in 1823. The latter philoso- 

 phers even quote experiments in which a very fine platina wire, which had been coiled 

 up and digested in nitric, sulphuric, or muriatic acid, became ignited when put into 

 a jet of hydrogen gas;}:. This effect I can now produce at pleasure with either wires or 

 plates by the processes described (570. 601. 605.) ; and by using a smaller plate cut 

 so that it shall rest against the glass by a few points, and yet allow the water to flow 

 off (fig. 4.), the loss of heat is less, the metal is assimilated somewhat to the spongy 

 state, and the probability of failure almost entirely removed. 



610. M. Dobereiner refers the effect entirely to an electric action. He considers 

 the platina and hydrogen as forming a voltaic element of the ordinary kind, in which 

 the hydrogen, being very highly positive, represents the zinc of the usual arrange- 

 ment, and like it, therefore, attracts oxygen and combines with it^. 



611. In the two excellent experimental papers by MM. Dulong and Thenard||, 

 those philosophers show that elevation of temperature favours the action, but does 

 not alter its character. Sir Humphry Davy's incandescent platina wire being the same 

 phenomenon with Dobereiner's spongy platina. They show that all metals have 

 this power in a greater or smaller degree, and that it is even possessed by such bodies 

 as charcoal, pumice, porcelain, glass, rock crystal, &c., when their temperatures are 

 raised ; and that another of Davy's effects, in which oxygen and hydrogen had com- 

 bined slowly together at a heat below ignition,. was really dependent upon the pro- 



* Annales de Chimie, tcm. xxiv. p. 93. 



t Ibid. torn, xxiii. p. 440.; torn. xxiv. p. 380. . X Ibid. torn. xxiv. p. 383. 



§ Ibid. torn. xxiv. pp. 94, 95. Also Biblioth^que Universelle, torn,, xxiv. p. 54. 



II Annales de Chimie, torn, xxiii. p. 440. ; torn. xxiv. p. 380. 



