INTERFERENCES WITH THE ACTION OP PLATINA. 73 



with them for seventy hours. When the plates were removed they had lost all power 

 over pure oxygen and hydrogen, and the interference of these gases was therefore of a 

 different nature from that of the two former, having permanently affected the plate. 



650. A small piece of cork was dipped in sulphuret of carbon and passed up through 

 water into a tube containing oxygen and hydrogen (638.), so as to diffuse a portion of 

 its vapour through the gases. A plate being introduced appeared at first to act a 

 little, but after sixty-one hours the diminution was very small. Upon putting the 

 same plate into a pure mixture of oxygen and hydrogen it acted at once and power- 

 fully, having apparently suffered no diminution of its force. 



65 1 . A little vapour of ether being mixed with the oxygen and hydrogen retarded 

 the action of the plate, but did not prevent it altogether. A little of the vapour of 

 the condensed oil-gas liquor* retarded the action still more, but not nearly so much 

 as an equal volume of olefiant gas would have done. In both these cases it was the 

 original oxygen and hydrogen which combined together, the ether and the oil-gas 

 vapour remaining unaffected, and in both cases the plates retained the power of act- 

 ing on fresh oxygen and hydrogen. 



652. Spongy platina was then used in place of the plates, and jets of hydrogen 

 mingled with the different gases thrown against it in air. The results were exactly of 

 the same kind, although presented occasionally in a more imposing form. Thus, mix- 

 tures of one volume of olefiant gas or carbonic oxide with three of hydrogen could 

 not heat the spongy platina when the experiments were commenced at common tem- 

 peratures ; but a mixture of equal volumes of nitrogen and hydrogen acted very well, 

 causing ignition. With carbonic acid the results were still stronger. A mixture of 

 three volumes of that gas with one of hydrogen caused ignition of the platina, yet that 

 mixture would not continue to burn from the jet when attempts were made to light 

 it by a taper. A mixture even of seven volumes of carbonic acid and one of hydrogen 

 will thus cause the ignition of cold spongy platina, and yet, as if to supply a contrast, 

 than which none can be greater, it cannot burn at a taper, but causes the extinction 

 of the latter. On the other hand, the mixtures of carbonic oxide or olefiant gas, 

 which can do nothing with the platina, are inflamed by the taper, burning well. 



653. Hydrogen mingled with the vapour of ether or oil-gas liquor causes the ig- 

 nition of the spongy platina. The mixture with oil-gas burns with a flame far brighter 

 than that of the mixture of hydrogen and olefiant gas already referred to, so that it 

 would appear that the retarding action of the hydro-carbons is not at all in proportion 

 merely to the quantity of carbon present. 



654. In connexion with these interferences, I must state that hydrogen itself, pre- 

 pared from steam passed over ignited iron, was found when mingled with oxygen 

 to resist the action of platina. It had stood over water seven days, and had lost all 

 fetid smell ; but a jet of it would not cause the ignition of spongy platina, commencing 

 at common temperatures ; nor would it combine with oxygen in a tube either under 



* Philosophical Transactions, 1825, p. 440. 

 MDCCCXXXIV. L 



