Dr.W.JC. Henry's Experiments on Gaseous Interference. 327 



one volume oxygen was unaffected by the prepared platina 

 plate in several days." (S?*.) I found however that after 

 four days' contact with the plate, an appreciable diminution 

 had ensued. Thus 3 cu. in. of such a mixture were reduced 

 to 2|, indicating the formation of nearly \ cu. in. of carbonic 

 acid. But the union of carbonic oxide with oxygen was much 

 accelerated by causing the gases to stand in contact with the 

 platina over a solution of caustic potassa, instead of distilled 

 water, which had been used by Dr. Faraday. In such experi- 

 ments thei-e was a daily decrease of volume in the confined 

 gases, till the fluid by ascending covered the greater part of 

 the plate. Thus 3j cu. in. were reduced to 1 cu. in. in about 

 seven days. 



Platina in the form of sponge had been previously stated 

 to cause the slow union of carbonic oxide and oxygen*. 

 This action I found was also quickened by admitting potassa 

 fusa with or without water above the confining surface of 

 mercury. Thus TIO cu. in. of a mixture of carbonic oxide 

 and oxygen in equivalent proportions became 1 "25 in the first 

 five minutes after introducing the platina sponge and potassa; 

 in the next five minutes 1*15, and in half an hour much less 

 than 1 cu. in. remained. In two hours less than half a cubic 

 inch was left, and the potassa, by rising so as to moisten the 

 sponge, terminated the experiment. Finally, the black pow- 

 der of Liebig admitted into mixtures of carbonic oxide and 

 oxygen became incandescent at the moment of contact, and 

 continued to glow until all the carbonic oxide v.as converted 

 into carbonic acid. Platina therefore, in all its forms, deter-i 

 mines, at atmospheric temperatures, the union of carbonic 

 oxide with oxygen. In the state of plate the change goes on 

 with extreme slowness; in that of sponge, much more quickly; 

 and in the most minutely divided condition of powder, with 

 ignition and with great rapidity. 



In this unequivocal action of platina upon mixtures of 

 oxygen with carbonic oxide only, it appears to me, is to be 

 found the interpretation of the property residing in the latter 

 gas, of suspending the combining tendencies of hydrogen and 

 oxygen in mixtures of the three gases. Possessing, as has been 

 already shown, a stronger affinity for oxygen than is inherent 

 in hydrogen, carbonic oxide seizes, when mingled with those 

 two gases and exposed to the agency of platina, a much larger 

 proportion of the oxygen than is due to its comparative vo- 

 lume. In such complex mixtures, just as in simple mixtures 

 of carbonic oxide and oxygen, the slow formation of carbonic 



• Phil. Trans., 1824, p. 267. [Phil. Mag., vol.lxv. p. ?69.-Edit,] 



