390 RECENT PEOGEESS IN PHYSICS. 



ones may not always he at hand, it will do to use a thin platinum 

 wire having its end fused into a small knob about one line in diameter. 



§ 96. Electrical odor in the electrolysis of ivater. — The electrical 

 odor appears not only on the escape of electricity from points, but 

 also in the electrolytic decomposition of water, where we find it ac- 

 companied by the same reaction and effects which were considered''in 

 the preceding paragraph. 



On closer investigation it appears that electrical odor manifests 

 itself at the positive pole, where oxygen is given off; for on collecting 

 the gases resulting from the decomposition of water separately, the 

 odor in question was perceived only in that vessel which contained the 

 oxygen, no trace of it being found in the one containing the hydrogen. 



The gases when obtained together have the electrical odor. 



On suspending a paper covered with the paste of iodide of potas- 

 sium in oxygen, or in the mixed gases to which the ozone odor has 

 been imparted by electrolysis, the paper turns blue. A platinum 

 plate exposed for a time to the action of this, gas indicates the same 

 electro-negative polarization as though it had been acted on by the 

 electrical brush. 



Chemically pure oxygen gas produces none of these effects ; it has 

 not the odor, does not turn the iodide paste blue, and is not in the 

 condition to polarize a platinum plate negatively. 



The gas obtained by electrolytic decomposition produces, in all 

 these cases, the same effects as the air which issues from a strongly 

 electrified point. 



§ 97. Fi'oduction of ozone in tJie chemical ivay. — The so-called electri- 

 cal odor can be produced by purely chemical means without any aid 

 from electricity. A piece of phosphorus made perfectly dry by blotting 

 paper, so that it has a clean surface, emits a peculiar alliaceous odor. 

 Placing such a piece of phosphorus in a jar of air, the vapor of phos- 

 phorus will in the cold soon diffuse itself through the whole jar. A 

 platinum plate being then suspended in the jar a short time it will 

 be polarized positively. 



The polarization of the platinum plate is to be ascribed to the phos- 

 phoric vapor diffused in the jar, but the odor very probably is due to 

 the phosphoric acid, which is formed by the partial oxidation of the 

 phosphorus vapor. 



If a little water be now introduced into the jar, (as much as will 

 half cover the piece of phosphorus,) the phosphoric odor becomes 

 weaker and weaker, and at length wholly disappears, and in its place 

 a decided ozone odor will be perceived. At rather high temperatures 

 the ozone smell appears very soon. 



This odor is not to be distinguished from that produced in the 

 electrical way, and it is accompanied by all the reactions and effects 

 which characterize the agency of the electrical odor. A paper with the 

 iodide paste on it becomes blue when suspended in the jar, and a 

 platinum plate exposed to its action is polarized electro-negatively . 



With the ozone obtained in the chemical way the reactions can be 

 ])roduced almost exactly in the same form as with a point emitting 

 electricity. For this purpose a bottle of the capacity of several quarts 



