Bakerian Lecture.—A chemically active modification of nitrogen, produced by the electric discharge

Abstract

It is known that vacuum tubes frequently show a luminosity of the contained gas after discharge is over. In a previous paper I was able to show that this effect, as it occurs in air, is of the nature of a phosphorescent combustion, and is due to the mutual reaction of nitric oxide and ozone, each formed in the discharge. In a second paper it was shown that other phosphorescent combustions can be observed in ozone, notably of sulphur, sulphuretted hydrogen, acetylene, and iodine. Some of these give continuous spectra, but the majority band spectra. In the first paper it was stated that pure nitrogen gives no afterglow whatever, and, with the simple induction coil discharge with which I was then working, this has been frequently verified since. Mr. Percival Lewis has however, described an afterglow obtained in nitrogen when a jar discharge with spark-gap is used. I had no difficulty in obtaining this glow as soon as the jar discharge was used, and have applied to its examination the method used in the former papers. This is due to Sir James Dewar, and consists in drawing a current of gas through the vacuum tube into an observing vessel, where the glow is developed, and thence into an air pump, which must be a mechanical one of good construction, driven by power. It is thus possible to examine the properties of the glowing nitrogen much more satisfactorily than can be done by intermittent examination after successive discharges.