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

1.General . The properties of active nitrogen have been described throughout on the assumption that it is to be classed with other chemical substances, and that its reversion to ordinary nitrogen is to be regarded simply as a chemical reaction, as one would regard the change of ozone to oxygen, or of red to ordinary phosphorus. I see no reason to abandon this position. There are, however, some circumstances not at first sight falling in very naturally with it. One of these is the acceleration of the change by cooling, a phenomenon without parallel in any recognised reaction. Another is the development of many of the bands of the nitrogen spectrum. This spectrum has never been produced by any other purely chemical process, but (apart from active nitrogen) is only observed when an electric current is actually passing through the gas at the moment of observation. Lastly, the ionisation associated with a stream of glowing nitrogen has suggested serious doubts whether its chemical peculiarities are really due to the presence of a definite chemical substance in the ordinary sense, or to some unexplained survival of the conditions of the disruptive discharge. Evidence will he brought forward in this paper which is considered to be entirely in favour of the former alternative. 2.Energy of Active Nitrogen . These considerations have made it important to determine whether the energy emitted by active nitrogen in reverting to ordinary nitrogen is comparable with that liberated in other chemical changes. The experiments to be described answer this question in the affirmative.