The rapid progress which has been made in the last few years in the knowledge of the rotational, vibrational, and electronic energy of molecules has extended the range of chemical investigation, particularly in the region of chemical kinetics. This knowledge is derived chiefly from the study and interpretation of band spectra, and one of the most obvious cases to examine is that of “active” nitrogen which emits a characteristic spectrum and is capable of energetic chemical reaction with a wide range of substances. For most of the early work, including spectroscopic observations, we are indebted to the excellent and thorough investigations of Strutt.