Spectrum of the flame of ethylene

Abstract

In the course of a detailed examination of the spectra of the flames of carbon compounds, which was undertaken at the suggestion of Professor A. Fowler, it has been found that the flame of ethylene shows, in addition to the familiar bands of C 2 , CH and HO, a system of bands which has not previously been adequately described. These bands occur feebly in the ordinary Bunsen flame, as noted by Rassweiler and Withrow, and with greater intensity in the flame of ether, as shown in a photograph by Emeléus. Other flames which exhibit these bands have also been found in the course of the present investigation, but as the bands appear to have their greatest intensity in ethylene, they may conveniently be called the “ethylene flame bands” for the purposes of the present paper. The bands are degraded to the red, and have been observed to extend from λ 4100 to λ 2500. For the production of the bands under the most favourable conditions it was necessary to use a Smithells’ flame separator to divide the inner and outer cones. The separator employed, fig. 1, considered to two concentric tubes, F and G, the inner tube, F, being mounted on the outer nozzle, D, of a two-way blow-pipe. The inner tube was made of Pyrex, 15cm in length and 1·2 cm in diameter, while the outer one—12 cm long and 1·5 cm in diameter—was made of quartz so as to permit observations in the ultra-violet. The inlet A was connected to a cylinder of ethylene gas (rated 100% pure), the arrangement being such that the gas could then pass through the outer nozzle, D. Through the inner nozzle, E, could be passed air blown through the other inlet, B, by an electric blower. In the absence of air, the gas burnt with a smoky flame on the outer tube, G. When air was blown through, the flame became non-luminous and, with suitable adjustment of air and gas supply by the handle, C, the inner cone was clearly developed. Then, on sliding the inner tube of the separator about 4 cm below the top of the outer tube, the cones were completely separated, the inner cone burning steadily on the inner tube. Under these conditions the inner cone was about 2 cm high, and was of greenish colour.