Spectrum of an electrically heated carbon rod

• Publisher: Elsevier Science
• Year: 1911
• Tongue: English
• Weight: 65 KB
• Volume: 172
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/s0016-0032(11)90320-2

✦ Synopsis

Spectrum of an Electrically Heated Carbon Rod. M. LA RosA.

(Ann. Physik., xxxiv, 222.)--When a carbon rod of 2 or 3 mm. diameter is heated white hot by a current of 15-18 amp&res per square mm. passed through it, it is surrounded by a layer of incandescent gases, the spectrum of which was investigated. It consists of a faint continuous background on which a number of bands or lines are seen. The bands are those of the Swan spectrum, with faint traces of the so-called cyanogen spectrum, while the lines are those of the metallic impurities found in the carbon. When the rod is heated in pure nitrogen (after all occluded gases are removed) no metallic lines appeared, and scarcely any trace of the cyanogen bands, while those of the Swan spectrum (presumably due to carbon vapor) were seen better than when the rod was heated in air.' This, and similar experiments, show that oxygen is necessary for the appearance of the metallic lines. The explanation suggested is that in the hot carbon rod the metallic impurities form carbides, which are broken up only by oxygen, thus leaving the metal free to radiate.