Chromium Spectrum

Compounds of chromium impart no distinctive colour to the non-luminous flame. The spectrum, however, is somewhat complicated, especially the spark spectrum. Careful and complete measurements have been made, for which the reader is referred to the literature. Exner and Haschek state that the most intense lines ("hauptlinien") in the arc and spark spectra are as follows:

Arc Spectrum

Wave-Length.	Intensity (Max. = 100).
3578.81	30 u*
3593.64	30 u*
3506.49	30 u*
4254.51	50 u*
4275.00	50 u
4289.90	50 u*
[4646.31]	2
4646.35	20
5204.71	20 *
5206.24	30 u*
5208.60	30 u*
[5345.95]	1
5345.99	20
5410.01	20 *

Spark Spectrum

Wave-Length.	Intensity (Max. = 100).
2677.27	20 *
2830.63	20
2835.71	30
3125.11	20 *
3132.20	20 *
3360.50	20 §
3368.19	20 *
3408.90	20 § *
3422.89	20 §
3578.81	20 u
[3578.86]	3
3593.63	20 u
[3593.67]	3
[3605.44]	1
3605.48	20
4254.50	50 *
4274.95	30 *
4289.89	30
4558.89	20
4588.43	20
5208.61	20 *
Abbreviation: u=reversed, §=diffuse; *=not displaced; []=λ of displace line at low intensity

It does not follow, however, that those lines which are greatest in intensity are the most persistent The spark spectrum of chromium has been studied quantitatively by Pollok and Leonard from this point of view, and the residuary lines (those last to disappear upon dilution) recorded. Their method of procedure was as follows:

There was made a concentrated or saturated solution of chromic chloride, as well as solutions containing 1 gram of the element in 100, 1000, 10,000, and 100,000 parts of solution. Gold electrodes were used, and a photograph of the spark between them was first taken using a long slit; the slit was then shortened and the chromium solution sparked, thus giving the spectrum of gold with long lines and the spectrum of chromium with short lines. The process was then reversed, the chromium being taken long and the gold short, so that any lines coincident with the gold lines might be seen. A photograph was next taken with both the concentrated solution and the gold electrodes long and the metal itself short, to show any lines developed by the chromium, but not by its solutions. Then the last four spectra taken gave the gold electrodes long, with short lines between, of the spark spectra of solutions containing 1, 0.1, 0.01, and 0.001 per cent, of the chromium respectively.

It has been found that the majority of the enhanced lines of chromium occur in the solar Fraunhofer spectrum, although some appear to be missing.

It has been stated that all solutions of violet salts of chromium show similar Chromium Absorption Spectrum due to the chromium ion. The band extends from 461μμ to 364.5μμ, while the beginning of complete absorption is at 260μμ in half-molar solution. In solutions of green complex salts of chromium, the absorption band and the limit of complete absorption are both inclined towards the red.

The absorption of X-rays by chromium in the form of potassium chromate has been studied.