|The reported data are not always in good agreement owing to the fact that vanadium in varying conditions of purity has been used for the determination of constants by the various investigators. Vanadium has been variously described as: a bright grey metal which appears as lustrous, silver-white crystals under the microscope; a grey powder in which glistening, needle-like crystals can be seen with the naked eye; small crystals, of differing crystalline form, which appear blue or olive-green on the surface, and which possess flat, glistening faces; silvery, well-formed crystals of twin rhomboids, belonging to the hexagonal system; similar in appearance to cast iron which is rich in carbon, and sometimes forms long prisms. X-ray analysis shows, however, that vanadium possesses a body-centred cubic lattice crystal of side equal to 3.04 A; the distance between the nearest atoms is 2.63 A. The metal is rather brittle but extremely hard; its hardness on Mohr's scale is 7.5, so that it cannot be scratched even by quartz or steel. The density of pure vanadium is 6.0 at 22° C., 6.025 at 15° C. Other reported figures vary with the purity of the sample: 5.688 at 18.7° C. for a specimen 98 per cent, pure; 5.53, 5.5 at 15° C., 5.8 at 20° C., 5.97 and 5.987 at 20° C. for samples about 95 per cent, pure. The melting-point of the purest vanadium obtainable is given as 1720°±20° C. Other reported figures are 1650° C., 1680° C., about 1700° C., 1715° C., 1750°±30° C., below 1760° C. The specific heat of vanadium is 0.120 between 20° and 100° C., 0.1153 between 0° and 100° C., 0.1240, 0.1259, 0.1235 to 0.1258. The metal is non-magnetic; even when subjected to a temperature of -259° C. it gives only very feeble indication of ferromagnetism. The specific electrical resistance of cold-worked vanadium metal is 26×10-6 ohms per cc. at 20° C.; the temperature coefficient of resistance between 20° and 150° C. is 0.0028. Vanadium can be cold-rolled into wire; it has a tendency to become harder when so treated and annealing is beneficial. Photomicrographs of vanadium metal are given in the reference cited. |
The refractive index of vanadium is 3.03, the coefficient of absorption 3.51, and the reflexion capacity 57.5 per cent, for yellow light of wave-length λ = 5790. Vanadium compounds do not impart any coloration to the ordinary Bunsen flame, and do not furnish any characteristic line spectra even in the oxyacetylene flame. The flame produced between carbon electrodes consists of a reddish-purple core with a yellowish-green shell and a red edge.
Lockyer and Baxendall investigated the arc spectrum of vanadium by volatilising vanadium chloride and vanadium oxide between poles of pure silver. Using a Rowland grating, over 650 lines were obtained in the region between λ 3887 and λ 4932, the more intense of which are indicated in the following table:
Arc spectrum of Vanadium
|Wave-length||Intensity of Line. Max. = 10.|
The most intense lines produced by vanadium in the spark spectrum are set out in the table on the opposite page.
The most intense lines in the spark spectrum of a metal are not necessarily the most persistent when solutions containing the metal in gradually increasing dilution are sparked. By photographing the spectra given by solutions containing one gram of the metal, usually in the form of its chloride, in every 100, 1000, 10,000, and 100,000 parts of solution, it has been possible to draw up a table showing the most persistent lines under these conditions. The application of the knowledge of the residuary lines given by a metal renders possible its estimation in a solution of unknown strength.
Spark spectrum of Vanadium
|Wave-length.||Relative Intensity of Line. *|
|*There is a general want of uniformity in the standards that have been adopted by different observers for measuring the relative intensities of spectral lines. The intensity figures given in this table and in the preceding table do not refer to a common standard of measurement.|
Measurements of wave-lengths in X-ray high frequency spectra are given in the references cited. The electron configuration of vanadium atoms has been investigated. Attempts have been made,to bombard the vanadium atom with the view to obtaining hydrogen nuclei, but without result. Vanadium is not radioactive.