The lattice constant and coefficient of expansion of chromium

The most important use of chromium, other than as an alloying element in the manufacture of stainless steel, is for electroplating; to form a coating on other metals for corrosion prevention in order to procure longer life, and to achieve a decorative effect. The physical properties of chromium are important in the effectiveness of its uses, and its lattice constant, as well as coefficient of thermal expansion, seem worthy of exact determination. A number of research workers, over a span of thirty years, have spent considerable effort in determining the aforementioned constants. However, their results do not check, and the degree of accuracy differs from person to person. Chromium near 37° C was identified by M. E. Fine as showing discontinuous changes of coefficient of expansion, Young\u27s modulus, internal friction, electrical resistivity and thermoelectric power. Although the X-ray diffraction pattern gave no clue, a difference in the thermal expansity has been found. D. MacNair determined the expansity of chromium by means of an interferometric dilatometer, with the result that near 38° C the thermal expansity curve went through an inflection point, corresponding to a minimum in the coefficient of expansion found by Fine. The purpose of this research is to check the results obtained by MacNair and Fine concerning the expansion of chromium, and to determine the exact lattice constant and thermal expansion of this metal by the X-ray powder method, using different samples, and at different temperatures within the range of 10° to 50° C --Introduction, pages 1-2