(L. cadmia; Gr. kadmeia - ancient name for calamine, zinc carbonate) Discovered byStromeyer in 1817 from an impurity in zinc carbonate. Cadmium most often occurs in smallquantities associated with zinc ores, such as sphalerite (ZnS). Greenockite (CdS) is theonly mineral of any consequence bearing cadmium. Almost all cadmium is obtained as aby-product in the treatment of zinc, copper, and lead ores. It is a soft, bluish-whitemetal which is easily cut with a knife. It is similar in many respects to zinc. Failure toappreciate the toxic properties of cadmium may cause workers to be unwittingly exposed todangerous fumes. Silver solder, for example, which contains cadmium, should be handledwith care. Serious toxicity problems have been found from long-term exposure and work withcadmium plating baths. Exposure to cadmium dust should not exceed 0.01 mg/m3 (8-hour time-weighted average, 40-hourweek). The ceiling concentration (maximum), for a period of 15 min, should not exceed 0.14mg/m3. Cadmium oxide fumeexposure (8-hour, 40-hour week) should not exceed 0.05 mg/m3, and the maximum concentration should notexceed 0.05 mg/m3. Thesevalues are presently being restudied and recommendations have been made to reduce theexposure. In 1927 the International Conference on Weights and Measures redefined the meterin terms of the wavelength of the red cadmium spectral line (i.e. 1m = 1.553,164.13wavelengths). This definition has been changed (see under Krypton).