Prepd by heating cadmium in a current of hydrogen selenide and subliming the product in hydrogen at a dull red heat: Margottet, Recherches sur les Sulfures, les Séléniures, et les Tellures Métalliques, Paris (1879); by passing hydrogen selenide over heated cadmium chloride and washing with warm water: Grzenkowsky, Ueber Selenide und Erdalkaliferrocyanide (Danzig, 1925); from cadmium sulfate and hydrogen selenide: Wagenknecht, Juza in Handbook of Preparative Inorganic Chemistry vol. 2, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1965) p 1099. Prepn of high purity CdSe: Taylor, Conn, US 3540859 (1970 to Merck & Co.).