Cadmium Yellow

Also called Kings Yellow, this was a permanent color, but extremely poisonous. It is arsenic sulphide and could be quite lethal for the careless artist.

Chrome Yellow

WARNING! CONTAINS LEAD. FOR PROFESSIONAL USE ONLYNet vol 4 ozChrome Yellow Light is a chromate of lead, and is similar to the lead salt PbCrO4 that occurs naturally as the mineral crocoite. It is obtained synthetically as a yellow crystalline powder by precipitation from a solution of a lead salt (such as lead nitrate) and sodium chromate or sodium dichromate, and is used as a pigment either alone or in admixture with other compounds. Synthetic chrome yellow pigments are among several bright pigments with good hiding power that vary from light greenish yellow to reddish medium yellow, consisting essentially of normal lead chromate usually without extenders (such as barite or clay) but often other lead compounds (such as lead sulfate) for the lighter shades.

Introduced in 1797 the Chrome Yellows and the red and orange versions became popular due to their opacity, their bright colors and because they were inexpensive. Unfortunately they are also impermanent and tend to darken and react with other pigments. They survived until quite recently, but have shared the fate of other lead pigments in recent years.