Barium Chromate, also known as Baryte yellow or in older literature as lemon yellow of even ultramarine yellow. This is a very rare color in oils, and is currently only produced by Michael Harding. Blockx used to manufacture this color, but the Blockx version has not been seen available in the United States for some time. It is an enchanting green-yellow. However this fascinating color is also has its hazards. It often has a greenish note to the pale yellow.
This pigment is toxic.
Field wrote in the late 19th century that the term Lemon Yellow referred to Barium Chromate. He also cautioned that well-made forms are permanent but that at that time they were sometimes lacking in stability due to poor manufacture. He also mentions offhandedly that they are the only chromate that could be called "perfectly permanent". Whether that has been borne out in the last century is unclear, but it is an interesting historical comment.
Field mentions two different kinds of Lemon Yellow, the regular color as well as a paler variety. He describes regular lemon yellow as "Is of a vivid lemon hue, very pure and clear, and entirely free from the slightest tinge of orange. It has not much power, and is semi-opaque." The lighter kind is more of a "primrose hue."
