For all the portrait painters out there..
Sometimes known as Barium Yellow, this is Barium Chromate, introduced into painting after the Lead Chromates, circa 1820.
Unlike those, it has proved to be permanent and non-reactive. By itself a sick looking, acidy yellow with weirdly green overtones, its low tint power facilitates mixes with Magenta and the cooler reds, producing beautifully modulated greys sought in certain passages of flesh painting.
Average Drying. Opaque. Excellent Lightfastness. Low Oil Content. Toxic