From Williamsburg Oil s:
Genuine Vermillion Oil Color The real Mercuric Sulphide. This has become very scarce lately and in fact is not always available. The touches of pure red in French Impressionist painting are true Vermillion. It is very high-keyed, almost orange, but never glaring and is, quite sweet. Health Hazard: Please note that this is very toxic paint. Use with extreme caution, do not eat, drink, or smoke when using this paint. Clean hands immediately after use. This paint is intended for use by professional artists only. It is not safe for use by children or amateurs.