True Emerald Green is some form of paris green made from blue vitriol, acetic acid and white arsenic. While very beautiful in shade from its brightness and vivacity of color, its drawbacks are so many as to have caused its use as a paint to be practically discontinued. Though permanent when used as an oil color and so brilliant as to cause ordinary chrome green to appear dull and lifeless; it is very transparent, weak, and above all, extremely poisonous, as are all the copper arsenate greens. It is particularly adapted for use on surfaces exposed to the action of salt water, where it is quite permanent, and is, therefore, used in paints and anti-fouling compositions for ships bottoms.

Paris green is of interest mainly as an insecticide. Its purity can be tested by adding a little of the suspected sample to a boiling solution of dilute nitric or muriatic acid. It should dissolve perfectly and give no precipitate when a few drops of barium chloride solution are added. An undissolved residue indicates barytes or some similar adulterant.