1814

Paris Green

There are several broad themes in the history of chemistry: stronger and better materials, life-saving new drugs, and life-destroying weapons and explosives, among others. Then there are the pigments and dyes that make paints and clothing colorful. This area of chemistry has had huge successes and a few huge failures. The story of Paris green falls into both categories. Developed in 1814 as a replacement for the less durable Scheele’s green, this vivid crystalline powder was used to dye clothing, wallpaper, candles, and even food in the nineteenth century. It was relatively inexpensive and more colorful than the alternatives, but unfortunately it was also a compound of arsenic. As such, some very decorative William Morris wallpapers have turned out to be dangerously arsenic-laden, and Morris himself was even on the board of directors for one of the largest arsenic mining companies in the world. Coloring cakes and saturating one’s fashionable walls with green arsenic compounds is exactly as bad an idea as it sounds, and toxicologists are still not sure what the worst aspect of those green walls might have been. The powdery flakes of pigment released over time were bad enough, but dampness (and the enzymatic actions of mold) also released volatile arsenic compounds into the air. Arsenic’s poisonous effects are notoriously slow-moving, so although people understood that some forms of it were toxic, the realization that there were actually no safe forms took a painfully long time. Fortunately, other less insidious pigments were invented that displaced Paris green, which stayed on the market as an insecticide and rat poison.

Notably, the high levels of arsenic found in forensic samples of Napoléon Bonaparte’s hair have led some researchers to speculate that the green wallpaper of his prison home on the island of Helena may have contributed to his demise. The era of poisonous Paris green left quite a mark in some areas of the world. Well into the twentieth century, dyed green candies sold poorly in Scotland, as older customers regarded them with suspicion. By then there was no cause for alarm, but one can understand the reaction.

Some of William Morris’s favorite wallpaper is displayed in this nineteenth-century room interior. Who would have thought that interior decorating could be so deadly?