All forms of arsenic are toxic to some degree, but arsenic trioxide is especially scary because its arsenic is bioavailable and it doesn’t take much to be effective. Arsenic trioxide, also known as “the poison of kings and the king of poisons” and “inheritance powder” is a white powder with no taste or odor that dissolves readily in warm food or drink. According to the book The Arsenic Century: How Victorian Britain was Poisoned at Home, Work, & Play” by James C. Whorton, it was used to poison people for centuries until a reliable method of detecting arsenic in tissues was developed in the mid 1800’s. Not all arsenic trioxide makes a good poison though – no one is likely to mistake the gray/black arsenic trioxide waste material (ATWM) generated during gold mining operations for something that belongs in food. For more information about why arsenic used to make a good poison, check out our October 2019 newsletter or read Whorton’s fascinating book.