arsenic
[U] Uncountable
This word carries a heavy association with clandestine crime and historical poisonings. While it is a legitimate chemical element used in semiconductors and wood preservatives, in common parlance it evokes a sense of lethal danger and betrayal. Because of its colorless and tasteless nature when dissolved, the term is often used in literature and film as a symbol for a hidden, invisible threat that kills slowly and silently.
Used as a mass noun to describe the chemical substance or the element itself.