c. 13) was an Act of the Parliament of the United Kingdom, passed in 1851, during the reign of Queen Victoria.

Arsenic was at the time widely used as a pigment and in agricultural products such as sheep dressings; the Act was introduced to address increasing public concern over accidental and deliberate arsenic poisonings.

The Act required those selling such products to maintain a written and signed record of those to whom they had sold arsenic, including the quantity and its stated purpose.

It also required that unless the arsenic was to be used for a purpose that would make such treatment unsuitable, for example in medical or agricultural applications, it had to be coloured with either soot or indigo.

[3] The maximum penalty for breaching the terms of the Act, or providing false information, was £20,[4] equivalent to about £13,000 as of 2014.