Treatise on Poisons by Sir Robert Christison

4. _Arsenite of Potass_.

This salt is an object of some importance to the medical jurist, as it forms the basis of a common medicine, Fowler’s Solution, or the Tasteless Ague Drop. This preparation contains in every ounce four grains of arsenious acid. It has a brownish-red colour, and an odour of lavender. It is strongly alkaline to litmus. When acidulated with hydrochloric acid, hydrosulphuric-acid gas causes in it a dirty brownish-yellow precipitate; and Reinsch’s process will detach arsenic from it upon copper in a state capable of being subjected to the usual tests [see p. 214].