Treatise on Poisons by Sir Robert Christison

1. _When concentrated_ it is oily-looking, colourless, or brownish from

having acted on organic particles, without odour, much heavier than water, and capable of quickly corroding animal substances. If from these properties, and its effect in reddening litmus, its exact nature be not considered obvious, it may be heated with a few chips of copper; when sulphurous acid is disengaged and may be readily recognised by its odour.