A strong solution of ALCOHOL in water. Proof spirit is one containing 57 per cent of alcohol by volume or 49 per cent by weight, and is so-named because it can stand the proof of just catching fire. Rectified spirit contains 90 per cent of alcohol by volume or over 85 per cent by weight. Methylated spirit (also known as wood naphtha or wood spirit) is distilled from wood; when taken internally it is a dangerous poison producing NEURITIS, especially neuritis of the optic nerves, which may result in blindness. Methylated spirit is used to harden the skin for the prevention of bed sores and foot soreness.