Definition. - A solution of hydriodic acid, HI, containing not less than 10 per cent. by weight of the absolute acid, and about 90 per cent. of water.

Description and Properties. - A clear, colorless liquid, odorless, and having an acid taste. It should not become colored on keeping. Miscible in all proportions with water or alcohol. In the present preparation there is a small quantity of hypo-phosphorous acid. This acts as a preservative by reducing any iodine set free to hydriodic acid. The method of preparing it (for which see the Pharmacopoeia) is that recommended in the 1890 U. S. Pharmacopoeia in connection with the preparation of Syrupus Acidi Hydriodici; the latter is now prepared from the Acidum Hydriodicum Dilutum. The method is simple and requires no special apparatus or chemicals (Hunt).

Dose. - Average dose: 8 minims (0.5 Cc), U. S. P.

Caution. - Should be kept in small, amber-colored, glass-stoppered bottles, protected from the light.