Characters. - A transparent, colourless, or not more than straw-coloured, liquid, odourless, and having a sweet acidulous taste. Sp. gr. 1.300.

Tests. - If bisulphide of carbon be poured into a small portion of the syrup and a little chlorine water added, the disulphide will separate with a violet colour in shaking. Gelatinised starch should not give to the syrup more than a faint bluish tinge; and the precipitate by silver nitrate ought to be insoluble in ammonia. 3I.9 grammes of the syrup require, for complete precipitation, 25 cubic centimetres of the standard solution of nitrate of silver.

Dose. - 1 to 4 fluid drachms.

Action and Uses. - Hydriodic acid may be given in asthma and bronchitis instead of iodide of potassium, to which its action is similar (p. 560).