Prep. The same as iodide of potassium, substituting an equivalent quantity of bromine for iodine. It can also be formed by the second or iron process.

Prop. & Comp. This salt forms white transparent cubic crystals, closely resembling the iodide, with no odour, but a pungent saline taste, readily soluble in water, less soluble in spirit. Its watery solution gives a white crystalline precipitate with tartaric acid. When its solution is mixed with a little chlorine, ether agitated with it, on rising to the surface exhibits a red colour. A solution of the salt mixed with mucilage of starch and a drop of an aqueous solution of bromine, does not exhibit any blue colour, indicating the absence of iodine. Composition (K Br). Ten grains require for complete decomposition 84 measures of the volumetric solution of nitrate of silver, equivalent to 6.72 grains of bromine.

Therapeutics. Bromide of potassium, when pure, does not give rise to the symptoms of coryza produced by the iodide. It acts as a powerful alterative, and may be used with advantage in certain forms of chronic disease, as syphilitic skin affections, etc. In large doses, sleepiness, drowsiness, and dull headache are sometimes produced, and in still larger doses it causes some loss of power over the lower extremities, and exerts a most powerful influence on the generative organs, lowering their functions in a remarkable degree; it is found to be a most valuable remedy in diseases dependent on and accompanied by excitement or over-action of these organs, and may be given with advantage in nymphomania, priapism, and certain forms of monorrhagia; as likewise in nervous convulsive diseases dependent on uterine irritation, and in some ovarian tumours. It appears also to produce an anaesthetic condition of the larynx and pharynx, and hence has been usefully employed in examinations and operations on these parts.

Dose. 5 gr. to 15 gr. and upwards.

Adulteration. A few years since bromide of potassium was apt to contain iodide of potassium, sometimes in large amounts; this can be detected by the starch test above given. It may likewise contain bromate of potash (KO, Br O5).