Origin. - Prepared by neutralizing freshly prepared solution of hydriodic. acid with strontium carbonate, concentrating the filtrate, and crystallizing.

Description and Properties. - Colorless, transparent, hexagonal plates, odorless, and having a bitterish, saline taste; deliquescent and colored yellow by exposure to air and light. Soluble in 0.5 part of water, also soluble in alcohol, and slightly in ether. It should be kept in dark, amber-colored, glass-stoppered vials.

Dose. - 2-30 grains (0.12-2.0 Gm.) [7 1/2 grains (0.5 Gm.), U. S. P.].