The salicylate of colchicine is stable in water and may be given in doses of about one-thirtieth of a grain.
It is obtained by the oxidation of xanthene (methylene diphenylene oxide) with chromic acid; by the action of phosphorus oxychloride on disodium salicylate; by heating 2 2'-dioxybenzophenone with concentrated sulphuric acid; by distilling fluoran with lime; by the oxidation of xanthydrol (R.
Sodium phenolate is heated in a stream of carbon dioxide in an iron retort at a temperature of 180-220° C., when half the phenol distils over and a basic sodium salicylate is left.
CO 2 Na being thus formed; by continuing the heating under pressure this carbonate gradually changes into mono-sodium salicylate.
When boiled with calcium chloride and ammonia, salicylic acid gives a precipitate of insoluble basic calcium salicylate, C 6 H 4 ‹ 0 2 i Ca, a reaction which serves to distinguish it from the isomeric metaand para-hydroxybenzoic acids.