Treatise on Poisons by Sir Robert Christison

throw down any lead which may remain in solution. It is then to be filtered while _cold_, and evaporated sufficiently in a vapour-bath. The solution in this state will sometimes be sufficiently pure for the application of the tests for morphia; but in most cases it is necessary, and in all advisable, to purify it still farther. For this purpose the morphia is to be precipitated with carbonate of soda; and the precipitate having been collected, washed, and drained on a filter, the precipitate and portion of the filter to which it adheres are to be boiled in a little pure alcohol. The alcoholic solution,—filtered, if necessary,—will give by evaporation a crystalline residue of morphia, which becomes orange-red with nitric acid, and blue with perchloride of iron. The latter property I have sometimes been unable to develope when the former was presented characteristically.