The following confirmatory tests should be applied: (1) Upon treating the substance with nitric acid, it acquires a blood-red color; (2) the addition of a solution of a persalt of iron produces an evanescent blue coloration; (3) chloride of gold is colored blue, when treated with the alkaloid; (4) the substance reduces iodic acid: this reduction is detected by adding to the acid a little starch-paste, which turns blue upon the liberation of the iodine; (5) permanganate of potassa, if heated with the substance, is reduced and acquires a green color. IDENTIFICATION OF DIGITALINE, PICROTOXINE AND COLCHICINE. It has already been remarked that in exhausting the first acid solution with ether--previous to the neutralization, according to Otto's method--colchicine, a weak alkaloid, digitaline, an indefinite mixture, picrotoxine (which appears to possess the properties of an acid), and traces of atropine, pass into solution. The ether is evaporated on a water-bath to dryness, the residuary mass treated with slightly warmed water and the solution filtered from the undissolved resinous matter. The aqueous solution is next rendered feebly alkaline by addition of soda lye, and then well agitated with ether, until this fluid ceases to leave a residue upon evaporation. The ethereal solution is now decanted, and the water present removed by means of chloride of calcium. If it is evaporated, a residue containing the _colchicine_, _digitaline_ and traces of atropine (mixed possibly with a minute quantity of picrotoxine, which is here left out of consideration) is obtained. _a._ The _alkaline solution_, from which the ether has been removed, is acidulated with hydrochloric acid and again shaken with ether. The _picrotoxine_ present is now dissolved, and upon dehydrating (by means of fused chloride of sodium) and evaporating the ethereal solution can be obtained in crystals. The crystals of picrotoxine are easily recognized by their forming in feathery tufts as well as by their length and silky brilliancy. Should crystals fail to form in a short time, it is advisable to take up the residue, left by the evaporations of the ether, with slightly warmed alcohol, and to allow the latter to spontaneously evaporate on a watch-glass, or, if the quantity of substance is exceedingly minute, on the slide of a microscope. After determining the form of the crystals, it should be ascertained that they possess an intense bitter taste and exhibit the other characteristic properties of picrotoxine. The following reaction is distinctive: If the crystals are dissolved in an aqueous solution of soda and a few drops of "Fehling's solution"[O] added, a reddish precipitate of cuprous oxide is formed. [O] An alkaline solution of tartrate of copper, employed in the examination of sugar, urine, and wine.--_Trans._