β. The solution in sulphuric acid β. It dissolves with a yellow remains yellow; potassic cyanide colour, changing into fallow- and caustic potash colour it, on brown. warming, blood-red. _Constituents of aconite plant _Picric acid._ and products of the decomposition of Aconitine._ B. IT IS COLOURLESS, LIQUEFIES B. IT IS WHITE, SHARP-TASTING, EASILY, AND SMELLS STRONGLY. AND REDDENS THE SKIN. _Camphor and similar matters._ _Capsicin._ It may be expected that the substances mentioned under the heads 1, 2, and 3 will be, in general, fully obtained by degrees. This is not the case, however, as regards piperin and picric acid. IV. The watery fluid is now similarly shaken up with benzene, and the benzene removed and evaporated. Should the evaporated residue show signs of an alkaloid (and especially of theine), the watery fluid is treated several times with a fresh mixture of benzene, till a little of the last-obtained benzene extraction leaves on evaporation no residue. The benzene extracts are now united, and washed by shaking with distilled water; again separated and filtered, the greater part of the benzene distilled from the filtrate, and the remainder of the fluid divided and evaporated on several watch-glasses. The evaporated residue may contain theine, colchicine, cubebin, digitalin, cantharidin, colocynthin, elaterin, caryophylline, absinthin, cascarillin, populin, santonin, &c., and traces of veratrine, delphinine, physostigmine, and berberine. A remnant of piperin and picric acid may remain from the previous treatment with petroleum ether. THE BENZENE RESIDUE FROM THE ACID SOLUTION. 1. IT IS CRYSTALLINE. 2. IT IS AMORPHOUS. A. WELL-FORMED, COLOURLESS A. COLOURLESS OR PALE YELLOW CRYSTALS. RESIDUE. α. Sulphuric acid dissolves the α. Sulphuric acid dissolves it at hair-like crystals without change first yellow; the solution be- of colour; evaporation with chlo- coming later red. Fröhde’s re- rine water, and subsequent treat- agent does not colour it violet. ment with ammonia, gives a _Elaterin._ murexide reaction. _Theine._ β. Sulphuric acid leaves the β. Sulphuric acid dissolves red; rhombic crystals uncoloured. The Fröhde’s reagent violet-red;[333] substance, taken up by oil, and tannic acid does not precipitate. applied to the skin, produces a _Populin._ blister. _Cantharidin._