Dr. Guy’s “subliming cell” is a ring of glass tubing about ⅛-inch long and ⅓ to ½-inch diameter, ground true and smooth at top and bottom, resting on a circle of thin microscope glass, and covered with another similar circle. The alkaloid, thoroughly dry, is placed on the lower disc (a drop of the solution may be evaporated on it), the whole fitted together, and floated on mercury, or better, fusible metal, contained in a small glass beaker nearly full, supported on wire gauze over a small flame. A thermometer held by a clamp dips in the liquid metal. With a hand lens of as high power as possible, the melting point, and also the point when the first sublimate occurs on the upper glass, may be observed. As soon as the sublimate has become sufficiently distinct, the upper disc is removed, replaced by another, and examined under ¼-inch power of the microscope. The heat is slowly raised till charring occurs, and anything characteristic noted. _Morphia_ gives a clouding, consisting of minute dots, at 150° C.; from 188° to 200° C., distinct crystals are obtained; then it commences to brown, melt, and carbonize. _Strychnia_ gives a minute sublimate of fine needles at 169° C., and melts at about 221° C. _Brucia_ melts at 151° C., browns easily, but gives no true sublimate. _Aconitine_ or aconitia melts at 183° to 184° C. _Pseudaconitine_ melts at 104° to 105° C., and easily decomposes, giving off water. _Commercial aconitine_ usually melts below 100° C., and gives an amorphous sublimate above 150° C. The reactions of the other alkaloids will be found in Blyth’s Practical Chemistry. In order to avoid repetition, the mode of preparing the general reagents for alkaloids will be given here. 1. _Mayers Reagent_, potassio-iodide of mercury, already described (p. 7; Liebig’s Annalen, 133, 286), gives white precipitates with almost all alkaloids. The latter can be recovered from the precipitate by treating it with a solution of zinc chloride mixed with caustic soda. (Mayer.) 2. _Potassium tri-iodide_, a solution of iodine in potassium iodide, gives a brown or reddish precipitate.[6]