260 poisons: their effects and detection. [§§ 319,320. 
§ 319. Behrens’ Method of Identification of the Alkaloids.—The micro-chemical 
methods of Behrens, aided by a few special tests, are useful for the identification of 
certain «of the alkaloids. The results are trustworthy, provided similar tests are 
applied to pure samples of the particular alkaloid believed to be present. 
Behrens 1 divides the alkaloids as follows :— 
1. Alkaloids which are capable of being distilled from an aqueous solution. 
2. Alkaloids soluble in water, but which cannot be distilled. 
3. Difficultly soluble bases precipitable by sodium carbonate soluble in soda, but 
precipitable from the alkaline solution by sodium bicarbonate or ammonium carbonate, 
such as morphine, apomorphine, and cupreine. 
4. The rarer opium bases precipitable by sodic carbonate insoluble in caustic 
soda solution, such as narceine, narcotine, papaverine, and thebaine. 
5. Bases precipitable by sodium carbonate, but not precipitable by sodium 
bicarbonate ; strychnine, brucine, veratrine. 
6. Quinine bases precipitable by sodium carbonate, also by sodium bicarbonate 
if not in too dilute solution. 
7. The rare quinine bases. 
The individual members of the group are then identified by their behaviour to 
potassic ferrocyanide, cobalt thiocyanide, platin chloride, and other reagents described 
in this work under the particular alkaloid. 
§ 320. Sublimation of the Alkaloids. —A very beautiful and elegant 
aid to the identification of alkaloids, and vegetable principles generally, 
is their behaviour towards heat. 
Alkaloids, glucosides, the organic acids, etc., when carefully heated, 
either—( 1 ) sublime wholly without decomposition (like theine, cytisin, 
and others) ; or (2) partially sublime with decomposition ; or (3) are 
changed into new bodies (as, for example, gallic acid) ; or (4) melt and 
then char ; or (5) simply char and burn away. 
Many of these phenomena are striking and characteristic, taking place 
at different temperatures, subliming in characteristic forms, or leaving 
characteristic residues. 
One of the first to employ sublimation systematically, as a means of 
recognition of the alkaloids, etc., was Helwig . 2 His method was to place 
a small quantity (from \ to 40 V 0 a mgrm.) in a depression on platinum 
foil, cover it with a slip of glass, and then carefully heat by a small 
flame. After Helwig, Dr Guy 3 greatly improved the process by using 
porcelain discs, and more especially by the adoption of a convenient 
apparatus, which may be termed “ the subliming cell.” It is essentially 
composed of a ring of glass from J to f of an inch in thickness, such as 
may be obtained by sections of tubing, the cut surfaces being ground 
perfectly smooth. This circle was converted into a closed cell by resting 
on it one of the ordinary thin discs of glass used as a covering for micro¬ 
scopic purposes, and supporting a similar disc. The cell was placed on 
a brass plate, provided with a nipple, which carried a thermometer, and 
was heated by a small flame applied midway between the thermometer 
and the cell ; the heat was raised very gradually, and the temperature at 
1 Zeit. f. anal. Ghemie, 1904, p. 333. 
2 Das Mikroscop in der Toxicologic. 
3 Pharm. Journ. Trans. (2), viii. 719 ; ix. 10, 58. Forensic Medicine , London, 1875. 
