§§ 3 i 6 - 3 I 8 .] identification of the alkaloids. 259 
§ 316. Scheibler’s Process. —This is to precipitate the phosphotungstate of the 
alkaloid, and then to liberate the latter by digesting the precipitate with either 
hydrate of barium or hydrate of calcium, dissolving it out by chloroforfii, or, if 
volatile, by simple distillation. The details of Scheibler’s process are as follows :— 
The organic mixture is repeatedly extracted by water strongly acidified with 
sulphuric acid ; the extract is evaporated at 30° to the consistence of a thin syrup ; 
then diluted with water, and, after several hours’ standing, filtered in a cool place. 
To the filtered fluid phosphotungstic acid is added in excess, the precipitate filtered, 
washed with water to which some phosphotungstic acid solution has been added, 
and, while still moist, rinsed into a flask. Caustic baryta or carbonate of potash is 
added to alkaline reaction, and after the flask has been connected with bulbs con¬ 
taining HC1, it is heated at first slowly, then more strongly. Ammonia and any 
volatile alkaloids are driven over into the acid, and are there fixed, and can be 
examined later by suitable methods. The residue in the flask is carefully evaporated 
to dryness (the excess of baryta having been precipitated by C0 2 ), and then extracted 
by strong alcohol. On evaporation of the alcohol, the alkaloid is generally sufficiently 
pure to be examined, or, if not so, it may be obtained pure by re-solution, etc. The 
phosphotungstate is more conveniently decomposed by lead acetate. 
Scheibler’s process cannot be used with advantage directly on watery- 
acid extracts of the organs, for it not only precipitates alkaloids, but 
also invariably gives voluminous precipitates with ordinary flesh ex¬ 
tracts, so that a preliminary purification from albuminous matters by 
alcohol or glycerin tannin is necessary. 
§ 317. Grandval and Lajoux’s Method . 1 —The alkaloids are precipitated from a 
solution slightly acidified by hydrochloric or sulphuric acid by a solution of hydrarg- 
potassium iodide. The precipitate is collected on a filter, washed, and then trans¬ 
ferred to a flask ; drop by drop, a solution of sodium sulphide is added ; after each 
addition the suspended precipitate is shaken and allowed to stand for a few minutes, 
and a drop of the liquid taken out and tested with lead acetate ; directly a slight 
brown colour appears, sufficient sodio sulphide has been added. The liquid is now left 
for half an hour, with occasional shaking. Then sulphuric acid is added until it is 
just acid, and the liquid is filtered and the mercury sulphide well washed. In the 
filtrate will be the sulphate of any alkaloid in solution ; this liquid is now made 
alkaline with soda carbonate and shaken up, as in Dragendorff’s process, with 
appropriate solvents ; such, for example, as ether, or chloroform, or acetone, or amylio 
alcohol, according to the particular alkaloid the analyst is searching for, and the 
solvent finally separated and allowed to evaporate, when the alkaloid is found in the 
residue. 
§ 318. Identification of the Alkaloids. —Having obtained, in one way or other, 
a crystalline or amorphous substance, supposed to be an alkaloid, or, at all events, an 
active vegetable principle, the next step is to identify it. 
In medico-legal researches there is seldom any considerable quantity of the 
material to work upon. Hence the greatest care must be taken from the commence¬ 
ment not to waste the substance in useless tests, but to study well at the outset what 
—by the method of extraction used, the microscopic appearance, the reaction to 
litmus-paper, and the solubility in different menstrua—it is likely to be. However 
minute the quantity may be, it is essential to divide it into different parts, in order 
to apply a variety of tests ; but as any attempt to do this on the solid substance will 
probably entail loss, the best way is to dissolve it in a watch-glass in half a c.c. of 
alcohol, other, or other suitable solvent. Droplets of this solution are then placed 
on watch-glasses or slips of microscopic glass, and to these drops, by the aid of a 
glass rod, different reagents can be applied, and the changes watched under the 
microscope as the drops slowly evaporate. 
1 “ Dosage des alcaloides a l’aide de l’iodure double de mercure et de potassium,” 
par MM. A. Grandval et Henri Lajoux, Journ. de Pharmacie, 5 ser., xxviii. 152-156. 
