PART VL— ALKALOIDS AND POISONOUS VEGETABLE 
PRINCIPLES SEPARATED FOR THE MOST PART BY 
ALCOHOLIC SOLVENTS. 
DIVISION I.—VEGETABLE ALKALOIDS. 
I.—General Methods of Testing and Extracting Alkaloids. 
§ 307. General Tests for Alkaloids. —In order to ascertain whether 
an alkaloid is present or not, a method of extraction must be pursued 
which, while disposing of fatty matters, salts, etc., shall dissolve as little 
as possible of foreign substances—such a method, e.g ., as the original 
process of Stas, or one of its modern modifications. 
If to the acid aqueous solution finally obtained by this method a 
dilute solution of soda be added, drop by drop, until it is rendered 
feebly alkaline, and no 'precipitate appear, whatever other poisonous 
plant-constituents may be present, all ordinary alkaloids 1 are absent. 
In addition to this negative test, there are also a number of sub¬ 
stances which give well-marked crystalline or amorphous precipitates 
with alkaloids. 
§ 308. These may be called “ group reagents.” The chief members 
of the group reagents are—iodine dissolved in hydriodic acid, iodine 
dissolved in potassic iodide solution, bromine dissolved in potassic 
bromide solution, hydrargo-potassic iodide, bismuth-potassic iodide, 
cadmic potassic iodide ; the chlorides of gold, of platinum, and mercury ; 
picric acid, picrolonic acid, gallic acid, tannin, chromate of potash, bi¬ 
chromate of potash, phospho-molybdic acid, phospho-tungstic acid, silico- 
tungstic acid, and Frohde’s reagent. It will be useful to make a few 
general remarks on some of these reagents. 
Iodine in hydriodic acid gives either crystalline or amorphous pre¬ 
cipitates with nearly all alkaloids ; the compound with morphine, for 
example, is in very definite needles ; with dilute solutions of atropine, 
1 In the case of morphine tartrate, this test will not answer. See the article on 
Morphine. 
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