3. METHOD OF EFFECTING THE DETECTION OF STRYCHNIA IN BEer, BY Graham and A. W. Hofmann.*

§ 250.

This method, which is based on the known fact that a solution of a salt of strychnia, when mixed and shaken with animal charcoal, yields its strychnia to the charcoal, will undoubtedly be found applicable also for the detection of other alkaloids. The process is conducted as follows:

Shake 30 grm. animal charcoal in 1 litre of the aqueous neutral or feebly acid fluid under examination; let the mixture stand for from 12 to 24 hours, with occasional shaking, filter, wash the charcoal twice with water, then boil for half-an-hour with 120 c.c. of spirit of wine of 80-90 per cent., avoiding loss of alcohol by evaporation. Filter the spirit of wine hot from the charcoal, and distil the filtrate; add a few drops of solution of potassa to the residual watery fluid, shake with ether, let the mixture stand at rest, then decant the supernatant ether. The ethereal fluid leaves, upon spontaneous evaporation, the strychnia in a state of sufficient purity to admit of its further examination by reagents.

MACADAM+ employed the same method in his numerous experiments to detect strychnia in the bodies of dead animals. He treated the comminuted matters with a dilute aqueous solution of oxalic acid in the cold, filtered through muslin, washed with water, heated to boiling, filtered still warm, from the coagulated albuminous matters, shook with charcoal, and proceeded in the manner just described. According to his statements, the residue left by the evaporation of the alcoholic solution was generally at once fit to be tested for strychnia. Where it was not so, he treated the residue again with solution of oxalic acid, and repeated the process with animal charcoal.

4. SEPARATION BY DIALYSIS.

§ 251.

The dialytic method devised by GRAHAM, and described in § 8, may also be advantageously employed to effect the separation of alkaloids from the contents of the stomach, intestines, &c. Acidify with hydrochloric acid, and place the matter in the dialyser. The alkaloids, being crystalloids, penetrate the membrane, and are found, for the greater part, after 24 hours, in the outer fluid; from this they may, then, according to circumstances, either be thrown down at once, after concentration by evaporation; or they may be purified by one of the above described methods.

II.

GENERAL PLAN OF THE ORDER IN WHICH SUBSTANCES
SHOULD BE ANALYSED FOR PRACTICE.

§ 252.

It is not a matter of indifference whether the student, in analysing for the sake of practice, follows no rule or order whatever in the * Chem. Soc. Quart. Journ., 5, 173. + Pharm. Journ. Trans., 16, 120, 160.

selection of the substances which he intends to analyse, or whether, on the contrary, his investigations and experiments proceed systematically. Many ways, indeed, may lead to the desired end, but one of them will invariably prove the shortest. I will, therefore, here point out a course which experience has shown to lead safely and speedily to the attainment of the object in view.

Let the student take 100 compounds, systematically arranged (see below), and let him analyse these compounds successively in the order in which they are placed. A careful and diligent examination of these will be amply sufficient to impart to him the necessary degree of skill in practical analysis. When analysing for the sake of practice only, the student must above all things possess the means of verifying the results obtained by his experiments. The compounds to be examined ought, therefore, to be mixed for him by a friend who knows their exact composition.

A. From 1 to 20.

AQUEOUS SOLUTIONS OF SIMPLE SALTS: e.g., sulphate of soda, nitrate of lime, chloride of copper, &c. These investigations will serve to teach the student the method of analysing substances soluble in water which contain but one base. In these investigations it is only intended to ascertain which base is present in the fluid under examination; but neither the detection of the acid, nor the proof of the absence of all other bases besides the one detected, is required.

B. From 21 to 50.

ONE ACID, or one

SALTS, ETC., CONTAINING ONE BASE AND METAL AND ONE METALLOID (in form of powder): e.g., carbonate of baryta, borate of soda, phosphate of lime, arsenious acid, chloride of sodium, bitartrate of potassa, acetate of copper, sulphate of baryta, chloride of lead, &c. These investigations will serve to teach the student how to make a preliminary examination of a solid substance, by heating in a tube or before the blowpipe; how to convert it into a proper form for analysis, i.e., how to dissolve or decompose it; how to detect one metallic oxide, even in substances insoluble in water; and how to demonstrate the presence of one acid. The detection of both the base and the acid is required, but it is not necessary to prove other bodies are present.

C. From 51 to 65.

that no

These inves

AQUEOUS OR ACID SOLUTIONS OF SEVERAL BASES. tigations will serve to teach the student the method of separating and distinguishing several metallic oxides from each other. The proof is required that no other bases are present besides those detected. No regard is paid to the acids.

D. From 66 to 80.

DRY MIXTURES OF EVERY DESCRIPTION. A portion of the salts should be organic, another inorganic; a portion of the compounds soluble in water or hydrochloric acid, another insoluble; e.g., mixtures of chloride of sodium, carbonate of lime, and oxide of copper :-of phosphate of magnesia and ammonia, and arsenious acid;-of tartrate of

lime, oxalate of lime, and sulphate of baryta ;-of phosphate of soda, nitrate of ammonia, and acetate of potassa, &c.

These investigations will serve to teach the student how to treat mixtures of different substances with solvents; how to detect several acids in presence of each other; how to detect the bases in presence of phosphates of the alkaline earths;-and they will serve as a general introduction to scientific and practical analysis. All the component parts must be detected, and the nature of the substance ascertained.

E. From 81 to 100.

NATIVE COMPOUNDS, ARTICLES OF COMMERCE, &c. Mineral and other waters, minerals of every description, soils, potash, soda, alloys, colors, &c.

III.

ARRANGEMENT OF THE RESULTS OF THE ANALYSES PERFOR MED FOR PRACTICE. § 253.

The manner in which the results of analytical investigations ought to be arranged is not a matter of indifference. The following examples will serve to illustrate the method which I have found the most suitable in this respect.

PLAN OF ARRANGING THE RESULTS OF EXPERIMENTS, Nos. 1-20. Colorless fluid of neutral reaction.

PLAN OF ARRANGING THE RESULTS OF EXPERIMENTS, Nos. 21—50. White powder, fusing in the water of crystallization upon application of heat, then remaining unaltered-soluble in water-reaction neutral.

The detected base being MgO, and the analysed substance being soluble in water, the acid can only be Cl, I, Br, S O,, NO,, A, &c. The preliminary examination has proved the absence of the organic acids and of nitric acid.

Ba Cl produces a white precipitate which H Cl fails to dissolve; consequently SULPHURIC ACID.

S and SO, not, because the substance is readily soluble in nitric acid.

Cr O, not, as the nitric acid solution is colorless.