remove the last trace of ammonia, the dish containing the alkaloid is placed for a moment in vacuo, over sulphuric acid. We thus obtain the alkaloid in the pure state; to ascertain its nature, we must now carefully examine its physical and chemical properties.

Conicine is easily distinguished from nicotine by its penetrating and benumbing odor. When mixed with a little water, it floats on its surface as an oily drop, while nicotine dissolves. If, to this mixture of conicine and water, some chlorine-water is added, drop by drop, a white precipitate is produced (v. § 105). If, to this mixture, or solution, of alkaloid and water, a solution of iodine is added, a sulphur-yellow precipitate is at first produced; on addition of a larger quantity of the reagent, a brown, hydrous precipitate is thrown down. The same liquid gives yellow precipitates with terchloride of gold and with bichloride of platinum. On neutralizing the alkaloid with oxalic acid, its odor disappears, and is again brought forth on addition of caustic soda (v. § 104–105).

§ 120. If the indications, obtained by evaporating a portion of the ethereal solution (§ 117), do not point to the presence of a volatile alkaloid, the contents of the vessel from which this portion was taken are treated in the same manner as described § 118. But to effect a complete solution of the alkaloid, a larger quantity of ether is required, because the fixed poisonous alkaloids are only little soluble in this liquid.*

*It is the insolubility in ether of the salts of the alkaloids which enables us to free them from substances soluble in this liquid, and which would otherwise prevent their crystallization, and interfere

The different ethereal solutions are united, and exposed to spontaneous evaporation. There remains either a solid residue, or a colorless, milky liquid, in which solid particles are held in suspension. It smells strongly of animal matter, offensive but not pungent, and changes permanently the color of red litmus-paper.

It frequently happens that, on evaporation of the ethereal solution, there remains, in the upper part of the dish, a yellow ring, consisting of the alkaloid in an amorphous, and rather impure condition, but

with the reactions. I consider this treatment with ether a very necessary operation, not only in cases of a volatile, but also in those of a fixed alkaloid. Let us take, by way of illustration, an article of food containing strychnine. Let the substance be treated with strong alcohol, and oxalic or tartaric acid; let the extract be separated from the resi due by filtration, and evaporated; let the resulting aqueous solution be again filtered, to remove fatty and resinous matters, etc., which may have separated; let the filtrate again be evaporated, and the residue be exhausted with cold anhydrous alcohol; let the alcoholic solution be evaporated, and the residue be dissolved in a small quantity of water (the process described § 116-117). Let this solution be divided into two portions. To the first portion, let some bicarbonate, or caustic alkali be added; let the mixture be agitated with ether, and the ethereal solution be evaporated. Let the second portion be agitated with ether as long as this solvent takes up any coloring matter, and the colored ether be removed; let, then, the alkaloid be set free by an alkali, dissolved in ether, and this solution be evaporated. On comparing the two residues, a great difference will be found. The second process yields the alkaloid in a state of greater purity than the first, and almost invariably in a crystallized condition. This is of paramount importance, since it enables us to observe the characteristic reactions with the greatest distinctness. Granted even that ether takes up a trace of the salts of the alkaloid, still the second method deserves the preference, since a small quantity of the alkaloid, in a pure condition, is infinitely more valuable for our purposes than a larger quantity in a state of impurity.

intermixed with some in the pure state, forming more or less distinct crystals. Narcotine occurs in comparatively large crystals; strychnine in small scattered scales; morphine in a similar manner; veratrine pulverulent, or resinous; colchicine resinous. Those particles which appear the purest should be removed with the point of a pen-knife, and preserved for the purpose of being tested with the proper reagents (v. § 122).

§ 121. In order to obtain the largest possible quantity of the alkaloid in a crystallized condition, the residue from the evaporation of the ethereal solutions ($120) is dissolved in a few drops of dilute alcohol, and the solution allowed to evaporate. There is usually too much foreign matter present to allow the formation of crystals. The residue must then be treated with water, acidulated with sulphuric acid; the alkaloid is dissolved as a sulphate, and the impurities remain as a greasy coating on the surface of the dish. The limpid solution is poured off, the dish washed with a few drops of acidulated water, and the whole of the liquid placed for a short time in vacuo, or over sulphuric acid, to effect a suitable concentration. To the residue, a very concentrated solution of pure carbonate of potassa is added, and the mixture treated with anhydrous alcohol; the alkaloid enters into solution, and the sulphate of potassa, together with the excess of the carbonate, remains undissolved. The alcoholic solution, on evaporation, yields the alkaloid in crystals, the nature of which has now to be ascertained.

§ 122. It has been remarked before that, in the majority of cases, the analyst will only have to prove

the presence or absence of a certain alkaloid, the nature of which is known from other circumstances. Then, of course, the crystals should first be examined with those reagents which most satisfactorily indicate the presence of this certain alkaloid. It may, however, happen that suspicion does not point to any particular alkaloid, and, in this case, there remains nothing but to make some preliminary tests.* The order to be pursued is of no material consequence. We may, for example, proceed in the following

manner:

A particle is placed in a few drops of sulphuric acid, and heat applied: a red color is indicative of veratrine.

A particle is dissolved in cold, concentrated sulphuric acid, and tested for strychnine with a piece of bichromate of potassa.

A particle is placed in a few drops of a solution of iodic acid; a yellow color and odor of iodine points to morphine; on addition of a little starch-paste, the mixture ought to become blue.

A particle is dissolved in water, acidulated with a drop of hydrochloric acid, and a dilute solution of sesquichloride of iron added, by means of a glassrod; a blue color, more or less pure, betrays also the presence of morphine.

*The examination with those reagents which produce a characteristic color-the color-tests-are best performed in small porcelain dishes, since the colors appear on a white surface most distinctly, and in greatest purity. Those tests which consist in the production of colorless or but little colored precipitates, are best performed in watch-crystals, placed on a dark-colored support; slight precipitates are thus easily perceived.

A particle is mixed with a few drops of concentrated nitric acid: a violet color indicates colchicine.

A particle is dissolved in water, containing a little caustic soda, and tested with blue vitriol for picrotoxine (v. § 115).

If the nature of the alkaloid has thus been determined, the remaining portion of the residue is used for making the other reactions. It may, for instance, be dissolved in water, slightly acidulated with sulphuric, or hydrochloric acid, and the solution be tested with tannine, terchloride of gold, bichloride of platinum, sulphocyanide of potassium, etc.

[Another mode to distinguish the different fixed alkaloids of which the residue in question might consist, is that proposed by Schneider.*

A portion of the residue is neutralized with dilute hydrochloric acid, and thus a concentrated aqueous solution prepared. To this liquid, a solution of caustic potassa is very gradually added. If a precipitate is formed, the reagent is added in excess, to ascertain whether an excess of the alkali dissolves the precipitate, or not. If the precipitate disappears, the alkaloid is either morphine or colchicine. They are easily distinguished by the reactions given in § 106 and § 113.

If the precipitate did not dissolve in an excess of the reagent, it is collected on a filter, washed with a little water, and then dissolved in dilute sulphuric acid. The acid liquid is mixed with a solution of bicarbonate of soda (saturated in the cold), until the acid reaction has just disappeared, well agitated, and

* Die gerichtliche Chemie, von Dr. F. C. Schneider. Wien. 1852.