All the simple cyanides are decomposed by boiling with concentrated hydrochloric acid, into metallic chlorides and hydrocyanic acid. Their analysis is therefore never difficult. But the ferrocyanides, &c., to which indeed the method described § 202 more exclusively refers, suffer by acids such complicated decompositions that their analysis by means of acids is a task not so easily accomplished. Their decomposition by potassa (or soda) is far more simple. The alkali yields its oxygen to the metal combined with the ferrocyanogen, &c., the oxide thus formed precipitates, and the reduced potassium or sodium forms with the liberated radical soluble ferrocyanide, &c., of potassium (or sodium, as the case may be). But several oxides are soluble in an excess of potassa, as, e. g., oxide of lead, oxide of zinc, &c. If, therefore, the double ferrocyanide of zinc and potassium, for instance, is boiled with solution of caustic potassa, it dissolves completely in that menstruum, and we may assume that the solution contains ferrocyanide of potassium, and oxide of zinc dissolved in potassa. Were we to add an acid to this solution, we should of course simply re-obtain the original precipitate of the double ferrocyanide of zinc and potassium, and the experiment would consequently be of no avail. To prevent this failure, conduct hydrosulphuric acid into the solution in potassa. This serves to convert into sulphides all the heavy metals which the potassa holds in solution as oxides. Those sulphides which are insoluble in potassa, such as sulphide of lead, sulphide of zinc, &c., precipitate, whilst those which are soluble in alkaline sulphides, such as bisulphide of tin, tersulphide of antimony, &c., remain in solution, and separate only upon the addition of an acid.

The fluid filtered from the precipitated oxides and sulphides accordingly always contains the cyanogen as ferrocyanide, &c., of potassiumprovided, of course, the analyzed compound is really a double ferrocyanide, &e. From most of these compounds-ferrocyanide, ferricyanide, chromicyanide, and manganocyanide of potassium-the cyanogen partly separates as hydrocyanic acid, upon boiling the solutions with sulphuric acid, and may thus be readily detected by this means, should the direct way of detecting the radicals not succeed. But the cobalticyanide of potassium is not decomposed by sulphuric acid, and the analyst is accordingly directed to effect the detection of the compound radical in that salt by means of solution of nickel, manganese, zinc, &c. By fusion with nitrate of potassa, all these double compounds suffer decomposition, cobalticyanide of potassium not excepted. The reason why the fusion

of these double compounds with nitrate of potassa should be preceded by evaporation with an excess of nitric acid, is simply to prevent the occurrence of explosions. Caution is always highly advisable in this operation.

If you simply wish to examine for certain bases in simple or compound cyanides, and for that purpose to destroy the cyanogen compound, mix the body under examination with 3 parts of sulphate and 1 part of nitrate of ammonia, and heat in a porcelain crucible under a chimney, to carry off the fumes. Complete decomposition ensues even at a moderate heat, the whole of the cyanide volatizing in form of cyanide of ammonium and products of the decomposition of the latter, whilst the metals are left behind as sulphates (Bolley).

APPENDIX.

I.

DEPORTMENT OF THE MOST IMPORTANT MEDICINAL ALKALOIDS WITH REAGENTS, AND SYSTEMATIC METHOD OF EFFECTING THE DETECTION OF THESE SUBSTANCES.

§ 227.

THE detection and separation of the vegeto-alkalies, or alkaloids, is a task of far greater difficulty than that of most of the inorganic bases. Although this difficulty is in some measure owing to the circumstance that scarcely one of the compounds which the alkaloids form with other substances is absolutely insoluble or particularly characterized by its color or any striking property, yet the principal cause of it must be ascribed to the want of accurate and minute investigations of the salts and other compounds of the alkaloids, and of the products of their decomposition. We consequently generally see and apprehend the reactions only in their external manifestation, but without being able to connect them with the causes producing them, which makes it impossible to understand all the conditions which may exercise a modifying influence.

Although therefore, in the present imperfect state of our knowledge of these bodies, an attempt to define their deportment with reagents, and base thereon a method of effecting their separation, or, at least, their individual detection in presence of each other, must of necessity fall very short of perfection, yet, having made a great many experiments on the nature and behavior of these substances, I will attempt here, for the benefit of young chemists, and more particularly pharmaceutists, to describe in some measure the reactions which the most important of the alkaloids manifest with other bodies, and to lay down a systematic method of effecting their individual detection.

The classification of the alkaloids into groups, which I have adopted, is based upon their deportment with certain general reagents. I have verified by numerous experiments the whole of the reactions described in the succeeding paragraphs.

I. VOLATILE ALKALOIDS.

The volatile alkaloids are fluid at the common temperature, and may be volatilized in the pure state as well as when mixed with water. They are accordingly obtained in the distillate when their salts are distilled with strong fixed bases and water. Their vapors, when brought in contact with those of volatile acids, form a white cloud.

1. Nicotia, in its pure state, forms a colorless, oily liquid, of 1.048 sp. gr.; the action of air imparts a yellowish or brownish tint to it. It boils at 482° F., suffering, however, partial decomposition in the process; but, when heated in a stream of hydrogen gas, it distils over unaltered, between 212° and 392° F. It is miscible in all proportions with water, alcohol, and ether.

Nicotia has a peculiar, disagreeable, somewhat ethereal, tobacco-like odor, an acrid, pungent taste, and very poisonous properties. Dropped

on paper, it makes a transparent stain, which slowly disappears; it turns turmeric paper brown, and reddened litmus paper blue. Concentrated aqueous solution of nicotia shows these reactions more distinctly than the alkaloid in the pure state.

2. Nicotia has the character of a pretty strong base; it precipitates metallic oxides from their solutions, and forms salts with acids. The salts of nicotia are freely soluble in water and alcohol, insoluble in ether; they are inodorous, but taste strongly of tobacco; part of them are crystallizable. Their solutions, when distilled with solution of potassa, give a distillate containing nicotia. By neutralizing this with oxalic acid, and evaporating, oxalate of nicotia is produced, which may be freed from any admixture of oxalate of ammonia, by means of spirit of wine, in which the former salt is soluble, the latter insoluble.

3. If an aqueous solution of nicotia, or a solution of a salt of nicotia mixed with solution of soda or potassa, is shaken with ether, the nicotia is dissolved by the ether; if the latter is then allowed to evaporate on a watch-glass, the nicotia remains behind in drops and streaks; on warming the watch-glass, it volatilizes in white fumes of strong odor.

4. Bichloride of platinum produces in aqueous solutions of nicotia whitish-yellow, flocculent precipitates. On heating the fluid containing the precipitate, the latter dissolves, but upon continued application of heat it very speedily separates again in form of an orange-yellow, crystalline, heavy powder, which, under the microscope, appears to be composed of roundish crystalline grains. If a rather dilute solution of nicotia, supersaturated with hydrochloric acid, is mixed with bichloride of platinum, the fluid at first remains clear; after some time, however, the double salts separate in small crystals (oblique, four-sided prisms), clearly discernible with the naked eye.

5. Terchloride of gold produces a reddish-yellow, flocculent precipitate, sparingly soluble in hydrochloric acid.

6. Solution of iodine in iodide of potassium and water, when added in small quantity to an aqueous solution of nicotia, produces a yellow precipitate, which after a time disappears. Upon further addition of iodine solution, a copious, kermes-colored precipitate separates; but this also disappears again after a time.

7. Solution of tannic acid produces a copious, white precipitate, which redissolves upon addition of hydrochloric acid; but if a large quantity of hydrochloric acid is then added to the solution, an abundant precipitate again makes its appearance.

8. If an aqueous solution of nicotia is added to a solution of chloride

of mercury in excess, an abundant, flocculent, white precipitate is formed. If solution of chloride of ammonium is now added to the mixture in sufficient quantity, the entire precipitate, or the greater part of it, redissolves. But the fluid very soon turns turbid, and deposits a heavy, white precipitate.

1. Conia forms a colorless, oily liquid, of 0.89 sp. gr.; the action of the air imparts to it a brown tint. In the pure state it boils at about 392° F.; when heated in a stream of hydrogen gas, it distils over unaltered; but when distilled in vessels containing air, it turns brown and suffers partial decomposition; with aqueous vapors it distils over freely. It dissolves sparingly in water, 100 parts of water of the common temperature dissolving 1 part of conia. The solution turns turbid on warming. Conia is miscible in all proportions with alcohol and ether. The aqueous and alcoholic solutions manifest strong alkaline reaction. Conia has a very strong, pungent, repulsive odor, which affects the head, a most acrid and disagreeable taste, and very poisonous properties.

2. Conia is a powerful base; it accordingly precipitates metallic oxides from their solutions, in a similar way to ammonia, and forms salts with acids. The salts of conia are soluble in water and in spirit of wine, but nearly insoluble in ether. The solutions of the salts turn brownish upon evaporation with partial decomposition of the conia. The dry salts of conia do not smell of the alkaloid; when moistened, they smell only feebly of it; but upon addition of solution of soda, they at once emit a strong conia odor. When salts of conia are distilled with solution of soda, the distillate contains conia. On neutralizing this with oxalic acid, evaporating to dryness, and treating the residue with spirit of wine, the oxalate of conia formed is dissolved, whilst any oxalate of ammonia that may be present is left undissolved. As conia is only sparingly soluble in water, and dissolves with still greater difficulty in solutions of alkalies, a concentrated solution of a salt of conia turns milky, upon addition of solution of soda. The minute drops which separate unite gradually, and collect on the surface.

3. If an aqueous solution of a salt of conia is shaken with solution of soda and ether, the conia is dissolved by the ether. If the latter is then allowed to evaporate in a watch-glass, the conia is left behind in yellowish-colored, oily drops.

4. Concentrated nitric acid imparts a fine blood-red tint to conia; sulphuric acid, a purple-red color, which subsequently turns to oliveyellow.

5. Terchloride of gold produces a yellowish-white precipitate, insoluble in hydrochloric acid; chloride of mercury, a copious white precipitate, soluble in hydrochloric acid. Bichloride of platinum does not precipitate aqueous solutions of salts of conia, the conia compound corresponding to ammonio-bichloride of platinum being insoluble in spirit of wine and ether, but soluble in water.

6. With solution of iodine in iodide of potassium and water, and with solution of tannic acid, conia comports itself the same as nicotia. 7. Chlorine water produces in a mixture of water and conia a strong, white turbidity.

The volatile alkaloids are easily recognised when pure; the great object of the analyst must accordingly always be to obtain them in that state. The way of effecting this is the same for nicotia as for conia, and has already been given in the foregoing paragraphs, viz., to distil with addition of solution of soda, neutralize with oxalic acid, evaporate, dissolve in alcohol, evaporate the solution, treat the residue with water, add solution of soda, shake the mixture with ether, and let the latter evaporate spontaneously. Conia is distinguished from nicotia chiefly by its odor, its sparing solubility in water, and its comportment with chlorine.

II. NON-VOLATILE ALKALOIDS.

The non-volatile alkaloids are solid, and cannot be distilled over with water.

FIRST GROUP.

NON-VOLATILE ALKALOIDS WHICH ARE PRECIPITATED BY POTASSA OR SODA FROM THE SOLUTIONS OF THEIR SALTS, AND REDISSOLVE READILY IN AN EXCESS OF THE PRECIPITANT.

Of the alkaloids of which I purpose to treat here, one only belongs to this group, viz.,

+

1. Crystallized morphia (Mo+ 2 aq.) usually appears in the form of colorless, brilliant, four-sided prisms, or, when obtained by precipitation, as a white crystalline powder. It has a bitter taste, and dissolves very sparingly in cold, but somewhat more readily in boiling water. Of cold alcohol it requires about 90 parts by weight for solution; of boiling alcohol from 20 to 30 parts. The solutions of morphia in alcohol as well as in hot water manifest distinctly alkaline reaction. This alkaloid is nearly insoluble in ether. At a moderate heat the crystallized morphia loses the two equivalents of water.

2. Morphia neutralizes acids completely, and forms with them the SALTS OF MORPHIA. These salts are readily soluble in water, and in spirit of wine, but insoluble in ether; their taste is disagreeably bitter. Most of them are crystallizable.

3. Potassa and ammonia precipitate from the solutions of salts of

+

morphia-generally only after some time-Mo + 2 aq., in the form of a white crystalline powder. Stirring and friction on the sides of the vessel promote the separation of the precipitate, which redissolves with great readiness in an excess of potassa, but more difficultly in ammonia. It dissolves also in chloride of ammonium and, though with difficulty only, in carbonate of ammonia.

4. Carbonate of potassa and carbonate of soda produce the same precipitate as potassa and ammonia, but fail to redissolve it upon addition in excess. Consequently if a fixed alkaline bicarbonate is added to a solution of morphia in caustic potassa, or if carbonic acid is conducted