Hydrochlorate of Morphia.—The muriate or hydrochlorate must be carefully attended to by the medical jurist, because it is extensively used in medical practice instead of opium. As now prepared, it is snowy-white and apparently pulverulent, but is in reality a congeries of filiform crystals. It decrepitates slightly when heated, then melts, and at the same time chars, exhaling a strong odour somewhat like that of truffles. Nitric acid and perchloride of iron act on it as on morphia. Boiling water dissolves fully its own weight, and very easily three-fourths of its weight of hydrochlorate of morphia; and on cooling down to 60° F. it retains seven parts per cent., and deposits the rest in tufts of beautiful filiform crystals. The solution commonly employed in medicine contains one per cent. of the salt. Nitric acid turns the solution yellow, acting distinctly enough when the water contains a hundredth, and perceptibly when it contains only a two-hundredth of its weight. Perchloride of iron strikes a deep blue with a solution containing a hundredth of its weight, very distinctly when the proportion is a two-hundredth, and even perceptibly when it is only a five-hundredth. A solution much more diluted than even the last has a strong bitter taste. When moderately concentrated, morphia is precipitated from it by the alkalis.
Of the preceding properties of morphia and its salts, those which constitute the most characteristic tests are the effects of perchloride of iron and of nitric acid on all of them, the effect of heat on morphia, and the effect of an alkali on its solutions in acids.
Of the Tests for Narcotine.—Narcotine is rather distinguished by negative than by positive chemical properties. When pure, it is in transparent colourless pearly crystals, which, as formed from alcohol, may be either very flat, oblique, six-sided prisms, or oblong four-sided tables obliquely bevelled on their sides. But when crystallized from sulphuric ether the crystals are prisms with a rhombic base. They fuse with heat, and concrete on cooling into a resinous-like mass. They are soluble in ether, and fixed oil, less so in alcohol, insoluble in water or the alkalis, very soluble in the diluted acids, but without effecting neutralization; and if perfectly pure, they do not undergo the changes produced on morphia by perchloride of iron or nitric acid. Few specimens of narcotic, however, are so pure as not to render nitric acid yellow. Care must be taken not to confound narcotine with morphia. When crystallized together from alcohol and not quite pure, narcotine forms tufts of pearly thin tabular crystals, while morphia is in short, thick, sparkling prisms.
Of Codeïa.—This substance is, like morphia, an alkaloid, capable of combining with acids. It differs from morphia and narcotine in being moderately soluble in water; and from this solution it may be crystallized in large crystals affecting the octaedral form. It is unnecessary to detail its chemical properties.
Of the Tests for Porphyroxine.—This principle is a neutral crystalline body, insoluble in water, soluble in alcohol and ether, and also soluble in weak acids, which part with it unchanged on the addition of an alkali. When heated with hydrochloric acid, a fine purple or rose-red solution is produced; whence its name. It is supposed that this property may be of use in medico-legal researches; and the following mode of developing it has been proposed by Dr. Merck, its discoverer.[[1684]] Decompose the suspected fluid with caustic potash; agitate the mixture with sulphuric ether; dip a bit of white filtering paper repeatedly in the etherial solution, drying it after each immersion; then wet the paper with hydrochloric acid, and expose it to the vapour of boiling water; upon which the paper will become more or less acid.
Of the Process for detecting Opium in mixed fluids and solids.
Having stated these particulars of the chemical history of opium and its chief component ingredients, I shall now describe what has appeared to me the most delicate and satisfactory method of detecting it in a mixed state.
1. If there be any solid matter, it is to be cut into small fragments, water is to be added if necessary, then a little acetic acid sufficient to render the mixture acidulous, and when the whole mass has been well stirred, and has stood a few minutes, it is to be filtered, and evaporated at a temperature somewhat below ebullition to the consistence of a moderately thick syrup. To this extract strong alcohol is to be gradually added, care being taken to break down any coagulum which may be formed: and after ebullition and cooling, the alcoholic solution is to be filtered. The solution must then be evaporated to the consistence of a thin syrup, and the residue dissolved in distilled water and filtered anew.
2. Add now the solution of acetate of lead as long as it causes precipitation, filter and wash. The filtered fluid contains acetate of morphia, and the precipitate on the filter contains meconic acid united with the oxide of lead.
3. The fluid part is to be treated with hydrosulphuric acid gas, to throw down any lead which may remain in solution. It is then to be filtered while cold, and evaporated sufficiently in a vapour-bath. The solution in this state will sometimes be sufficiently pure for the application of the tests for morphia; but in most cases it is necessary, and in all advisable, to purify it still farther. For this purpose the morphia is to be precipitated with carbonate of soda; and the precipitate having been collected, washed, and drained on a filter, the precipitate and portion of the filter to which it adheres are to be boiled in a little pure alcohol. The alcoholic solution,—filtered, if necessary,—will give by evaporation a crystalline residue of morphia, which becomes orange-red with nitric acid, and blue with perchloride of iron. The latter property I have sometimes been unable to develope when the former was presented characteristically.