Section I.—Of the Chemical History and Tests of Opium.
Opium is the inspissated juice of the capsules of the Papaver somniferum. It has a reddish-brown colour, and a glimmering lustre on a fresh surface. It is soft and plastic when recent; but if pure, may be dried so as to become brittle. Its smell is strong and quite peculiar. It has a very bitter and most peculiar taste. In consequence of this taste one would suppose it no easy matter to administer opium secretly. The plan resorted to by thieves and robbers seems to be, to deaden the sense of taste by strong spirits, and then to ply the person with porter or ale drugged with laudanum, or the black drop, which possesses less odour.
The following account of the chemical history of opium will be confined in a great measure to the leading properties of the principles, in which its active qualities are concentrated, or which are likely by their chemical characters to supply proof of its presence.
The common solvents act readily on opium. Water dissolves its active principles even at low temperatures. So does alcohol. So particularly do the mineral and vegetable acids when much diluted. Ether removes from it little else than one of its active principles, narcotine. By the action of these agents are procured various preparations in common use. Laudanum is a spirituous infusion, and contains the active ingredients of a twelfth part of its weight of opium. Scotch Paregoric Elixir, a solution in ammoniated spirit, is only one-fifth of the strength of laudanum; and English Paregoric, tincture of opium and camphor for its chief ingredients, is four times weaker still. Wine of opium contains the soluble part of a sixteenth of its weight. The black drop and Battley’s sedative liquor are believed to be solutions of opium in vegetable acids, and to possess, the former four, the latter three times the strength of laudanum. But their strength has been greatly exaggerated; neither of them, according to my own experience, being above half what is supposed. The juice and infusion of the garden poppy are also powerfully narcotic, so as even to have caused death both when given by the mouth and in the way of injection.[[1677]] Many other pharmaceutic preparations contain opium.
If opium be infused in successive portions of cold water, the water dissolves all its poisonous principles, and also a peculiar acid possessing characteristic chemical properties. These principles are separated by means of the alkalis, the alkaline carbonates, or the alkaline earths. The most important of them are morphia, the chief alkaloid of opium,—narcotine, a feeble poison, not an alkaloid,—a peculiar acid, termed meconic acid,—and a resinoid substance. Other crystalline principles also exist in opium, though apparently in too small proportion either to affect its action or to be available in medico-legal analysis as the means of detecting the drug. These are codeïa, meconine, narceïne, paramorphia, and porphyroxine.
Of the various principles now indicated it is necessary to notice here only morphia, narcotine, codeïa, porphyroxine and meconic acid. They require mention either as being active poisons, or because a knowledge of their leading characters may be useful in conducting a medico-legal analysis in a case of poisoning with opium.
Meconic acid, as procured by evaporation, is usually in little scales of a pale brown or yellowish tint, being rendered so by adhering resin or extractive matter; but when nearly colourless, it forms long, extremely delicate tabular crystals, which in mass have a fine silky appearance like spermaceti. 1. When heated in a tube, it is partly decomposed, and partly sublimed; and the sublimate condenses in filamentous, radiated crystals. 2. When dissolved even in a very large quantity of water, the solution acquires an intense cherry-red colour with the perchloride of iron. The sublimed crystals have the same property. Only one other acid is so affected, namely, the sulpho-cyanic, a very rare substance. It has been repeatedly stated,[[1678]] that the redness produced by meconic acid may be distinguished by the effect of an alkali, which is said to bleach the colour produced by sulpho-cyanic acid, but to deepen the cherry-red tint occasioned by the meconic. This is not correct; an alkali added to the red solution of meconate of iron precipitates oxide of iron and renders the liquid colourless. The best distinction yet proposed is the following which has been suggested by Dr. Percy. Acidulate the red fluid with sulphuric acid, drop in a bit of pure zinc, and suspend at the mouth of the tube a bit of paper moistened with solution of acetate of lead: If the redness be caused by sulpho-cyanic acid, hydrosulphuric acid gas is evolved, and blackens the paper; but no such effect ensues, it the redness be owing to meconic acid.[[1679]]—According to Dr. Pereira, solutions of the acetates, an infusion of white mustard, decoctions of Iceland moss, and of the Gigantina helminthocorton, besides other more rare substances, are reddened, like solution of meconic acid, by the salts of peroxide of iron.[[1680]] 3. The solution of meconic acid gives a pale-green precipitate with the sulphate of copper, and, if the precipitate is not too abundant, it is dissolved by boiling, but reappears on cooling.
Of the Tests for Morphia and its Salts.—Morphia, when pure, is in small, beautiful, white crystals. Various forms have been ascribed to it; but in the numerous crystallizations I have made, it has always assumed when pure the form of a slightly flattened hexangular prism. It has a bitter taste, but no smell.
A gentle heat melts it, and if the fluid mass is then allowed to cool, a crystalline radiated substance is formed. A stronger heat reddens and then chars the fused mass, white fumes of a peculiar odour are disengaged, and at last the mass kindles and burns brightly.—Morphia is very little soluble in water. It is more soluble, yet still sparingly so, in ether. But its proper solvents are alcohol, or the diluted acids, mineral as well as vegetable. All its solutions are intensely bitter, and that in alcohol has an alkaline reaction.—From its solutions in the acids crystallizable salts may be procured; and morphia may be separated by the superior affinity of any of the inorganic alkalis; but it is easily redissolved by an excess of potash.—Morphia when treated with nitric acid is dissolved with effervescence, and becomes instantly orange-red, which, if too much acid be used, changes quickly to yellow. The coloration of morphia by nitric acid is a characteristic property; which, however, it possesses in common with some other alkaloids, such as brucia, and also strychnia when not quite pure. The change of colour is said by some chemists to depend on adhering resinoid matter, and not to be possessed by perfectly pure morphia; but this is a mistake. It is probable that some other vegetable substances besides the three alkaloids, morphia, brucia, and strychnia, may be turned orange-red by nitric acid. Dr. Pereira says that oil of pimento undergoes the same change.[[1681]]—When suspended in water, in the form of fine powder and then treated with a drop or two of perchloride of iron containing little or no free hydrochloric acid, it is dissolved and forms a deep blue solution, the tint of which is more purely blue, the stronger the solution, and the purer the morphia. This is a property even more characteristic than the former, since no such effect is produced on any other known alkaloid. Like the effect of nitric acid, it is said not to be essential to morphia, but to depend on adhering resinoid matter; yet the blue colour is always strongly produced with powdered morphia of snowy-whiteness.—Another property by which morphia maybe also distinguished is the decomposition of iodic acid. A solution of iodic acid is turned brown either by morphia or its salts, owing to the formation of iodine; and the test is so delicate that it affects a solution containing a 7000th of morphia.[[1682]] So many other substances, however, possess the property of disengaging iodine from iodic acid, that little importance can be attached to this criterion.
Acetate of Morphia is in some countries the common medicinal form for administering morphia; but it has been almost entirely superseded in this city by the hydrochlorate, since Dr. W. Gregory pointed out a cheap mode of procuring that salt in a state of purity.[[1683]] The acetate is in confused crystals, often of a brownish colour from impurities. The stronger acids disengage acetic acid. The alkalis throw down morphia from its solution in water. Nitric acid and perchloride of iron act on it as on morphia itself.