Chapter XCII: 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.

_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.

4. It is useful, however, to separate the meconic acid also; because, as its properties are more delicate, I have repeatedly been able to detect it satisfactorily, when I did not feel satisfied with the result of the search for morphia. Dr. Ure made the same remark in his evidence on the trial of Stewart and his wife. He detected the meconic acid, but could not separate the morphia. It may be detected in one of two ways,—by means of hydrosulphuric acid, or by sulphuric acid.

If the former method be chosen, suspend in a little water the precipitate caused by the acetate of lead (par. 2); transmit hydrosulphuric acid gas till the whole precipitate is blackened; filter immediately without boiling; then boil, and if necessary filter a second time. A great part of the impurities thrown down by the acetate of lead will be separated with the sulphuret of lead; and the meconic acid is dissolved. But it requires in general farther purification, which is best attained by again throwing it down with acetate of lead, and repeating the steps of the present paragraph. The fluid is now to be concentrated by evaporation at a temperature not exceeding 180° F., and subjected to the tests for meconic acid, more particularly to the action of perchloride of iron, when the quantity is small. If there is evidently a considerable quantity of acid, a portion should be evaporated till it yields crystalline scales; and these are to be heated in a tube to procure the arborescent crystalline sublimate formerly described. About a sixth of a grain of meconic acid, however, is required to try the latter test conveniently.

If the method of separating meconic acid by means of sulphuric acid be preferred, the precipitate formed by acetate of lead is to be treated with weak sulphuric acid, which forms insoluble sulphate of lead, and disengages the meconic acid. The liquid obtained by filtration is then to be evaporated as above, to obtain crystals, which are to be examined by the tests for meconic acid. Orfila thinks this method more delicate than the mode by hydrosulphuric acid gas. I am inclined from my own experiments to doubt his statement.

5. If there be a sufficiency of the original material, Merck’s process for detecting porphyroxin may be tried [see p. 534]. But I doubt whether this process is sufficiently delicate for medico-legal purposes.

I wish I could add my testimony to the opinion, expressed on a remarkable occasion by Professor Chaussier, in favour of the delicacy of the tests for morphia and its compounds, that they might be detected “jusqu’à une molécule.”[1685] In one sense this statement may be correct. Morphia, separated from the complex mixture of principles with which it is combined in opium, may be detected in extremely small quantities. Accordingly, M. Lassaigne has supplied, for the discovery of acetate of morphia in mixed fluids, an excellent process, whence the chief part of the three first paragraphs of the preceding method for opium are borrowed; and from the facts stated by him in his paper,[1686] as well as from the experimental testimony of Professor Orfila,[1687] it appears that Lassaigne’s process will furnish strong indications, if not absolute proof of the presence of that salt, in the proportion of two grains to eight ounces of the most complex mixtures. Hence the search for acetate of morphia in a suspected case is by no means hopeless. But the detection of acetate of morphia is an object of small moment, compared with the detection of morphia in its natural state of combination in opium. Now my own observations lead me to entertain serious doubts, whether the best method of operating hitherto known could be successfully applied to the detection of the equivalent opium in complex mixtures. By the process I have recommended it is easy to procure, from an infusion of ten grains of opium in four ounces of water, satisfactory proof of the presence of morphia by the action of ammonia, perchloride of iron and nitric acid, and equally distinct proof of the presence of meconic acid by perchloride of iron, as well as sulphate of copper. But on proceeding to apply the process to organic mixtures, I have found that when the soluble part of ten grains of opium was mixed with four ounces of porter or milk, I could develope no property of morphia but its bitterness, and no indication of meconic acid but the action of perchloride of iron. MM. Larocque and Thibierge, it is right to add, have in similar circumstances found the process somewhat more delicate.[1688]

It is of great consequence, however, to remark, that in cases of poisoning with opium, the medical jurist will seldom have the good fortune to operate even upon so large a proportion of the poison as in my experiments; because the greater part of it disappears from the stomach before death. This will not happen always, as may be seen from various cases mentioned afterwards in the section on the morbid appearances caused by opium. But, according to my own observations, the poison will often disappear in a short time, so far as to render an analysis abortive. Thus in the case of a young woman who died five hours after taking not less than two ounces of laudanum, I could apply to the fluid, procured from the contents of the stomach, by paragraphs 1, 2, and 3 of my process, only the test of its taste, which had the bitterness of morphia. In the case of another young woman, whose stomach was emptied by the stomach-pump four hours after she took two ounces of laudanum, I could obtain from the evacuated fluid, when properly prepared, only the indications of the presence of morphia supplied by its bitterness and the imperfect action of nitric acid,—and the indication of the presence of meconic acid supplied by the imperfect action of perchloride of iron. In a third case, where the stomach was evacuated two hours after seven drachms of laudanum had been swallowed, even the first portions of fluid withdrawn had not any opiate odour, and did not yield any indication of the presence even of meconic acid. Now, on the one hand, the quantity taken in these instances is rarely exceeded in cases of poisoning with laudanum; and, on the other hand, the interval during which it remained in the stomach subject to vital operations is considerably less than the average in medico-legal, and above all in fatal cases. It may be laid down, therefore, as a general rule, that in poisoning with opium the medical jurist, by the best methods of analysis yet known, will often fail in procuring satisfactory evidence, and sometimes fail to obtain any evidence at all, of the existence of the poison in the contents of the stomach. In a case published by Dr. Bright from the experience of Mr. Walne of London, it is stated that the matter removed from the stomach only half an hour after an ounce and a half of laudanum had been taken, while the stomach was empty, did not smell of opium.[1689] This case is quoted to put the reader on his guard. But at the same time it does appear extremely improbable that the whole opium had disappeared from the stomach in so short a time, and much more likely that it might have been found by analysis in the matter first withdrawn.

I have taken some pains to establish the proposition laid down above, because in a matter of such importance it is always essential, that the medical inspector know the real extent of his resources; and it has appeared to me that, greatly as the hand of the chemist has been strengthened by late discoveries in vegetable analysis, his power has been overrated both by his scientific brethren, and by the medical profession generally. I am happy to find, since the first publication of these remarks, that they coincide with the experience and opinion of so eminent an authority as Professor Buchner; who has observed that a chemical analysis must often fail to detect opium where there could be no doubt of its having been administered in large quantity.[1690]

It is of moment to add, that in two of the instances mentioned above the odour of laudanum was perceived in the subject of analysis,—faintly, however, and only for a few hours after it was removed from the stomach. Although the peculiar odour of opium is a delicate criterion of its presence, it does not follow that it should be preferred to an elaborate chemical analysis. For it is a test of extreme uncertainty. There is in the contents of the stomach such a complication of odours, that with a rather delicate sense of smell, I have sometimes been unable to satisfy myself of the presence of the opiate odour where others were sure it existed. At the same time the medical jurist should not neglect it as a subsidiary test. It is always strongest and most characteristic, first, when the stomach is just opened, or the contents just withdrawn, and again, when the fluid, in the course of preparation, as directed in paragraph 1 (p. 535), is just reaching the point of ebullition. The latter odour is somewhat different from the former, yet quite peculiar, and such as every chemist must have remarked on boiling an infusion of opium. It is further to be observed, that although the odour of opium is a very delicate test of its presence even in complex organic mixtures, chemical analysis may be successful, where this character fails. Dr. Morehead of the Bombay service, in applying my process to the fluid withdrawn by the stomach-pump, detected morphia both by nitric acid and perchloride of iron, although he could not detect any odour of opium in the fluid.[1691]

So much for the delicacy of the process. As to its precision,—from what I have myself witnessed, as well as from the experience of Dr. Ure, it will often happen in actual practice, that the only indication of opium to be procured by the process consists in the deep red colour struck by perchloride of iron with the meconic acid. Now, will this alone constitute sufficient proof of the presence of opium? On the whole, I am inclined to reply in the affirmative. Sulpho-cyanic acid, it is true, has the same effect, and this acid has been proved by Professors Gmelin and Tiedemann to exist in the human saliva,[1692]—a fact which was called in question by Dr. Ure in his evidence on the trial of the Stuarts, but which at the time I had verified, and which Dr. Ure has since been compelled by experiments of his own to admit.[1693] But it must be very seldom possible to procure a distinct blood-red coloration from the saliva, after it has been mixed with the complex contents of the stomach, and subjected to the process of analysis detailed above;[1694] and the check proposed by Dr. Percy (p. 532) will distinguish it.