Chapter VII: Part 7

3. _Symptoms of the third and highest degree._ Soon after a large dose of Arsenic has been swallowed, an austere taste, and a sense of heat and constriction of the pharynx and œsophagus are perceived; in a short period excruciating pains in the stomach and bowels, accompanied with vomiting of the most violent character, the matter voided being generally of a brown colour, and not unfrequently mixed with blood; with these symptoms are conjoined an inexpressible anxiety about the præcordia, and frequent faintings; the stomach at the same time acquires such a high degree of irritability, as to reject the mildest fluids. The alvine discharges now become frequent and painful, and consist of dark and extremely fœtid matter, frequently mixed with blood. The thirst is unquenchable, and the heat of the surface becomes extreme. The pulse is small, frequent, and irregular; palpitations of the heart, violent cramps in the legs, sometimes a painful strangury and bloody micturition ensue. The powers of life begin to fail, respiration becomes laborious, cold sweats break out, hiccup occurs, the countenance assumes a singular character of anxiety and distress, a livid circle appears around the eyes, the pulse is imperceptible, the body swells and sometimes becomes covered with a species of miliary eruption, or with dark purple spots. In some cases convulsions ensue, but delirium, or loss of reason, is very rarely the consequence of this species of poisoning, and the unfortunate sufferer is conscious until a few moments before the termination of his existence. Such are the general symptoms, but it is rare to see them all united in the same case; sometimes the greater part of them are absent. _M. Chaussier_ reports the case of a robust middle aged man, who swallowed a quantity of arsenious acid in large lumps, and died without discovering any other symptom than slight syncope; other cases are related where only vomiting and purging[223] have been observed, and the symptoms have been mistaken for those of _cholera spontanea_.

The practitioner is therefore not to withhold his belief in a case of poisoning, on account of the absence of several of those symptoms which are enumerated in systematic works on Toxicology.

It is only by the study of individual cases, that he can learn to appreciate the just value of those pathognomonic combinations which afford the least exceptionable evidence upon such occasions.

_The different modes of Poisoning by Arsenious Acid._

It has been proved by numerous experiments that the life of an animal may be destroyed with equal certainty by arsenious acid, whether it be _internally_ administered, or _externally_ applied to abraded surfaces, sores, or bleeding wounds; and it has been, moreover, shewn, that in either instance the symptoms will be analogous, except in the latter case they will often be more rapid in their course.

_Lionardo di Capoa_ relates the case of a child killed by the violent vomiting and purging arising from a slight wound made in the head by a comb, wet with oil in which arsenic had been infused for the purpose of killing vermin; and we have numerous instances on record, where the application of arsenical cerates and ointments has been followed by violent and dangerous symptoms. We also learn from the different historians of the Plague of London, that the arsenical amulets which were worn, as preservatives, on that occasion, were sometimes attended with deleterious consequences; _Crato_[224] observed an ulcer of the breast produced by them. _Verzascha_, violent pains and syncope. _Diemerbroeck_,[225] and Dr. _Hodges_,[226] death itself. Amongst the foreign authors who have related cases of poisoning by the external application of arsenic we may mention _Desgranges_,[227] who records the history of a chambermaid, poisoned by having rubbed her head with an arsenical ointment for the purpose of destroying vermin; and _Roux_,[228] who confessed to have killed a girl of eighteen by an application of the “_Pâte Arsenicale_” to a cancerous breast. _M. Renault_ has also given us the results of his experiments upon Arsenic when applied externally to dogs; when the skin was sound, it excited a pustular eruption without inflammation; but, when the skin was broken, more serious effects followed, both general and local, and in some cases death.[229]. In an experiment performed by Mr. _Hunter_, and Mr. _Home_, in which arsenic was applied to a wound in a dog, the animal died in twenty-four hours, and the stomach was found to be considerably inflamed. Mr. _Brodie_ repeated the experiment several times, always with the precaution of tying a bandage, to prevent the animal licking the wound; the results were uniform; the stomach was, in every case, not only more violently, but more rapidly, inflamed, than when the poison had been internally administered, and it even preceded any inflammatory appearance of the wound. In the _Journal de Medecine_, the following case is related of a woman who was killed by her husband having insinuated powdered arsenic into the vagina,[230] at the moment of enjoying the conjugal rites. “A woman at _Leneux, departement de l’Ourthe_, aged forty, having died after a short illness, attended with considerable tumefaction of the genital parts, uterine hemorrhage, vomiting, and purging, the body was inspected by order of the mayor, when the surgeons reported that they found the vulva in a state of gangrene, the abdomen much distended with air, and the intestines inflamed and gangrenous. The culprit was arrested, convicted, and executed.” In the _Acts of the Society of Copenhagen_, a similar crime stands recorded, and which was also committed by a peasant; in this latter case, although some small pieces of arsenic were found within the vagina, yet some doubts arose respecting the possibility of such a species of poisoning, and the magistrates accordingly consulted the College of Medicine of Copenhagen, who decided the question in the affirmative, having first instituted a series of experiments upon horses.

Death may also be produced by the introduction of arsenic into the rectum; it is said that Sir _Thomas Overbury_, after the failure of the various poisons[231] that were administered to him, was at last despatched by an arsenical glyster.

With respect to the quantity of arsenic required for the production of such effects it is difficult to offer a decided opinion, as its operation must in every case be liable to contingency; but a very few grains are in general amply sufficient.

_Physiological action of Arsenious Acid._

It had long been supposed that arsenic occasioned death by inflaming the stomach; but Mr. _Brodie_[232] has very satisfactorily proved, that its influence arises from its being absorbed, and that it must be regarded as a _vital_ rather than as a _chemical_ agent, and as having a constitutional, not a local mode of operation.

In the first place, he has in many instances found the inflammation of the stomach so slight,[233] that on a superficial examination it might have been easily overlooked; and in most of his experiments with arsenic, death took place in too short a period to be considered as the mere effect of inflammation. In the next place we have already shewn that in whatever manner the poison is applied, whether _externally_ to a wound, or _internally_, to the alimentary canal, the same inflammatory appearance will be visible in the stomach; a fact which can only be explained by admitting that the poison is absorbed, and that it acts upon these organs through the medium of the circulation; it acts at the same time upon the brain, and heart, but with different degrees of force in different cases; so that it is sometimes difficult to ascertain which of these organs is the first to fail in its functions. According then to these experiments and observations, inflammation of the alimentary canal is not to be considered as the general cause of death in poisoning by arsenic; and yet cases will occur, where the local affection may prove fatal, the animal having survived the effects produced on the organs more immediately subservient to life, as the brain and heart. Mr. _Henry Earle_ communicated to Mr. _Brodie_ a case highly illustrative of this fact, which occurred in St. Bartholomew’s hospital; a woman had taken arsenic, and having recovered from the alarming symptoms which first occurred, died at the end of four or five days, when upon dissection, there appeared extensive ulcerations of the stomach and bowels. This then was evidently a case of “_Consecutive_” poisoning.

The dissertation of _Dr. Jaeger_, to which we have before alluded, contains the result of a very extensive series of experiments, in illustration of the physiological action of the arsenic. He diligently examined its effects upon all classes of organized beings, as well of the vegetable as of the animal kingdoms. The general conclusions which he has drawn from his experiments on vegetables are, that arsenic is in most cases a rapidly destructive poison to them, with the exception perhaps of a few of the simplest forms of existence;[234] and that their death was induced by means of the gradual absorption and distribution of the poison by the vessels and cellular membrane, so that the parts died in succession, as the particles of the poison reached them. _Dr. Jaegar_ also found that arsenic was a quick and destructive poison to animals, and that death was preceded, in every instance, from the infusory animalcula up to man, by inordinate motions; and that the secretion was most remarkably increased from the mucous membranes. His experiments also proved that arsenic exerted the most powerful effects, when it was injected into the veins, or applied to a bleeding wound; next, when it was introduced into the stomach; but less so, when injected into the large intestines, which have fewer absorbing vessels.[235]

_Organic Lesions, discovered on Dissection._

The examination of the bodies of persons poisoned by arsenic, must not be expected to furnish constant and uniform results, since they will be found to vary very considerably in different cases. As we have already considered the value of accelerated and retarded putrefaction, as an indication of poisoning, we shall at once proceed to the description of the morbid phenomena which are presented by the internal organs on dissection. The stomach and intestines are the parts in which we may expect to find the most decided marks of the ravages from arsenic. The former viscus will be found more or less inflamed; in some instances, the dusky redness will appear in patches, interspersed with points and streaks of a brighter hue; the villous coat of the stomach will be almost always softened, and, as if macerated, can be easily rubbed off in pieces with the fingers from the coats beneath; actual ulceration and sloughing are, according to the observations of _Mr. Brodie_, never found unless where death is late in taking place, in which case extensive ulceration of all the coats, amounting to actual perforation, may be expected to happen. This statement agrees with the observation of _Ruysch_, who says that where there had been sufficient time, he found the stomach ulcerated in those who had died from the effects of arsenic, but that if death supervened earlier, he only discovered bloody points, distant from each other, throughout the viscus. On the subject of sloughs upon such occasions, our enlightened author remarks, that anatomists have often been betrayed into a fallacy respecting their true nature; on opening the stomach of a dog which had taken a large quantity of arsenic, _Mr. Brodie_ observed a dark brown spot about an inch in diameter, having all the appearance of a slough; on a closer examination, however, it appeared that this spot was no other than a very thin layer of coagulated blood, of a dark colour, and adhering very firmly to the surface of the mucous membrane, and having a few particles of arsenic entangled in it. He states that he has at several times observed a similar appearance but occupying a less extent of surface; and he informs us that, in the Hunterian museum, there is a human stomach, which was preserved for the sake of exhibiting what was considered a slough, produced by the action of arsenic; but that, on examining the preparation carefully, the dark coloured spot was discovered to be simply a layer of coagulated blood, similar to that before described. _Dr. Baillie_ and _Dr. Yelloly_ have found the stomach thickened in several parts, as if by coaguable lymph, and in one case the thickening of the coats was the only alteration of structure observable; and _M. Renault_ relates a case, where the arsenic was taken in large pieces, which produced no other effect than slight syncope on the approach of death; and that, upon opening the body, the arsenic was found in the state it was swallowed, but there was neither inflammation nor erosion of the stomach. Where the arsenic has been swallowed in substance, it will be generally found attached to the membrane of the stomach by a peculiar glairy fluid; if the poison should have been administered in solution, the same organic lesions will be discovered, but the presence of the arsenic in the stomach can scarcely be expected, although the contents of the viscus, as well as all the matter ejected from the body before death, must be carefully examined by a chemical process to be hereafter described. The duodenum, like the stomach, generally affords evidence of the same inflamed and disorganized condition; and the whole track of the intestinal canal will be found more or less affected, according to the quantity of arsenic that has been administered, the period of time which has elapsed before death, and other circumstances which have been already enumerated as capable of modifying the action of this destructive substance. It however deserves notice that in many cases the rectum appears to be more affected than the other intestines; _Dr. Male_[236] states, that he has frequently found it abraded and ulcerated, and even more inflamed than the stomach itself; _Mr. Brodie_ likewise observed, in his physiological experiments upon this substance, that the inflammation produced by it was greatest in the stomach and the rectum. _Dr. Baillie_ has recorded several instances where a mortification of the rectum followed as an effect of this poison; and in the case of _Mr. Blandy_, detailed in the _Appendix_, p. 237, _Dr. Addington_ stated, that the extremity of the rectum was extremely painful, and surrounded by excoriations and ulcers.

_Mr. Brodie_ has stated, in the paper to which we have so often alluded, that the organic lesions occasioned by arsenic are confined to the stomach and intestines, and that he _never found any appearance of inflammation in the pharynx or œsophagus_. This statement, however, is at variance with a great weight of authority; we have ourselves witnessed cases in which dissection has demonstrated extensive inflammation in these parts; indeed it would appear, that this poison acts more particularly on the mucous membranes; and it is reasonable therefore to conclude, that those with which it comes in actual contact will not escape its virulence. The serous membranes which receive less blood, and more lymphatics, are necessarily less affected by it.

In the case of _William Mitchell_, as related at _page_ 188, the patient complained of soreness of the eyes, heat and uneasiness in the mouth and throat; and the surgeon observed the membrane on the palate and uvula to be detached; so in that, again, of _Mr. Blandy_, _Dr. Addington_ found on inspection that “his tongue was swelled, and his throat inflamed and excoriated; his lips, especially the upper one, dry and rough, and having angry pimples on them; the inside of his nostrils in the same condition, and his eyes a little blood shot.” (_Append._ _l. c._). In the celebrated Scotch case of _Oglivy_ and _Nairne_ (_see page_ 184) _Peter Meik_, surgeon of Alyth, deposed, that, upon inspecting the body four or five days afterwards, he found “the tongue swelled beyond its natural size, and cleaving to the roof of the mouth, which he had never observed after a natural death.” Many more instances might be adduced to shew that the fauces, pharynx, and œsophagus are very frequently inflamed and excoriated by the ingestion of arsenic. Mortification of the pudenda[237] has been said to be an effect peculiar to the action of arsenic; certain it is that in males, priapism is sometimes a symptom of this poison, and the penis is found swollen and red after death, as was observed in the case of _William Mitchell_ (p. 190). The scrotum was also enlarged and of a dark colour. We have been long aware that persons exposed to the fumes of arsenic, or accustomed to handle any of its preparations, have been liable to a peculiar affection of these parts, but we have generally explained the fact by supposing that the poison had in such cases, been locally applied to them. The author has been lately informed by his friend _Mr. Parkes_, that several persons in his establishment were thus attacked, during the time they were engaged in preparing an arsenical solution, as a dye for the calico printers; and we have stated on another occasion,[238] that the smelters and workmen engaged in the copper works, and tin burning houses of Cornwall, are occasionally affected with a cancerous disease in the scrotum, somewhat similar to that which infests chimney sweepers. It is also singular that _Stahl_, in describing the putrescent tendency in the bodies of those who die from this poison, mentions in particular the gangrenous appearances of the parts of generation. The other organs of the body do not exhibit any particular appearances, which ought to be regarded as characteristic of death by arsenic; we must necessarily expect to find the traces of morbid action, especially where life has been unusually protracted; and the serous effusions found in the body of _William Mitchell_, are to be referred to such a cause.

_Mr. Brodie_ has stated that, in animals killed by arsenic, the blood is usually found fluid in the heart and vessels after death; this agrees with the observation of _Ruysch_, who says that he never found the blood coagulated in the human body, after death occasioned by this poison; as well as with that of _Dr. Jaeger_, who describes the cavities of the heart, especially of the right side, to be, upon these occasions, turgid with blood, but that coagula are very seldom found in them.

A question, of a very considerable importance in a forensic point of view, has arisen with respect to the means, by which we may distinguish whether arsenic, found in the body, had been introduced into the digestive canal during life, or after death. In general, this fact is placed beyond suspicion by the testimony of those to whose care the body had been confided, previous to dissection. But cases have occurred where a poisonous substance has been introduced into the rectum of a dead body, with the diabolical intention of accusing an innocent person of having been the perpetrator of the poisoning. We are not aware of any English case of this kind, but _M. Orfila_ states that in the proceedings of the Criminal Court of Stockholm such a case stands recorded. Fortunately there would not be much difficulty in detecting the crime; for were the arsenic applied to the rectum after death, the change of structure would not extend beyond the part in actual contact with it, but would be distinctly separated from the rest of the intestine _by a well defined line of demarcation_, which can never happen where the arsenic has acted during life; for, in this latter case, the transition from the diseased to the healthy structure will be gradual, and the limits of each imperceptible.

Before we conclude our observations upon the organic lesions occasioned by arsenic, we may caution the anatomist not to confound the red or violet colour which characterises inflammation, with that which has been occasionally found to arise from the ingestion of certain coloured drinks. The following case related by _Foderé_, and cited by _Orfila_, may serve to illustrate this subject. “A private person of Châlons sur-Marne, who was in a state of convalescence from a disease under which he had laboured, took a slight purgative, and died very shortly afterwards. He was believed to have been poisoned through some error in the medicine, and in order to be assured of this, the body was opened. The œsophagus and stomach were found to be red, and in certain places livid, as if in a state of gangrene. These appearances at first induced a belief that the deceased had died from poison; but _M. Varnier_, a physician of Châlons, concluded from the appearances, that death was the consequence of the disease, and that the apparent convalescence was only an insidious respite. It became therefore necessary to give some account of the state of the œsophagus and stomach; and having learnt that the deceased was in the habit of using a _strong infusion of red poppies_, the idea immediately struck him that the extraordinary colour of these organs might possibly depend on this infusion. In order to determine the validity of this explanation, he caused a dog to swallow, several times, a similar infusion; when upon opening its body, he discovered that the corresponding parts of this animal had assumed the same colour as had been observed in the stomach of the deceased above-mentioned, and, moreover, that this violet red colour was so firmly fixed that it resisted the action of repeated washings.” _Tincture of Cardamoms_ will also be liable to occasion a coloured appearance in the stomach, as described in _Mr. Stanley’s_ case of the death of a woman by a dose of opium.[239]

_Of the Chemical Processes, by which the presence of Arsenious Acid may
be detected._

This poison may either be submitted to the judicial physician for examination, in its solid form, or in that of solution; and in this latter state it may be mixed with various alimentary substances, whose presence will necessarily embarrass the inexperienced operator, and multiply the apparent difficulties of his task. It becomes our duty, therefore, upon this occasion, to enter very fully and minutely into the history of the various processes, which have been proposed for the solution of the important problem under consideration; to appreciate the relative value of each, and to point out the sources of fallacy and failure, to which they are severally exposed.

Such a review of the subject would, moreover, appear to be essentially necessary at the present period, since the evidence, lately delivered on an extraordinary trial,[240] has, to a certain extent, very unjustly shaken the public confidence in the tests of chemistry. We shall therefore proceed to consider the processes which are calculated to lead to the detection of _Arsenic_, in relation to the different circumstances under which it may be presented for investigation, viz. 1, In a solid form; 2, In the simple state of solution; and 3, In the state of combination with various alimentary substances.

1. _The Arsenic is in a solid form._ This is the most simple case which can occur, and the experiments by which its presence is to be demonstrated, will constitute the basis of the inquiry, which we shall be hereafter called upon to institute, for the detection of the same substance under other circumstances of mixture and combination.

The order of succession to be observed in the different experiments which we are about to describe, must, in a great measure, be regulated by the quantity of the material to be submitted to examination. Should it be small, it will be prudent to reserve the process of metallization, by which a considerable loss must necessarily arise, until we have submitted it to the various re-agents which are calculated to afford indications of its nature. If, on the contrary, the quantity of the substance exceed two or three grains, it will be adviseable to proceed in its examination by the following processes, reserving a portion for future analysis.

A. _By its reduction to a metallic state._ Mix a portion of the suspected substance in powder, with three times its weight of _black flux_[241]; put the mixture into a thin glass tube, about eight inches in length, and a quarter of an inch in diameter, and which is hermetically sealed[242] at one end. Should any of the powder adhere to the sides of the tube it must be carefully brushed off with a feather, so that the inner surface of its upper part may be perfectly clean and dry. The closed end of the tube, by way of security, may be thinly coated with a mixture of pipe-clay and sand[243]; but this operation is not absolutely necessary. The open extremity of the tube is to be loosely plugged with a piece of paper. The coated end must now be submitted to the action of heat, by placing it in a chaffing dish of red hot coals, for ten minutes, or a quarter of an hour; when, if our supposition respecting the nature of the substance has been correct, metallic arsenic will sublime, and be found lining the upper part of the tube with a brilliant metallic crust. The glass tube, when cold, may be separated from its sealed end by the action of a file, which will enable us to collect and examine the metallic sublimate. If a portion of this brilliant matter be laid on heated iron, it will indicate its nature by exhaling in dense fumes, having a powerful smell of garlic. Another portion should be reserved for future experiments.

This method of detecting the presence of _Arsenious acid_ has been considered the most decisive, and indeed the only unexceptionable one, but of this we shall speak hereafter; at present we have only to observe, that it is very far from being a minute test, for _Dr. Bostock_[244] confesses that where less than _three-fourths of a grain_ were used, he could not say that the metallic crust was clearly perceptible; and _Dr. Black_[245] appears to have considered that _one grain_ was the smallest quantity which could be distinctly recognised by such a process.

Chemists were formerly[246] in the habit of at once projecting any substance, supposed to be _Arsenic_, on some burning body, in order to develope the alliaceous odour; we have accidentally stumbled upon an instance of this kind, in the fourth volume of the _London Medical and Physical Journal_, which may serve as an illustration; it is a case communicated by _F. Thackeray, Esq._ of a child poisoned by arsenic, in which the author says, “_the inner surface of the stomach was very red, and was studded throughout with a white powder, which when exposed to the flame of a candle, yielded fumes, and a garlic odour was emitted, proving it was arsenic; of which there can be no doubt, as the girl afterwards confessed that she had given arsenic to the infant_.”

After the facts we have offered with respect to the _alliaceous odour_ of arsenical fumes, it is only necessary to state, in this place, that such a test, when conducted in the manner just related, must be considered as extremely equivocal.

Another method of identifying “_White Arsenic_,” by metallization, is to form at the moment of its reduction, an alloy with copper, which may be easily effected in the following manner: Mix the suspected powder with _black flux_, as in the former experiment, and place the mixture between two polished plates of copper; bind them tightly together by iron wire, and expose them to a low red heat; if the included substance contain arsenic, a silvery white stain will be left on the surface of the copper, which is an alloy of the two metals. In this, as in the former experiment, the presence of an _alkali_ in the flux is essential, since it forms immediately an _arsenite of potass_, and thereby fixes the arsenious acid, and prevents it from being volatilized before the temperature is sufficiently high to enable the charcoal to decompose it; we therefore differ with _Dr. Bostock_, when he states that _powdered charcoal_ may be substituted for the _black flux_.

The property of _whitening_ copper is regarded as a very satisfactory test of the presence of arsenic; but _Dr. Bostock_ has pointed out some circumstances attending it, which we shall here enumerate for the instruction and satisfaction of the less experienced operator. “It may be necessary,” says he, “in the first place, to describe the phenomena that take place when copper is heated according to the process that is described above, but without the addition of the arsenic. Two copper disks, of nearly an inch and a half in diameter, scoured bright with sand, had one grain of powdered charcoal, made into a paste with oil, placed between them; they were bound together with an iron wire, and then kept red hot for ten minutes. When they were withdrawn from the fire, the metal was found to have lost its former appearance, and to have acquired the dull white colour of lead or zinc; the insides of the disks were found to present the same whitish appearance, except on the spot where the charcoal was placed, a small part of which still remained unconsumed. As the disks cooled the whitish matter which covered them began to separate, and fly off with some force, in the form of small scales, leaving a clean surface of the proper copper colour. The charcoal was rubbed off, and the surface below it was found smooth and polished; it had acquired a light colour, resembling that of brass; and, near the centre, there was a small spot, which approached to a steel grey. This appearance still continued, after it had been rubbed with fine sand. The above description,” concludes _Dr. Bostock_, “will probably impress the Society[247] with the same idea, that, I confess, it gave to myself, that if I had performed this experiment upon a substance, which had been suspected to contain arsenic, and I had not been aware of the appearance that I was to meet with, I should have conceived that I had detected its presence. Upon repeating the process, in precisely a similar manner, except that one grain of arsenic was added to the charcoal, the oxidation of the copper took place as before, and a small part of the charcoal remained unconsumed; but upon rubbing it, the white stain was perfectly visible. However, when these disks were compared with those in which the former experiment had been made, the difference between them seemed more in _degree_ than in _kind_; so that I should not choose to decide upon the presence of arsenic, as indicated by this test, unless the result were more obvious than we can ever expect to find it, where the quantity of arsenic is so small. It may be proper to observe, that copper, whitened in this manner by arsenic, is very subject to tarnish; in three days I could with difficulty distinguish which of the disks had been employed in these two experiments.”

In connection with the different modes of identifying arsenic by metallization, we may relate a test lately proposed by _Mr. A. Thomson_, which, as a collateral proof, merits some attention. “Into any solution, in which arsenic may be suspected, stir a moderate quantity of charcoal powder; allow it to settle; then pour off the clear supernatant liquor, or filter the mixture; and when the powder which remains on the filter is dry, sprinkle some of it on a red hot poker; if the solution contain arsenic, the odour of garlic will be rendered sensible. This effect becomes more obvious if a few grains of dry sub-carbonate of potass be added to the dried charcoal powder.”[248]

If, instead of _Black flux_, or charcoal, the arsenious acid be heated in a glass tube with quick-lime, a sudden ignition will take place, when one part of the white arsenic will be metallized, and the other farther acidified, so as to produce an _arseniate of lime_; in this case, therefore, a certain portion of the arsenious acid is robbed of its oxygen to complete the acidification of the rest.

The habitudes of arsenious acid with the _nitrates_, as first observed by _Kunkel_, deserve also some attention. If they be heated together, the former will be oxygenated at the expense of the nitric acid, nitrous acid vapour will be disengaged, and an _arseniate of potass_ remain. The forensic chemist may avail himself of these facts, and obtain a very useful test, which may be applied in the following manner.[249] Take a grain or two of the suspected powder, and mix it with double the quantity of _Nitrate of Potass_; introduce this mixture in a small glass tube, and apply the flame of a spirit lamp under the powder; when, if it contain arsenic, the nitrate will be decomposed, nitric oxide and nitrous acid be evolved in a gaseous form, and an arseniate of potass remain.

The acid vapour may be easily recognised by its colour and smell, or by placing a piece of moistened litmus paper within the tube. The _arseniate_ may be identified by the _brick-red_ precipitate, produced in its solution, by _Nitrate_ of Silver. So small is the quantity of arsenic required for this latter mode of trial, that _Mr. Smithson_, in a late paper, observes “that a drop of a solution of arsenious acid in water, which at the height of 54·5 _Fah._ contains not more than 1/80th of the acid, put to nitrate of potass in a platina spoon, and fused, affords a considerable quantity of _arseniate_ of silver. Hence when no solid particle of oxide of arsenic can be obtained, the presence of it may be established by infusing in water the matters which contain it.”[250]

B. _By the application of certain re-agents, or tests, to its
solutions._

_a._ _Fused Nitrate of Silver, or Lunar Caustic._ For this test we are indebted to _Mr. Hume_, who first suggested its application in the Philosophical Magazine for May 1809, (vol. xxxiii). His method of using it is as follows: into a clean Florence flask introduce two or three grains of the suspected substance, in the state of powder, to which add about eight ounces of rain or distilled water, and heat the solution until it begins to boil; then while it boils frequently shake the flask, and add to the hot solution a grain or two of sub-carbonate of potass, agitating the whole to make the mixture uniform. Pour into a wine glass about two table spoonsful of the solution, and touch the surface of the fluid with a stick of lunar caustic. If arsenic be present, a beautiful yellow precipitate will instantly proceed from the point of contact, and settle towards the bottom of the glass as a flocculent and copious precipitate. By this test the 60th part of a grain may be satisfactorily recognised in two ounces of water. The presence of some alkali is essential to the success of the experiment, since arsenious acid is incapable, by the operation of simple affinity, to decompose the _nitrate of silver_.[251] The validity of this test has been questioned on several distinct grounds, and which the author has endeavoured to answer in another work[252]; such, however, is the importance of the question in its judicial consequences, that we shall re-consider it on the present occasion.

OBJECTION 1. _The alkaline Phosphates are found to produce precipitates with silver, analogous in colour and appearance to the arsenite of silver._ This constituted one of the principal points in the evidence for the defence, on the trial of _Donnall_ for the murder of _Mrs. Downing_ (_see Appendix_, p. 299), and it must be admitted as a valid objection, if the experiment be performed in the manner just stated; but there are other reagents which will immediately distinguish these bodies, as we shall presently have occasion to state, under the history of the _Ammoniuret of silver_, as a test for arsenic. The author has also shewn that there is a mode of so modifying the application of the present test, that no error or doubt can arise in the use of it, from the presence of any phosphoric salt. This method consists in conducting the trial on writing paper, instead of in glasses; thus—drop the suspected fluid on a piece of white paper, making with it a broad line; along this line a stick of _lunar caustic_ is to be slowly drawn several times successively, when a streak is produced of a colour resembling that known by the name of _Indian Yellow_; and this is equally produced by the presence of arsenic, and that of an alkaline phosphate, but the one from the former is rough, curdy, and flocculent, as if effected by a crayon, that from the latter is homogeneous and uniform, resembling a water-colour laid smoothly on with a brush; but a more important and distinctive peculiarity soon succeeds, for, in less than two minutes the phosphoric yellow fades into a _sad green_, and becomes gradually darker, and ultimately quite black; while, on the other hand, the arsenical yellow remains permanent, or nearly so, for some time, when it becomes brown. In performing this experiment the sun-shine should be avoided, or the transitions of colour will take place too rapidly. It would be also prudent for the inexperienced operator to perform a similar experiment on a fluid known to contain arsenic, and on another with a phosphoric salt, as a standard of comparison.

In this way the _nitrate of silver_, without the intervention of any other test, is capable of removing every ambiguity, and of furnishing a distinguishing mark between the chemical action of arsenic and that of the phosphates. _Mr. Hume_[253] states that he has repeated this modification of his experiment with entire satisfaction; and that, in a late unfortunate case of poisoning, he derived considerable information by its application. One of the great advantages of this test is the very small quantity that is required for examination, and which will therefore never prevent our pursuing the subject through the other channels of investigation.

OBJECTION 2. _The muriates produce precipitates with silver, so copious and flocculent, as to overcome every indication which the presence of arsenic would otherwise afford._

From the general use of common salt, the chemist must be prepared to meet with a _muriate_ in almost every examination after arsenic, besides which this latter substance is occasionally adulterated with the _muriate of baryta_ and by _sulphate of lime_. _Dr. Marcet_ proposes to obviate the difficulties which the presence of a _muriate_ must occasion, by adding to the fluid to be examined dilute _nitric_ acid, and then cautiously applying the _nitrate of silver_ until all precipitation ceases; in this way the muriatic acid will be entirely removed, while the arsenic, if present, will be retained in solution, and may be afterwards rendered evident by the affusion of ammonia, which will instantly produce the yellow precipitate in its characteristic form. It must, however, be confessed, that this mode appears complicated, and, moreover, requires some chemical address for its accomplishment; it should be also known that the yellow precipitate thus produced is not always permanent, for it is soluble in an excess of _ammonia_. Under these circumstances, it is surely preferable to precipitate at once from the fluid under examination, all the substances which nitrate of silver can affect, and then to expose the mixed and ambiguous precipitate, so obtained, to a low heat, in a glass tube, when the arsenious acid will be separated by sublimation. In this way the presence of _muriates_ and even _phosphates_, may, in certain cases, be serviceable, especially if the quantity of arsenic be very minute; for, by increasing the bulk of the precipitate, we shall decrease the difficulty of its examination.

OBJECTION 3. _Chromate of potass produces with nitrate of silver a yellow precipitate, which, when placed side by side with one produced by arsenious acid, cannot be distinguished by colour or appearance from it._ This fact has lately been announced by Dr. Porter, of the University of South Carolina (_Silliman’s Journal_, _iii._ 355); but as the presence of _Chromate of Potass_ can never be suspected in any research after arsenic, in cases of forensic interest, it is unnecessary to enter into any details respecting it.

We have stated above, that in consequence of the inability of arsenious acid to decompose _nitrate of silver_ by simple elective attraction, the presence of _some_ alkali becomes indispensable in the examination; and for this purpose _Dr. Marcet_ suggested the superior advantages which would attend the application of _ammonia_, in all those cases where the arsenic had not been previously combined with a fixed alkali; since the former does not, when added singly, decompose nitrate of silver; a circumstance which, in using the fixed alkalies, is very liable to occasion fallacy. This led _Mr. Hume_ to improve his original plan, by forming at once a compound,[254] which he calls the _Ammoniaco-nitrate of silver_, but which may with more propriety be designated, as an _ammoniuret_ of that metal.

_b._ The _Ammoniuret of Silver_. This is an improvement of considerable value; for, while it obviates the necessity of ascertaining the exact proportion[255] of alkali required in each experiment, it possesses the desirable property of not in the least disturbing the solution of _phosphate of soda_.

_c._ _Sulphate of Copper._ This test of arsenic is the one discovered by _Scheele_; when added to the _arsenite of potass_ a beautiful green precipitate (constituting a pigment known by the name of _Scheele’s green_) is produced; “so decidedly,” says _Dr. Bostock_, “does this phenomenon indicate the presence of arsenic, that I thought it desirable to ascertain, as exactly as possible, what were the best proportions in which the ingredients should be employed, and in what way they should be mixed, so as to exhibit the effect in the most obvious manner. After a number of trials, in which the substances were employed in various quantities, and under different circumstances, I am disposed to recommend that the proportions of the _arsenic_, the _potass_, and the _sulphate of copper_, should be to each other as the numbers _one_, _three_, and _five_, respectively; for instance, if one grain of arsenic and three grains of potass, be dissolved in two drachms of water; and, in another equal quantity of water, five grains of sulphate be dissolved, we have two solutions, which are transparent, and nearly colourless; but upon mixing them together, the whole is converted into the most beautiful grass-green, from which a copious precipitate of the same hue slowly subsides, leaving the supernatant fluid nearly without colour. If the same materials are employed, in the same manner, but without the arsenic, a delicate _sky-blue_ is formed, which is so decidedly different from the former colour as not to admit of the possibility of error.” In this experiment then, as well as in that with the nitrate of silver, it is necessary that the arsenious acid should be combined with an alkaline base; and for the same reason, in order to bring the double elective attractions into play; _Mr. Hume_ has accordingly availed himself of the property of ammonia, to form an _ammoniuret of copper_, which is to be made according to the formula already given for the preparation of the silver test.

_d._ _Ammoniuret of Copper._ In using this test care must be taken that it be not too highly concentrated, for in that state it will not produce precipitation.

Notwithstanding the confidence with which _Dr. Bostock_ has supported the pretensions of the _Sulphate of Copper_, as an infallible test for arsenic, its validity has been lately called in question, and it has been stated that a _decoction of onions_ has the property of imparting to the copper precipitate, produced by a fixed alkali, a green colour and appearance completely analogous to that which is occasioned by the presence of arsenic. This opinion was boldly advanced, and supported, on the trial of _Donnall_, before alluded to, and of which we have given a very ample report in the _Appendix_. Since this event an opportunity occurred which enabled the author to examine this alleged fact, by a fair and appropriate series of experiments,[256] the result of which has satisfactorily proved that the opinion was grounded on an optical fallacy, arising from the _blue_ precipitate assuming a _green_ colour, in consequence of having been viewed through a yellow medium.[257] The phosphoric salts may also, under similar circumstances, be mistaken for arsenic; for the intense blue colour of the _phosphate of copper_ will, when viewed through a yellow medium, necessarily appear green. Such instances of optical fallacy are by no means uncommon in the history of chemical reagents; thus _corrosive sublimate_ has been said to possess alkaline characters, in consequence of appearing to turn the syrup of violets green, whereas this apparent change is to be solely attributed to the optical combination of the yellow hue of the sublimate with the blue colour of the violet.

Whenever therefore such a source of fallacy can be suspected, the operator would do well to repeat his experiment on white paper, in the manner we have already pointed out, when treating of the silver test; and let it be remembered that the results, when obtained in glasses, should always be examined by day light, and viewed by reflected, and not by transmitted light. _Dr. Bostock_ observes, that a weak solution of the sulphate of copper, without any addition, when held between the eye and the window, frequently presents a greenish tinge. It should be also known that the usual reaction of the _ammoniuret of copper_, upon a diluted solution of arsenic, is prevented by the presence of _tannin_; strong tea may therefore render the test inefficient.

_e._ _Sulphuretted hydrogen._ This is a very delicate test for arsenic, producing with its solution a beautiful golden coloured liquor, which, after a short time, lets fall a precipitate, and which will take place sooner if a small quantity of acetic acid be added. By this re-agent so small a quantity as 1/100000 may be detected in solution. The test, however, is not, says _Dr. Bostock_, sufficiently discriminative to be depended upon alone; since _tartarized antimony_ and some other bodies, will produce phenomena that may be mistaken for the effects of arsenic. It has, however, the merit of not being affected by _tannin_, and may therefore be conveniently employed for precipitating arsenious acid, when dissolved in tea.

_f._ _Lime water_ produces with the solution of arsenic a beautiful white precipitate of _arsenite of lime_, which easily dissolves in an excess of arsenious acid.

The precipitates occasioned by the foregoing reagents, should be carefully collected, and treated with _black flux_, in a glass tube, for the purpose of obtaining the metallic sublimate, as above described.

We cannot quit this part of our subject without directing the reader’s attention to the chemical evidence given by _Dr. Addington_, on the trial of _Mary Blandy_ (_see Appendix, p._ 241) to prove that arsenic was contained in a powder with which she was supposed to have poisoned her father. To those in the least acquainted with the habitudes of arsenious acid, it must be evident, that no one of the appearances described by _Dr. Addington_ indicates the presence of arsenic;[258] and his evidence is only to be reconciled upon the supposition that, instead of the arsenic itself, he, in this case, detected the foreign substances with which it had been adulterated; thus it has been before stated that _white arsenic_, as sold by the druggists, is often adulterated with _sulphate of lime_; and the decomposition of this substance by the _sub-carbonate of ammonia_ (“_Spirit of sal-ammoniac_”) or by the _sub-carbonate of potass_ (“_Lixivium of tartar_”) would occasion the precipitation of a white substance, as stated in the evidence; it is however difficult to account for the “considerable precipitation of a lightish coloured substance” by muriatic acid (_spirit of salt_) by the presence of any impurity likely to be contained in the arsenic, or in the water employed for its solution. If any lime were present, it would probably give “white glittering crystals” of sulphate of lime, by the addition of sulphuric acid (_spirits of vitriol_). The only plausible evidence of the presence of arsenic in the suspected powder is “the alliaceous smell and white flowers” which _Dr. Addington_ describes as occurring when it was thrown on red hot iron; it must however be confessed, that from the fallacy of the other experiments, it is even impossible to place any confidence in those last mentioned.

Arsenic does not blacken a knife by which it is cut, as stated on the trial of _Eliza Fenning_; nor does it, when mixed with dough, prevent its rising.[259]

We have now concluded our history of the different tests which have been proposed for the detection of arsenic. Much has been said and written upon the relative degree of confidence to which they are respectively entitled, and it has been asserted on several occasions, that nothing short of the reproduction of the metal ought to be received by the tribunals of justice, as an unequivocal proof of the presence of arsenious acid. (See _Dr. Neale’s Evidence on the trial of Donnall_. _Appendix, p._ 297.) In taking an impartial review of all the evidence which the investigation of this subject can furnish, it must appear to the most fastidious, that the _Silver_ and _Copper_ tests, above described, are capable, under proper management and precaution, of furnishing striking and infallible indications; and that in most cases they will be equally conclusive, and in some even more satisfactory in their results, than the metallic reproduction upon which so much stress has been laid; and for this obvious reason, that unless the quantity of metal be considerable, its metallic splendour and appearance is often very ambiguous and questionable. The author is personally acquainted with a case, where the medical person, by no means deficient in chemical address, actually ascribed the presence of arsenic to that which was no other than a film of finely divided charcoal: in this state of doubt the last resource was to ascertain whether it yielded, or not, upon being volatilized, an alliaceous odour. Surely an unprejudiced judge would prefer the evidence of _sight_, as furnished by the tests, to that of _smell_, as afforded in the experiment to which we allude; especially after the various fallacies, which we have shewn in the course of the present enquiry, to have occurred with regard to this latter sense. But the question at issue may be easily disposed of to the satisfaction of all parties; for let it be remembered, that the application of chemical reagents on solutions suspected to contain arsenic, so far from throwing any obstacle in the way of the _metallic reproduction_ of that substance, are the very steps which should be adopted as preparatory to the “_experimentum crucis_.” It is only necessary to collect the precipitates, and to decompose them in the manner already described; and this confirmation of our results should never be neglected, for it is the bounden duty of the forensic chemist, who is called upon to decide so important a question as the presence of a corrosive poison, to prosecute by the fullest enquiry every point which admits of the least doubt; he should also remember that in a criminal case, where the life of a human being depends upon his testimony, he has not only to satisfy his own conscience, but that he is bound, as far as he is able, to convince the public mind of the accuracy and truth of his researches.

2. _The Arsenious Acid is mixed with various alimentary and other
substances._

The detection of the presence of arsenic, amidst a complicated mass of alimentary matter, has long been a problem of interest and difficulty. In the directions which have been already offered for the discovery of arsenic in solution, we have in some measure anticipated several of the resources, of which we are now to avail ourselves. It has been seen how greatly coloured fluids are capable of obscuring, and changing, and even altogether preventing, the arsenical indications. _M. Orfila_, with an assiduity and accuracy which so eminently characterise all his toxicological labours, has accordingly investigated the peculiar appearances assumed by the arsenical precipitates in different media, such as bile, tea, coffee, wine, broth, jelly, &c. Since the publication of the great work[260] in which these phenomena are recorded, its author has proposed a new method[261] of removing its difficulties and embarrassments, occasioned by the colouring matter of the above media; which consists in a previous application of _Chlorine_, so as to change the colour to a shade, that will not offer any optical impediment to the characteristic indications of the tests in question. We are ready to admit that such a mode of proceeding may, on certain occasions, assist the accomplished chemist in his analysis; but in the hands of a person less accustomed to chemical manipulation, we hesitate not to declare that it is subject to fatal fallacies; whereas, by collecting the precipitate, and submitting it to the process of sublimation we shall at once obtain the arsenious acid in a pure form, and be enabled to test it, in distilled water without the chance of error. Why then should we attempt to pursue our game through the windings of a labyrinth, when a direct road lies before us by which we may drive it into the open plain?

We accordingly recommend the juridical chemist, who suspects the presence of arsenious acid in broth, coffee, or any coloured liquid, to add a solution of _ammoniuret of silver_, and thus to precipitate indiscriminately all the bodies which it may be capable of so affecting. The precipitate may then be collected, and submitted to heat in a glass tube, as before directed.