The greek word Αρσενικον was employed by _Dioscorides_, and other
writers of that period, to denote a particular mineral of a reddish
colour, which _Aristotle_ had already described by the name of
σανδαρακη,[214] and his disciple _Theophrastus_, by that of αρρενικον.
It was employed by the ancients both as a pigment and as a medicine, and
appears to have been a compound of Sulphur, and a peculiar metal, to
which the name of _Arsenic_ is now exclusively applied. At what period
this metal was first discovered seems very doubtful; and although a
process for obtaining it is described in the Pharmacopœia of
_Schroeder_, published in 1649, yet its peculiar nature was examined,
for the first time by _Brandt_, in 1733.
The metal, Arsenic, is distinguished by the following properties, viz.
It has a bluish-grey colour, not unlike that of steel, and a
considerable lustre; its texture is grained, and sometimes scaly; its
hardness not very considerable, but its fragility is so great that it
falls to pieces under a moderate blow of the hammer, and admits of being
easily reduced to a very fine powder; according to _Bergman_ its
specific gravity is 8·31. When cold, it emits no sensible odour, but if
heated, it yields a strong _alliaceous_, or garlic-like smell, which is
to be considered as the most characteristic of its properties. Its point
of fusion is unknown, for it is the most volatile of all the metals, and
sublimes, before it melts, at the temperature of 540° Fah., and if the
process be conducted slowly in close vessels, the metallic sublimate
will assume a _tetrahedral_[215] form of crystallization; if the air be
admitted, and the temperature still farther raised, it will burn with an
obscure bluish flame.
Arsenic is extremely susceptible of oxidation, and, by mere exposure to
the air, shortly loses its metallic lustre; and yet it may be kept under
the surface of _cold_ water, for any length of time without exhibiting
the signs of oxidation, or solution; a covering of this fluid, or of
alcohol, is therefore considered as affording the best means of
preserving the metal in a state of integrity.
Arsenic is capable of combining with two proportions of oxygen, and of
forming two definite compounds, which we shall hereafter consider under
the title of _Arsenious_ and _Arsenic_ acids. The substance described by
some authors as the _black oxide_ of this metal would seem to be an
indefinite mixture of the metal itself, and the arsenious acid.
Arsenic does not appear to possess any deleterious properties, but it is
almost impossible to reduce the metal to powder, so as to adapt it for
exhibition without its becoming oxidized. _M. Renault_ therefore, in
order to decide the question, had recourse to its alloys; and he found
that _Mispickel_ (an alloy of Arsenic and Iron), when given to the
extent even of two drachms, scarcely produced any effect; a result which
very satisfactorily accords with the conclusion drawn by _Bayen_, in his
work on Tin, and which proves that the arsenic contained in that metal,
need not excite the least alarm, since it exists in a metallic state. We
have upon another occasion[216] observed, that the vapours characterised
by an alliaceous odour are probably less noxious than the arsenical
fumes which are inodorous; and that the little injury experienced by
workmen who solder silver filligree with an arsenical alloy, may
probably depend upon the deoxidized state of its fumes.
ARSENIOUS ACID, or WHITE OXIDE OF ARSENIC.
This is justly considered as the most fatal of all mineral poisons, and
is the one more frequently selected than any other, as the instrument of
assassination and suicide; while its numerous applications in medicine
and the arts, by making it an article of general and indiscriminate
sale, have rendered it an accidental as well as criminal source of
suffering and death.
It is seldom prepared by the chemist, since it exists in a native state,
and is moreover procured abundantly and economically, during the
extraction of the other metals from their ores.[217] In the commercial
world the substance is still known by the name of _White Arsenic_; and
continues to be expressed in popular language, by the simple term
_Arsenic_.
It generally occurs in the form of white compact masses, opaque on their
exterior surface; transparent, and presenting a vitrified aspect in the
interior. Its taste is acrid and corrosive, but not to a degree
corresponding with its virulence. _Specific gravity_ 3·7. When reduced
to powder it bears a strong resemblance to refined sugar, for which it
has sometimes been fatally mistaken, and with which it has been often
mingled for criminal purposes. At the temperature of 383° _Fah._ it is
volatilized, and is capable of crystallizing in tetrahedrons with
truncated angles, or rather in octohedrons; by a strong heat, in close
vessels, it is vitrified and becomes pellucid, and acquires the specific
gravity 5·000[218]; but when exposed to the air, it shortly returns to
its former appearance. _In the state of vapour it is quite inodorous_,
although the contrary is positively asserted in several chemical works
of high authority, and it is stated to be characterised by a smell like
that of garlic; the fact is, that the _alliaceous or garlic-like smell
is wholly confined to metallic arsenic in a state of vapour_; and
whenever the arsenious acid seems to yield such an odour, we may very
confidently conclude that its decomposition has taken place, and that it
has been reduced to its _metallic_ state. Such a reduction will
generally happen when it is projected upon ignited charcoal, or when
heated in contact with those metallic bodies which readily unite with
oxygen, such as _Antimony_, _Zinc_, &c. It is stated by _Orfila_ and
other writers, that if it be projected upon heated copper the alliaceous
odour is evolved. This assertion is undoubtedly true, but the fact
requires to be explained with more precision, or we may fall into an
important error respecting it. The author has shewn by several
experiments, already published in his _Pharmacologia_,[219] that the
phenomenon takes place only when the copper is in a state of ignition,
at which temperature its affinity for oxygen enables it to reduce the
arsenious acid, and consequently to develope the metallic odour. We have
ascertained by repeated experiments that if a few grains of arsenious
acid be heated on a plate of copper, by means of a spirit lamp or the
blow-pipe, no odour is perceptible; for, in this case, the whole of the
acid will be dissipated before the copper can acquire a temperature
sufficiently exalted to deoxidize, and reduce it. If the arsenious acid
be heated on a plate of zinc, the smell will not be evolved until the
latter metal is in the state of fusion. If, instead of the foregoing
surfaces, we employ in our experiments those of gold, silver, or
platina, no alliaceous smell whatever is produced, at any temperature,
provided every source of fallacy be carefully avoided; but it deserves
particular notice, that the author has found the flame of the spirit
lamp to be in itself, capable of decomposing the arsenious acid, in
consequence, it is presumed, of the operation of its hydrogen;[220] a
fact which is very likely to betray the experimenter, as in the first
instance it did the author, into a belief that the arsenious acid does
actually yield the odour in question.
The term Arsenious _acid_ was first bestowed upon this substance by
_Fourcroy_, since it was found to possess many of the essential
habitudes of an acid; as for instance, that of combining with the pure
alkalies to saturation. It dissolves in water; but, according to
_Klaproth_, although it requires for its solution 400 parts of that
fluid, at the temperature of 60° _Fah._ it requires not more than 13, at
212°; and it moreover appears that if 100 parts of water be boiled on
the arsenious acid, and suffered to cool, it will retain 3 grains in
solution, and deposit the remainder in crystals. This fact shews the
great importance of employing boiling water in every chemical
examination of substances supposed to contain arsenic. It proves also
that a fatal dose of the poisonous mineral may be very easily
administered in any watery vehicle, a fact which was denied on the trial
of _Ogilvy_ and _Nairne_[221] by _Dr. James Scott_, who deposed that
“Arsenic would not dissolve in warm water, but almost instantly subside
to the bottom of the vessel,” although, at the same time, he
acknowledged that “if it were put into tea with milk and sugar, and
stirred about, it _might_ be suspended long enough to kill those who
should drink the potion.” It is soluble in alcohol, and in fixed oils,
the former taking up two per cent. By the addition of an alkali, an
_arsenite_ of great solubility will result, and a solution of extreme
virulence may be thus effected. With _lime-water_ arsenious acid
produces a white precipitate of _arsenite of lime_, but which is soluble
in an excess of the acid. With _magnesia_ it also forms a very soluble,
and extremely active, _arsenite_.
_Symptoms of Poisoning by the Arsenious Acid._
_Hahnemann_, in his work on Arsenic, proposes a classification of its
effects founded on their relative duration and violence, and which it is
our intention to adopt on the present occasion, without any other
alteration than that of reversing the order of the classes.
Poisoning by Arsenic may accordingly be considered as admitting of three
degrees of intensity, viz. 1st. Where the case, although attended with
dangerous symptoms, does not terminate fatally. 2d. Where death does not
follow until after a lapse of twenty-four hours. 3d. Where death takes
place within twenty-four hours after the exhibition of the poison.
1. _Symptoms of the first and lowest degree._ In the slighter cases in
which the operation of arsenic is recorded as producing poisonous
effects, the symptoms were, uneasiness of the præcordia; cholics;
thickness, redness, and stiffness of the palpebræ; soreness of the gums;
ptyalism; itching over the surface of the body, sometimes attended with
a slight eruption; restlessness; cough; head-ache; strangury, and _ardor
urinæ_. Where the dose of poison has been somewhat greater, although
still inadequate to the destruction of life, violent vomiting is
commonly the first symptom, preceded in some instances with a sense of
heat and dryness in the fauces; in such cases where the vomiting has
very shortly succeeded the ingestion of the Arsenic, and the stomach has
at the same time been filled with food, the patient may owe his escape
to the poison being discharged before it had time to act. _Morgagni_
relates a case of poisoning at an Italian feast, where the dessert was
intentionally sprinkled with Arsenic instead of flour; those who had
previously eaten but little speedily perished, but those who had eaten
heartily were saved by vomiting. Although in this degree of poisoning
the life of the patient may be spared, yet a variety of _consecutive_
symptoms may continue to harrass him for a longer or shorter period,
such as indigestion, debility, partial paralysis, and epilepsy. The
history[222] of the cases of _Mr. Turner_ and his family, of Chancery
lane, for the poisoning of whom _Eliza Fenning_ was executed, will
afford a striking illustration of this fact. The hair of the head has
also been observed, in some cases, to fall off. _Dr. Male_ is also of
opinion that the long protracted and injudicious use of this mineral, as
a medicine, will induce exostosis and caries of the bones.
2. _Symptoms of the second degree._ In this case where the patient lives
two or three days, or perhaps longer, as in the case of _William
Mitchell_ above described (p. 190), the earliest symptoms are heat and
thirst, or vomiting, and inexpressible uneasiness and anxiety, the
former of which is less frequently observed than the two latter;
purging, or sometimes a repeated but ineffectual desire to go to stool;
wandering pains; quick, but feeble pulse; head-ache; distended and
painful abdomen; priapism; towards the close of the scene the patient
often becomes more tranquil and is inclined to sleep, although, in some
instances, the pains, attended with convulsions, continue to the latest
moments. In general, death takes place suddenly. In cases where the
effects of the poison are not immediately fatal, we must necessarily
expect the occurrence of many phenomena, indicative of the re-action of
the system, and which will be better illustrated by a reference to the
history of individual cases, such for instance, as those of _William
Mitchell_, (p. 190) and _Mr. Blandy_, (_Appendix_) than by any general
description which can be given in this place. It is also worthy remark
that in such cases, from the length of time, there will necessarily
occur a greater opportunity for the co-operation of other contingent
causes, whether they be connected with previously existing diseases, or
the action of remedies; and the intelligent practitioner will not
neglect to appreciate their influence in modifying the character of each
particular case. There are besides symptoms highly characteristic when
they do arise, but which are of comparatively rare occurrence, such as
the ulcerated condition of the fundament, as in the case of _Mr.
Blandy_, and the inflamed eyes and state of the mucous membranes, in
that of _William Mitchell_.
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.
But the _Arsenious acid_ may perchance be so mixed with various foreign
matter as to render its separation by filtration difficult; in such a
case, after having boiled it in distilled water, in order to procure all
the soluble matter from it, the residual mass may be evaporated to
dryness, care being taken that the heat applied for such a purpose never
exceeds 250° _Fah._ or we shall lose the arsenic, should any be present,
by volatilization. The residue thus obtained may then be submitted to a
higher temperature in a subliming vessel, in order to procure the
arsenious acid in its pure state. This process applies particularly to
the examination of the matter vomited, or the feculent evacuations
passed, by the patient. Should the arsenious acid have, in the first
instance, been dissolved in oil, _Dr. Ure_ proposes to boil the solution
in distilled water, and to separate the oil afterwards by the capillary
action of wick threads. If the arsenious acid be mixed with resinous
bodies, _Oil of Turpentine_ may be employed as their solvent, which will
leave the arsenic untouched. _Dr. Black_ directed the application of
alcohol for this purpose, but this is obviously improper, since
arsenious acid is soluble in that fluid.
If the physician be called upon to investigate the contents of the
alimentary canal after death, and the arsenious acid cannot be
discovered amongst the suspected matter, the stomach itself must be cut
into small pieces, and in compliance with the directions of _Orfila_,
boiled in ten or twelve times their weight of distilled water, which
should be renewed as fast as a portion of it flies off in vapour; this
liquor should be cooled and decanted, in order to put a few drops of it
into the solutions of the different re-agents which we have before
described. If the precipitates should indicate the presence of arsenic,
we may proceed according to the directions we have already laid down;
if, on the other hand, the fluid offers no indication of poison, the
mass exhausted by water should be treated, according to the process
suggested by _Rose_, by boiling it for some time in a solution of
potass, by which means the stomach will be partly decomposed and
dissolved, and the arsenious acid, with which it might have been
combined, saturated by the alkali. In this state the liquor is to be
filtered, again boiled, and nitric acid added, little by little, until
it passes from a dark to a clear yellow colour. The object of the acid
in this stage of the process being to decompose and destroy the animal
matter. The excess of acid should be saturated with potass, when an
_Arsenite of Potass_ will be formed, if there really existed any
arsenious acid in the stomach. This _M. Orfila_ recommends us to
precipitate by the _Hydro-sulphuret of Ammonia_, and a few drops of
nitric acid; (_Rose_ prefers _lime water_ for the same purpose); a
yellow _sulphuret of Arsenic_ will be the result, from which the whole
of the metal may be obtained, by drying it upon a filter, mixing it with
an equal bulk of potass, and melting it in a small glass tube.
This complicated mode of proceeding will rarely be found necessary; but
it should not be neglected, where the presence of arsenic cannot be
otherwise detected in the alimentary canal of those who are suspected to
have died from its ingestion, especially in the examination of a body
where, from the length of time it may have been under ground, there is
reason to suppose that the acid exists in a state of intimate
combination with the animal matter. And we may take this opportunity to
observe, that advanced putrefaction, however disagreeable it may render
such researches, will not, in the case of arsenic, defeat their success;
let the forensic physician, then, remember, that the length of time
which may have elapsed since the death of the body, ought never to be
urged as a plea for not having proceeded in its dissection. The task may
be personally disagreeable, but it will be less painful than the
reflections which must attend a breach of duty; upon such an occasion we
would address the anatomist in the quaint but expressive words of
_Teichmeyer_[262], “_Præstat enim manus quam conscientiam cruentare et
contaminare._”
ARSENIC ACID, and ITS SALTS.
It has been stated, that the Metal Arsenic is susceptible of two degrees
of oxidizement, the result of its first degree being Arseni_ous_ acid,
and that of its second Arsen_ic_ acid. This latter compound, of which we
are now to treat, may be obtained by the repeated distillation of white
arsenic with nitric acid. In a solid state it is white, not
crystallizable; of a sour, and at the same time, metallic taste; its
specific gravity is 3·391; when exposed to the action of heat in a close
vessel, it does not become volatile, but melts and vitrifies; thrown on
burning coals, it swells, parts with its water, and becomes opaque; if
the process of deoxidation be continued, it will, at length, rise in
vapours, like those of arsenious acid, and which, like them, will yield
an alliaceous odour, or not, according to the circumstances already
explained. The _Arsenic acid_ dissolves very readily in water, and is
even indeed deliquescent. With alkalies, earths, and oxides, it
constitutes a class of salts, called “_Arseniates_,” all of which, as
well as the pure acid, are extremely active poisons; fortunately,
however, they are not much employed[263] in this country, and are not
likely to become the instruments of crime. These salts, like those of
the arsenious acid, are obedient to the different re-agents which were
enumerated under the consideration of this latter substance, but with
different results; thus the _silver_ test, instead of producing the
yellow indication, occasions an equally characteristic precipitate of a
red, or brick colour. The ammoniuret, and acetate of copper, furnish a
bluish-white precipitate. The arsenic acid, in a solid form, or the
arseniate, mixed with black flux, will, like white arsenic, furnish a
metallic sublimate, when heated in a glass tube.