already contain hydrochloric acid, it is unnecessary, in most cases, to
institute a search for this compound. Nevertheless, it may be well to
take a quantity of the solution, corresponding to a known weight of the
original substance, and precipitate the acid by adding nitrate of
silver. The precipitate formed is dried and weighed. It is then heated
in a current of chlorine, in order to completely convert it into
chloride of silver, and its weight again determined. Only in case the
amount of chloride found is very large, is it to be inferred that the
poisoning has been caused by hydrochloric acid.
_h._ HYDROSULPHURIC ACID.--(_Sulphuretted hydrogen_). If the precipitate
produced by nitrate of silver possesses a black color, it may consist of
a _sulphide_. Upon treating a portion with solution of hyposulphite of
soda, all but the sulphide of silver is dissolved. In case a residue
remains, it is calcined with nitrate of soda, and the sulphate formed
detected by adding a soluble barium salt to its solution.
Sulphates, chlorides, carbonates and phosphates are most frequently met
with in the preceding examination, and it should be carefully noticed
which of these salts exist in the greatest abundance. If acids of
comparatively rare occurrence (such as the oxalic and tartaric) are
found, their approximate amount is also to be noted. These facts,
together with the original acidity of the materials and the absence of
other toxical bodies, would lead to the conclusion that the poisoning
was caused by the reception of an acid, as well as to the identification
of the special acid used. In subsequently effecting the detection of the
poison by the determinative tests, the danger of destroying other
poisons possibly contained in the substance will be obviated, as the
question of the absence or presence of these latter will have been
previously decided.
(5). The examination for acids concluded, the various fluids which have
accumulated, and from which the acids present have been separated, are
united and the whole evaporated to dryness. The organic substances,
present in the residue obtained, are destroyed by means of nitric acid,
and the residual mass examined for _soda_. If this substance has not
been introduced into the portion of fluid examined, and is discovered in
a quantity largely in excess of the amount normally contained in the
organism, it is probable that poisoning has been caused by its
administration, and that an acid has also been given, either in order to
mask the poison, or to act as an antidote. In this case, it is necessary
to carefully search for acetic acid, as this is the substance usually
employed as an antidote for alkalies.
(6.) Whatever results have been obtained by the preceding examinations,
the portion of the fluid which has been treated with soda (_vide_ p.
87) is evaporated to dryness. The organic matters possibly present
are destroyed by means of nitric acid, or _aqua regia_, and the residue
taken up with water. The solution so obtained is then examined for
metals (including potassa, which salt has not been introduced into this
portion of the fluid in any of the preceding operations) by the usual
methods.
(7). The soluble portion of the suspected materials having been
thoroughly tested, the undissolved substances remaining on the filter
are next examined.
_b._ SOLID PORTION.
(1). The organic matter present is first destroyed by treatment with
_aqua regia_. The fluid is then evaporated to dryness, and the residue
heated until the nitric acid is entirely expelled; the escaping vapors
being collected in a cold receiver. The residue is next taken up with
water, the solution filtered, and sulphuric acid added. Should a
precipitate of sulphate of lime, sulphate of baryta or sulphate of
strontia form, it is separated from the fluid and further examined. The
filtered solution is then introduced into Marsh's apparatus, sodium
amalgam being employed for generating the hydrogen, and tested for
_arsenic_ and _antimony_ by means of the reactions previously given.
(2). Whether one of the above poisons be discovered or not, the still
acid fluid is removed from the flask, a current of chlorine conducted
through it for several hours and the solution then examined for
_mercury_ by Flandin and Danger's method. In case mercury is found it
could scarcely have originated from the metal in Marsh's apparatus, as
this would not be attacked by cold dilute sulphuric acid: however, to
remove all doubts, the test should be repeated with a portion of the
substances reserved for the examination by the determinative tests.
(3). Whatever have been the results of the above examinations, it is
still to be ascertained if the fluid, which has been successively
treated by Marsh's and Flandin and Danger's methods, does not contain
other metals. This is accomplished by means of the ordinary reactions.
THE SUBSTANCE POSSESSES A NEUTRAL OR AN ALKALINE REACTION.
The examination is conducted in precisely the same manner as in the
preceding case, excepting that the materials are first acidulated with
oxalic or tartaric acids. Particular attention should be given to the
search for soda, potassa, lime, baryta and strontia, and the
determinative tests subsequently applied according to the indications
obtained.
DETERMINATIVE TESTS.
In many instances the tests we have termed indicative become
determinative in their character. This is the case when the isolation of
an alkaloid or a metal (unless mercury be found under the circumstances
already mentioned) is accomplished; the results obtained are then
_conclusive_. If, on the other hand,--not being able to separate either
an alkaloid or a metal--upon saturating the originally acid fluid with
potassa, or soda, the salts of these bases have been found in abundance,
there is reason to _infer_ that the poisoning has been caused by an
acid; or, if, after the neutralization of the originally alkaline
solution with an acid, potassa or soda are discovered in a large
quantity, poisoning by an alkali is _indicated_.
In case the fluid is neutral, but more or less colored and odoriferous,
and iodides or bromides are detected, we may justly _suspect_ that the
poisoning has been caused by the reception of iodine or bromine.
According to the indications furnished, iodine, bromine, one, or all of
the acids, the caustic alkalies, etc., are then detected by means of the
methods to be employed in cases where the expert has a clew to the
poison present. In this manner, the presence of potassa and soda, and of
bromine and iodine, even in mixtures, is easily ascertained. It only
remains to mention the course to be pursued when suspicion exists that
poisoning has been caused by the administration of a mixture of several
acids. The suspected materials are boiled with water, and alcohol added
to the solution in order to coagulate the animal matters. The solution
is next filtered, the filtrate placed in a retort provided with a
receiver and distilled until the residual portion acquires a pasty
consistency. In this way, the acids present are separated into two
classes: (_a_) those that are sufficiently volatile to have passed into
the receiver, such as, acetic, nitric, hydrochloric and sulphuric acids
(the latter acid will only be partially volatilized); and (_b_) those
that remain in the retort. The former are detected by examining the
distillate as previously directed.
The residue remaining in the retort is treated with absolute alcohol,
the fluid filtered, and a solution of acetate of lead added to the
filtrate: sulphuric, phosphoric and oxalic acids, if present, are
precipitated. The precipitate is suspended in water and decomposed by
means of sulphuretted hydrogen. The acids contained are now set free,
and are detected by applying the tests already mentioned.
If there be reason to suspect the presence of both sulphuric and oxalic
acids, the distillation is discontinued after a short time. The two
acids are dissolved by shaking the moderately concentrated fluid
remaining in the retort with ether, and, upon evaporating the solution,
will be obtained in a state suitable for examination. Oxalic acid is
then detected by means of sulphate of lime; sulphuric by means of
oxalate of baryta.
The above examinations would fail to effect the detection of
_phosphorus_, and it is necessary to examine a separate portion of the
original substance for this body.
IV.
MISCELLANEOUS EXAMINATIONS.
DETERMINATION OF THE NATURE AND COLOR OF THE HAIR AND BEARD.
A criminal, in order to conceal his identity, may change the color of
the hair and beard by artificial means; either to a darker shade, in
case they were naturally of a light color, or, to a lighter hue, if they
were originally dark, and the chemical expert may be called upon to
detect this artificial coloration, and restore the original color of the
hair.
It may also happen, that portions of hair still adhere to the clots of
blood sometimes found on an instrument which has been employed in the
commission of a crime, and consequently the question may arise as to the
nature of the hair, whether it be human or animal.
DETERMINATION OF THE COLOR OF THE HAIR AND BEARD.
The mode of examination necessary when the hair has been blackened is
different from that used when it has been decolorized.
_The hair has been blackened._
As various methods of dyeing hair black are in use, the means of
restoring the original color differ. The following are the methods most
usually employed in dyeing:
1º. The hair is well rubbed with a pomade, in which finely pulverized
charcoal is incorporated. This preparation, which is sold under the name
of "_mélaïnocome_," possesses the disadvantage of soiling the fingers
and clothing, even for several days after its application.
2º. The hair is moistened with a dilute solution of ammonia, and a
perfectly neutral solution of a bismuth salt (chloride or nitrate) is
then applied. It is subsequently washed, and allowed to remain in
contact with a solution of sulphuretted hydrogen.
3º. The same operation is performed, a lead compound being substituted
for the bismuth salt.
4º. A mixture of litharge, chalk, and slacked lime is applied, and the
head covered with a warm cloth. The hair is afterwards washed, first
with dilute vinegar, then with the yolk of an egg.
5º. The hair is first cleansed with the yolk of an egg, and then
moistened with a solution of plumbate of lime; or,
6º. It is moistened with a solution of nitrate of silver, to which a
quantity of ammonia sufficient to dissolve the precipitate first formed
has been added.
The first method merely causes a mechanical admixture of a coloring
matter with the hair. In the four succeeding processes, a black metallic
sulphide is produced; either by the subsequent application of a solution
of sulphuretted hydrogen, or by the action of the sulphur normally
present in the hair.
In the last method, the formation of sulphide of silver doubtless
occurs; but the principal change that takes place is probably due to the
action of light, which, as is well known, decomposes the salts of
silver.
In order to restore the original color to hair which has been treated
with "_mélaïnocome_," it is only necessary to dissolve in ether the
fatty matters present, and then remove the charcoal by washing with
water.
In case the hair has been dyed by means of a bismuth or lead salt (as in
methods 2, 3, 4 and 5), it is immersed for several hours in dilute
hydrochloric acid: the metal present dissolves, as chloride, and the
original color of the hair is rendered apparent. It then remains to
detect the metal dissolved in the acid solution, in order to establish,
beyond doubt, the fact that a dye has been employed. This is
accomplished by means of the methods used for the detection of metals in
cases of supposed poisoning.
If, finally, an ammoniacal solution of nitrate of silver has been
employed to cause the coloration, the hair is immersed, for some time,
in a dilute solution of cyanide of potassium, and the fluid subsequently
examined for silver. In case a portion of the salt has been converted
into the sulphide, it will be difficult to restore the original color,
as the removal of this compound is not easily effected.
_The hair has been decolorized._
Black hair can be bleached by means of chlorine-water, the various
shades of the blonde being produced by the more or less prolonged action
of the reagent. In this case, the odor of chlorine is completely removed
only with great difficulty, and the hair is rarely uniformly
decolorized. The expert may therefore be able to observe indication that
will greatly assist him in arriving at a definite conclusion. The hair
should be carefully examined up to the roots: if several days have
elapsed since the decolorization has been performed, the lower portion
of the hair will have grown and will exhibit its natural color. No
method has yet been proposed that restores the original color to
bleached hair. It is very possible, however, that this end would be
attained by allowing nascent hydrogen to act upon the decolorized hair.
For this purpose, it would be necessary to immerse it in water
containing some sodium amalgam, and slightly acidulated with acetic
acid.
DETERMINATION OF THE NATURE OF THE HAIR.
In examinations of this character use is made of the microscope. The
hair to be examined is suspended in syrup, oil, or glycerine and placed
between two thin glass plates. Human hair is sometimes cylindrical;
sometimes flattened. It consists either of a central canal, or of a
longitudinal series of oblong cavities which contain oily coloring
matter, and possesses the same diameter throughout its entire length.
The brown hair of the beard and whiskers, medium-sized chestnut hair,
the hair of a young blonde girl, and the downy hair of a young man
possess respectively a diameter of 0.03 to 0.15; 0.08 to 0.09; 0.06; and
0.015 to 0.022 millimetres. These exhibit on the surface slightly
projecting scales, which are irregularly sinuous at the border,
separated from each other by a space of about 0.01 m.m., and are
transparent, whatever may be their color.
The hair of ruminants is short and stiff, and is characterized by
containing cavities filled with air. Wool, however, forms an exception,
as it consists of entire hairs, homogeneous in appearance and possessing
imbricated scales, which bestow upon it the property of being felted.
The hair of the horse, ox and cow never exceeds 12 m.m. in length, and
is tapering, its diameter gradually diminishing from the base. It is
perfectly opaque, and does not appear to possess a central canal; has a
reddish color, and frequently exhibits lateral swellings, from which
small filaments occasionally become detached, in the same manner as a
twig separates itself from the parent branch.
EXAMINATION OF FIRE-ARMS.
(_Proposed by M. Boutigny._)
The examination of fire-arms is sometimes useful in determining the date
at which a weapon has been discharged or reloaded. The methods used in
examinations of this nature vary, as the weapon under inspection is one
provided with a flint or an ordinary percussion lock. The value of the
tests employed is also affected by the kind of powder used; _i. e._,
whether common gunpowder, gun-cotton or white gunpowder (prepared by
mixing yellow prussiate of potassa, chlorate of potassa and sugar) has
been taken.
THE GUN IS PROVIDED WITH A FLINT-LOCK, AND WAS CHARGED WITH ORDINARY
POWDER.
In case the weapon has been wiped or exposed to moisture subsequent to
its seizure, it is impossible to form any conclusion as to the date of
its discharge, etc. It is therefore advisable, upon receiving the
weapon, to carefully wrap the lock in a woollen cloth, and to close the
barrel. The exterior of the gun is at first submitted to a careful
examination, and notice taken of the approximate thickness of any
existing rust spots. The fire-pan and adjacent portion of the barrel are
also examined by aid of a magnifying glass, especial attention being
given to the detection of traces of a moist and pulverulent incrustation
of a greyish or blackish color, formed by the combustion of the
gunpowder, and of crystals of sulphate of iron. If the weapon is loaded,
the wad is withdrawn and the color of its cylindrical portion and of the
powder, as well as the size of the ball or shot, noted.
This preliminary examination ended, the barrel and fire-pan are
separately washed with distilled water, and the washings passed through
filter paper which has previously been well washed, first with pure
hydrochloric acid, then with distilled water. The filtrate is next
divided into three portions, and these separately examined for: (1)
sulphuric acid, by addition of chloride of barium; (2) for iron, by
oxidizing the salts contained in the fluid with a few drops of nitric
acid and adding a solution of ferrocyanide of potassium, the presence of
iron being indicated by the formation of a blue coloration, or a blue
precipitate; and (3) for sulphides, by means of a solution of subacetate
of lead.
If a bluish-black incrustation is discovered on the fire-pan or on the
neighboring portions of the barrel, and both rust and crystals of
sulphate of iron are absent, and the washings, which were originally of
a light-yellow color, assume a chocolate-brown coloration upon the
addition of solution of subacetate of lead, _the gun has been discharged
within two hours at the longest_.
If the incrustation possesses a lighter color and traces of iron have
been detected in the washings, but neither rust nor crystals have been
discovered on the barrel or fire-pan, _the weapon has been discharged
more than two, but less than twenty-four hours_.
In case minute crystals of sulphate of iron and spots of rust are found,
and the washings contain iron in a considerable quantity, _the weapon
has been discharged at least twenty-four hours, at the longest ten
days_.
If the quantity of rust found is considerable, but iron is no longer to
be detected, _the discharge of the gun occurred ten days, at the longest
fifty days, previously_.
_If the weapon has been reloaded immediately after its discharge without
having been previously washed_, the portions of the wadding which have
come in contact with the barrel will possess a greyish-black color
during the first four days, the color gradually becoming lighter, until,
at the fifteenth day, it turns grey and remains so permanently. In this
case, the washings will contain sulphuric acid. The objection has been
advanced to the last test that sulphuric acid might be discovered, even
if the gun had not been discharged, if the paper of which the wadding
was made contained plaster. M. Boutigny states, however, that this
objection is untenable, if the wadding has not been moistened by the
water introduced into the barrel.
_In case the gun has been washed and dried before being reloaded_, the
cylindrical portion of the wadding possesses an ochre-yellow color up to
the first or second day, assumes a decided red hue on the days
following, and acquires a clear rusty color on the sixth day. During the
fifth day the powder also possesses a reddish appearance, owing to an
admixture of rust. Sulphuric acid is not present in the washings.
_If the weapon has been reloaded immediately after being washed_, the
wadding possesses a greenish-yellow appearance for the first few hours,
and subsequently acquires a reddish color, as in the preceding case.
_If, finally, the barrel has been washed with turbid lime-water_, rust
is still to be found and the wadding possesses the color mentioned
above. The following colorations are also to be observed in case the gun
has not been washed, or has been dried near a fire:
BARREL DRIED NEAR A FIRE. UNWASHED BARREL.
After 1 day slight reddish yellow color greenish yellow color.
2 or 3 days a little darker " reddish-brown "
4 days a redder " reddish-brown "
5 or more days a rusty-red " rusty-red. "
THE GUN IS NOT PROVIDED WITH A FLINT LOCK.
At present weapons having flint-locks have almost entirely gone out of
use and have been superseded by the ordinary percussion gun; these
latter, in turn, are being gradually replaced by breech-loaders, charged
with or without a metallic cartridge. The indications obtained in the
preceding examinations by means of the fire-pan, will therefore
disappear; the results given by the inspection of the barrel may
possibly hold good. In regard to breech-loaders, all the useful
indications furnished by the coloration of the wadding and powder fail
to occur; the latter being enclosed either in a paper cylinder or in a
copper socket.
The fact that gun cotton and white gunpowder are occasionally made use
of, adds to the difficulty of obtaining reliable results by the mere
inspection of a weapon. White gunpowder does not oxidize the gun, fails
to give rise to any salt of iron, and possesses a white color;
gun-cotton produces distinctive indications varying with its purity.
Owing to these facts, it is evident that the method proposed by M.
Boutigny is of no real value, save in the rare instances where a gun
provided with a fire-pan, and charged with ordinary powder, is under
examination, and the question of the lapse of time since the discharge
of a weapon must remain undetermined so far as scientific tests are
concerned.
DETECTION OF HUMAN REMAINS IN THE ASHES OF A FIRE-PLACE.
This class of examinations is particularly necessary when the crime of
infanticide is suspected. As the complete incineration of a cadaver is a
long and difficult operation, it frequently occurs that bones--partially
or completely carbonized, but retaining their original form--are
discovered by the careful examination of the ashes of the fire-place in
which the combustion was accomplished.
When this is not the case and complete incineration and disaggregation
have occurred, recourse must be had to the indications furnished by a
chemical analysis. These indications are reliable, however, only when
the certainty exists that bones of animals have not been consumed in the
same fire-place; otherwise, the results obtained are entirely worthless,
the reactions given by ashes of animal bones being identical with those
produced by the ashes of a human body. Two tests are employed to detect
the presence of bones in the residue left by the combustion of animal
matter.
1. A portion of the ashes is placed in a silver crucible, heated with
potassa, and the mass afterwards treated with cold water. If animal
matter is contained in the consumed materials, cyanide of potassium will
be present in the aqueous solution. In order to detect this salt, the
fluid is acidulated with hydrochloric acid, and a solution of
persulphate of iron added: the formation of a blue precipitate indicates
the presence of the cyanide.
2. The ashes are next examined for phosphate of lime. As wood, coal, and
the other substances usually employed for heating purposes contain none
or little of this salt, its detection in a notable quantity would lead
to the inference that bones have been consumed. The ashes are allowed to
digest for twenty-four hours with one-quarter of their weight of
sulphuric acid. Water is next added to the pasty mixture, and the fluid
filtered. If phosphate of lime be present, it is converted by this
treatment into a soluble acid phosphate, which passes into the filtrate.
Upon adding ammonia to the filtrate, a precipitate of neutral phosphate
of lime is formed, neutral phosphate of ammonia remaining in solution.
The fluid is again filtered, the filtrate acidulated with nitric acid,
and then boiled with a solution of molybdate of ammonia likewise
acidulated with nitric acid: in presence of a phosphate, a yellow
precipitate, or at least a yellow coloration of the fluid, will be
produced. It has been stated that the disengagement of sulphuretted
hydrogen, upon treating the ashes with sulphuric acid, is an indication
that the combustion of a human body has occurred; this reaction is,
however, valueless, inasmuch as coal and certain vegetable ashes
likewise evolve the gas when subjected to the same treatment.
EXAMINATION OF WRITINGS.