The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1836-11-29 00:00:00

THE I, P , STAN MA)

POPULAR COURSE ON CHEMISTRY, AT THE

MECHANICS' INSTITUTION

LECTURE 111

. ,
On Wednesday evening Ar. Hemming delivered his third lec-
ture to an overflawine audience, upon the tests and antidote• of
various poiseus. The beauty of his experimeatt was only
equalled by the peculiar neatness of his manipulation.
Chemical alliaity is successfully applied to the detection of
liaisons. One of trie most frequently administered, as well as
the must destructive of these, is arsenic. Without entering
into a detail of the processes for extracting this peison from the
stomach, which would he both tedious and offensive, let us sup-
pose that the poison has been extracted, and we wish to ascer-
tain beyond a doubt whether it be arsenic or not. Arsenious
acid, which is the most fatal of the common poisons, is a
chemical combination of the metal arsenic and oxygen. As a
metal, arsenic is innoxious, and it owes its poisonous properties
to its combination with that vital principle of our atmosphere
without which we could not exist ten minutes. If there were
no oxygen combined with it, we might swallow a great quan-
tity of it with perfect impunity. Almost the whole of the
arsenic we employ in Europe comes from the Cobalt mines of
Saxony. It is to be found in copper pyrites combined as a
sulphuret; but this arsenic is not considered to be equal in
purity to that obtained from the Cobalt works of Saxony. These
Cobalt works are now considered very valuable, but a century
and a half age the ores of Cobalt were thrown aside as worthless.
Indeed the ores of Cobalt aro very hard to reduce, and on ac-
count of the great quantities of Cobalt these ores contained, the
mines were aeandoned. So pernicious was it considered, that
the workmen put up prayers to heaven to deliver them from evil
spirits 'and Cobalt. The name Cobalt is derived from Cobalus,
whom the Saxons believed to be a lady. There is a sermon in
the British Museum which was delivered by a divine against
this lady, in which he calls her the consort of Satan. It was,
however, discovered that this-ore contained a very valuable ox-
ide of the metal Cobalt, 'which, when properly prepared, has
the property of imparting an, indestructible blue to all vitrifia-
ble substartee;4 assglatiersaiacelaiti, See. The blue tints on our
plates are affixelastitli,o4nre of Cobalt. It is first ground and
mixed with :oily:kind -theteespplied• with a brush to the plates.
Th&plates,are thetioeitrified and:burntawben the Cobalt causes
an indelible ,blue 'ste.inaaAhisirie in Saxony, whiff hi bad been
abandoned for a ceeturyerwae.teopetterLami worked by the pro-
prietor- with Audi, titiceest, that .fora 'bag period to the time of
his death:he netted s£l4,oooperattaintrin by the:Cobalt extracted
from his ruinea'!The oxide-of-cabals was a few years ago worth
two guineas aniattuce;but The first step iftnow•worfh less-.
towards the purifaction of' the Cobalt ore is to roast it to drive
off the arsenic and sulphur with which it is combined. This is
done in a reverberatory furnace furnished with an horizontal
flue extending for 400 yards. In this flue the arsenic and sul-
phur become condensed, and in the course of a few months
choke it up. This flue terminates in a large chamber for the
purpose of- preventing the escape of the arsenic fumes. The
Cobalt is fused with glass, or the materials for making glass, with.
which it enters into combination, and produces a strong blue co-
lour. This compound is poured whilst hot into water, when it
becomes brittle, and forms the smelts which are so useful in the
arts. When the Cobalt is more inteusely combined with
the glass, the coliiur becomes almost black, and is imported un-
der the name of Zaffre. It becomet necessary to remove the
concrete matter when the Hues become choked, and it is so
highly dangerous a task that none but criminals condemned to
die are employed forthatpurpoee, and although they take every
precaution to prevent the arsenic power from entering the lungs,
very few of them survive inure than a few months. Indeed the
symptoms they present exactly resemble those of persons rho
have taken a portion of arsenic. It becomes necessary to re-
duce the arsenic and sulphur to a minute powder, and to mix
them with potass. Heat being applied, the arsenic sublimes in
a white state, and the sulphur unites with potash, forming the
sulphu ref of potash. 'rho arsenic (arsenious acid) is then ground
into a powder as we generally see it. It is barely soluble
in cold water, rather more so in boiling water, and it does not
precipitate the least of it when cold. The lecturer did not know
whether its insoluble property was more fortunate or unfortunate.
When it is taken in the state of mechanical mixture by those
who destroy life, those portions of it which are undissolved will
,arthere with singular obstinacy to the stomach and intestines
And where this takes place inflammation ensues, which extends,
to the adjacent parts. If the powder were soluble, by means of
the stomach pump we could extract it, and many lives might
be preserved; but to attempt to withdraw the undissolved
arsenic would be useless, as we should have to inject many
gallons of water before we could dissolve the arsenic. Let us
suppose that we have withdrawn the puison from the stomach,
and here it may be well to remark that in all cases of poisoning
wa should preserve the bottle, vial, or glass from which the
poison has been taken; and take it to a medical man, so that he
may tell what poison has been taken, and be able to bring the
antidote, by which in all probability the life may be saved.
We will suppose that the poison has been extracted, and that
we wish to emploaseheinical tests for its detection. We have
many valuable liquid tests for arsenic, but none of these can be
depended upon where taken isolatedly. Indeed,. in these days,
although we have two or three tests corroborating each other,
we do not find juries believe us unless we get the arsenic in its
metallic state. - If we have only the I,oooth part of a grain of
arsenic, we cats always reduce it to its metallic state, which
is always conclusive evidence. We should then convert part
of this metal into the poison, which we can do by heating it
with freo access to the atmospheric air. We have, therefore,
analytical and synthetical proofs as to the patine of the poison.
Although none of the four liquid tests can be depended upon in
their simple and separate state, yet when we find therm corro-
borating each other, we conclude that arsenic is present, for we
have no other substance in chemistry to which the four tests
will apply with the same results. The first of these is a solution
of sulphate of copper. Upon adding it to the solution of arsenic
there will be no precipitate, butmerely a change in colour; but
if we add ammonia, we have a precipitate of a grass-green
colour which will indicate the presence of arsenic. The next
test is to add a solution of the nitrate of silver, an exceedingly
beautiful and delicate test; and here again we shall have no
precipitate, unless it be a taint white one, arising from any im-
purities in the water; but here again, when a small quan-
tity of liquid ammonia is added, we shall have a yellow preci-
pitate, and, nada the former instance, dropping from the glass
rod with which we introduce the ammonia. We may then.
apply another test, but One which the lecturer did not reconi-
mena—a solution of lime, and this will give another precipitate,
but it requires to stand several minutes before any effect takes
place. The fourth test is applied with the best effect of all our
tests; it is a solution of sulphttretted hydrogen gas. For the
purpose of detecting the poison we do not employ the gas con-
densed in water, but pass a current of the gas through the
water, and this saves us a great deal of trouble. When either
the'solution or the gas itself is applied, a precipitate, the mil-
phnret of arsenic, is found. We may then proceed to reduce
'these precipitates to their metallic state. We first filter and
dry them, and, having mixed them with black flux, heat them
in a tube, when the arsenic is reduced- to a metallic state and
deposited on the tube. Tho ammonia should be added in test-
ing very cautiously and sparingly, otherwise the precipitate
will he immediately dissolved. These are the modes resorted to
by the chemists for the detection of arsenic; but, within the
last few weeks, we have been presented with a new test, su-
perior to all others, the most delicate and the most infallible.
It wil enable us to detect minute quantities and without any
precipitate whatever. If we adopt the test of Mr. Marsh,
of Woolwich, it is unnecessary to adopt any means traseparate
the poison from the stomach, which is en exceedingly offensive
operation. Mr. Marsh ascertained by means of this operation
the presence of one grain of arsenic mixed in a pint of soup, a
pint of coffee, &c. Hydrogen, in hs nascent state, will dissolve
arsenic and other metals. In lieu, therefore, of attempting to
separate the arsenic front the contents of the stomach, we place
substance supposed to contain arsenic in a vessel and add zinc
and sulphuric acid. Mr. Hemming used a Dobereiner's lamp
for this purpose, with great success. Hydrogen will thus
be generated and take up the arsenic with it, becoming arsenu-
rated hydrogen gas. This gas weritay ignite as it issues through
a small aperture, when, by hulling a piece of glass in front of
the flame, the metallic arsenic, or arsenious acide'according to
our mode of performing the operation, will be deposited upon
it. BY holding the glass near the dame metallic arsenic, is ob-
tained, and at a greater distance arsenious acid. A smell of
garlic likewise accompanies the burning of arsenic, besides what
the colour of the thole indicates of its presence. Now, with
respect to the remedies, it twist be admitted that it is difficult to
sav whether there is any. Mr. Hume, to whom we are indebt-
icaer one of the best tests of the presence of arsenic—the nitrate
of silver, informed the lecturer of a remarkable case of poison-
ing by arsenic, in which he hail been called. iii. Happening to
Kaye road of the virtues of Carbonate of niagnesie in cases of
poisoning, he administered a dose of it with opium. The
lady recvered, and he üblished an account'of it. Shortly
afterwards, a medical gentleman in the country administered
the same remedy with the utmost success. It does, therefore,
appear strange that this efficacious remedy.: should not be
better known. It certainly can do no hartwif it does no good.
The next poison in 'Orilet biehloride of mercury or coro-
sive sublimate. This is a poison seldom given, but there occur
many cases of poisoning by it, and the lecturer had read in the
Sr/trawls, of last week that a:portion of it had been taken in-.
stead of sulphur. How it could be mistaken for sulphur he
could not tell, as sulphur was yellow, and corrosive sublimate
white. The latter was hard, and the former brittle. This poison
will seldom be administered wilfully, and seldom could be taken
by the suicide, as it is se nauseous in its taste that he could not
bear it in his mouth. If we were to touch the tongue with the
smallest portion of it, the nauseous taste would remain for days.
This poison is alwaye formed at the same time as the useful me-
dicine, calomel; indeed, the only difference between them is,
that the one contains more chlorine than the other. They are,
however, easily separated, as corrosive subliinate is soluble in
water, and calomel is not. 'We have frequently a specific an-
atidote for corrosive sublimate in our kitchen; and that is albu-
men or the white of an egg, which immediately neutralizes it,
.and converts it into caloinel. In addliion to this test we have
many others whiCh lead to infallible results. We may apply
the alkalies such as lime water, ammonia, and
.potash. These
will all give Us' peculiar appearances. Ammouta gives a dense
White precipitate. Potash will afford a bright yellow, and lime
water will give us a yellowish red precipitate. By adding an
acid these colours will again be rendered transparent, in con-
sequence of the oxides being distiolved. We have one other
test which ought never to be omitted for we never can multiply
tests too abundantly when the life of a fellow-creature depends
on our evidence. This test is a solution .of the hydriodate of
potash, which will give us a yellow precipitate at the first, but
which will gradually redden into a deep crimson. But the most
delicate and the tnost infallible of all tests is obtained by the
voltaic decomposition of the substance; that is if we decom-
pose it by the contact' of two dissimilar metals. In every in-
stance ono metal should be gold, and on that we should drop a
, little of the suspected substance if it be corrosive sublimate a
small piece Of leadnr copper will cause it to adhere with great
violence to the gold. As much as can be taken up on the point of
a needle will be sufficientiwthis :way to plate the surface of a
sovereign. Heat will remove the mercury from the gold.
The next poison we have to consider is copper. Copper is
not a poison in its metallic state, but when combined with oxy-
gen it becomes so. The salts of copper are exceedingly den-
geroes. Copper is not wilfully taken or given, but deaths by
copper poisannig are not rare. It is usual to employ copper
stew-pans, and although they may be tinned, the tin isliable to
wear away, and if some articles of food remain in such a pot
for a few hours iu all probability they will become deadly pi,iVnt
for the acetate of copper or verdigris will he formed. Vu C u
that copper is wilfully employed .for,. the purpose of imp rf"c o ng-
the appearance ofsoine articles of food. Some articles °
lectionary are greened by copper. Mr. Hemming hadtextasate•tiencl.
copper from conifits. In some cases a large quantity
ployed, as in making of green pickles, as gherkins aturekidoney;
beans. The pickles, we are told in cookery book)st,tao t
y green. The
heated in brass or copper vessels, but if these are e
green, but he
a few halfpence will make the pickles delightful
'lecturer was not certain whether they would bed
was certain that a deadly poison walla be formed acetate
.of
fair aelerci:lisaertho,oniew fair.
copper. They had in London a
At the perii et of this fair all the gingerbread midst be gilt, and
the gilding is performed with copper leaf. A child would think
it infra dig, or indicative of bad taste to eat might gingerbread
' atsthat time. But if parents thought of the cousequences of the
gilding they would not permit their children to eat it. In al-
most every ' species of gilding
certain preparations are neces-
sary if we gild copper we
are obliged to amalgamate the gold;
;
if we gild wood certain
preparations are necessary ; but in gild-
ing giugerbread no such precautions are required; the artist
who perform; that office passes his tongue over the gingerbread,
and the. deposition of the saliva causes the copper to adhere to

it. It may not be known that there is in every instance sulli
dent copper to destroy the children, as the acid of the stern tch
acts on the copper, and turns it into verdigris, but fortunately,
at the same time that the child eats the.poison, it eats the antidote,
as the saccharine matter in the gingerbread deseroys the powers
of the copper; were it not for that many children Would be
poisoned. In order to detect the poisons of copper one or two
simple tests will only he necessary. Slice the pickles, and wash
them in distilled water ; neutralize the acid if there be any,"aml
add ammonia which will produce a deep blue tint. The copper
is first precipitated and then dissolved by the ammonia. We
then have a solution of the ferrocyanuret of potassium which
will give us a chocolate-coloured precipitate which has been used
as a pigment. -
The next poison is lead, whichis never administered or taken
wilfully; nevertheless lead has been the cause of many deaths,
accidentally and wilfully. In Devonshire a disease prevails
which is generally called the Devonshire cholic. This arises
from the practice of pressing the apples in leaden vessels,
whereby the acid of the apples combines with the lead, anti
forms that very deadly poison sugar of -lead or acetate of lead.
When the cyder I:weenies dead, the farmer sweetens it by push-
ing a piece of lead through the bung-hole. Acetate of lead is
also employed in adulterating wines for the purpose of making,
find old pert and fine old sherry. Lead, too, has become poi-.
sonous in consequence of leaden vessels containing water for a
considerable time, by which carbonate of lead, or white lead, is
formed. It is a little singular that spring or river water is not
liable to this, but that rain water is. Carbonate of lead is net
soluble in water, but may be separated by simple filtration. It
is very welljknown,that our lead pipes, through which the water
proceeds, become Corroded; but the corrosion takes place exter-
nally. Nevertheless all these evils might be prevented if plum-
bers would use the tinned lead pipe which has been introduced
within the last few years. The lead pipe is introduced before it
is drawn into a bath of tin, and the coating of tin is drawn out
with the pipe. Sheets of lead are tinned and drawn in the
same manner. Tin is not acted upon either internally or exter-
nally, and it' every cistern were made of this tinned lead, no
apprehensions need be entertained. It is not, however, a mat-
ter of surprise that these are not used ;—" it is too, dear," says
the plumber; "it lasts too long; it will never wear out." The
antidotes to lead are the sulphate of soda or the sulphate of
magnesia (Glauber's salts and Epsom salts.) These convert it
into harmless insoluble sulphate of lead. They are powerful
tests and antidotes. We have many other•tests which may be
employed fur this purpose. Hydriiitlate of potass, chromate of
potass, and sulphuretted hydrogen are amongst these. The
latter forms a black precipitate; the hydriodate of potass and the
bichromate of potass give a beautiful yellow.
We must now consider the effects of the vegetable acids, and
we may confine ourselves to one only, as what is said with re-
spect to that will in every case apply to the others, and the
remedies will almost always apply. Oxalic acid is frjquently
taken by mistake for Epsom salts, for which it is sometimes sold
by the druggist. It is somewhat difficult to account for one
being taken for the other as a medicine, the taste being so dif-
ferent, one being a perfect acid, and the other having a bitter
taste; but this may be accounted for, as persons taking salts
gulp them down without tasting them. We have, however,
powerful tests to distinguish the poison from the medicine. The
first is by dropping a little ink into water. Oxalic acid wi I
destroy the colour of the ink, but Epsom salts will not. It lime
water is poured into a solution of oxalic acid, the mixture will
become turbid, forming au oxalate of lime But in private fa-
milies there is no better test than this. A piece of chalk is
,as
good a test as can be desired; fur if it is plunged into a solution
of oxalic acid, an effervescence will ensue, which will not take
place in Epsom salts. An infusion of violets will hi like Man-
ner be reddened by the oxalic acid, whilst the Epsom salts pro-
duce no change in it. In cases of poisoning by oxalic acid, or
any other acid, the remedies are chalk, whiting, or potash mixed
with water, or, when these are not at hand, a large quantity of
soap suds. Were any of these antidotes qhickly administeted,
many lives would be saved.
In the lecture of to-morrow evening, Mr. Hemming will show
the most improved modes of obtaining and supplying artificial
light, and new contrivances for procuring instantaneous light by
friction, percussion, and chemical action. As this will, un-
doubtedly, be the most brilliant lecture of the course, so we have
no doubt it will be the most interesting and attractive.