Sir William Crookes.

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vapour; and it is called a pulsating still because, as each fresh charge
of wort is introduced into the heating-chambers of the still, the tem-
perature of the condensing and separating apparatus falls back or
recedes by the automatic operation, so that the distillation of each
separate charge forms a separate complete operation, beginning at a
fixed low temperature, and increa&ing to the maximum temperature
until the distillation is complete.

Improvements in the method of and apparatus for smelting or extract-
ing iron, copper, or other metals from their ores. R. Stone, Liverpool,
Lancaster. December 14, 1874.— No. 4298. This invention has for
its object, first, the utilisation of the waste and inflammable gasee
given off during combustion in the furnace or cupola used for the
smelting of metals. The waste gases are brought down through suit-
able pipes or flues from the mouth of the furnace or cupola (where
they are emitted), and returned to the bottom of the furnace either
separately by a distinct exhaust and blowing apparatus for that pur-
pose, or m combination and conaeCtion with the ordinary blast-pipe
or pipes. Secondly. The introduction of steam separately into the
furnace, or in combination with the return waste gases, or in com-
bination with gases generated by heat from any of the known salts
that^ve off oxyg'en. Thirdly. The introduction of a spray, jet, or
jets of hydrocarbon oil or spirit into the furnace, either in combination
with a jet or jets of steam, or cold or heated atmospheric air, or sepa-
rately. Fourthly. The utilisation of the said waste heat and gases
arising from the furnace or cupola for heating a chamber or pipes
through which pass the blast-pipes of the furnace or cupola. Filthly.
Apparatus and arrangement ot same for carrying the before-mentioned
method into operation.

An improved method of treating curried or dressed leather cuttings
and waste so as to obtain valuable products. M. Murphy, Liverpool,
Lancaster. December 17, 1874. — No. i)355. This consists— First. In
treating the leather waste or scraps in a liquid or gas«>us bath of
hydrocarbon or other suitable oil or solvent to remove the animal or
vegetable oils or fats. Second. In d^tilling and condensing the pro-
duct lelt by the treatment described under the first part so as to sepa-
rate the solvent from the oils or fats.



NOTES AND QUERIES.



Commercial Analysis of Phosphates.^Will some corresponden
be kind enough to explain the method of determining the percentage
of phosphate of lime in insoluble precipitated phosphate calcined ?—
Agriculturist.



MEETINGS FOR THE WEEK.



NOONDAY, Feb. 7th.<— Medical, 8.

London Institution, 5.

Royal Institution, 2. General Monthly Meeting.

Society of Arts, 8. Cantor LeCturev. " Iron

and Steel Manufacture," by W. Mattieu
Williams, F.C.S.
Tuesday, 8th.— Civil Engineers, 8.

Photographic, 8. (Anniversary.)

Royal Institution, 3. " On the Classification of the

Vertebrated Animals," by Prof. Garrod.

Wrdmesday, 9th.— Society of Arts, 8. " The Cultivation of Hardy
Fruits, with a View to Improvement of Quality
and Ensuring Constant and Abundant Produc-
tion," by Shirley Hibberd.

Thursday, 10th.— Royal, 8.30.

Royal Institution, 3. " On the Chemistry of the

N on- Metallic Elemtnts," by Prof. Gladstone.

- Mathematical, 8.
London Institution, 7.

Friday, 11th.— Royal Institution, 9. " Mechanical ACtion'of Light,**
by William Crookes, F.R.S.

- Astronomical, 3. (Anniversary).

Quekett Microscopical Club, 8.

Society of Arts, 8. Chemical SeClion. " Sole-Leather

Tanning, with some Remarks on the Import of
Hides and Cattle," by Soarke Evans.
Saturday, X2th.— Royal Institution, 3. " On the Vegetable King-
dom," by W. Thiselton Dyer.

- Physical, 3.



TO CORRESPONDENTS.

T. Birdsall.—y/t do not know. You will probably obtain the infor-
mation bjr advertising.

J. S. Rigby. — We believe the process is patented in England, A
reference to the Patent Office Library will give the desired infer*
mation.

W.B.-^Yaa can obtain it from any Urge operative chemist.



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D^vdQpm^t of th^ Qk^mkal Arts.



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THE CHEMICAL N^WS.

Vol. XXXII. No. 846.

CRYSTALLISED GLYCERIN.
Br DR. PAUL F. VAN IUM£L ROOS.

According to an observation of Wohler in 1867, the
glycerin seems to get in the solid state by exposing it
continually to movement at a low temperature.

As I have had the opportunity of experimenting on
crystallised glycerin I beg to call attention to the follow-
ing points : —

It seems that the glycerin only by being in the highest
state of chemical purity can be solidified.

When this chemically pure and perfedly anhydrous
crystallised glycerin is melted and afterwards exposed to
a temperature of 30** F., the smallest crystal of crystallised
glycerin transforms all the liquid again in a solid body.

If the temperature is 24*^ F. the transformation is
spontatuoust f.^., without putting any crystal into the
melted glycerin it gets solid by stirring the liquor vigor-
ously. The sp. gr. of this glycerin is at its melting-point
6o* F. 1-261.

When this glycerin is exposed to the adlion of hydro-
cyanic acid no alteration in the colour can be observed
after several weeks.

If it is mixed with yeast and exposed to a temperature
of 70* F. to 80* F. no fermentation results (after two or
three weeks of contad). Prof. Redtenbacher describes
tuch a fermentation, with propionic acid as one of the
results.' No acid has been observed in the mixture of
glycerin and yeast. If a glycerin contains one-tenth per
cent of water or more, the solidification is impossible.

The crystals of glycerin seem to have a prismatic
Ibrm, but it is very difficult to undertake crystallographic
measurements) the melting-point being so low and the
crystals very small. I am trying to get bigger crystallisa-
tions, and I hope to be able to mention soon some other
experiments about this rare material.

Stirling Chemical Workt, Stratford, E.,
Febraary a, 1876.



NOTE ON THE PREPARATION OF

METALLIC TITANIUM.

By SERGIUS KERN. St. Petersburg.

In many manuals of chemistry it is proposed to prepare
this metal by the ignition of metallic potassium or sodium
with the double fluoride of titanium and potassium

S'iKaFle). The titanium obtained by this process in the
rm of a grey powder decomposes water very easily at
100* ; but experiments proved that the titanium obtained
by this method always contains an excess of unoxidised
potassium or sodium, and the presence of these metals
explains well why the titanium decomposes water at such
a low temperature.

By the following method analogous to the produdion
of metallic silicon titanium is very easily prepared : —

Throup;h a tube with a bulb in the middle of it in which
•odium IS melted, vapours of titanium tetrachloride are
passed. Then oy the following rcadtion titanium is
obtained :—

TiCl4+4Na=Ti+4NaCl.

The mixture of titanium and sodium chloride is washed
by mean* of cold water ; the remaining precipitate of
titanium is washed with ethyl-ether and dried over sul-
phuric acid. Titanium carefully prepared by this process
hat fko adioa on water at 100^ and onl^ decompoiM it at
ibout ^oa*»



RJiPORX

ON THS

DEVELOPMENT OF THE CHEMICAL ARTS

DURING THE LAST TEN YEARS.*

By Dr. A. W. HOFMANN.

(Contianed from p. 50.)

II. Cold from Spontaneous Evaporation.
Liquids capable of forming vapours require, as is wel
known, for theh- 'transformation into the gaseous or
aeriform state, considerable quantities of heat, which are
necessary to maintain them in that condition. The heat
of evaporation is not indicated by the thermometer, and
is therefore often spoken of as combined heat in contra-
distindion from the so-calle(!^ free heat which ads upon
the thermometer and determines temperature. The com-
bined heat of different liquids variee greatly ; that of
water, «.^., at a temperature of evaporation b34'*» amount-
ing to 58*3 heat-untts, whilst that of an f<iual weight of
ether evaporating at the same temperature is only 90.

In the process of evaporation liquids are compelled to
draw their supply of heat for evaporation in the first place
from their own store of free heat. In consequence the
temperature sinks. As, however, heat is conveyed from
without to every substance whose temperature is lower
than that of its surroundings, and as this influx is the
more rapid, the greater the difference of temperature the
cooling process is not without its limits. A state of
Muilibrium is attained as soon as at a certain redudion
of temperature the loss of free heat caused hy continued
evaporation is compensated by the access of heat from
without.

The depth of the lowest temperature of an evaporating
liquid is more or less dependent on external circumstances.
This point is, however, in all cases reached the more
readily because as the temperature of evaporation falls
the tension of the vapour, and at the same time its density
and its quantity, decrease. The volume, #.^., of z cubic
metre, which, at 54*, can be filled with 37*25 grms. of
saturated watery vapour, admits, at o*, only 476 grms.,
and at — zo** ooty a'ag grms. Hence it is perfedly plain
that at — zo% circumslsances being otherwise unaltered*
evaporation proceeds much more slowly, and consequently
the accession of heat from without must have a greater
effea than at 34''.

The case is similar with other liquidst but so, in general
terms, that those evaporate most rapidly which, at a
given temperature of evaporation, possess the greatest
maximum tension, or, what amounts to the same thing,
those whose boiling-point lies lowest. Thus, if ether
evaporates spontaneously, the volume of i cubic metre
contains at 34*, 3750 grms. ; at o% Z5Z5 grms. ; and even
at - zo', 654 grm8.,of vapour ; whilst at this temperature
water yields only 2*29 grms. The much lower latent heat
of the vapour of ether is, as we see, amply compensated
by the far greater weight of the mass that evaporates
under equal conditions; Thus the strong cooling power
of evaporating ether is easily intelligible.

Still more striking in this respe^ are liquid sulphurous
acid and liquid ammonia, whose boiling-points are respec-
tively — zo* and —33*.

The intensity of the cooling of an evaporating liquid is
greatly augmented bv cutting ofi^ as far as possible, the
acces^on of heat n-om wiUiout. This is effeded, of
course, by the use of coverings which condud badly. On
the other hand an attempt is made to remove influences
which interfere with the speed of evaporation. An
essential point is removal oi the external atmospheric
pressure, since the air opposes a mechanical hindrance,
not, indeed, to the formation of the vapour rising from
any liquid, but to its rapid dispersal Hence a given



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58



Ready Means of Detecting Arsenical Compounds.



f Chemical Nswi,
\ Feb. zx. 1876.



space, for whose perfe^ repletion with saturated vapour
several minutes would not suffice, is almost instan-
taneously saturated if the air be withdrawn.

For the removal of the air a good air-pump is in most
cases employed. The air-pump alone as a promoter of
evaporation would, however, in general, prove insufficient,
since its action is not powerful enough to remove the
vapours with the same speed as they are produced in a
space free from air. But the evaporation is completely
interrupted as soon as the given space is filled with
vapour of the same temperature at which the evaporation
goes on. This purpose of a speedy removal of the
vapours arising from an evaporating liquid is satisfadorily
efifeded by their absorption ; thus the vapour of water is
removed by means of concentrated sulphuric acid.
(To be continued.)



ON A READY MEANS OF DETECTING
ARSENICAL COMPOUNDS.'

By EDMUND W. DAVY, M.A., M.D.
Profetsor of Forensic Medicine, Royal College of Surgeons, Ireland

The extensive employment of certain compounds of the
metal arsenic for the criminal destrudion of human life
has rendered their detedion under different circumstances
a matter of great importance to society, and to attain this
end they have long been objeds of much interest to the
chemist and toxicologist. Fortunately for mankind, the
metal itself, as well as its combinations, have been found
to be endowed with very chara<acristic chemical proper-
ties, and on these are based several excellent tests, by
which, in the hands of the chemist or in those skilled in
the deteAion of poisons, very minute quantities of arsenic
or of its compounds can be identified with more or less
facility ; and the fear of such detedion has aded as a
great preventative against their criminal employment as
poisons ; for, before such means of recognising their pre-
sence were discovered, secret poisoning by arsenious acid
— which is popularly known as ** arsenic " — was carried
on to a fearfiil extent, a greater number, perhaps, of indi-
viduals having been already deprived of life by that sub-
stance than by all the other known poisons put together.
But now, owing to our possessing the means by which
even very minute quantities of arsenical compounds can
be deteded with almost unerring certainty, and there
having been of late years certain legal restridions placed
on the sale of arsenic, cases of homicidal poisoning
by that substance have become comparatively rare.
Still, as such cases or those from accident do from time to
time occur, and as different arsenical compounds are used
for a number of industrial purposes, some of which are
highly objedlionable, endangering as they do the health,
and even lives, of many individuals, it is very desirable
that we should be able readily to deted those virulent
substances, not only where they may occur by design or
accident in different articles of food or drink, or in the
bodies of .those who have died from their effedts, but like-
wise where they may exist in various manufadured pro-
duds, the use of which might be attended with very
serious consequences. The test Which I would now pro-
pose, being one of such simplicity and ease of execution
that it might be performed by almost any one, will, I
should hope, be found useful for the objeds stated, espe-
cially to those who are not very conversant with the
details of chemical manipulation. As it is a modification
of Mr. Marsh's test, it is necessary for me briefly to refer
to that method before describing the one I would now
suggest. That gentleman^s test, as is well known, is
founded upon the circumstance that nascent hydrogen in
presence of certain compounds of arsenic will give rise to
the formation of arseniuretted hydrogen,— a gas which,



• A Paper read before the Royal Iriah Academy.



being possessed of very charaderistic properties, may be
easily recognised, and thus very minute quantities of ar-
senic under different circumstances can be readily deteded.
This method, as proposed by its discoverer, consists in
generating, in a suitable apparatus, hydrogen by the adion
of dilute sulphuric acid on metallic zinc, and then adding
in the stafe of solution the arsenical compound, when
arseniuretted hydrogen will be quickly generated, and a
fine jet of the gas being ignited, and a cold surface placed
down on the top of the flame, very charaderistic spots or
stains of metallic arsenic will be produced ; or the gas
being passed through a heated tube, it will be decomposed,
and a metallic sublimate formed at a short distance beyond
the heated portion. I need not refer to the apparatus re-
commended by Mr. Marsh for carrying out his test, as it is
now so well known, nor to the modifications of it which
have been subsequently proposed ; and I must acknow-
ledge that this beautiful means of deteding arsenic, owing
to its great delicacy and very conclusive results in the
hands of the experienced chemist, leaves but little to be
desired. It, however, labours under this serious disad-
vantage, that the acid and the zinc which are employed
in the process may one or other of them, or even both,
contain more or less of arsenic as an impurity, and con-
sequently the indications of that substance which are thus
obtained may be due not to its existing in the suspeded
matter or objed under investigation, but to its occurring
as an impurity in the materials employed in this process
for its detedion ; and I may add that it is difficult to get
in commerce the zinc and sulphuric acid required perfedly
free from arsenic.

To obviate more or less this source of fallacy several
modifications of the original process of Marsh have been
suggested. Thus Fleitmann, some years ago, proposed
the use of a strong solution of caustic potash, assisted by
heat, instead of the acid, to ad on the zinc as a means of
generating the hydrogen gas, and in this way one source
of arsenical contamination was avoided. It was found,
however, to be too slow a means of generating hydrogen
to deted arsenic in the usual way by Marsh's roetlu>d.
Prof. Bloxam has suggested the employment of a galvanic
battery for the generation of the same gas, and in this
way obviates the use of zinc, and thus excludes another
possible source of fallacy ; but, owing to the trouble and
expense attendant on the use of a galvanic battery, which
for this purpose must be of some power, and the arrd!nge.
ment being of rather a complicated charader, and still
requiring sulphuric acid, it has, I believe, been but little
employed. I should also add that the metal aluminium,
and more recently magnesium, have been proposed as
substitutes for zinc in Marsh's process or in Fleitmann's
modification of it, as being less likely to be contaminated
with arsenic than that metal. The modification which I
would now suggest, and which, a~s far as I can ascertain,
has not hitherto been proposed, is the employment of an
amalgam of sodium and mercury as a means of generating
the hydrogen required for the test ; and by the use of this
substance I do away with, altogether, the necessity of any
acid, and I employ two metals which are not liable to
arsenical contamination, ^s to sodium, I am not aware
that arsenic has ever been pointed out as one of its impu-
rities ; and as to its presence in mercury, that is, I believe,
a circumstance of very rare occurrence ; but, should it
exist in that metal as an impurity, it can be readily re-
moved from it by digesting the mercury in diluted nitric
acid, and afterwards well washing it with water. The
amalgam which I have found to answer very well for the
detedion of arsenic consists of i part by weight of so-
dium to 8 or 10 parts of mercury, and is easily made by
heating moderately in a test-tube over a lamp the mercury,
and then adding gradually in small pieces the sodium,
taking care to keep away the face, if unproteded from the
mouth of the tube, lest some of that metal in an ignited*
state might be spirted out during the addition of the first
portions. Those metals readily combine under these cir-
cumstaoces, forming an alloy (hat is liquid whilst liot, but



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Ready Means of Detecting Arsenical Compounds.



59



becomes hard and brittle when cold. The contents of the
tube, while still hot and liquid, are quickly poured out on
a clean plate, and, when cool, broken up in small tumps,
which are then immediately placed in a well-corked or
stoppered bottle.

The way I employ this amalgam is simply to place the
suspedled solution, or solid matter along with a little
water, in the bottom of a test-glass ; then add a small bit
of the amalgam, about the size of a grain of wheat ;
and lastly, place without delay, on the top of the
glass, a piece of white filtering-paper or the cover of a
white porcelain crucibU moistened with a drop of a dilute I
solution of nitrate of silver, slightly acidulated with nitric
acid, when — if arsenic is present — a dull black or deep
brown stain on the ^aper, or a dark silvery one on the
porcelain, will be quickly developed in the part moistened,
owing to the silver of the salt being reduced to the metal-
lic condition by the agency of the arseniuretted hydrogen
thus evolved, which, coming in conta^ with the nitrate
of silver, gives rise to the following readion : —

H3A8+6AgN03+3HaO=6HN03 + H3A803-|-3Aga.

The silver solution, which I have found to answer very
well for this purpose, was made by dissolving 20 grains of
the nitrate in an ounce of distilled water, and then adding
2 drops of strong nitric acid, to render the solution slightly
acid. I may further add that I generally place a small
disc of bibulous paper between the mixture in the glass
and the paper or cover moistened with the silver solution,
to intercept any particles of the liquid which might other-
wise be projeded against them, producing there minute
black spots, and thus interfering with the results of this
test.

I have found that exceedingly minute quantities of arse-
nic can be readily deteded by this very simple process :
thus the i-xoooth part of a grain of arsenious acid, dis-
solved in I c.c. of distilled water, gives a very decided
efifed in a few moments ; but much smaller quantities are
delegable by it : thus the i-xoo,oooth or even the
i-i,ooo,oooth part of a grain of arsenious acid, dissolved
in the same quantity of water {1 c.c), will afford, by the
blackening of the silver salt, alter a little time, an indi-
cation of the presence of arsenic. I have also ascertained
that this method of deteding arsenic is not only diredly
applicable to where it exists as arsenious acid, but likewise
to several other compounds of arsenic, whether they are
soluble or insoluble in water : thus, for example, the two
sulphides of arsenic (orpiment and realgar), the alkaline
arseniates, and even metallic arsenic itself if reduced to
powder, will readily show their arsenical nature by this
test *, and we may in a few moments deted by it the oc-
currence of arsenic in different green, yellow, and orange
pigments, which are still much employed in the manufac-
ture of wall-papers, in painting, and in the colouring of
certain textile and other articles used in dress or for orna-
mentation. Thus, for example, if a little of the colouring
matter of any arsenical pigment be scraped off from a
wall-paper, or a small piece of the paper itself be taken
and placed in a test glass with a little water, and having
been stirred or shaken to detach the colour, a piece of the
amalgam be added, it will — by the blackening of the
silver salt employed as before described — soon indicate
the presence of arsenic. In the same way it can be easily
demonstrated that the colouring matter in certain green
tarletans, calicoes, and other articles used for dress or for
ornament, are arsenical. I may further state that the
presence of organic matter seems to interfere but little
with this test, for I have found that very minute quantities
of arsenious acid, when mixed with considerable amounts
of milk, tea, coffee, ale, porter, soup, or stirabout, could —
.jwith almost the same facility — be deteded by this method,
*as where they were only simply dissolved in water ; thus
showing that the cases to which it is applicable are very
extended.

But I should here observe that, as in the case of
Marsh's original method, there is one other metal which



under certain circumstances, will produce with the sodium
amalgam results closely resembling those occasioned by
arsenic : the metal I refer to is antimony, which is capable
of uniting with nascent hydrogen to form a gas (antimo-
niuretted hydrogen), which, coming in contad with nitrate
of silver, produces a black antimonide of that metal, by
the following readion : —

H3Sb-}-3AgN03=xAg3Sb4-3HN03,

and the blackening of the silver salt from the formation
of that compound might be easily mistaken for the effed
produced by the arsenical gas.

But owing to the fad, nrst pointed out by Flettmann,
that antimoniuretted hydrogen is not evolved fexcept,
perhaps, as a mere trace) from strongly alkaline solutions,
though the conditions may exist there for its formation,
and as the adion of the sodium amalgam is to render the
mixture quickly alkaline, there will be only a very minute
quantity of the antimony that may be present so evolved ;
and, by previously rendering the mixture strongly alkaline,
we may almost altogether prevent the evolution of that
gas. If, however, we make the mixture containing the



Online LibrarySir William CrookesThe Chemical news and journal of industrial science; with which ..., Volume 33 → online text (page 14 of 82)