Michael Faraday.

Experimental researches in chemistry and physics online

. (page 15 of 49)
Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 15 of 49)
Font size
QR-code for this ebook

water, the gas was collected, the excess of liquid being allowed
to boil over. The hydrogen was received in the usual manner
into jars filled with the water of the trough, the transferring jar,
when filled, being entirely immersed in the water, so as to ex-
clude the air from every part, even of the stopcock. The first
jar of gas was thrown away, and only the latter portions used.

The gas being ready, the experimental tube was attached to
the transferring jar by a connecting piece, so that the part of
it containing the zinc and potash was horizontal, whilst the
other portion descended directly downwards. A cup of clean
mercury, the metal being about an inch in depth, was then
held under the open end of the tube, and by lowering the jar
containing the hydrogen in the water of the pneumatic trough,
so as to give sufficient pressure, and opening the stopcock, the
hydrogen in the jar was made to pass through the tube, and
sweep all the common air before it. When from 100 to 150
cubic inches, or from 200 to 300 times the contents of the tube
had passed through, the cup of mercury was raised as high as
it could be, so as to prevent the passage of any more gas, the
pressure from the jar in the water-trough was partly removed,
and the stopcock closed ; then, by lowering the cup of mercury
a little, the surface of the metal in it was made lower than that
within the tube, and in this state of things the flame of a spirit-
lamp applied to the contracted part of the tube (a, fig. 3, plate I),
sealed it hermetically, without the introduction of any air, and
separated the apparatus from the jar on the water-trough.

In this way every precaution was taken that I could devise
for the exclusion of nitrogen ; yet, when a lamp was applied to
the potash and zinc, the alkali no sooner melted down and

148 On the Formation of Ammonia, $c. [1825*

mingled with the metal, than ammonia was developed, which
rendered the turmeric paper brown, the original yellow re-ap-
pearing by the application of heat to the part.

Still anxious to obtain a potash which should be unexcep-
tionably free from any source of nitrogen, I heated a portion of
potash with zinc, endeavouring to exhaust anything it might
contain which could give rise to the formation of ammonia : it
was then dissolved in pure water, allowed to settle, the clear
portion poured off and evaporated in a flask by boiling ; but
the potash thus prepared gave ammonia, when heated with
zinc, in hydrogen gas.

With regard to the evidence of the nature of the substance
produced, it was concluded to be ammonia in the experiments
made in hydrogen, from its changing the colour of turmeric
paper to reddish- brown ; from the disappearance of the red-
dish-brown tint and' reproduction of yellow colour by heat ;
from its solubility in water, as evinced by the greater depth of
colour on moist turmeric paper than on dry ; from its odour ;
and from its yielding white fumes with the vapour of muriatic
acid. When formed in open tubes, its nature was still further
tested by its neutralizing acids and restoring the blue colour
of reddened litmus paper ; by its rendering a minute drop of
sulphate of copper on a slip of white paper deep blue ; and
also, at the suggestion of Dr. Paris, by introducing into it a
slip of paper moistened in a mixed solution of nitrate of silver
and arsenious acid, the yellow tint of arsenite of silver being
immediately produced.

These experiments upon the production of ammonia from
substances apparently containing no nitrogen, will call to mind
that made by Mr. Woodhouse, of Philadelphia, on the action
of water on a calcined mixture of charcoal and potash, during
which much ammonia was produced * ; and also the strict
investigation of that experiment made by the President of the
Royal Society during his inquiries into the nature of elementary
bodies f. Sir Humphry Davy found that when one part of
potash and four of charcoal were ignited in close vessels
cooled out of contact of the atmosphere, pure water admitted
to the mixture, and the whole distilled, small quantities of am-
monia were produced. That when the operation was repeated

Nicholson's Journal, xxi. 290. t Phil, Trans. 1809, p. 100; 1810, p. 43.

1825.] On the Formation of Ammonia, c. 149

upon the same mixture ignited a second time, the proportion
diminished ; in a third operation it was sensible ; in a fourth
barely perceptible. The same mixture, however, by the ad-
dition of a new quantity of potash, again gained the power of
producing ammonia in two or three successive operations ; and
when any mixture had ceased to give ammonia, the power was
not restored by cooling it in contact with air.

Sir Humphry Davy refrains from drawing conclusions from
these processes, observing with regard to the composition of
nitrogen in these experiments, that till the weight of the sub-
stances concerned and produced in these operations are com-
pared, no correct decision on the question can be made : I am
anxious to be understood as imitating the caution of one whose
judgment stands so high in chemical science ; and therefore
draw no positive conclusion from the experiment I have de-
scribed, or from the results I have yet to mention. As, how-
ever, I think they may lead to elucidations of the question, I
shall venture to give them, not with the minute detail of the
preceding experiment, but in a more general manner.

Potash is not the only substance which produces this effect
with the metals and vegetable substances. Soda produces it ;
so also does lime and baryta, the latter not being so effective
as the former, or producing the phenomena so generally. The
common metallic oxides, as those of manganese, copper, tin,
lead, &c., do not act in this manner.

Water or its elements appear to be necessary to the experi-
ment. Potash or soda in the state of hydrates generally con-
tain the water necessary. Potash, dried as much as could be
by heat, produced little or no ammonia with zinc ; but re-dis-
solved in pure water and evaporated, more water being left in
it than before, it was found to produce it as usual. Pure
caustic lime, with very dry linen, produced scarcely a trace of
ammonia, whilst the same portion of linen with hydrate of lime
yielded it readily.

The metals when mixed with the potash appear to act by, or
according to their power of absorbing oxygen. Potassium,
iron, zinc, tin, lead, and arsenic evolve much ammonia, whilst
spongy platina, silver, gold, &c., produce no effect of the kind.
A small portion of fine clean iron wire dropped into potash
melted at the bottom of a tube, caused the evolution of some

150 On the Formation of Ammonia, $c. [1825,

ammonia, but it soon ceased, and the wire blackened upon its
surface ; the introduction of a second portion of clean wire
caused a second evolution of ammonia. Clean copper wire, in
fused potash, caused a very slight evolution of ammonia, and
became tarnished.

The following, among' other vegetable substances supposed
to contain no nitrogen, have been tried with potash in tubes
open to the air : Lignine, prepared by boiling linen in weak
solution of potash, then in water, afterwards in weak acid, and
finally in water again ; oxalate of potassa, oxalate of lime, tar-
trate of lead, acetate of lime, asphaltum, gave very striking
quantities to turmeric and litmus paper: acetate of potash,
acetate of lead, tartrate of potash, benzoate of potash, oxalate
of lead, sugar, wax, olive oil, naphthaline, produced ammonia,
but in smaller quantity : resin appeared to yield none, nor
when potash was heated in the vapour of alcohol or ether* or
in olefiant gas, could any ammonia be detected.

It may be remarked, that much appeared to depend upon
the quantity of potash used ; sugar, for instance, which with a
little potash would with difficulty yield traces of ammonia, does
so very readily when the quantity of potash is doubled or
trebled ; and linen, which with potash gives ammonia very
readily, yields it the more readily, and in greater quantity, as
the proportion of potash is increased.

The experiments with the substances which contain carbon,
assimilate, in consequence of the presence of that body, with
the one by Mr. Woodhouse. Whether the substances act
exactly as charcoal does, probably cannot be decided until the
correct nature of the action is ascertained; but there are
apparently some very evident differences. The ammonia in
the charcoal experiment does not exist until after the ignition,
nor before the addition of water; but in several experiments
of the nature of those described in this paper, the ammonia is
evolved before the substances acting or acted upon are charred.
Thus, if linen fibre, cut small, be mixed in the tube with hy-
drate of lime, and heated, ammonia is evolved before the heat
has risen so high as to render the linen more than slightly
brown; and oxalate of potash, in a tube with potash, when
heated, gives much ammonia before any blackening is produced.
Mr. Woodhouse's experiment may be very readily repeated.

1825.] On the Formation of Ammonia, $c, 151

though not in an exact way, by heating a little tartrate of lead
with potash in a tube in the flame of a spirit-lamp, driving off
the water and first products, and raising the residue to dull
redness. If a drop of water be allowed to flow down on to the
residue when cold, and it be then heated, ammonia will be
found to rise with the water.

I was induced in the course of these experiments to try again
and again, whether the potash or lime would not yield ammonia
when heated alone ; but when well prepared, and the tubes
experimented in perfectly clean, they gave no indications of it.
By exposure to air for three days in a room, hydrate of lime
appeared to have acquired the power of evolving a little am-
monia when heated, and caustic lime so exposed gave still
stronger traces of it. Potash also exhibited an effect of this
kind, and potash which had been heated with zinc, and con-
tained oxide of zinc, most decidedly. Some potash and zinc were
heated together ; a part was immediately put into a clean close
bottle ; another part was dissolved in pure water, decanted, the
solution evaporated in a covered Wedgewood's basin, and then
also set aside in a close vessel for twenty-four hours : at the end
of that time the first portion, heated in a tube, gave no decided
trace of ammonia, but the latter yielded very distinct evidence
of its presence, having apparently absorbed the substance which
was its source from the atmosphere during the operations it
had been submitted to. White Cornish clay being heated red-
hot, and then exposed to the air for a week, gave plenty of
ammonia when heated in a tube. When the substances were
preserved in well-stoppered phials, these effects were not pro-

Such are the general and some of the particular facts which
I have observed relative to this anomalous production of am-
monia. I have refrained from all reasoning upon the proba-
bility of the compound nature of nitrogen ; or upon what might
be imagined to be its elements, not seeing sufficient to justify
more than private opinion on that matter. I have endeavoured
to make the principal experiments as unexceptionable as pos-
sible, by excluding every source of nitrogen, but I must con-
fess I have not convinced myself I have succeeded. The results
seem to me of such a nature as to deserve attention, and if it
should hereafter be proved that nitrogen had entered in some

152 On the substitution of Tubes for Bottles. [1825

unperceived way into the experiments, they will still show the
extreme delicacy of heat, or heat and potash, as a test of its
presence by the formation of ammonia.

With respect to the delicacy of the test, it may be observed
that it offers many facilities to the detection of nitrogen when in
certain states of combination, which chemists probably were
not before aware of. A portion of asbestos, which had been
heated red-hot, was introduced into a tube by metallic forceps
and heated ; it gave no ammonia ; another similar portion, com-
pressed together, and introduced by the fingers, gave ammonia
when heated. A very minute particle of nitre was dropped
into hydrate of potassa, and heated to dull redness ; it gave no
ammonia ; a small piece of zinc-foil, dropped in and the heat
applied, caused an abundant evolution of that substance.

The circumstance also of absorption by lime and other bodies,
of something from inhabited atmospheres, which yields am-
monia when thus tested, is very interesting ; and Dr. Paris has
suggested to me that this power may probably be applicable to
the examination of the atmosphere of infected and inhabited
places, and may perhaps furnish the means of investigating
such atmospheres upon correct principles.

February 17,

On the Substitution of Tubes for Bottles, in the preservation
of certain Fluids, such as Chloride of Sulphur, Protochlo*
rides of Phosphorus and Carbon, $c*

THERE are many fluids in the laboratory which are much more
conveniently retained in tubes, such as that depicted, fig. 5,
plate I, than in bottles, and from which they may be taken in
a less wasteful manner when required for the purpose of expe-
riment. A piece of glass tube, a quarter of an inch or more in
diameter, being selected, is to be closed at one end by the
blowpipe ; and then, being softened near the other end, is to
be drawn out obliquely, so as to form the long narrow neck
represented in the figure, but to which, in the first case,
the short piece of tube is to be left attached ; this forms a
funnel, into which the preparation to be preserved is to be put.
Then, warming the body of the tube, the expanding air passes
* Quarterly Journal of Science, xix. 149.

1825.] Composition of Crystals of Sulphate of Soda. 153

out through the fluid ; and afterwards, on cooling the vessel,
the liquid descends into it. A small spirit-lamp flame being
now applied at the upper part of the long neck, softens the
glass, which is then to be drawn out to a fine point and sealed.
In this state the substance may be preserved clean and pure
for any length of time.

If a small portion be required for an experiment, the extreme
point of the neck is to be opened by pinching it off, the tube
is then to be inclined until the quantity required has entered
the neck, where, by capillary attraction, it will form a small
column, and the tube being warmed by the hand, the atmo-
sphere within it will expand and expel the portion of fluid on
to the place required. A very little practice will enable the
experimenter to judge of the quantity he is forcing out, and in
this way he may take a portion not larger than the l-20th of a
common drop, or he may take the whole contents of the tube.
When the quantity required has been taken out, the tube is to
be placed in an upright position, and the flame of a lamp or
candle, or even a piece of paper, closes the aperture in a
moment and as perfectly as before.

I have found these tubes very serviceable when working with
substances either very small in quantity or obtained with great
difficulty, in consequence of the entire prevention of waste
resulting from their use. They are easily labeled by scratch-
ing the name of the substance with a diamond on them, and
may conveniently be retained by putting several of them toge-
ther into a tumbler, or other glass of that kind.

Composition of Crystals of Sulphate of Soda*.
IT is known that when a hot strong solution of sulphate of
soda is put into a vessel and closed up, it may be reduced to
common temperatures without crystallizing, although, if the
vessel be opened, abundance of crystals will immediately form.
It has also frequently been observed, that in some circumstances
crystals would form in the solution during cooling, even though
the vessel had not been opened or agitated. These crystals,
when observed in the solution, are very transparent and of a
large size ; they are quadrangular prisms, with dihedral summits.

* Quarterly Journal of Science, xix. 153.

t On new Compounds of Carbon and Hydrogen, $c. [1825.

Upon opening the vessel, the surrounding solution crystallizes
rapidly, enveloping the first-formed set of crystals with others,
which, however, are very readily distinguished from them in
consequence of their immediately assuming a white opake
appearance. Upon taking out the crystals, those first formed
are found to be much harder than the usual crystals of sulphate
of soda, and, when broken, it is found that the opacity is not
merely superficial, but that it penetrates them to a considerable
depth, and even at times throughout.

These harder and peculiar crystals are readily obtained by
closing up a solution of sulphate of soda, saturated at 180, in
a Florence flask, boiling the solution in the flask so as to expel
the dir before closing it. Upon standing twenty-four hours,
fine groups of crystals are formed. When the flask is opened,
the solution deposits fresh crystals ; but on breaking the flask,
the latter may be scraped off by a knife in consequence of the
superior hardness of the first set.

The hard crystals when separated are found to be efflo-
rescent, like those of the usual kind, and they ultimately give
off all their water, leaving only dry sulphate of soda. When
a given weight was heated in a platina crucible, one half their
weight passed off as water, the rest being dry salt ; they
consequently contain eight proportionals of water, or 72 sul-
phate of soda, and 8x9 = 72 water. The usual crystals of
sulphate of soda contain 10 proportionals of water.

When crystallized sulphate of soda is heated in a flask, a
part of it dissolves in the water present, whilst the rest is thrown
down in an anhydrous state. The solution at 180 appears to
contain one proportional of salt 72, and 18 proportionals of
water 162; from which, if correct, it would result, that when
the crystals are heated to 180 of the salt take all the water,
whilst | separate in the dry state.

On new Compounds of Carbon and Hydrogen, and on certain
other Products obtained during the Decomposition of Oil by
Heat*. [Read June \ t 1925.]

THE object of the paper which I have the honour of submitting

at this time to the attention of the Royal Society, is to describe

* Phil. Trans. 1825, p, 440; and Phil. Mag. Ixvi. p. 180.

1825.] On new Compounds of Carbon and Hydrogen^ $<?. 155

particularly two new compounds of carbon and hydrogen, and
generally, other products obtained during the decomposition of
oil by heat. My attention was first called to the substances
formed in oil at moderate and at high temperatures, in the
year 1820; and since then 1 have endeavoured to lay hold of
every opportunity for obtaining information on the subject. A
particularly favourable one has been afforded me lately through
the kindness of Mr. Gordon, who has furnished me with con-
siderable quantities of a fluid obtained during the compression
of oil-gas, of which I had some years since possessed small
portions, sufficient to excite great interest, but not to satisfy it.

It is now generally known, that in the operations of the
Portable Gas Company, when the oil-gas used is compressed in
the vessels, a fluid is deposited, which may be drawn off and
preserved in the liquid state. The pressure applied amounts
to 30 atmospheres ; and in the operation, the gas previously
contained in a gasometer over water, first passes into a large
strong receiver, and from it, by pipes, into the portable vessels.
It is in the receiver that the condensation principally takes
place ; and it is from that vessel that the liquid I have worked
with has been taken. The fluid is drawn off at the bottom by
opening a conical valve : at first a portion of water generally
comes out, and then the liquid. It effervesces as it issues
forth ; and by the difference of refractive power it may be seen
that a dense transparent vapour is descending through the
air from the aperture. The effervescence immediately ceases ;
and the liquid may be readily retained in ordinary stoppered,
or even corked bottles, a thin phial being sufficiently strong to
confine it. I understand that 1000 cubical feet of good gas
yield nearly one gallon of the fluid.

The substance appears as a thin light fluid ; sometimes trans-
parent and colourless, at others opalescent, being yellow or
brown by transmitted, and green by reflected light. It has the
odour of oil-gas. When the bottle containing it is opened,
evaporation takes place from the surface of the liquid ; and it
may be seen by the striae in the air that vapour is passing oft'
from it. Sometimes in such circumstances it will boil, if the
bottle and its contents have had their temperature raised a few
degrees. After a short time this abundant evolution of vapour
ceases, and the remaining portion is comparatively fixed*

156 On new Compounds of Carbon and Hydrogen, ftc. [1825.

The specific gravity of this substance is 0*821. It does not
solidify at a temperature of F. It is insoluble, or nearly so,
in water ; very soluble in alcohol, ether, and volatile and fixed
oils. It is neutral to test colours. It is not more soluble in
alkaline solutions than in water ; and only a small portion is
acted upon by them. Muriatic acid has no action upon it.
Nitric acid gradually acts upon it, producing nitrous acid,
nitric oxide gas, carbonic, and sometimes hydrocyanic acid, &c.,
but the action is not violent. Sulphuric acid acts upon it in a
very remarkable and peculiar manner, which I shall have occa-
sion to refer to more particularly presently.

This fluid is a mixture of various bodies ; which, though
they resemble each other in being highly combustible, and
throwing off much smoke when burnt in large flame, may yet
by their difference of volatility be separated in part from each
other. Some of it drawn from the condenser, after the press-
ure had been repeatedly raised to 30 atmospheres, and at
a time when it was at 28 atmospheres, then introduced rapidly
into a stoppered bottle and closed up, was, when brought home,
put into a flask and distilled, its temperature being raised by
the hand. The vapour which came off, and which caused the
appearance of boiling, was passed through a glass tube at 0,
and then conducted to the mercurial trough ; but little uncon-
densed vapour came over, not more than thrice the bulk of the
liquid; a portion of fluid collected in the cold tube, which
boiled and evaporated when the temperature was allowed to
rise ; and the great bulk of the liquid which remained might
now be raised to a comparatively high point, before it entered
into ebullition.

A thermometer being introduced into another portion of
the fluid, heat was applied, so as to keep the temperature just
at the boiling-point. When the vessel containing it was opened,
it began to boil at 60 F. As the more volatile portions were
dissipated, the temperature rose : before a tenth part had been
thrown off, the temperature was above 100. The heat con-
tinued gradually to rise, and before the substance was all
volatilized it had attained 250.

With the hope of separating some distinct substances from
this evident mixture, a quantity of it was distilled, and the
vapours condensed at a temperature of into [separate por-

1825.] On neiv Compounds of Carbon and Hydrogen, $c. 157

tionsj the receiver being changed with each rise of 10 in the
retort, and the liquid retained in a state of incipient ebullition.
In this way a succession of products were obtained, but they
were by no means constant; for the portions, for instance,
which came over when the fluid was boiling from 160 to 170,
when re-distilled began to boil at 130, and a part remained
which did not rise under 200. By repeatedly rectifying all
these portions, and adding similar products together, I was
able to diminish these differences of temperature, and at last
bring them more nearly to resemble a series of substances of
different volatility. During these operations I had occasion to
remark, that the boiling-point was more constant at or between
176 and 190, than at any other temperature, large quantities
of fluid distilling over without any change in the degree, whilst
in other parts of the series it was constantly rising. This
induced me to search in the products obtained between these
points for some definite substance ; and I ultimately succeeded
in separating a new compound of carbon and hydrogen, which
I may by anticipation distinguish as bicarburet of hydrogen.

Bicarburet of Hydrogen. This substance was obtained in

Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 15 of 49)