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Higgins in the year 1777J, and in which tones are produced
by burning a jet of hydrogen within a glass jar or tube. These
tones vary with the diameter, the thickness, the length, and
the substance of the tube or jar ; and also with changes in the
jet. They have frequently attracted attention, and some at-
tempts to explain their origin have been made.

After Dr. Higgins, Brugnatelli in Italy, and M. Pictet at
Geneva, described the experiment, and the effects produced
by varying the position and other circumstances of the jet and
tube ; and M. De la Rive read a paper at Geneva (published
in the * Journal de Physique,' Iv. 165), in which he accounted
for the phenomenon by the alternate expansion and contrac-
tion of aqueous vapour. That they are not owing to aqueous
vapour, will be evident from some experiments to be described.
I have no doubt they are caused by vibrations, similar to those
described by M. De la Rive ; but the vibrations are produced

* See ' Condensation of Gases.'

t Quarterly Journal of Science, v. 274.

Nicholson's Journal, vol. i. p. 130.



22 On the Sounds produced by Flame in Tubes. [1818.

in a different manner, an^.1 may result from the action of any
flame.

I was induced to make a few experiments on this subject, in
consequence of the request of Mr. J. Stodart that it should
be introduced at one of the .evening meetings of the Members
and friends of the Royal Institution ; and was soon satisfied
that no correct explanation had been given. That the sounds
were not owing to any action of aqueous vapour, was shown
by heating the whole tube above 212; and still more evidently
by an experiment, in which I succeeded in producing them
from a jet of carbonic oxide. That they do not originate in
vibrations of the tube, caused by the current of air passing
through it, was shown by using cracked glass tubes, tubes
wrapped up in a cloth ; and I have obtained very fine sounds
by using a tube formed at the moment by rolling up half a
sheet of cartridge-paper, and keeping it in form by grasping it
in the hand. The sounds have been accounted for, as well as
their supposed peculiarity of production by hydrogen, by the
supposition of a rapid current of air through the tube ; but
that this is not essential, is shown by using tubes closed at one
end, and bell-glasses, as described by Mr. Higgins in his first
experiment.

I was surprised to find, on my first trials with other gases,
that I could produce those sounds from them which had been
supposed to be generated exclusively by hydrogen ; and this,
with the insufficiency of the explanations that had yet been
given, induced me to search after the cause of an effect which
appeared to be produced generally by all flame.

In examining attentively the appearance of a flame when
introduced into a tube, it will commonly be found, that, on
coming within its aperture, a current of air is established
through the tube, which compresses the flame into a much
smaller space ; it is slightly lengthened, but its diameter is
considerably diminished : on being introduced a little further,
and as the tube becomes warm, this effect is increased, and the
flame is gradually compressed a little above its commencement
at the orifice of the jet, more than at any other part ; a very
faint sound begins to be heard, and as it increases, vibrations
may be perceived in the flame, which are most evident in the
upper part, but frequently also perceptible in the lower and



1818.] On the Sounds produced by Flame in Tubes. 23

smaller portion ; these increase with the sound, which at last
becomes very loud, and if the flame be further introduced into
the tube, it is generally blown out. Such are the general
appearances with hydrogen. If a jet of olefiant or coal-gas,
both of which I have ascertained may be used successfully,
be substituted, then, in addition to those appearances, it will
be perceived, that as the bright flame of the gas enters the
tube, its splendour is diminished, and it burns with less light.

By substituting other gases and inflammable vapours for
hydrogen, and using other vessels than tubes, I was enabled
so to magnify the effects, as to perceive more distinctly what
took place in the flame at these times, and soon concluded
that the sound was nothing more than the report of a con-
tinued explosion.

Sir H. Davy has explained the nature of flame perfectly;
and has shown that it is always a combination of the elements
of explosive atmospheres. In continued flame, as of a jet of
gas, the combination takes place successively, and without
noise, as the explosive mixture is made. In what is properly
called an explosion, the combination takes place at once
throughout a considerable quantity of mixture, and sound
results from the mechanical forces thus suddenly brought into
action ; and a roaring flame presents some of the characters of
both. If a strong flame be blown on by the mouth, a pair of
bellows, the draught of a chimney, or other means, the air and
the gaseous inflammable matter are made to mix in explosive
proportions in considerable quantities at once, and these being
fired by the contiguous flame, combine at once throughout
their whole extent, and produce sound : the effect is rapidly
repeated in various parts of the flame as long as the air is mixed
thus forcibly with it, and a repetition of noise is produced,
which constitutes the roar.

Now this I believe to be exactly analogous to that which
takes place in what have been called the singing tubes ; but
in them the explosions are generally more minute and more
rapid. By placing the flame in the tube, a strong current of
air is determined up it, which envelopes the flame on every
side. The current is stronger in the axis of the tube than in
any other part, in consequence of the friction at the sides and
the position of the flame in the middle; and just at the en-



24 On the Sounds produced by Flame in Tubes. [1818.

trance of the tube an additional effect of the same kind is pro-
duced, by the edge obstructing the air which passes near it;
the air is therefore propelled on to the flame, and mingling
with the inflammable matter existing there, forms portions
of exploding mixtures, which are fired by the contiguous
burning parts, and produce sound, in the manner already
described, with a roaring flame ; only, the impelled current
being more uniform, and the detonations taking place more
rapidly and regularly, and in smaller quantities, the sound
becomes continuous and musical, and is rendered still more so
by the effect of the tube in forming an echo.

That the roaring flame gives sound in consequence of ex-
plosion, can hardly be doubted ; and the progress from a roar
to a musical tone is easily shown in the following manner:
Take a lamp with a common cotton wick, and trim it with aether
or alcohol ; light it, and hold a tube over the flame (that which
I have used is a thin tube of glass about an inch in diameter,
and nearly 30 inches long) ; in a few seconds after introducing
the flame, the draught will be sufficiently strong to blow it
out, but if the current be obstructed by applying the fingers
round the lamp at the bottom of the tube, combustion will go
on, though irregularly ; then, by a little management in ad-
mitting the air on one side or the other, and in greater or
lesser quantity, it may be impelled on to the flame in various
degrees, so as to produce a rough roaring sound, or one more
continued and uniform, of a higher note, and more musical ;
and these may be made to pass into each other at pleasure :
then, by substituting a stream of aethereal vapour for the wick,
which may be easily done from a small flask through a tube,
the tones may be brought out more and more clearly, until
they exactly resemble those of hydrogen.

A similar experiment may be made with coal-gas : light a
small Argand burner with a low flame, and bring a glass tube,
which is very little larger than the diameter of the flame,
down upon it so as nearly to include it : the current of air will
be impelled on the external part of the flame, it will remove
the limit of combustion a little way up from the burner, that
part of the flame will vibrate rapidly, burning with continued
explosions, and an irregular tone will be obtained. Remove
the burner, and fix on a long slender pipe to the gas-tube, so



1818.] On the Sounds produced by Flame in Tubes. 25

as to afford a candle-flame that may be introduced into the
tube ; light it, and introduce it about 5 or 6 inches, and a clear
musical tone will be obtained.

During the experiments that were made in consequence of
this view of the subject, many appearances occurred which
might be added to the above account, to support the opinion
that the vibration of the flame, in consequence of rapid suc-
cessive explosions, is the cause of the sound ; but they are
neglected, because they are supposed unnecessary.

If the explanation given be true, then the only requisite to
the production of these sounds is the successive sudden in-
flammation of portions of gaseous explosive mixtures. These
mixtures are most easily made by propelling a stream of air on
to a stream of inflammable gaseous matter ; but it is also pos-
sible to make them in other ways, and the same phenomenon
may be produced in a different manner.

That the tube is not essentially necessary, is shown by making
it swell out into a cylinder of 3 or 4 inches diameter, except
above and below ; or part of it may be extended into a globe.
I took two air-jars that were open above, but with contracted
apertures ; one of these was inverted over an inflamed jet of
hydrogen, so as to form a lamp or bell-glass about it : there
was no effect of sound, because the downward currents from
above interfered with the stream of air issuing up from be-
neath, and made it irregular ; but placing the second receiver
on the first, applying them edge to edge, so as to preserve the
current of air upwards from disturbing forces, the sounds were
immediately produced ; and lastly, I succeeded in obtaining
the tones by the draught of a common chimney ; for, by attach-
ing a large inverted air-jar to the end of a funnel-pipe that
came from the flue, closing the other lower opening into it, and
introducing an inflamed jet of hydrogen within the lower con-
tracted orifice of the glass, the sounds were produced.

That the same sounds may be obtained by means different
to those above described, though depending on the same cause,
is shown by some experiments made by Sir H. Davy, in his
first researches on the miners' safety-lamp. Small wire-gauze
safety-lamps being introduced into air-jars filled with explosive
atmospheres, the gases burnt on the inside of the cylinder, and



26 On the Sounds produced by Flame in Tubes. [1818.

produced sounds similar to those obtained from a jet of flame
in a tube.

Having thus endeavoured to account for the phenomenon of
sounds produced by jets of flame, in tubes and other vessels, I
shall notice shortly the combustible bodies I have tried. Car-
bonic oxide, olefiant gas, light hydrocarbonate, coal-gas, sul-
phuretted hydrogen, and arseniuretted hydrogen, were burned
at the end of a long narrow brass tube rising up from a trans-
ferring jar placed under pressure in a pneumatic trough. ./Ether
was burned from the end of a tube fixed in a flask containing a
small quantity which was heated ; but a better method, and
one I afterwards adopted, is to pour a little aether into a blad-
der, and then force common air in ; so much aether rises in
vapour as to prevent the mixture being detonating, and it may
be pressed out and burnt at the end of a tube. All these were
very successful. Alcohol was more difficult to manage from
being less volatile; but it succeeded when raised in vapour
from a flask and burnt at a tube. In trials made with a wax
taper, no distinct tone could be produced ; but when the tube
was made very hot, so as to assist the current through it,
something like the commencement of a sound was heard at the
moment the taper was blown out by the current.

Hydrogen is by far the best substance by which to produce
these tones ; and its superiority depends upon the low tempe-
rature at which it inflames, the intense heat it produces in com-
bustion, and the small quantity of oxygen that a given bulk of
it requires. It is in consequence less easily extinguished by
the current than other gases, the current formed is more power-
ful and rapid, and an explosive mixture is sooner made. With
gases producing little heat by combustion, and therefore occa-
sioning but a feeble current, the effect is increased by first
heating the tube at a fire, and when not heated previously, the
tone is perceived to improve as the tube becomes hot from the
flame playing in it.

Some variations of the form of the vessel enclosing the flame,
and the material used, have been mentioned. Globes from
7 to 2 inches in diameter, with short necks, give very low
tones : bottles, Florence flasks, and phials have always suc-
ceeded : air-jars from 4 inches diameter to a very small size



1821.] Action of Boracic Acid on Turmeric. 27

may be used. I constructed some angular tubes of long nar-
row slips of glass and wood, placing three or four together, so
as to form a triangular or square tube, tying them round with
packthread, and easily obtained tones from hydrogen by means
of them ; and it is evident that variations of the channel, the
use of which is to form and direct the current of air, may be
made without end. May 11, 1818.



Boracic Acid, action on Turmeric*.

IT may be observed, in connexion with the changes of colour
produced by acids, that boracic acid reddens turmeric paper in
all states of dilution. When a very weak solution is used, it
requires a few minutes to produce the effect ; but when pro-
duced, it exactly resembles that of alkali. It has been said
that strong solutions of alkaline borates, which have been made
purposely acid, have become alkaline on being diluted. This
has probably arisen from a careless observance of the effect
above noticed, and a want of corroboration by the effect on
litmus paper of the diluted solution. I find that solutions once
made acid redden litmus paper, however diluted ; though at
the same time they also redden turmeric paper. Paper co-
loured by rhubarb is not affected in this way.



Boracic Acid^.

I MENTIONED above the property possessed by boracic acid
in all states of dilution, of reddening turmeric paper in the
manner of an alkali. Since then the attention of M. Desfosses
has been drawn to the action of boracic acid on this colouring
matter (Annales de Chimie, xvi. p. 75), apparently without a
knowledge of the previous remark ; and he has shown that a
mixture of boracic with other acids, reddens turmeric very
deeply, and that turmeric, when acted on by this mixture of
acids, has its nature altered, for it approaches somewhat to
turnsole, and is rendered blue by alkalies.

There is something so curious in this action of boracic acid
on turmeric, that I am tempted to offer a few more results on
the subject.

* Quarterly Journal of Science, vi. 152. f Ibid. xi. 403.



28 Boracic Acid. [1821.

Turmeric paper dipped into a solution of pure boracic acid
very speedily receives a slight tint of brownish-red, which, when
the paper is dry, is very marked, and resembles that produced
by a weak alkali. In this state the properties of the colouring
matter are entirely different to what they were before : sul-
phuric, nitric, muriatic, and phosphoric acids, even when very
dilute, produce a bright red colour on this paper, and a strong
solution of oxalic acid also reddens it. Alkalies, on the con-
trary, make it blue, gradually passing to shades of purplish-
blue, yellowish-red, &c. As long as the acids or alkalies
remain on the paper, if not so strong as to destroy the colour-
ing matter, the new colour remains, but a slight washing removes
them, and then the boracic acid tint returns, and the paper has
its first peculiar properties. When altered by muriatic acid or
ammonia, the mere volatilization restores the paper to its first
state ; with the ammonia the restoration is very ready and per-
fect ; with the acid it is longer and not so complete. If the
paper reddened by boracic acid be heated, the yellow of the tur-
meric is almost restored, and then it takes from acids a weaker
red tinge, and from alkalies a more purplish colour than before.

Turmeric, thus altered by boracic acid, is readily restored to
its original state by washing ; altered turmeric paper when put
in water for two or three hours resumes its original properties,
and acts, as at first, in testing the alkalies.

When the altered paper is placed in sunlight a few days,
the colour is soon destroyed as with turmeric alone, and then
neither acid nor alkali will affect it.

When turmeric paper is dipped into neutral or slightly alka-
line borate of ammonia, it soon becomes of the red tint produced
by boracic acid, and is in every respect as if altered by bo-
racic acid alone ; when this paper is made blue by ammonia,
the ammonia easily washes out and the blue tint disappears,
and afterwards the boracic acid or borates will wash out and
leave the paper as at first.

Borax itself at first reddens turmeric paper because of the
excess of -alkali, but as the colouring matter becomes altered by
the presence of the boracic acid, the tint becomes of a dirty
bluish colour, and then the paper is changed by acids or alka-
lies, just as if it had been altered by boracic acid.

Hence it is probable that the neutral borates have the same



1822.] On Alkaline Colour Properties. 29

power as the boracic acid, of altering the colouring matter of
turmeric, for it is not probable there should be an actual sepa-
ration of the elements of the salts by it, especially as they both
wash out from it and leave it unaltered.

Hence also both acid and alkaline borates redden turmeric.

M. Desfosses proposes this effect of boracic acid as a test
for its presence ; for a very small quantity of it mixed with
other acid has the power of reddening turmeric paper in con-
sequence of these changes.



On the Changing of Vegetable Colours as an Alkaline Pro-
perty, and on some Bodies possessing it*.

THE changes produced by acids and alkalies on vegetable
colours have long been considered as very distinctive and
peculiar effects, and even sufficient of themselves to indicate
the presence of these bodies. Since the introduction of sub-
stances before excluded, as of silica, various oxides, and vege-
table substances, into the class of acids, and of oxide of lead,
morphia, &c., into the class of alkalies, it becomes more import-
ant to substantiate any particular property as peculiar to those
classes, or show its fallacy, by pointing out to what substances
excluded from them it also belongs.

At present I shall detail the results of a few experiments
made on the colouring matter of turmeric and rhubarb, com-
paring the changes produced on them by alkalies to those occa-
sioned by some other bodies. Formerly t I mentioned the
property possessed by muriatic acid gas and strong acids in
general, of reddening or browning turmeric paper. I find that
in general they have the same effect on rhubarb paper, and a
very weak nitric acid gives a brown tint to it, exactly like that
of an alkali : strong solution of muriatic acid does not affect it
much, but sulphuric acid does.

At pp. 27) 28, &c. I have shown the effect of boracic acid in
reddening turmeric paper. Mr. South, I believe, first showed
that the subacetate of lead reddened turmeric, and this has been
considered sufficient evidence by many, that the oxide of lead
merited, in some degree, the name of an alkali. I find on trial,

* Quarterly Journal of Science, xiii. 315. f Ibid. v. 125.



30 On Alkaline Colour Properties. [1822.

however, so many substances possessing this property, that it
must either be limited more exactly than has yet been done, or
else given up as a distinguishing property.

All the soluble salts of iron that I have tried, except the ace-
tate, brown turmeric paper. Weak solutions of the green and
red muriate seem very alkaline indeed, and even common green
vitriol strongly so. They do not, however, produce the same
effect on rhubarb paper, but the persalts give it an olive-green
tint, whilst the protosalts produce no change at first, but gra-
dually give green tints, apparently from becoming persalts.

If a strong solution of muriate of zinc be boiled on zinc, it
gradually oxidizes the metal and dissolves it ; and a concen-
trated solution is obtained, which, when diluted, deposits either
an oxide or a submuriate of zinc. This strong solution is
apparently alkaline to turmeric paper. If it be diluted with
about its bulk of water, and filtered, it will still redden turmeric
paper, though it proves slightly acid by litmus paper. If
further diluted, more precipitate will fall, and the solution will
appear alkaline or not, according as the dilution has been small
or great. This substance has the same effect on rhubarb paper,
and the tint is very like that of a true alkali.

The acid nitrate of bismuth appears alkaline to turmeric ; if
diluted till a little oxide becomes deposited, it is more so : the
common solution of chloride of antimony in muriatic acid added
to water till a precipitate falls, appears alkaline : permuriate
of tin produces a strong change ; protomuriate of tin a very
decided reddening; sulphate of tin, slight only. When the
acid nitrate of bismuth, and the three salts of tin mentioned,
are applied to rhubarb paper, they produce but little effect at
first, but if dried by the fire, it becomes quite brown.

A strong solution of chloride of manganese seems feebly but
evidently alkaline to turmeric paper.

It may be supposed, that with many of these substances the
effect is produced principally by the acid present, inasmuch as
they were all more or less acid to litmus, and it has been shown
that these bodies, especially nitric acid, have this power. But
the very slight excess in some of them, as in the salts of iron,
zinc, manganese, &c., and the greater effect produced by further
dilution, as with bismuth and antimony, show that the whole
substance must act ; for if it be considered due to the acid



1820.] Chloride of Silver, Hydrogen, and Zinc. 31

alone, it is not, in the first case, of sufficient quantity, and in
the second, it would be diminished by dilution.

It is probable that if the tints produced be compared exactly
with those occasioned by alkalies, slight differences might be
perceived among some of them ; or that if the properties of
the altered colouring matter were examined, they would be
found different with the different substances, as M. Desfosses
has shown with regard to boracic acid and other acids ; but my
object has not been to trace these changes as far as possible,
but merely to show their general appearance ; to guard against
any deceptive conclusion with respect to solutions tested by
turmeric ; and to call attention to the distinguishing characters
of acids and alkalies.



Action of Salts on Turmeric Paper*.

AMONG the salts not alkaline, which have the power of affecting
turmeric paper like alkalies (see pp. 29, 30), those of uranium
are perhaps most powerful. The muriate, sulphate and acetate
affect turmeric paper strongly even when considerably diluted;
but the nitrate is the most powerful. A strong solution scarcely
seems to have its power diminished by dilution with ten or
twelve times its weight of water, and even when the solution
contains only ^^th of dry nitrate of uranium, it sensibly browns
turmeric paper.

The muriate of zirconia also possesses this same property to
a considerable degree.



On the Decomposition of Chloride of Silver by Hydrogen

and by Zinc }.

M. ARFVEDSON some time ago communicated to me a mode of
reducing chloride of silver by hydrogen J. In a few experi-
ments made some time since, in consequence of this communi-
cation, I found myself unable to decompose the chloride by a
stream of pure hydrogen gas, or by allowing an atmosphere of
the gas to remain for a long time in contact with it ; I supposed,
therefore, that the effect was produced by the hydrogen in its

* Quarterly Journal of Science, xiv. 234.
t Ibid. viii. 374. t Ibid. v. 360.



32 Chloride of Silver, Hydrogen, and Zinc. [1820.

nascent state. But lately resuming the experiment, with the
intention of ascertaining why the nascent state was more favour-
able for the combination of the elements than that of develop-



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