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It would seem, therefore, that in the long tube the pressure or
elasticity of the olefiant gas diminishes less rapidly than that
of the hydrogen, or that its velocity increases more rapidly.

Perhaps these effects may be accounted for by the suppo-
sition of some power of expansion peculiar to each gas, which,
if existing, a tube would for many reasons be well calculated
to exhibit. The experiment requires numerous repetitions and
much time, and I have not yet had sufficient to satisfy myself
on the subject. I will therefore refrain from mixing up crude
notions with facts, and at some more convenient opportunity
endeavour to supply what is wanting in this paper.



1818.] Combustion of the Diamond. 11

Combustion of the Diamond*.

SIR H. DAVY was the first to show that the diamond was
capable of supporting its own combustion in oxygen without
the continued application of extraneous heat, and he thus
obviated one of the anomalies exhibited by this body when
compared with charcoal. This phenomenon, though rarely
observed, is easily exhibited. If the diamond, supported in the
perforated cup, be fixed at the end of a jet, so that a stream
of hydrogen can be thrown on to it, it is easy, by inflaming the
jet, to heat the gem, and whilst in that state to introduce it
into a globe or flask containing oxygen. On turning off the
hydrogen the diamond enters into combustion, and will remain
burning until nearly consumed. The loss of weight in the
diamond, the formation of carbonic acid, and the actual com-
bustion are thus very easily shown.



Description of a New Apparatus for the Combustion of the

Diamond-\.

IN the course of the experiments which Sir Humphry Davy
made at Florence on the combustion of the diamond, he dis-
covered that when the gem began to burn in an atmosphere of
pure oxygen, having free access to it on all sides, it would
continue burning, though the original source of heat were
removed, until the particles were rendered so small as to be
too readily cooled by the little platinum tray which supported
them. (Philosophical Transactions, 1814, p. 557.) In conse-
quence of this observation, an idea arose, that if the diamond
were well heated, and then introduced into oxygen, it would
go on burning, and afford an easy method of exhibiting- its
combustibility. Upon trial this was found to be the case, and
a notice to that effect put in this Journal (see above). Since
then, an apparatus of this kind has been perfected, and is now
represented in Plate I. fig. 1.

It consists of a glass globe, of the capacity of about 140
cubic inches, furnished with a cap, having a large aperture ;
the stopcock, which screws into this cap, has a jet A rising

* Quarterly Journal of Science, iv. 155. t Ibid. ix. 264.



1 2 Combustion of the Diamond. [ 1 820.

from it, nearly into the centre of the globe ; this is destined to
convey a small stream of hydrogen or other inflammable gas.
Two wires, c c t terminate at a very little distance from each
other, just above this jet, and are intended to light the stream
of hydrogen by electFical sparks ; one of them commences
from the side of the jet, the other is enclosed and insulated
nearly in its whole length in a glass tube : the tube and wire
pass through the upper part of the stopcock, and the wire
terminates on the outside in a ball or ring, D, at which sparks
are to be taken from the machine, either directly or by a chain.
On the end of the jet is fixed, by a little socket, a small
capsule, B, made of platinum foil. This capsule is pierced
full of small holes, and serves as a grate to hold the diamonds.
Its distance is about three-quarters of an inch from the end
of the jet; and the arm, by which it is supported, is bent
round, so that the stream of hydrogen shall not play against
it. The stopcock screws, by its lower termination, on to a
small pillar fixed on a stand, and at the side of this pillar is an
aperture by which a bladder filled with gas may be connected
with the apparatus.

On using the apparatus, the diamond is to be placed in the
capsule, and then the globe being screwed on to the stopcock,
the latter is to be removed from the pillar and placed on the
air-pump ; the globe is then to be exhausted and afterwards
filled with pure oxygen : or, lest the stream of oxygen in
entering should blow away the diamond, the globe may be
filled with the gas first, and then, dexterously taking out the
stopcock for a short time, the diamonds may be introduced
and the stopcock replaced. The apparatus is then to be fixed
on the pillar, and a bladder of hydrogen gas attached to the
aperture. Now, passing a current of sparks between the wires,
a small stream of hydrogen is to be thrown in, which inflaming,
immediately heats the capsule and diamonds white-hot ; the
diamonds will then enter into combustion, and the hydrogen may
be immediately turned off and the bladder detached. The
diamonds will continue to burn, producing a strong white heat,
until so far reduced in size as to be cooled too low by the
platinum with which they lie in contact.

When the fl;ime of hydrogen is used to heat the diamonds,
it is evident a little water will be found in the globe ; but this



1818.] Oxide of Silver in Ammonia. 13

is of no consequence, except in attempts to detect hydrogen in
the diamond ; the inconvenience may be obviated, if required,
by using the flame of carbonic oxide. As, however, no hydro-
gen has at any time been detected in the diamond, it is better
to use that gas as the heating agent; for then the carbonic
acid, produced by the combustion, is unmixed with that from
any other source, and may be collected, and its quantity ascer-
tained.

On the Solution of Silver in Ammonia*.

THE ease with which the compounds of silver are dissolved
by ammonia, and the frequent formation of powerfully de-
tonating and dangerous substances in these solutions, are well
known. I have been induced to examine some of the phe-
nomena presented by these bodies, and perhaps an account of
what is, I believe, original, may not be unacceptable as an
addition to the scanty stock of information published on this
subject.

When the oxide of silver, precipitated either by the alkalies
or alkaline earths, is put into solution of ammonia, it is entirely
dissolved, producing a pale brownish solution. If this solution
be exposed in an open vessel, a brilliant pellicle forms on its
surface, which, when removed, is succeeded by another and
another, until most of the metal is separated.

This, which is an oxide of silver, was noticed long ago by
Berthollet in the ' Annales de Chimie,' tome i., and he there
states its production to be dependent on the abstraction of
ammonia by the atmosphere.

From some difference which exists between this solution
of silver and that of the nitrate when treated by precipitants,
and from other circumstances, I was induced to collect and
analyse some of the oxide, to ascertain its identity with the
common oxide, or that previously dissolved. 20 grains that
had been dried for some hours on the sand-bath, were put
into a small glass retort, they were decomposed by heat, and
the gas liberated received over water ; it equalled 2*75 cubical
inches. 18 grains of silver remained in the retort, and the
2'75 of oxygen being equivalent to '935 grain, we have those
numbers as the proportions of the elements in the oxide, the
* Quarterly Journal of Science, iv. 268.



14 Oxide of Silver in Ammonia. [1818.

loss being supposed to be water, some of which had condensed
in the neck of the retort. Now

Oxygen. Silver. Oxygen. Silver.

-935 18 7-5



The same method of analysis was applied to oxide of silver,
precipitated by potash from nitrate of silver, it having been
well washed and dried : 40 grains gave 7*9 cubical inches, and
36*4 grains of silver remained. The 7*9 cubical inches = 2*686
grains, and

Oxygen. Silver. Oxygen. Silver.

2-686 36-4 7-5 101-6,

the number for silver very nearly as given in the most correct
elementary treatises on chemistry. There appears, therefore,
to be no error in the mode of analysis, and the oxide by am-
monia seems to contain less oxygen than that precipitated by
alkalies. Again,

30 grains of the oxide of silver were put into a retort, and
decomposed with every precaution as before ; the silver left
weighed 27*4 grains, and the quantity of gas given off was 4*125
cubical inches. I suspected that a small portion of carbonate
of silver had been mixed with the oxide, for when the ammo-
niacal solution has been long exposed to the air, much carbo-
nate of ammonia and of silver is formed in it ; the gases were
therefore placed over solution of potash, and were reduced in
bulk to 3-625, which was pure oxygen. This volume is equi-
valent to 1-2325 gr., and 1-2325 : 27'4 : : 7'5 : 166-7, a propor-
tion of silver still higher than in the first experiment, but
which may be accounted for by the purification of gas and the
small quantity of oxygen that remained in the retort.

In a third experiment, 24 grains of silver were left ; 4*25
cubical inches of gas were given off*, which decreased over
potash to 4. In order to estimate the proportion of azote
arising from the air in the retort, the 4 were treated with
nitrous gas of known purity, and gave results equal to 3*475
of pure oxygen. This is equal to 1*1815 gr., and 1*1815 : 24
: : 7-5 : 152'3.

One or two other experiments varied considerably from
this, giving a greater proportion of silver, but the mean of
many gave the oxygen to the silver as 7*5 to 157*4.



1818.] Oxide of Silver in Ammonia. 15

There is every reason, therefore, to believe this a protoxide
of silver, containing about two-thirds the quantity of oxygen
found in the common oxide, or that obtained by precipitation
from the nitrate ; and there are also other circumstances
observable in its solution and during its formation which
favour this notion.

When this oxide forms on the surface of an ammoniacal
solution by slow spontaneous evaporation, it takes a crystal-
line form, which, however, is quickly lost by its covering the
whole surface of the liquor.. It is of a grey colour by re-
flected light, and highly resplendent ; the light transmitted
through thin films is of a bright yellow colour. When heated
gradually it is reduced, giving off oxygen without change of
form ; but heated suddenly, it fuses first, and leaves a solid
button of silver : under pressure, it perhaps might be fused
without decomposition.

Potash precipitates the solution of oxide of silver in am-
monia white ; carbonate, or subcarbonate more abundantly,
and white ; alcohol and aether throw down precipitates, at first
white, but rapidly changing colour ; when dry, they detonate
by heat or friction. Chromate of ammonia does not pre-
cipitate until nitric acid be added. Tincture of galls gives
a very copious black precipitate, different in appearance to
that obtained from the nitrate of silver by adding ammonia
after the tincture. Solution of iodine in water gives a brown
curdy precipitate, but with nitrate of silver a yellow turbidness.
Muriatic acid or muriates always form chloride of silver.

It is probable, from these circumstances, that part of the
silver exists in the solution in the state of protoxide, and as no
gas is given off during the solution of the original oxide, that
a portion of nitric acid and water have been formed.

M. Berthollet has in the paper before referred to, described
a fulminating compound of silver and ammonia, obtained from
solutions similar to those from which the above oxide had been
obtained, and has stated it to be his opinion that it is a com-
pound of protoxide of silver and ammonia. As it is frequently
left in the form of a black powder when oxide of silver is dis-
solved in ammonia, I imagined it might be a compound of the
peroxide with the alkali, as protoxide was formed and held in
solution ; and that the circumstance of the liberation of azote,



16 Oxide of Silver In Ammonia. [1818.

which gave rise to the idea of its being a combined protoxide,
might be explained by the further formation of a portion of
oxide similar to that already described.

The method of obtaining this compound has been to pre-
cipitate oxide of silver from the nitrate by alkalies, or better,
by lime-water, to wash and dry it well, and then to leave it in
contact with liquid ammonia for ten or twelve hours ; the
greater part is dissolved, but a black powder remains, which
is fulminating silver ; if the solution be heated, azote is given
off, and a further quantity of fulminating silver is obtained
(Annales de Chimie, tome i.).

I find that fulminating silver may be formed from any
precipitated oxide of silver, whether moist or dry, recent or
old. Boil the oxide carefully in a tube with a mixed solution
of potash and ammonia for a few moments ; the potash absorbs
all the carbonic acid that may have been united to the oxide,
and to a certain degree prevents its solution in the ammonia ;
a black powder, similar to that procured by the other process,
results.

In order to gain some evidence respecting the nature of the
oxide combined with the ammonia in fulminating silver, I
endeavoured to ascertain the mode of formation of that com-
pound. It appears to be formed in every case where common
oxide of silver is dissolved in ammonia, and the entire solution
of all solid matter is no evidence of its non-existence, for the
compound is itself soluble in ammonia, though not so much so
as the oxide. When there is an excess of oxide, unless it
predominate in a great degree, the undissolved portion will be
found to contain fulminating silver, and when the whole is dis-
solved, by heating the solution, it is thrown down.

To ascertain whether the liberation of azote depended upon
the formation of the fulminating compound, I boiled, for a
few moments, a solution of the oxide in ammonia; the solu-
tion became highly coloured, azote was given off, and a black
curdy precipitate formed, which left the liquid colourless ;
separated by a filter, the precipitate proved to be fulminating
silver. The solution was again heateo 1 , it again blackened,
gave off azote, and again a precipitate formed ; this was not
fulminating silver, but merely oxide : filtered and again heated,
it gave off azote, and more of the oxide was formed ; and this



1818.] Oxide of Silver in Amm onia. 17

occurred with the same solution a fourth and fifth time. The
liberation of the azote, therefore, does not belong exclusively
to the formation of fulminating silver, but seems rather to
depend on the production of protoxide.

I endeavoured to form fulminating silver by using the prot-
oxide described in the first part of this paper, but could not
succeed : I got nothing but a black powder from it, which ap-
peared to be the same oxide in another form. I endeavoured
also to form fulminating silver from those portions of oxide
given off by the further boiling of solutions which had pre-
viously yielded the detonating compound, but failed ; I presume
from its being also a protoxide. When the fulminating com-
pound is dissolved in the acids, it gives off a gas which I
believe to be oxygen, but I could not work with quantities
sufficient to ascertain this point. Perhaps to these reasons
for supposing fulminating silver to be a compound rather
of the peroxide than the protoxide, may be added the easy
solubility of the protoxide in ammonia, and the difficult solu-
bility of the detonating compound.

The oxide which is obtained by boiling solution of silver
in ammonia, I have supposed to be a protoxide similar to the
one obtained by spontaneous evaporation. This opinion is
founded on the liberation of azote during its formation in con-
sequence of the decomposition of ammonia by oxygen, and on
its apparent incapability of forming fulminating compounds :
the idea is supported by the following circumstance. A tube,
in which solutions of silver in ammonia had been repeatedly
boiled, became coated on the inside with the oxide, so as to
be perfectly opake; on pouring dilute nitric acid into it to re-
move the oxide, the tube became lined with brilliant metallic
silver, which, however, was soon dissolved by the continued
action of the acid. I attribute this phenomenon to the reduc-
tion of one part of the oxide by another, which was thus ren-
dered soluble in the acid.

When a portion of the ammoniacal solution is evaporated to
dryness in a platinum capsule, it leaves a film of oxide, which,
when decomposed by heat, gives a perfectly continuous and
smooth coat of silver to the vessel. I have also covered other
metals, as iron and copper, with silver in the same way, and
found that the burnisher might be applied without any injury

c



18 Combinations of Ammonia with Chlorides. [1818.

to the coating. It is probable that a solution of silver of this
kind might be applied in some cases in the arts, to the pur-
poses of ornament and utility.



Combinations of Ammonia with Chlorides *.
IT has been already shown, particularly by Sir H. Davy,
that several of the binary compounds of chlorine, as those of
phosphorus, tin, &c., exert a strong affinity for ammonia, con-
densing it when in the gaseous state, and neutralizing its
alkaline properties. The combinations which will here be
offered to notice are of a different kind, and if they deserve
any attention, it will be in consequence of the weakness of the
power which is exerted in their formation, and the slight
change of properties induced on the substances by union-
It has been frequently observed by chemists, that if well-
fused chloride of lime be placed in ammoniacal gas, there
is a rapid absorption of the gas, and the chloride becomes
covered with a white powder. If ammonia be repeatedly
added until the absorption ceases, the mass of chloride swells,
cracks, splits in all directions, and at last forms a white pul-
verulent substance.

Exposed to the atmosphere, it deliquesces, but not so
rapidly as chloride of lime. Thrown into water it dissolves,
forming a strong alkaline solution. Heated, it gives off am-
monia, and the chloride remains unchanged. Placed in chlo-
rine it inflames spontaneously, and burns with a pale yellow
flame.

The fused chlorides of barium and strontium suffer a very
slight change in ammoniacal gas in many days ; after more
than a fortnight, the chloride of strontium, weighing about 30
grains, had absorbed only a cubical inch of gas, and a slight
efflorescent appearance was seen on the broken edge.

A piece of fused chloride of silver, weighing about 30
grains, placed in ammoniacal gas, gradually absorbed more
than 40 cubical inches. The action took place over the
whole surface of the mass, but most speedily at the fractured
edges. The chloride swelled considerably, and crumbled into
powder. The substance formed was at first white, but it

* Quarterly Journal of Science, v. 74.



1818.] Combinations of Ammonia with Chlorides. 19

blackened by exposure to light, though without liberating any
gas. Thrown into water the ammonia was separated, forming
a solution, and the chloride remained unchanged. Heated,
the whole of the ammonia was given off. Placed in chlorine
it inflamed spontaneously, and the ammonia was decomposed.

Chloride of silver that had been well dried, but not fused,
gave the same compounds with ammonia, but in a much
shorter time.

A strong solution of chloride of silver in ammonia was left
for some weeks in a bottle stopped only by a piece of paper.
At the end of that time several perfectly colourless and trans-
parent crystals had formed in it ; some of them being as much
as a quarter of an inch in width. Their general form was
that of a flat rhomboid, but sometimes two acute angles of the
rhomboid were wanting, and then the crystals looked like
hexahedral prisms with oblique bases.

Exposed to the air, these crystals became opake, gradually
losing the whole of the ammonia, and were then so friable as
to fall into powder by a slight touch ; the substance remaining
was a dry chloride of silver. Placed in water, the same
change occurred, but more readily ; the water separated the
ammonia, and they instantly became opake. Heated, they
gave off much ammoniacal gas, and the chloride remained un-
altered. Exposed to light, they gradually blackened, though
covered by the solution from which they were deposited.

If the ammoniacal solution be weak, other crystals are
formed which are pure chloride of silver.

Dry corrosive sublimate placed in ammoniacal gas had
suffered no change in fourteen days, nor had any action been
exerted on the ammonia ; there was a diminution of a quarter
of a cubical inch of gas, probably owing to a little water being
present. The corrosive sublimate heated gave out no am-
monia, and the whole of the gas remaining was absorbed by
water.

The precipitate obtained by adding ammonia to a solution
of corrosive sublimate appears to be a compound of the two
bodies, but the alkali is neutralized in this case, and it is
therefore more analogous to the combination of ammonia with
the chloride of tin. When the precipitate is distilled, it gives
off ammoniacal gas and also some azote, and the corrosive sub-'



20 Combinations of Ammonia with Chlorides. [1818.

limate is converted into calomel in consequence of the action
of the ammonia at high temperatures. Heated with potash,
the ammonia is driven off, the chlorine is removed from the
mercury, and red oxide results.

Some crystals of calomel were introduced into ammoniacal
gas ; they immediately blackened on the surface, and gas was
absorbed. The action appeared to be exactly similar to that
exerted when calomel is thrown into solution of ammonia. A
black substance is produced, which though repeatedly washed
in distilled water, gives off ammonia by heat, and calomel with
a little mercury sublimes.

A piece of fused chloride of lead exerted but little action in
a fortnight ; a small quantity of gas was absorbed, and a very
superficial combination had been formed.

Chloride of bismuth absorbed a small quantity of ammoniacal
gas, which was again given out by heat ; there was no remark-
able change in appearance.

A small piece of chloride of nickel being placed in ammo-
niacal gas, absorbed it, and in twenty-four hours was converted
into a bulky powder of a pale rose tint. The ammonia was
separated by exposure to air, to water, or to heat.

Chloride of copper fused was powerfully acted upon by
ammonia. It immediately burst open upon being placed in
the gas, and absorbing great quantities fell into a blue powder.
The compound placed in water was decomposed, and an am-
moniacal solution of copper produced. Heated, it fused,
boiled, the ammonia flew off, and the chloride remained.

The protochloride of iron introduced immediately after
fusion into ammoniacal gas, exerted an instantaneous action ;
great quantities of gas were absorbed, and a very light ad-
hesive white powder was formed. Exposed to the air, it im-
mediately changed colour, became yellow, brown, then green,
and ultimately black : this effect resulted from the presence of
water in the atmosphere, and the separation of oxide by the
ammonia; and the substance offers a test, if one should be
wanted, for the presence of aqueous vapour. A portion of it
thrown up into a small receiver of common air over mercury,
immediately changed colour, and became brown. When the
powder was heated out of the contact of air it gave off am-
monia, and the chloride remained.



1818.] On the Sounds produced by Flame in Tubes. 21

I have not examined the action of ammonia upon the other
chlorides ; with some of them it would probably form neutral
compounds, with other combinations similar to those described.
Nearly all those mentioned are formed by the exertion of an
affinity so weak that it is overcome by the attraction of water
for the ammonia, and yet in one instance it is capable of giving
a definite crystalline form.

The facility with which many of them afford dry ammoniacal
gas at low temperatures in considerable quantities, may per-
haps in some cases make them convenient sources of that sub-
stance*; 19 grains of the compound with chloride of lime
which had been made many days, gave 19*4- cubical inches of
gas. They also offer a convenient means of ascertaining the
specific gravity of ammonia, by the quantity of gas given off,
and the loss of weight in the substance.



On the Sounds produced by Flame in Tubes, $c. f

THERE is an experiment usually made in illustration of the
properties of hydrogen gas, which was first described by Dr.



Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 2 of 49)