Michael Faraday.

Experimental researches in chemistry and physics online

. (page 14 of 49)
Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 14 of 49)
Font size
QR-code for this ebook

worked upon frozen chlorine, obtaining the results tfhich are
published in my paper in the ' Quarterly Journal of Science '
for the 1st of April, 1823J. On Sir Humphry Davy's return
to town, which 1 think must have been about the end of

* See page 124. f Paris's Life of Davy, pp. 390, 391, 392.

J Vol. xv. p. 71 or page 82.

1836.] On the Condensation of the Gases, 8fc. 137

February or the beginning of March, he inquired what I had
been doing, and I communicated the results to him as far as
I had proceeded, and said I intended to publish them in the
' Quarterly Journal of Science/ It was then that he suggested
to me the heating of the crystals in a closed tube, and I pro-
ceeded to make the experiment which Dr. Paris witnessed,
and has from his own knowledge described *. I did not at
that time know what to anticipate, for Sir Humphry Davy had
not told me his expectations, and I had not reasoned so deeply
as he appears to have done. Perhaps he left me unacquainted
with them to try my ability. How I should have proceeded
with the chlorine crystals without the suggestion I cannot now
say, but with the hint of heating the crystals in a close tube
ended for the time Sir Humphry Davy's instructions to me, and
I puzzled out for myself in the manner Dr. Paris describes,
that the oil I had obtained was condensed chlorine. This is
all very evident from the paper read to the Royal Society,
though it may seem at first to stand opposed to the notes and
papers that Sir Humphry Davy communicated in conjunction
with and after mine. When my paper was written, it was, ac-
cording to a custom consequent upon our relative positions,
submitted to Sir Humphry Davy (as were all my papers for
the * Philosophical Transactions ' up to a much later period),
and he altered it as he thought fit. This practice was one of
great kindness to me, for various grammatical mistakes and
awkward expressions were from time to time thus removed
which might else have remained.

The passage at the commencement of the paper which I
shall now quote was of Sir Humphry Davy's writing, and in
fact contains everything that, and perhaps rather more than, he
had said to me : " The President of the Royal Society having
honoured me by looking at these conclusions, and suggested
that an exposure of the substance to heat under pressure would
probably lead to interesting results, the following experiments
were commenced at his request f." I say "rather more,'
because I believe pressure was not referred to in our previous
verbal communication. However, I proceeded to make the

* Paris's Life, p. 391.

t Phil. Trans. 1823, p. 160, or Phil. Mag., First Series, vol. Ixii.p. 413 or
page 85.

138 On the Condensation of the Gases, $c. [1836.

experiment, and was making it when Dr. Paris came into the
laboratory as he has described, and my thoughts at that moment
are embodied and expressed in my paper in the following words:
" I at first thought that muriatic acid and euchlorine had been
formed ; then that two new hydrates of chlorine had been pro-
duced ; but at last I suspected that the chlorine had been en-
tirely separated from the water by the heat, and condensed
into a dry fluid by the mere pressure of its own abundant
vapour *." I then describe an experiment entirely of my own,
in which I proceed to verify this conjecture, and go on to say,
" Presuming that I had now a right to consider the yellow fluid
as pure chlorine in the liquid state, I proceeded to examine its
properties, &c. &c. f"

To this paper Sir Humphry Davy added a note J, in which
he says, " In desiring Mr. Faraday to expose the hydrate of
chlorine to heat in a closed glass tube , it occurred to me that
one of three things would happen : that it would become fluid
as a hydrate ; or that a decomposition of water would occur,
and euchlorine and muriatic acid be formed ; or that the chlo-
rine would separate in a condensed state." And then he makes
the subject his own by condensing muriatic acid, and states
that he had "requested" me (of course as Chemical Assistant)
" to pursue these experiments, and to extend them to all the
gases which are of considerable density, or to any extent
soluble in water;" &c. This I did ; and when he favoured me
by requesting that I would write a paper on the results, I began
it by stating " that Sir Humphry Davy did me the honour to
request I would continue the experiments, which I have done
under his general direction, and the following are some of the
results already obtained || :" and this paper being immediately
followed by one on the application of these liquids as mecha-
nical agents, by Sir Humphry Davy If, he says in it, "One of
the principal objects that I had in view in causing experiments
to be made on the condensation of different gaseous bodies, by
generating them under pressure, &c."

* Phil. Trans. 1823, p. 162. f Ibid. p. 163. J Ibid. p. 164.

Observe, not " to heat under pressure." See my remarks in the pre-
ceding page.

|| Phil. Trans. 1823, p. 189, or Phil. Mag., First Series, vol. lxii.p.417 or
page 89. ^ Phil. Trans. 1823, p. 199.

1836.] On the Condensation of the Gases, $c. 139

I certainly took up the subject of chlorine with the view of
pursuing it as I could find spare time, and at the moments
which remained to me after attending to the directions of my
superiors. It however passed in the manner described into
the hands of Sir Humphry Davy, and a comparison of the
dates will readily show that I at least had no time of my own
to pursue it. My original paper was published on the 1st
of April, 1823, that being the first Number of the * Quarterly
Journal ' which could appear after the experiments had been
made : but in the short time between the first experiment and
the publication, much that I have referred to had occurred'; for
not only had I communicated my results to Sir Humphry
Davy, and received from him the hint, but my paper on fluid
chlorine had been read (13th of March), and his note also, of
the same date, attached to it 5 and the Editor of the ' Quarterly
Journal,' Mr. Brande, had time, prior to the printing of my
original paper, to attach a note to it stating the condensation of
chlorine and muriatic acid, and expressing an expectation that
several other gases would be liquefied by the same means *.
On the 10th of April my paper on the condensation of several
gases into liquids was read, on the 17th of April Sir Humphry
Davy's on the application of condensed gases as mechanical
agents, and on the 1st of May his Appendix to it on the
changes of volume produced by heat.

I have never remarked upon or denied Sir Humphry Davy's
right to his share of the condensation of chlorine or the other
gases ; on the contrary, I think that I long ago did him full
" justice" in the papers themselves. How could it be other-
wise? He saw and revised the manuscripts; through his hands
they went to the Royal Society, of which he was President
at the time ; and he saw and revised the printer's proofs.
Although he did not tell me of his expectations when he sug-
gested the heating the crystals in a closed tube, yet I have no
doubt that he had themf; and though, perhaps, I regretted

* Quarterly Journal, xv. p. 74 or page 84,

t I perceive in a letter to Professor Edmund Davy, published by Dr. Davy
in the * Life/ vol. ii. p. 166, of the date of September \, 1823, that Sir Humphry
Davy said, " The experiments on the condensation of the gases were made
under my direction, and I had anticipated, theoretically, all the results." It
is evident that he considered the subject his own j but I am glad that here, as

140 On the Condensation of the Gases, $c. [1836.

losing my subject, 1 was too much indebted to him for much
previous kindness to think of saying that that was mine which
he said was his. But observe (for my sake) that Sir Humphry
Davy nowhere states that he told me what he expected, or
contradicts the passages in the first paper of mine which de-
scribe my course of thought, and in which I claim the develop-
ment of the actual results.

All this activity in the condensing of gases was simukaneous
with the electro-magnetic affair already referred to, and I had
learned to be cautious upon points of right and priority.
When therefore I discovered in the course of the same year
that neither I nor Sir Humphry Davy had the merit of first
condensing the gases, and especially chlorine, I hastened to
perform what I thought right, and had great pleasure in
spontaneously doing justice and honour to those who deserved
it*. I therefore published on the 1st of January of the fol-
lowing year (1824), a historical statement respecting the lique-
faction of gases f, the beginning of which is as follows: " I was
not aware at the time when I first observed the liquefaction of
chlorine gas, nor until very lately, that any of the class of bodies
called gases had been reduced into the fluid form ; but having
during the last few weeks sought for instances where such
results might have been afforded without the knowledge of the
experimenter, I was surprised to find several recorded cases.
I have thought it right, therefore, to bring these cases together,
and only justice to endeavour to secure for them a more general
attention than they appear as yet to have gained." Amongst
other cases the liquefaction of chlorine is clearly described J.
The value of this statement of mine has since been fully proved;
for upon Mr. Northmore's complaint ten years after, with some
degree of reason, that great injustice had been done to him in
the affair of the condensation of gases, and his censure of
" the conduct of Sir H. Davy, Mr. Faraday, and several other
philosophers for withholding the name of the first discoverer,"

elsewhere, he never says that he had informed me of his expectations. In
this, Sir Humphry Davy's negative, and Dr. Paris's positive testimony per-
fectly agree.

* Monge and Clouet had condensed sulphurous acid probably before the
year 1800. Northmore condensed chlorine in the years 1805 and 1806.

t See page 124. j See page 131.

1823.] Change of Musket Balls in Shrapnell Shells. 141

I was able by referring to the statement to convince him and
his friend that if my papers had done him wrong, / at least
had endeavoured also to do him right*.

Believing that I have now said enough to preserve my own
"honest fame" from any injury it might have risked from the
mistakes of Dr. Davy, I willingly bring this letter to a close,
and trust that I shall never again have to address you on the

I am, my dear Sir, yours, &c.,

Richard Phillips, Esq., $c. $c.

Change of Musket Balls in Shrapnell Shells -\.

MR. MARSH of Woolwich gave me some musket balls which
had been taken out of Shrapnell shells. The shells had lain in
the bottom of ships, and probably had sea-water amongst them.
When the bullets are put in, the aperture is merely closed by a
common cork. These bullets were variously acted upon : some
were affected only superficially, others more deeply, and some
were entirely changed. The substance produced is hard and
brittle, it splits on the ball, and presents an appearance like some
hard varieties of earthy haematite ; its colour is brown, becoming,
when heated, red ; it fuses on platinum foil into a yellow flaky
substance like litharge. Powdered and boiled in water, no
muriatic acid or lead was found in solution. It dissolved in
nitric acid without leaving any residuum, and the solution gave
very faint indications only of muriatic acid. It is a protoxide of
lead, perhaps formed in some way by the galvanic action of the
iron shell and the leaden ball, assisted, probably, by the sea-
water. It would be very interesting to know the state of the
shells in which a change like this has taken place to any extent ;
it might have been expected, that as long as any iron remained,
the lead would have been preserved in the metallic state.

* Phil. Mag. 1834, iv. p. 261.

t Quarterly Journal of Science, xvi. 163.

Purple Tint of Plate-glass affected by Light. [1823.

Action of Gunpowder on Lead*.

MR. MARSH gave me also some balls from cartridges about
fifteen years old, and which had probably been in a damp
magazine. They were covered with white warty excrescences
rising much above the surface of the bullet, and which, when
removed, were found to have stood in small pits formed be-
neath them. These excrescences consist of carbonate of lead,
and readily dissolve with effervescence in weak nitric acid,
leaving the bullet in the corroded state which their formation
has produced. It is evident there must have been a mutual
action amongst the elements of the gunpowder itself, at the
same time that it acted on the lead ; and it would have been
interesting, had the opportunity occurred, to have examined
what changes the powder had suffered.

Purple Tint of Plate-glass affected by Light ^.

IT is well known that certain pieces of plate-glass acquire, by
degrees, a purple tinge, and ultimately become of a comparatively
deep colour. The change is known to be gradual, but yet so
rapid as easily to be observed in the course of two or three years.
Much of the plate-glass which was put a few years back into
some of the houses in Bridge Street, Blackfriars, though at first
colourless, has now acquired a violet or purple colour. Wish-
ing to ascertain whether the sun's rays had any influence in
producing this change, the following experiment was made :
Three pieces of glass were selected, which were judged capable
of exhibiting this change ; one of them was of a slight violet
tint, the other two purple or pinkish, but the tint scarcely per-
ceptible, except by looking at the edges. They were each
broken into two pieces ; three of the pieces were then wrapped
up in paper and set aside in a dark place, and the correspond-
ing pieces were exposed to air and sunshine. This was done
in January last, and the middle of this month (September) they
were examined. The pieces that were put away from light
seemed to have undergone no change ; those that were ex-
posed to the sunbeams had increased in colour considerably ;

* Quarterly Journal of Science, xvi, 163. t Ibid, 164.

1825.] On the Formation of Ammonia, $c. 143

the two paler ones the most, and that to such a degree, that it
would hardly have been supposed they had once formed part
of the same pieces of glass as those which had been set aside.
Thus it appears that the sun's rays can exert chemical powers
even on such a compact body and permanent compound as glass.

On some Cases of the Formation of Ammonia, and on the
Means of Testing the Presence of Minute Portions of Ni-
trogen in certain states*.

THE importance of the question relative to the simple or com-
pound nature of any of the substances considered as elementary
in the present state of chemical science, is such as to make any
experimental information respecting it acceptable, however im-
perfect it may be. An opinion of this kind has induced me to
draw up the following account of experiments relative to the
formation of ammonia, by the action of substances apparently
including no nitrogen. The experiments are not offered as
satisfactory, even to myself, of the production of ammonia with-
out nitrogen ; indeed, I am inclined to believe the results all
depend upon the difficulty of excluding that element perfectly,
and the extreme delicacy of the test of its presence afforded by
the formation of ammonia : yet as, on the contrary, notwith-
standing my utmost exertions, I have failed to convince myself
that ammonia could not be formed, except nitrogen were pre-
sent, it has been supposed that the information obtained,
though incomplete, might be interesting.

Having occasion, some time since, to examine an organic sub-
stance with reference to any nitrogen it might contain, I was
struck with the difference in the results obtained, when heated
alone in a tube, or when heated with hydrate of potassa : in the
former case no ammonia was produced ; in the latter, abun-
dance. Supposing that the potash acted, by inducing the com-
bination of the nitrogen in the substance with hydrogen, more
readily than when no potash was present, and would therefore
be useful as a delicate test of the presence of nitrogen in bodies,
I was induced to examine its accuracy by heating it with sub-
stances containing no nitrogen, as lignine, sugar, &c. ; and was

* Quarterly Journal of Science, xix. 16.

144 On the Formation of Ammon ia, $c.

surprised to find that ammonia was still a result of the experi-
ment. This led to trials with different vegetable substances,
such as the proximate principles, acids, salts, c., all of which
yielded ammonia in greater or smaller quantity; and ultimately
it was found, that even several metals when treated in the same
way gave similar results ; a circumstance which appeared con-
siderably to simplify the experiment.

The experiment may be made in its simplest form in the
following manner : Put a small piece of clean zinc foil into a
glass tube closed at one end, and about one-fourth of an inch in
diameter 5 drop a piece of potash into the tube over the zinc ;
introduce a slip of turmeric paper slightly moistened at the
extremity with pure water, retaining it in the tube in such a
position that the wetted portion may be about 2 inches from
the potash ; then holding the tube in an inclined position, apply
the flame of a spirit-lamp, so as to melt the potash that it may
run down upon the zinc, and heat the two whilst in contact,
taking care not to cause such ebullition as to drive up the pot-
ash ; in a second or two the turmeric paper will be reddened
at the moistened extremity, provided that part of the tube has
not been heated. On removing the turmeric paper and laying
the reddened portion upon the hot part of the tube, the ori-
ginal yellow tint will be restored : from which it may be con-
cluded that ammonia has been formed ; a result confirmed by
other modes of examination to be hereafter mentioned.

The first source of nitrogen which suggested itself was the
atmosphere : the experiment was therefore repeated, very care-
fully, in hydrogen gas, but the same results were obtained.

The next opinion entertained was, that the potash might
have been touched accidentally by animal or other substances,
which had adhered to it in sufficient quantity to produce the
ammonia : the alkali was therefore heated red-hot, as a pre-
paratory step, and afterwards allowed to touch nothing but
clean glass or metals ; but still the same effects were produced.
The zinc used was selected from a compact piece of foil, was
well rubbed with tow dipped in alkali, washed in alkaline solu-
tion, afterwards boiled repeatedly in distilled water, and dried,
not by wiping, but in a hot atmosphere ; and yet the same pro-
ducts were obtained.

All these precautions, with regard to impurity from finger-

1825.] On the Formation of Ammonia, $c. 145

ing, were found to be essentially requisite, in consequence of
the delicacy of the means afforded by heat and turmeric paper
for testing the presence of ammonia, or rather, of matter con-
taining its elements. As a proof of this, it may be mentioned,
that some sea sand was heated red-hot for half an hour in a
crucible, and then poured out on to a copper-plate, and left to
cool ; when cold, a portion of it (about 12 grains) was put into
a clean glass tube ; another equal portion was put into the palm
of the hand, and looked at for a few moments, being moved
about by a finger, and then introduced by platina foil into an-
other tube, care being taken to transfer no animal substance
but what had adhered to the grains of sand : the first tube
when heated yielded no signs of ammonia to turmeric paper,
the second a very decided portion.

As a precaution, with regard to adhering dirt, the tubes
used in precise experiments were not cleaned with a cloth or
tow, but were made from new tube, the tube being previously
heated red-hot, and air then drawn through it ; and no zinc or
potash was used in these experiments, except such as had been
previously tried by having portions heated in a tube to ascer-
tain whether when alone they gave ammonia.

It was then thought probable that the alkali might contain
a minute quantity of some nitrous compound, or of a cyanide,
introduced during its preparation. A carbonate of potash was
therefore prepared from pure tartar, rendered caustic by lime
calcined immediately preceding its use, the caustic solution
separated by decantation from the carbonate of lime, not allowed
to touch a filter or anything else animal or vegetable, and boiled
down in clean flasks ; but the potash thus obtained, though it
yielded no appearance of ammonia when heated alone, always
gave it when heated with zinc.

The water used in these experiments was distilled, and in
cases where it was thought necessary was distilled a second,
and even a third time. The experiments of Sir Humphry Davy*
show how tenaciously small portions of nitrogen are held by
water, and that in certain circumstances the nitrogen may
produce ammonia. I am not satisfied that I have been able to
avoid this source of error.

At last, to avoid every possible source of impurity in the pot
* Phil. Trans. 1807, p. 11.


146 On the Formation of Ammonia> $c. [1S25.

ash, a portion of that alkali was prepared from potassium ; and
as the experiment made with it includes all the precautions
taken to exclude nitrogen, I will describe it rather minutely,
as illustrative of the way in which the other numerous experi-
ments were made. A piece of new glass tube, about half an
inch in diameter, was first wiped clean, and then heated red-
hot, a current of air passing at the same time through it ; about
six inches in length was drawn off at the blowpipe lamp, arid
sealed at one extremity. Some distilled water was put into a
new glass retort, and heated by a lamp ; when about one-half
had distilled over, the beak of the retort was introduced into
the tube before-mentioned, and a small portion of water (about
fifty grains) condensed into it. A solid compact piece of potas-
sium was then chosen, and having been wiped with a linen
cloth, was laid on a clean glass plate, the exterior to a con-
siderable depth removed by a sharp lancet, and portions taken
from the interior by metallic forceps, and dropped successively
into the tube containing the water before-mentioned. Of course
the water was decomposed, and the tube filled with hydrogen ;
and when a sufficient quantity of solution of potash had been
thus formed, the tube was heated in a lamp, and drawn out to
a capillary opening, about two inches from the closed extremity
(fig. 2, plate I). The tube now formed almost a close vessel ; and
being heated, as the water became vapour, it passed off at the
minute aperture, and ultimately a portion of pure fused hydrate
of potassa remained in the bottom of the tube. The aperture
of the tube was now closed, and the whole set aside to cool.

A piece of new glass tube was selected about 0*3 of an inch
in diameter; it was heated to dull redness, and air passed
through it : about 10 inches of it was then cut off, and being
softened near to one end by heat, it was drawn out at that part
until of small diameter (a, fig. 3, plate I) : that part was then
fixed into a cap, by which it could afterwards be attached to a
receiver containing hydrogen. The tube containing the potas-
sium potash being now broken in an agate mortar, a piece or
two of the potash were introduced by metallic forceps into the
tube at the open end, so as to pass on to the contracted part ;
a roll of zinc-foil, about one grain in weight, cleaned with all
the precautions already described, was afterwards introduced,
and then more of the potash. The tube was then bent near


Plate I.


1825.] On the Formation of Ammonia) fyc. 147

the middle to a right angle ; a slip of turmeric paper introduced,
so as just to pass the bend, and thus prepared, it was ready to
be filled with hydrogen.

. The precautions taken with regard to the purity of the hy-
drogen, were as follows : A quantity of water had been put into
a close copper boiler, and boiled for some hours, after which it
had been left all night in the boiler to cool. A pneumatic
trough was filled with this water just before it was required for
use. The hydrogen was prepared from clean zinc, which being
put into a gas bottle, the latter was filled entirely with the boiled
water, and then sulphuric acid being poured in through the

Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 14 of 49)