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THE GASES OF THE ATMOSPHERE



MACMILLAN AND CO., LIMITED

LONDON BOMBAY CALCUTTA
MELBOURNE

THE MACMILLAN COMPANY '

NEW YORK BOSTON CHICAGO
DALLAS SAN FRANCISCO

THE MACMILLAN CO. OF CANADA, LTD.

TORONTO




STEPHEN HALES.



THE -GASES



OF



THE ATMOSPHEEE



THE



HISTOKY OF THEIR DISCOVERY



BY



SIR WILLIAM RAMSAY, K.C.B., RR.S.

OFFICIER DE LA LEGION D*HONNEUR
EMERITUS PROFESSOR OF CHEMISTRY IK UNIVERSITY COLLEGE. LONDON



FOURTH EDITION



WITH



MACMILLAN AND CO., LIMITED

ST. MARTIN'S STKEET, LONDON

1915




"Modern discoveries have not been made by large collections of
facts, with subsequent discussion, separation, and resulting deduction
of a truth thus rendered perceptible. A few facts have suggested an
hypothesis, which means a supposition, proper to explain them. The
necessary results of this supposition are worked out, and then, and
not till then, other facts are examined to see if their ulterior results
are found in Nature." DE MORGAN, A Budget of Paradoxes, ed.
1872, p. 55.

Natura nihtt agit frustra is the only indisputed Axiome in
Philosophy. There are no Grotesques in Nature ; not anything
framed to fill up empty Cantons and unnecessary spaces." Sm
THOMAS BROWNE'S Rdigio Medici.

A




tf-O - <l t



.



Firrt

Second Edition, 1900.
Third Edition, 1905.
Fourth Edition, 1915.



PEEFACE TO THE FOUETH EDITION

SINCE 1905, progress has been made in our know-
ledge of niton or " radium emanation " ; and some
light has been thrown on the possible sources of
the rare gases of the atmosphere. This has been
incorporated at the end of the last chapter.

WILLIAM EAMSAY.

August 1915.



PEEFACE TO THE THIED EDITION

THE radioactive gases, products of the disintegra-
tion of the remarkable elements radium and radio-
thorium, have been recently added to the list of
the constituents of the atmosphere. An attempt
has been made in an additional chapter to give an
account of these ; but the reader who is interested
in the subject is advised to consult the much



399766



vi THE GASES OF THE ATMOSPHERE

more complete works by Professor Eutherford, Mr.
Frederick Soddy, and the Honourable E. J. Strutt,
if he wishes to learn more about the nature of the
disintegration of the parents of these gases, radium
and thorium, and the astonishing changes which
they spontaneously undergo. The beginning of
the twentieth century has been characterised by a
revolution in chemical thought more wonderful
than any which has ever been seen, and this has
had its influence on our conception of the nature
of the atmosphere. But the ground has only been
surveyed ; future years will certainly bring fuller
knowledge.

May 1905.



PEEFACE TO THE SECOND EDITION

SINCE the publication of the first edition, atmo-
spheric air has been found to contain other four
inactive gases, belonging to the same class of
elements as argon. These are helium, discovered
by myself in 1895 in certain rare minerals, but
first separated from the atmosphere in 1900 ; and
neon, krypton, and xenon, discovered in conjunc-
tion with Dr. M. W. Travers in 1898, and separated
from argon and from each other during the years
1899 and 1900. An additional chapter has been
added, giving an account of these elements. I
have also to thank Mr. S. Lupton and Dr. Harfcog
for some interesting details of the lives of Mayow
and of Priestley, which, along with some errata,
will be found at the end of the book.



December 1900.

vii



PREFACE TO THE FIRST EDITION

THE discovery of a new elementary gas in the
atmosphere in 1894 aroused much interest, and
public attention has again been directed to the air,
which was, for many centuries, a fruitful field for
speculation and conjecture. The account of this
discovery, communicated to the Koyal Society in
January 1895, was, however, necessarily couched in
scientific language ; and many matters of interest
to the chemist and physicist were written in an
abbreviated style, in the knowledge that the
passages describing them would be easily under-
stood by the experts to whom the communication
was primarily addressed. But persons without any
special scientific training have frequently expressed
to me the hope that an account of the discovery
would be published, in which the conclusions drawn



x THE GASES OF THE ATMOSPHERE

from the physical behaviour of argon should be
accompanied by a full account of the reasoning on
which they are based. An endeavour to fulfil this
request is to be found in the following pages.
And as the history of the discovery of the better
known constituents of the atmosphere is of itself
of great interest, and leads up to an acquaintance
with the new stranger, who has so long been with
us incognito, an effort has here been made to tell
the tale of the air in popular language.

January 1896.



CONTENTS



CHAPTEE I

PAGE

THE EXPERIMENTS AND SPECULATIONS OF BOYLE, MAYOW,

AND HALES 1



CHAPTEE II

" FIXED AIR " AND " MEPHITIC AIR " THEIR DISCOVERY

BY BLACK AND BY RUTHERFORD 39



CHAPTER III

THE DISCOVERY OF " DEPHLOGISTICATED AIR' BY
PRIESTLEY AND BY SCHEELE THE OVERTHROW
OF THE PHLOGISTIC THEORY BY LAVOISIER 69



CHAPTER IV

" PHLOGISTIC ATED AIR" INVESTIGATED BY CAVENDISH

His DISCOVERY OF THE COMPOSITION OF WATER 121
xi



xii THE GASES OF THE ATMOSPHERE



CHAPTEE V

PAGB

THE DISCOVERY OP ARGON . 148



CHAPTEE VI

THE PROPERTIES OF ARGON . . .182

CHAPTEE VII

THE POSITION OF ARGON AMONG THE ELEMENTS . 218

CHAPTEE VIII

THE OTHER INACTIVE GASES: HELIUM, NEON, KRYPTON,

AND XENON . . . . . 234

CHAPTEE IX

THE RADIOACTIVE GASES : THE " EMANATIONS " . 270



LIST OF POETEAITS

STEPHEN HALES . Frontispiece

EGBERT BOYLE . . . .To face page 8

JOHN MAYOW . 16

JOSEPH BLACK . .' / . . v ,, 48

DANIEL KUTHEEFORD . . .. . 62

JOSEPH PRIESTLEY . . . . ,, 72

CARL WILHELM SCHEELE . ..." . 84

ANTOINE AUGUSTE LAVOISIER . . , 102

HON. HENRY CAVENDISH 121



xiii



CHAPTER I

THE EXPERIMENTS AND SPECULATIONS OF BOYLE,
MAYOW, AND HALES

To tell the story of the development of men's
ideas regarding the nature of atmospheric air is in
great part to write a history of chemistry and
physics. This history is an attractive and varied
one : in its early stages it was expressed in the
quaint terms of ancient mythology, while in its later
developments it illustrates the advantage of careful
experimental inquiry. The human mind is apt to
reason from insufficient premises ; and we meet
with many instances of incorrect conclusions, based
upon experiment, it is true, but upon experiment
inadequate to support their burden. Further
research has often proved the reasoning of the
Schoolmen to be futile ; not indeed from want of
logical method, but because important premisses

had been overlooked.

B



2 'THE GASES OF THE ATMOSPHERE CHAP.

Among the errors which misled the older
speculators, three stand out conspicuously. These
are

First, The confusion of one gas with another.
Since gases are for the most part colourless, and
always transparent, they make less impression on
the senses than liquids or solids do. It was difficult
to believe in the substantiality of bodies which could
not be seen, but the existence of which had to be
inferred from the testimony of other senses ; indeed,
in certain instances only by the sense of touch, for
many gases possess neither smell nor taste. This
peculiarity led, in past ages, to the notion that air
possessed a semi-spiritual nature ; that its substan-
tiality was less than that of other objects more
accessible to our senses. We meet with a relic
of this view in words still in common use. Thus
the Greek words TH/OW, I blow, and Tr^eO/m, a spirit
or ghost, are closely connected ; in Latin we have
spiro, I breathe, and spiritus, the human spirit;
in English, the words ghost and gust are cognate.
And the same connection can be traced in similar
words in many other languages.

Our sense of smell is affected by extremely
minute traces of gases and vapours traces so small



BOYLE, MAYOW, AND HALES



as to be unrecognisable by any other method of
perception, direct or indirect. A piece of musk
retains its fragrant odour for years, and the most
delicate balance fails to detect any appreciable loss of
weight in it. We are capable of smelling gases only :
liquids and solids, if introduced into the nostrils,
irritate the olfactory nerves, but do not stimulate
them so as to incite the sense of smell ; yet the
admixture of a minute trace of some odorous vapour
with air appears entirely to change its properties.
The effect of inhaling such air, although sometimes
pleasant, is very different from the sensation produced
by pure inodorous air, and such admixtures were in
olden times naturally taken to be air modified in its
properties. But such modifications are obviously
almost infinite in number, for varieties of scent
are excessively numerous ; and it was therefore
perhaps deemed useless to attempt to investigate
such a substance as air, whose properties could
change in so inexplicable and mysterious a manner.
Owing, therefore, to its elusive and, as it were,
semi-spiritual properties, and to its unexpected
changes of character, it was long before its true
nature was discovered. It had not escaped ob-
servation that " air " obtained by distilling animal



4 THE GASES OF THE ATMOSPHERE CHAP.

and vegetable matter, or by the action of acids on
iron and zinc, differed from ordinary air by being
inflammable ; but such " airs " were regarded as
atmospheric air, modified in some manner, as it
is modified when perfumed. And " airs " escaping
from fermenting liquids, or produced by the action
of acids on carbonates, were neglected. For long no
attempt was made to catch them ; and the frothing
and bubbling were regarded as a species of boiling,
as is still seen in the use of our word " fermenta-
tion " (fervere, to boil).

Second, Erroneous ideas regarding the phe-
nomena of combustion. While it was recognised
that a burning candle was extinguished if placed
in a confined space, its extinction was attributed
not to the absence of air, but to the impossibility
of the escape of flame. Indeed, flame was regarded
as possessing the same semi-spiritual, semi-material
nature as air. Together with earth and water, air
and flame or fire formed the four elementary prin-
ciples of the Ancients ; and all substances stones,
metals, animals, and vegetables were regarded as
partaking of the properties of these elements, and
often as being constituted of the latter in varying
proportions, according as they were cold and dry



BOYLE, MAYOW, AND HALES



(earth), cold and moist (water), hot and moist (air),
or hot and dry (fire). It is not within the scope
of this book to enter into details regarding such
ancient views. Those who are interested in the
matter will find them expounded in Kopp's History
of Cliemistry, Kodwell's Birth of Chemistry, E.
von Meyer's History of Chemistry, and in other
similar works. But we shall be obliged to consider
the later developments of such ideas in the phlogistic
theory, by means of which all chemical changes
connected with combustion were interpreted from
the latter part of the seventeenth to the end of the
eighteenth century. With erroneous views regard-
ing the nature of combustion, and ignorance as to
the part played by the atmosphere in the phenomena
of burning, the true nature of air was undiscoverable.
Third, The lack of attention to gain or loss of
weight. It was in past times not recognised that
nothing could be created and nothing destroyed.
In popular language, a candle is destroyed when it is
burned, nothing visible being produced from it. The
products, we now know, are gaseous and invisible,
and possessed of greater weight than the unburnt
candle ; but for want of careful experiment, it was
formerly concluded that the candle, when burnt, was



6 THE GASES OF THE ATMOSPHERE CHAP.

annihilated. The formation of a cloud in a cloud-
less sky ; the growth of vegetables in earth, from
which, apparently, they did not derive their sub-
stance ; and the reputed growth of metalliferous
lodes in mines these were all adduced as proofs of
the creative power of Nature. With such ideas,
therefore, the necessity of controlling the gain or
loss of material during experiment, by determining
gain or loss of weight, did not appear imperative ; and
hence but few quantitative experiments were made,
and little importance was attached to these few.
It had, for example, long been noticed that certain
metals gained weight when burned and converted
into a " calx," or, as we should now say, a metallic
oxide, but such gain in weight was not regarded as
of any consequence. When considered in relation to
the supposed loss of " phlogiston" suffered by a metal
on being converted into a calx, it was explained by
the hypothesis that phlogiston possessed " levity,"
the antithesis of gravity, and that the calx weighed
more than the metal, owing to its having lost a
principle which was repelled instead of being
attracted by the earth.

Among the most remarkable early attempts to
elucidate the true nature of air, we meet with one



BOYLE, MAYOW, AND HALES



by the Hon. Kobert Boyle, who published about
the middle of the seventeenth century his Memoirs
for a General History of the Air. Boyle was one of
the most distinguished scientific men of his own, or
indeed of any, age, and in his spirit of calm philo-
sophical inquiry he was far in advance of his contem-
poraries. He was born in the early part of the year
1626, in Ireland, whither his father, Eichard Boyle,
had emigrated at the age of twenty-two. Boyle's
mother, daughter of Sir Geoffrey Fenton, prin-
cipal Secretary of State for Ireland, died while he
was still a child. Yet she must have lived in the
recollection of her son Eobert, for he wrote : "To
be such parents' son, and not their eldest, was a
happiness that our Philarethes (himself) would
mention with great expressions of gratitude ; his
birth so suiting his inclinations and designs, that
had he been permitted an election, his choice would
scarce have altered God's discernment."

In those days of early development, Boyle had
finished his school-days at Eton by his twelfth
year. He informs us that he devoured books om-
nivorously, and could hardly be induced to join in
games. The next six years of his life he spent on
the Continent with his elder brother; and on his



8 THE GASES OF THE ATMOSPHERE CHAP.

father's death, which happened when he was abroad,
he returned to England, and settled at Stalbridge,
in Dorsetshire, where he had inherited a manor.
Here he passed most of his life in great retire-
ment, with only an occasional visit to London ;
for though he lived through troublous times, he
avoided politics. Indeed, he is known only to
have appeared once on a public platform, and that
was in defence of the Royal Society, then in its
infancy, from attacks made upon it by some too
scrupulously loyal Churchmen.

Boyle did not confine his attention exclusively
to scientific pursuits : he interested himself deeply
in theology, and published numerous tracts on
religious subjects. He wrote with equal ease in
English, French, and Latin, and his books ap-
peared simultaneously in the first and last of these
languages. His researches are remarkable for their
wide range and for the boldness of his conceptions.
But Boyle, ingenious though he was, was unable
to fathom the mystery of atmospheric air. His
views regarding it are succinctly stated by him
in his Memoirs for a General History of the
Air, and in the same work he sums up the
views of the Ancients. His words are :




ROBERT BOYLE.



BOYLE, MAYOW, AND HALES



" The Schools teach the air to be a warm and
moist element, and consequently a simple and
homogeneous body. Many modern philosophers
have, indeed, justly given up this elementary purity
in the air, yet few seem to think it a body so
greatly compounded as it really appears to be.
The atmosphere, they allow, is not absolutely pure,
but with them it differs from true and simple air
only as turbid water from clear. Our atmosphere,
in my opinion, consists not wholly of purer aether,
or subtile matter which is diffused thro' the
universe, but in great number of numberless ex-
halations of the terraqueous globe ; and the various
materials that go to compose it, with perhaps some
substantial emanations from the celestial bodies,
make up together, not a bare indetermined fecu-
lency, but a confused aggregate of different effluvia.
One principal sort of these effluvia in the atmo-
sphere I take to be saline, which float variously
among the rest in that vast ocean ; for they seem
not to be equally mixed therein, but are to be
found of different kinds, in different quantities and
places, in different seasons. . . . Many men talk
much of a volatile nitre in the air, as the only salt
wherewith that fluid is impregnated. I must own



io THE GASES OF THE ATMOSPHERE CHAP.

the air, in many places, seems to abound in cor-
puscles of a nitrous nature ; but I don't find it
proved by experiments to possess a volatile nitre.
In all my experiments upon salt-peter, I found it
difficult to raise that salt by a gentle heat; and
spirits of nitre, which is drawn by means of a
vehement one, has quite different properties from
crude nitre, or the supposed volatile kind in the
air, for 'tis exceeding corrosive." l

Boyle then proceeds to collect and comment on
the effluvia from volcanoes and from decaying
vegetables and animals, and proposes tests for the
presence of such ingredients. He even attributes
the darkening of silver chloride to its being a
reagent for certain salts present in air at one time
and not at another, and draws attention to the
sulphurous smell produced by " thunder." Farther
on (p. 61) he writes :

" The generality of men are so accustomed to
judge of things by their senses, that because the
air is invisible they ascribe but little to it, and
think it but one remove from nothing. And this
fluid is even by the Schoolmen considered only as

1 Memoirs for a General History of the Air ; Shaw's Abridgment of
Boyle's works, edition 1725, vol. iii. p. 26.



i BOYLE, MAYOW, AND HALES 11

a receptacle of visible bodies, without exerting any
action on them unless by its manifest qualities,
heat and moisture; tho', for my part, I allow it
other faculties, and among them, such as are gener-
ative, maturative, and corruptive; and that, too,
in respect not only of animals and bodies of a light
texture, but even of salts and minerals."

In another place (p. 17) he states :

" I conjecture that the atmospherical air con-
sists of three different kinds of corpuscles : the
first, those numberless particles which, in the form
of vapours or dry exhalations, ascend from the
earth, water, minerals, vegetables, animals, etc. ;
in a word, whatever substances are elevated by the
celestial or subterraneal heat, and thence diffused
into the atmosphere. The second may be yet more
subtile, and consist of those exceedingly minute
atoms the magnetical effluvia of the earth, with
other innumerable particles sent out from the
bodies of the celestial luminaries, and causing, by
their impulse, the idea of light in us. The third
sort is its characteristic and essential property I
mean permanently elastic parts."

Boyle also relates experiments designed to " pro-
duce what appears to be air"; and he describes



12 THE GASES OF THE ATMOSPHERE CHAP

the production, by the action of oil-of-vitriol on
steel filings, of "air" (now known as hydrogen)
which possessed the property of elasticity ; although
he failed to notice its inflammability. He further
obtained carbon dioxide by the fermentation of
raisins, and probably also hydrogen chloride in the
gaseous form by breaking a bulb containing " some
good spirit-of-salt " in a vacuous receiver.

The result of shrewd reasoning power, applied,
however, to imperfect observations, is well illus-
trated by the following passages :

" For tho', by reason of its great thinness and
of its being, in its usual state, devoid both of
tast and smell, air seems wholly unfit to be a
menstruum [or solvent] ; yet it may have a dis-
solving, or at least a consuming, power on many
bodies, especially such as are peculiarly disposed to
admit its operations. For the air has a great
advantage by the vast quantity of it that may
come to work, in proportion to the bodies exposed
thereto. . . . Thus we find a rust on copper that
has been long exposed to the air." 1

Boyle, shortly after, describes the production
of " an efflorescence of a vitriolic nature " on mar-

1 "Suspicions about some hidden qualities of the Air," ibid. p. 77.



I BOYLE, MAYOW, AND HALES 13

casite (or sulphide of iron) which has been exposed
to the air ; and he relates that the " ore of alum,
robb'd of its salt, will in tract of time recover it
by being exposed to the air, as we are assured by
the experienced Agricola."

To account for such actions, and for combustion,
he proceeds (p. 81) :

" The difficulty we find in keeping flame and fire
alive, tho' but for a little time, without air, renders
it suspicious that there may be dispersed thro 7
the rest of the atmosphere some odd substance,
either of a solar, astral, or other foreign nature ;
on account whereof the air is so necessary to the
subsistance of flame. ... It also seems by the
sudden wasting or spoiling of this fine substance,
whatever it be, that the bulk of it is but very
small in proportion to the air it impregnates with
its vertue ; for after the extinction of the flame the
air in the receiver was not visibly alter'd ; and for
ought I could perceive by several ways of judging,
the air retained either all, or at least the far
greatest part of its elasticity ; which I take to be
its most genuine and distinguishing property. And
this undestroyed springyness of the air, with the
necessity of fresh air to the life of hot animals,



14 THE GASES OF THE ATMOSPHERE CHAP.

suggest a great suspicion of some vital sub-
stance, if I may so call it, diffused thro' the
air; whether it be a volatile nitre, or rather
some anonymous substance, sidereal or subter-
raneal ; tho' not improbably of kin to that which
seems so necessary to the maintenance of the
other flames."

The experimental part of Boyle's work in this
connection relates to the oxidation of cuprous to
cupric compounds, with the change of colour from
brown to blue or green, either in ammoniacal or in
hydrochloric acid solution ; and he goes so far as
to prove that two ounces of marcasites broken into
small lumps, and kept in a room " freely accessible
to the air, which was esteemed to be very pure,"
for somewhat less than seven weeks, gained above
twelve grains by oxidation.

In his Memoirs for a General History of the

Air, Boyle draws up a programme of research, of

the carrying out of which, however, there is no

record. He proposes (p. 23) :

"1. To produce air by fermentation in well clos'd

receivers.

" To produce air by fermentation in sealed
glasses.



BOYLE, MAYOW, AND HALES



" To separate air from liquors by boiling.

" To separate air from liquors by the air-pump.

" To produce air by corrosion, especially with

spirit of vinegar.
" To separate air by animal and sulphureous

dissolvants.
" To obtain air in an exhausted receiver by

burning-glasses and red-hot irons.
" To produce air out of gunpowder and other

nitrous bodies.

"2. To examine the produced aerial substances

by their preserving or reviving animals,

flame, fire, the light of rotten wood, and

of fish.

"To examine it by its elasticity, and the

duration thereof.
"To do the same by its weight, and its

elevating the fumes of liquors."
We shall all agree that if Boyle had successfully
carried out such experiments, our knowledge of the
true nature of air would have come quite a century
before it did. Some of these experiments were
indeed made by John Mayow, his contemporary,
whose work and speculations we shall now proceed
to consider.



16 THE GASES OF THE ATMOSPHERE CHAP.

John Mayow was born in the parish of
St. Dunstan in the West, London, in 1643. His
family was originally Cornish, having come from
Bree, in Cornwall. He entered Wadham College,
Oxford, on April 3rd, 1658, at the early age of
fourteen, and was shortly afterwards made a pro-
bationer-fellow of All Souls College. On May 30th,
1665, after nearly seven years of study, he took
the degree of B.A. ; in 1670, he graduated as
Doctor of Laws (LL.D.) ; but not being attracted


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