JOHN DALTON.
FEOM AN ENGEAvisra BY C. H. JEEXS.
(By permission of Messrs. Macmillan $ Co.}
ISBISTERS' HOME LIBRARY
THE
STORY OF CHEMISTRY
BY HAROLD W. PICTON B.Sc.
WITH A PREFACE BY SIR HENRY ROSCOE
M.P., D.C.L., LL.D., F.R.S.
LONDON
ISBISTER AND COMPANY LIMITED
15 & 16 TAVISTOCK STREET COVENT GARDEN
LONDON t
PRINTED BY J. S. VIRTUE AND CO., LIMITL'D,
CITY ROAD.
TV
PREFACE.
AM pleased to be asked to introduce
this little book to the notice of the
English public. The author has, in
my opinion, told his story brightly
and truly, and in a way to interest those who
have some knowledge of our science, as well as
those who wish to gain that knowledge.
A short and attractive history of Chemistry
PREFACE.
has long been wanted, and my friend the author
seems to have written just such a book as was
needed.
H. E. BOSCOE.
10, BRAMHAM GARDENS,
WETHERBY ROAD, g.W v
October, 1889.
CONTENTS.
PREFACE. BY SIR HENRY ROSCOE
INTRODUCTION
I. CHEMISTRY BEFORE THE ALCHEMISTS EMPIRICISM
FIRST PERIOD : ALCHEMICAL MYSTICISM.
II. ALCHEMICAL MYSTICISM
SECOND PERIOD : MEDICAL MYSTICISM.
III. BASIL VALENTINE .
IV. PARACELSUS VAN HELMONT
PAGS
5
13
23
37
55
79
THIRD PERIOD : THE DECLINE OF MYSTICISM.
V. GLAUBER 97
FOURTH PERIOD : THE BEGINNINGS OF SCIENCE.
VI. THE BEGINNINGS OF SCIENCE 113
Vir. THE ACKNOWLEDGMENT OF NESCIENCE . . .119
VIII. HOOKE MAYOW HALES ..... 137
yiii CONTENTS.
'FIFTH PERIOD: THE CHILDHOOD OF TRUTH.
CHAP. PAGE
IX, CULLEN BLACK 157
SIXTH PERIOD: THE CONFLICT WITH ERROR.
X. THE BIRTH OF ERROR 175
XI. THE FIRST OF AUGUST, 1774 185
XII. TRUTH IN DISGUISE . . , . . . .211
SEVENTH PERIOD : THE TRIUMPH OF TRUTH.
XIII. LAVOISIER 231
EIGHTH PERIOD : THE ATOMIC THEORY.
XIV. D ALTON'S IDEA 257
XV. THE DEVELOPMENT OF DALTON'S IDEA . . .277
XVI. THE ATOMIC THEORY OF TO-DAY .... 293
XVII. DAVY AND FARADAY 317
NINTH PERIOD : THE MODERN SCIENCE.
XVIII. MODERN INORGANIC CHEMISTRY .... 343
XIX. ORGANIC CHEMISTRY TO-DAY 360
CONCLUSION ......... 382
INTRODUCTION.
THE ALCHEMIST.
HE early history of chemistry sounds more
like fiction than fact. A romance clings
about the stories of the old alchemists
which lends them irresistible charm. We
may perhaps best get a notion of their
character by paying an imaginary visit to
an alchemistic laboratory of, say, the fourteenth cen-
tury.
It is a winter's evening and the wind moans melan-
choly without. We are in a long gloomy room.
Above us age-grimed oak rafters stretch away into
the dim shadows of the roof. Smoke and furnace-
fumes hang dusky in the air. Glowing eyes seem to
gleam at us through chinks in furnace doors. Strange
distorted alchemistic vessels stand silently working
i 4 INTRODUCTION.
out their secret wonders, or lie carelessly neglected
on their shelves. Phials filled with deep-coloured
liquids stand here and there picturesquely tinged by
fitful gleams of fire-light. Open folios lie scattered here
and there, the pages covered with mystic writing and
cabalistic signs. And there, bending over a heated
crucible and watching its contents with grave concern,
stands the alchemist himself.
Beside him an assistant is urging the bellows, and
the fire throws a ruddy glow on the face of each.
The alchemist is venerable and careworn. His dark
eyes look out from under shaggy eyebrows, and just
now the forehead is knit in anxious thought. Will
his labour succeed ? For years he has sought the
true method of preparing the substance at whose
touch all metals shall become gold. Now at last the
time of successful trial seems at hand. In that small
crucible his whole labour is to find its issue, and here
and now the great secret is to be won or lost. Two
metals are here molten together, and upon them the
miracle is to be worked. From their baseness is to
come forth pure, lustrous gold.
The alchemist knits his brows a little closer as the
time seems ripe for projection ; he motions his assis-
tant to stop the blast, and taking from his breast a
small piece of yellow wax enclosing a few red grains
dsops it upon the molten mass. A quick bubbling
is heard and light puffs of smoke are blown out from
the crucible. Presently the bubbling ceases, but the
smoke is pouring out faster than ever. It mounts
INTRODUCTION. 15
in the air and floats in light wreaths round alchemist
and servant. It grows denser and obscures the light
of the furnace, rolls upwards among the rafters and
down into the dark corners, making all darker and
mistier and more unreal. Crucibles, folios, alembics,
and alchemist are fast vanishing in it, and at length,
puff! the whole room, with its workers and their
mysteries, has vanished into the dreamland of fancy
.from which it sprang. We are back in the nineteenth
century again ; but, for all that, we have caught a
glimpse of the alchemist at his task.
Now let us ask who were the alchemists, and
what was their work ? The alchemists were a body
of men who flourished from the early centuries of
the Christian era to the close of the seventeenth
century,* and whose main guiding star in their
search for knowledge was their belief in the trans-
mutation of the baser metals into gold. They
sought to prepare the ''philosopher's stone," and
it was at the touch of this that transmutation was
to occur. Some, it is true, sought in the stone
a universal medicine rather than inexhaustible lucre.
It was to cure all diseases and ills of flesh. Among
such seekers was Geber, perhaps the first alchemist
of whom we have record. But Geber seems to have
been far more truly scientific than, with very few
exceptions, any of his successors for the next six
hundred years.
* Even at the close of the eighteenth century a fefa scattered alche-
mists like Peter Woulfe were known. Woulfe died in 1805.
i6 INTRODUCTION.
It cannot be said then that these men were in the main
moved by any very noble ambition. On the whole
their object was to find a way to make gold a desire
indeed not yet extinct. Still, the alchemist usually
had some other interests as well as this which dis-
tinguished him from his modern counterpart. Where
in his search he chanced to discover other interesting
bodies he would not seldom describe them with some
care, and in this way made real contributions to
science. The alchemists, we may with much proba-
bility say, never achieved the main hope of their
quest, but in their search for it they achieved much
that was far better. Their dreams were not healthy
enough to be realised, but the cold realities with
which they were disappointed were to fall as cherish-
ing snow-flakes above the hidden seeds of truth,
which else had withered with the frost. Put in its
most matter of fact way they looked for gold, and
instead of it they found nitric and sulphuric acids,
many other chemicals, and much useful apparatus.
This may seem somewhat paltry by comparison,
but is really not so. It reminds us of an old tale
of long ago in which a dying countryman informs his
sons that in the farm he is leaving them there lies a
hidden treasure. The man has much neglected his
farm, and it is thickly grown with weeds ; but among
them the treasure must be sought. The sons natu-
rally set about digging over the land here and there
in their search. But dig where they will the mine
of gold and gems they pictured is not found. At
INTRODUCTION. 19
last every inch is dug over, and they think their
father must have been wandering in his mind. But
now, things being as they are, they determine to
make the best of a bad business, and as the ground
is open they proceed to sow and plant. This is done,
and in due season, when the crops are growing and
the fruit is rounding on the branch, they bethink
them once more of the promised treasure. As the
money comes in for the immensely increased produce
of the farm it strikes them that the treasure their
father meant was the unused fruitfulness of the soil;
and now, in seeking for the apparently delusive pro-
mise, they have found what was much better, the
reward of honest industry.
Having thus briefly seen who were the alchemists
and how their work was connected with the chemistry
of to-day, we shall in the. next chapter sketch in out-
line the chemical knowledge already acquired before
their time, the material ready to hand for their use.
In the sequel we shall pass briefly in review some of
the more renowned and interesting alchemists in
chronological order, and endeavour to see more clearly
what they actually did for chemistry.
But before closing this chapter it may be suitable
to give one of the many stories of transmutation, which
we find related by writers of repute with apparently
the sincerest belief in their truth. The story is told
by Mangetus, the editor of " Bibliotheca Chemica
curiosa ...-." (1702) on the authority of M. Gros,
a clergyman of Geneva, said to be of the most unex-
2 o INTRODUCTION.
ceptionable character, a skilful physician and an expert
chemist. About the year 1G50 an unknown Italian
came to Geneva and took lodgings at the sign of the
Green Cross. Wishing to see what was to be seen
at Geneva he requested his landlord, De Luc, to pro-
cure him a guide to the to"vvn. De Luc was acquainted
with M. Gros, at that time about twenty, and a
student of Geneva, and knowing his proficiency in
Italian requested him to accompany the stranger
about the town. M. Gros at once acceded to this
request, and for the space of a fortnight acted the
part of guide to the Italian. When this time had
elapsed the stranger began to complain of want of
money. M. Gros became somewhat alarmed, fearing
that he might be asked for a loan, and not being in
a position to lose much money without inconvenience.
But the Italian only asked to be conducted to a gold-
smith who would lend him his blowpipe and utensils
for a short space.
Such a goldsmith was found in the person of
M. Bureau, to whom M. Gros conducted his acquaint-
ance. M. Bureau courteously placed his workshop
at the Italian's disposal, and there left him with
M. Gros and a workman, The Italian then at
once proceeded, before the astonished gaze of the
clergyman, to melt tin in one crucible and heat some
quicksilver in another. When the crucibles were
hot he poured the mercury upon the molten tin and
projected upon it "a red powder enclosed in wax/'
A rapid reaction seemed to occur, the mass bccrmo
INTRODUCTION. 21
agitated, fames were exhaled, and the metals were
forthwith converted into pure gold, yielding six heavy
ingots. The identity of the product with gold was
not allowed to rest upon its appearance alone, for it
was submitted to a 1 ! the tests then known and certi
fled by the goldsmith to be pure. Furthermore the
ingots were taken to the mint, so says the account,
and Jhere exchanged for a large sum in Spanish coin.
As eome token of his indebtedness, the stranger pre-
sented M. Gros with twenty pieces, while fifteen more
were given jointly to M. Gros and M. Bureau for their
own entertainment.
And now comes the dramatic climax to the scene.
The mysterious Italian proceeded to order for that
evening a sumptuous supper for the three with which
to celebrate the occasion. He then went out, and as
the day passed and the ; evening came they waited in
vain for his return. He never came back, and the
secret of the transmutation had gone with him.
This is a very circumstantial account ; but as no
detailed directions have ever been given for success-
fully performing such transmutation, and as the sub-
ject is one where imposture or inaccuracy must be
peculiarly liable to creep in, we can only conclude,
with a very high degree of probability, that the
above is not a case of the actual transmutation of
metals into gold. There is no doubt that the alche-
mists' ideas gave rise to a vast amount of deliberate
deception of others, and still more muddleheaded de-
ception of self. A race of jugglers, severely satirised
22 INTRODUCTION.
in Ben Jonson's Alchemist, arose who traded upon the
gullibility of their dupes most successfully and most
mercilessly. To these latter they could give easy evi-
dence of their power by stirring the mixture in their
crucibles with hollow rods containing oxide of gold
or silver within and having the lower end closed
with wax. In this way by the reduction of the oxide
they could obtain particles of metallic gold.
Another form of imposture, it is said, was to use
crucibles having a false fusible bottom, below which
oxide of gold or silver was contained. Or nails were
dipped into an appropriate liquid and drawn out half
converted into gold. The nails consisted of gold
soldered to iron, and covered so as to conceal their
colour. It was possible also for the alchemist himself to
be deceived by such an operation as that of cupelling
argentiferous lead* in a crucible of ashes or pulverised
bones. The lead then disappears, being oxidised and
sinking into the porous crucible, leaving the silver
behind. To one having imperfect knowledge of what
took place, it might well seem that the lead was con-
verted into silver. And so, indeed, the main fabric
of alchemy was a fairy palace resting upon the basis of
a false dream. Its ruin was sure, but from its shat-
tered fragments the workers of to-day are building a
fabric which to-morrow will be fairer than the fairest
dream.
* That is lead containing silver.
CHAPTER I.
CHEMISTRY BEFORE THE ALCHEMISTS. EMPIRICISM.
JKE GO many other accomplishments of civili-
sation chemistry may probably be traced
back to an Egyptian origin. In the mys-
teries of the Egyptian temples is found
the beginning of the sacred art. In the
third and fourth centuries the learning of
Egypt was the fashion. As the power of Egypt de-
clined the art passed thence, and from Greece, about
the beginning of the ninth century, into the hands of
the Arabians, who produced some of the earliest true
men of science.
The Arabians were certainly real enthusiasts, and in
their treaties with the Greeks of Constantinople there
occurred repeated stipulations for the surrender of
particular manuscripts. To show how strangely in
24 CHEMISTRY BEFORE THE ALCHEMISTS.
some respects knowledge remained for a long period
quiescent we may mention, as a small, though strik-
ing instance, that in Part V. of his Opus ALyns
Roger Bacon quotes from the Arabian philosopher
Alhazen. a description of the anatomy of the eye
which, in all essential particulars, is identical with
that set forth in modern anatomical text-books.
Having got so far, the progress of knowledge for
several centuries well-nigh ceased. Indeed, as for
chemistry itself, it has only since the opening of the
present century thrown off its swaddling clothes.
Alexander of Aphrodisia invented the term chymike
to describe the operations of the laboratory. Hence
the word che:nics, a word unknown in the fourth cen-
tury, and only popular some centuries later. Later,
when men reflected that the old name of Egypt was
Cham or Chemia, it flattered the chemists to call their
art the art of the ancient Ghemi. Such is the power
of words that this false derivation gave fresh impulse
to the science.
We must now give some account of the chemical
knowledge acquired, and the chemical notions enter-
tained, by the ancients previous to the time of Geber
(eighth century), and may in passing point out some
of its connections with the knowledge of a later day.
Their ideas were of course very vague, and their
knowledge had been arrived at by chance and empiri-
cally* rather than by intelligent research. Aristotle, the
* Empiric, empirical, empiricism, are words that need careful
definition. They are derived from a Greek word signifying experi-
ences. But all knowledge is derived from experience, and, therefore, at
CHEMISTRY BEFORE THE ALCHEMISTS. 25
great Greek philosopher, looked upon the universe as
built up from the four " elements," earth, fire, air,
and water, and with such theories science could not
progress far. We shall see later on how at the present
time we have come to regard an " element " as any
substance which we cannot by any known process split
up into two or more different things.
Seven metals were known to the ancients* gold,
silver, mercury, copper, tin, lead, and iron. None is
more commonplace to us now than the last, but
in these early days it was thought very precious
indeed, owing to the difficulty of working it. Copper
was then more extensively used than any other metal,
and generally alloyed with tin to form bronze. This
alloy, bronze, was much used for coinage and for
statuary. Here is an analysis of three different
bronzes for ' comparison. Each gives the amount of
copper and other metals in one hundred parts of the
bronze.
I. II. in.
Copper ... 84-53 99'3 8877
Tin .... 6-82 07 9-25
Lead .... 8-65 .. 070
Zinc 1*28
first sight, it would appear that empiricism must be the right method
of acquiring knowledge. The meaning of words, however, depends
not only on derivation, but on accidental use, and "empiricism"
happens to have been used chiefly of chance experiences occurring
irregularly and without any ordered plan of research An instance
of empiricism is found in the discovery of glass, described in Chapter
II. The researches of Black on lime and magnesia, described in a
later chapter, afford an example of ordered research or induction of a
high order.
* Many of the facts in this chapter are obtained from Thomson's
History of Chemistry,
26 CHEMISTRY BEFORE THE ALCHEMISTS.
I. A Roman bronze coin of Justinian.
If. Bronze statues of horses in the portal of St. Mark's, Venico
( about A.D. 430).
III. Thorwaldsen's " Shepherd " (cast in Berlin, 1825).
In working and casting metals the ancients were
very advanced. The bronze statue of Apollo placed in
the capitol in the time of Pliny* was forty-five feet in
height and cost five hundred talents, equal to about
50,000. The statue of the sun at Rhodes (the
" Colossus of Rhodes ") was the work of Chares, a
disciple of Lysippus. According to one account it
was a hundred and five feetf in height, was twelve
years in making, and cost three hundred talents
(30,000). It bestrode the entrance to the harbour,
and ships could pass full sail between its legs. A
winding staircase ran to the top, and the shoulders
afforded an excellent point of view. For about fifty-
six years this tower of bronze stood unhurt and was
then overthrown and partly ruined by an earthquake.
Money was subscribed to the Rhodians to restore it
to its place. This they divided among each other
and excused themselves by an oracle from Delphi
which forbade them to raise the statue. For nine
hundred years it lay on the ground and was at last
sold to a merchant who loaded nine hundred camels
with its fragments. Iron and steel were used in the
time of Pliny, but of the method of working them
there is little record.
Various mineral colouring matters were used, as
for instance, minium (red lead), which is an oxide of
* First century A.D.
t Thomson gives ninety feet.
CHEMISTRY BEFORE THE ALCHEMISTS. 27
lead ; cinnaberis (cinnabar) or sulphide of mercury,
&c. Some dyes were also prepared, the most impor-
tant being the celebrated Tyrrhian purple discovered
about 1500 B.C. This colouring matter was extracted
from two kinds of shell- fish found in the Mediter-
ranean. The ordinary process of calico-printing is to
stamp the material at certain parts with "mordants"
which fix the colour in its meshes. It is then
steeped in the dye, after which the colouring matter
may be washed out from the unmordanted portion,
leaving the pattern stamped in colour on the material.
This process seems to have been known in ancient
times in India and the East, and probably to the
Egyptians.
Among the most important chemical products
known to the ancients was the invaluable substance,
glass. Glass beads are found on Egyptian mummies
which date back to some thousands of years B.C.
Glass consists mainly of a compound of silica with
soda and lime. Silica is a white substance occurring
in nearly all rocks and existing almost pure in white
sand. The glass is made by fusing soda-ash with
sand, the lime being added in various forms such as
calc-spar, chalk or limestone, according to circum-
stances. Its original discovery as described by Pliny
has thus by no means any great improbability.
According to his account some Phoenician merchants,
in a ship loaded with carbonate of soda from Egypt,
stopped and went ashore on the banks of the river
Belus. Having nothing to support their kettles
they used lumps of carbonate of soda : the fires melted
28 CHEMISTRY BEFORE THE A L CHEMISTS.
this and fused it into the sand of the river, thus
.forming glass. In Pliny's time too, coloured glasses
were decolourised by the addition of manganese in
the making, just as now.
Starch was known to the Greeks and its manu-
facture is described by Pliny. It was prepared by
Avashing wheaten flour by processes similar to those of
the present day. It may not be out of place to
shortly describe these here. Wheat, maize, rice, and
potatoes consist very largely of starch. From these
sources it is obtained by rasping or grinding the
vegetable structure to pulp and washing the mass
upon a sieve, by which the torn cellular tissue of the
plant is retained. The starch passes through and
settles dwn from the liquid in the form of a fine
white powder. Examined by the microscope it is
seen to consist of little rounded, concentrically
striated particles, the appearance of which differs
characteristically in different plants. The chemical
constitution of starch is a subject which has given
rise to much labour and discussion. We may gain
some insight into the amount of labour involved in
the thorough study of one apparently commonplace
body by noticing that in a recent famous paper upon
starch by two chemists, Brown and Heron, the
authors in their introduction remark that more than
four hundred papers have already appeared on the
same subject.
Porcelain and stoneware are made by heating
various clays with a " frit," " flux," or fusible
CHEMISTRY BEFORE THE AL CHEMISTS. 29
material. Porcelain is obtained when the whole
mass is thoroughly permeated by the frit, and is
thus semi-transparent or translucent. Earthen-
ware is made from a coloured plastic clay which
forms a porous mass w 7 hen baked. It is then
glazed. The history of porcelain is of no little
interest. The first discovery is lost far back in the
unrecorded ages of the great Chinese empire. Like
much other knowledge which Europeans had pain-
fully to rediscover for themselves it lay there totally
hidden. To the Romans the art was wholly un-
known,* and remained so to the rest of Europe for
many centuries, till in 1709 the method of making it
was discovered by Eotticher and a manufactory was
established at Meissen, in Saxony. This manufacture
was kept strictly secret, and the King of Prussia
instructed the celebrated chemist Pott to find the
secret out. Pott could obtain no details as to the
materials actually used. His only plan was to choose
those which seemed suitable, to mix them together
in varying proportions and see what happened. It is
said that Pott's experiments in this w T ay reached the
enormous total of thirty thousand. After all he did
not discover what he sought, but to his work we owe
much valuable information. He was followed in the
search by Re'aumur and other French chemists, and
finally the lost art was rediscovered, and in 1769 the
great Sevres manufactory was founded. It is only
* The art of pottery, i.e. the opaque ware, of course never became
extinct.
30 CHEMISTRY BEFORE THE ALCHEMISTS.
during the present century that porcelain has become
an article of every-day use and is known to us more
familiarly as china. The knowledge of earthenware
or faience dates back to equally early times, but this
did not in the same way suffer extinction. In more
recent times it was the renowned Bernard Palissy
whose disinterested labours spread abroad a thorough
knowledge of this important product.
We shall next discuss the knowledge which the
ancients had attained of a very important article
important at least to us moderns. "The quantity
of soap," says Liebig, " consumed by a nation would
be no inaccurate measure whereby to estimate its
wealth and civilisation. Political economists, indeed,
will not give it this rank ; but whether we regard it
as joke or earnest, it is not the less true, that, of two
countries with an equal amount of population, we
may declare with positive certainty that the wealthiest
and most highly civilised is that which consumes the
greatest weight of soap. This consumption does not
subserve sensual gratification, nor depend upon
fashion, but upon the feeling of the beauty, comfort
and welfare attendant upon cleanliness ; and a regard
to this feeling is coincident with wealth and civilisa-
tion. The rich in the Middle Ages who concealed a
want of cleanliness in their clothes and persons under
a profusion of costly scents and essences, were more
luxurious than we are in eating and drinking, in
apparel and horses. But how great is the difference
between their days and our own, when a want of
32 CHEMISTRY BEFORE THE ALCHEMISTS.
cleanliness is equivalent to insupportable misery and
misfortune ! "
Before the time of Pliny soap seems to have been
unknown. The word is used in the Old Testament,
in one case for the Hebrew word nether, which
probably signifies trona or native carbonate of soda,
and in the other for borith, meaning the lye or solu-
tion obtained from the ash of a plant, arid which
contains the same ingredient. In the older Greek
period garments were washed with water onh r , and oil
was used to soften the skin after bathing.
Pliny is the first to mention soap. He describes
it as made from wood-ashes and tallow, and says it was
used as a pomade, and more among men than women.
In a work published in the second century soap is
stated to be used both as a medicine and for cleansing-
purposes. In early times, however, other cleansing
agents seem to have been more frequently used.
These included native carbonate of soda, the ashes of
sea-plants, and putrid urine. Among the many
secrets which the buried remains of Pompeii have
disclosed is the fact of the use of soap among the
Romans, at least in later times, for a complete soap-
boiling establishment has there been discovered. At
present soap is made from caustic alkalies (soda and
potash) and fats.
The ancients were acquainted with only one acid
vinegar, which is merely dilute acetic acid. It is
formed when alcoholic drinks turn sour, and is
obtained from alcohol by further fermentation. Its
CHEMISTRY BEFORE THE ALCHEMISTS. 33
solvent properties are said to have been known to
Cleopatra when she boasted to Anthony that she
would consume an incredible value of food to her own
share at one meal. Towards the close of the appointed
meal she produced a goblet containing some weak
vinegar and dropped into this the two finest pearls
then known in the world. They at once dissolved
in the acid and in this way her one draught cost ten
million sestertii. This story is, however, of very
doubtful authenticity, pearls, indeed, being insoluble
in weak vinegar.
Of gases we find in these times really no knowledge
at all. Pliny's whole account of the air is that it
condenses itself in clouds and rages in storms. So too
of that most common body, water, little was known.
Its properties were too simple to be explained without
much greater progress, and our knowledge of water
may be said to commence with Cavendish in 1785.
Another substance which has acquired a rather
questionable importance among us, and which was
known to the ancients, is the old English beverage,
beer. The story of beer is a very old story indeed,
and, as Prof. Huxley says, " among the earliest records
of all kinds of men you find a time recorded when
they got drunk." The process of fermentation has
apparently been made use of from the earliest periods
of which we have any records handed down. The
question may be asked what is fermentation ?
Well, in spite of the long ages it has been in use it is
impossible to sny certainly what it is. But the way
c
34- CHEMISTRY BEFORE THE ALCHEMISTS.
in which it is brought about is simple enough, and
much the same now as in ancient times. Grain
barley, for instance is steeped in cold water and
spread out, when it begins to sprout. In this
process part of its starch is changed into sugar.
The grain is now killed by heating it, and in this
state is called malt. The crushed malt is run into
a large vessel, the " mash tun," where it is mixed
with warm water. Here the rest of the starch
becomes changed into sugar, and it is this solution
of sugar which is fermented by adding common
yeast. Yeast is made up of a number
of little round bodies which are really
small plants. These grow in the li-
quid, and by their growth they some-
how manage to attack the sugar and
YEAST CELLS. form alcohol from it. If beer is being
-made the wort or infusion of malt is
first boiled with hops before fermenting. This gives
its characteristic bitter taste to the beer.
The Egyptians appear to have prepared beer from
malted grain, while wine, prepared by allowing grape-
juice to ferment, is mentioned in Homer and the Old
Testament. But as the ordinary methods of distil-
lation were in those times unknown, ardent spirits
and spirits of wine could not be obtained. Thus,
although alcohol had been for ages produced as a
drink, it was never obtained in anything like purity
till probably the time of the alchemist, Raymond
Lully, at the close of the thirteenth century,
FIRST PERIOD.
CHAPTER II.
FIRST PERIOD .- ALCHEMICAL MYSTICISM.
E shall now pass in review some of the work
of- the alchemistic teachers, and see how
air-built were their castles, and how they
failed to put foundations under them. We
shall find out how involved and mysterious
were their writings, but also how distinct
was their service to knowledge, and how patiently
they followed their lode-star even though it proved a
will-o'-the-wisp. In this Avay we may seek not in vain
among their broken alembics for some grains of a
wisdom whose price is more precious than gold or
rubies.
According to Suidas (who flourished in the eleventh
century), the art of alchemy was known as early as
the Argonautic expedition, the golden fleece being
3 8 ALCHEMICAL MYSTICISM.
actually a treatise written on skins concerning the
making of gold. Such is the subtlety of exegetics.
Alchemy was also said to have originated with a
mysterious Hermes Trismegistus, an Egyptian. In a
reputed writing of Albertus Magnus it is said that
Alexander the Great discovered the tomb of Hermes,
in which were many golden treasures, and, most
precious of all, an emerald ta,ble on which was
inscribed a description of the preparation of the
philosopher's stone capable of curing all diseases.
The description is of course unintelligible, and after
an immense amount of controversy as to the claims
which these directions have to authenticity, it is now
almost certain that both they and the tract, attributed
to Albertus Magnus, in which they were inserted, are
altogether forgeries. The Tractatus Aureus is attri-
buted to Herrnes and is of the same type. To pre-
pare this mystic philosopher's stone we are directed
to " catch the flying bird," by which is meant quick-
silver (mercury), " and drown it so that it may fly
no more." This is what was afterwards termed the
fixation of mercury by uniting it to gold. And so on ;
the total result in the end probably being to increase
the weight of the gold by addition of impurity. So
much for the reputed founder of alchemy !
The first alchemist of whom we have probably any
authentic record is Geber, an Arabian of the eighth
century, also known as Djafar, or in full as Abu Musa
Dschabir Ben Haijan Ben Abdallah el-Sufi el-Tarsusi
Kufi. If his writings are indeed authentic, they
ALCHEMICAL MYSTICISM. 39
present us with one of those extraordinary instances
of a man born hundreds of years before his time, for
which it is difficult on any hypothesis to account.
Geber's reputed works are precise and clear to a degree
surpassing the best writers in the later alchymical
period. Older writings there are none. Subsequent
treatises as clear do not appear till far more know-
ledge had been acquired. His work stands out alone.
There seems indeed to linger in it the after-glow of
some previous sunset of knowledge, soon to be plunged
in almost starless night.*
Geber describes a number of metallic compounds,
such as green vitriol (a sulphate of iron), saltpetre,
corrosive sublimate (a chloride of mercury) . Possibly
the accounts given of various acids and salts may
have been added to at a later date. But his claims
to be considered the first propounder of a chemical
theory are probably valid. According to Geber's views
* Geber is mentioned in the Kitab-al-Fihrist (tenth century), by
Ibn Khallickan (thirteenth century) and others. If these references
are correct he nourished in the eighth century. His birth-place was
probably Tarsus and he resided at Damascus and Kufa, but some
have gone the length of altogether questioning his existence. The
titles of no less than five hundred of Dschabir's works on chemistry
are given in the Fihrist, and have been catalogued by Hammer-
Purgstall ; nothing more is known about the majority of them.
Arabic manuscripts on alchemy bearing the name of Dschabir Ben
Haijan exist in Leyden, Paris, and London. Geber describes many
chemical operations, such as filtration, crystallisation, and sublimation,
and was able, it seems, to prepare nitric acid, or aquafortis, and from
it the mixture aqua regia, a liquid almost fulfilling, at least in its
solvent properties, Van Helmont's dreams of the alcahest or universal
solvent, and the only acid dissolving gold. It consists of mixed nitric
and hydrochloric acids.
40 ALCHEMICAL MYSTICISM.
all the metals are composed of the same " elements,"
so that the less perfect may be developed into the
more perfect, or as he somewhat fantastically puts it,
" Bring me the six lepers, so that I may heal them, 53
that is transmute the six imperfect metals into gold.
The elements which he considered to be combined in
various proportions to produce the different metals
are sulphur and mercury. The mercury was supposed
to give the body its metallic characteristics. The
more mercury the substance contained the more truly
metallic it became, and the less readily altered by
heat or chemical agents. If much sulphur were
present the metal would, said Geber, be less perfectly
metallic and would lose its metallic properties in the
fire. But this was not all ; the mercury and sulphur
could exist in different degrees of purity and of
division, and these conditions also affected the cha-
racter of the metal so composed. Thus either by
changing the proportion of mercury and sulphur, or
by altering their condition, or by combining both
changes, we might reasonably hope to convert one
metal into another, and to convert all metals into
gold. Gold and silver were supposed to contain a
very pure mercury, combined in the first case with a
red, and in the second with a white sulphur. These
ideas are, as we shall see, adopted by Roger Bacon in
his Mirrour of Alchemy.
Now what are we to say of such ideas as these ?
Are we to treat them scornfully as unscientific and as
unworthy of recapitulation ? The suppositions have
ALCHEMICAL MYSTICISM. 41
been disproved, it is true, but then so have innumer-
able hypotheses which were useful in their time.
The Copernican system which represented the planets
as moving round the sun in circular paths was given
up in favour of the view which regarded those paths
as an ellipse, but it was only by constructing the
first hypothesis and finding that to bo insufficient,
that the second could ever have been arrived at.
Again, the theory according to which matter is built
up of multitudinous minute particles called atoms
which cannot be divided, when philosophically con-
sidered, involves us in absurd inconsistencies. Never-
theless it has been an especially useful hypothesis in
helping us to a proper classification of chemical facts
for purposes of research. It is quite true that it will
not suffice in science to set about weaving fancies
without reference to fact ; but in trying to explain
things we are bound to make guesses at truth, and
some of our first guesses are sure to be wrong. The
proper way to treat the guesses which we call
hypotheses is to think out what logically follows
when we assume that they are true. If our deduc-
tions are found to coincide with fact the hypothesis
is probably valid, if not it is invalid. Thus if we were
to assume that the moon is made of green cheese, it
would follow from this that the weight of the moon
would be for its bulk very small, but this is known
not to be the case ; and moreover as many other
absurd and impossible or improbable results would
follow, such a hypothesis is obviously invalid. New-
42 ALCHEMICAL MYSTICISM.
ton assumed that the force of gravity varied inversely
as the square of the distance, and the validity of this
hypothesis was proved by showing that Kepler's laws
of planetary motion, which were known to be true,
followed naturally from this assumption.
When we have got a hypothesis which in many
cases is workable but in some cases also fails, it may
still be of immense service, but we should not
hastily describe it as a fact. Of such a hypothesis,
for instance, as the atomic theory* we can say that
there is between this idea and the actual constitution
of matter sufficient analogy to make the former a
great help towards the appreciative study of many
scientific facts. But we have no right whatever to
say that this theory in any form rightly represents
what is the constitution of matter. Shortly then
the use of any hypothesis is to lead to a more appre-
ciative study of facts. One of the first fruits of this
study may be the proof that the hypothesis itself was
invalid, but that does not destroy its value as a means
to progress. In this light Geber's idea was a first
guess. It was wrong, but it at least led people to
think of the metals together, and as a class ; and was
the first step in a series of conjectures as to what
were the " elements " or simple substances out of
which complex bodies were composed. It was a
decided advance on the old Aristotelian notion of the
four elements, earth, fire, air, and water ; and it was
something to have escaped so early from the thraldom
* For the atomic theory see p. 257
ALCHEMICAL MYSTICISM. 43
in which the ideas of Aristotle were destined to hold
the world for centuries to come.
After Geber we seem almost to go back. The
writings of his successors, for a long period, are in
most cases a farrago of mysterious nonsense broken by
rare deviations into sense. Their descriptions of their
experiments are among the most wonderful specimens
of a falsely metaphorical style on record. These
treatises are interesting, however, for the occasional
gleams of light they shed on the development of what
was to become a science. Some of the alchemists,
too, certainly did good work. After all they had few
means then of attaining their knowledge, and we can-
not justly scoff at those who, while seeking their
unsubstantial dreams, w r ere unconsciously preparing
the ground for the seed which later generations sowed,
seed now, though the sowers have long slept, spring-
ing forth into a full harvest of ripe grain.
Albert Groot, better known as Albertus Magnus
(1193 1282), was a German; a universal genius
he would probably be termed now, who after being
made Bishop of Ratisbon, gave up his bishopric to
follow science. He was theologian, physician, astro-
loger, and alchemist. In his chemical ideas, he fol-
lowed Geber, considering all metals to be composed
of sulphur and mercury. He describes various
apparatus, such as alembics and aludels, but it is
difficult, of course, to say how many of his ideas
were original. He is chiefly renowned as the com-
mentator of Aristotle. Alembics were used for
44 ALCHEMICAL MYSTICISM.
distilling liquids. The aludel was used chiefly for
distilling solids which vaporise without melting, i.e.
for sublimation.
We next come to a name which, like Geber's, stands
out alone, though the bearer of it was greater as a
philosopher than as a chemist. Hoger Bacon was
a contemporary of Albertus Magnus, though the
dates of his birth and death are somewhat uncertain
(perhaps 1214 1284). In the course of his life
he passed through many vicissitudes. After studying
at Oxford, he enrolled himself as a Franciscan friar,
probably in order to pursue his meditations in peace.
He engaged in experimental research, thereby ac-
quiring an unenviable notoriety. One who cared
to study God's work, must, it was thought in those
days, be in league with the devil. Accordingly Bacon
was ordered to Paris, and there confined to his cell,
without writing materials, it is said, for ten years.
Imagine the torment this insane act of barbarity
must have caused to a man whose brain was seething
with thoughts struggling to be uttered, and theories
waiting to be tested by fact. For ten mortal years
to be compelled to silence, when some of the greatest
purposes of life could only be fulfilled in speech ;
for ten years to be forced into idleness, when a
millennium would be all too short to accomplish the
work waiting to be done!
But at length there intervened one whose soul
seems, at least, to have been above the superstitious
prejudices of his subordinates, Pope Clement IV. wa.s
ALCHEMICAL MYSTICISM. 45
appealed to, and ordered Bacon forthwith to send him
any writings he might prepare. The restrictions as to
writing materials were then removed, and Bacon was
at work once more. The long pent-up flood of his
thoughts seems to have burst forth then in an over-
whelming torrent. In the next eighteen months
three large treatises were dispatched to the Pope
the Opus Majus, Minus, and Tertium the first itself
filling a large folio volume of print. In 12GS Bacon
returned to Oxford, and characteristically undaunted
by the penalties he had suffered, forthwith produced
a strongly-worded attack upon the Church, for
which he was once more promptly thrown into
prison. There it appears he remained for fourteen
years, being released in 1282, after which he pub-
lished his Campendium Studii Theologies and died
probably in. 12 84.
Condemnation of this treatment could not be ex-
pected for a long time after his death. The greater
a man is, indeed, the longer period must elapse
after his death before he is thought of as even not
below the level of the ordinary man. The ordinary
man is apt to honour people with reverence in pro-
portion as they conform more nearly to his own type,
so that a few flashes of diplomatic tact superimposed
upon invulnerable mediocrity afford an immediate
passport to popularity, though not to lasting fame.
Roger Bacon could not be mediocre, nor did he
stoop to be diplomatic. He was centuries in advance
of his contemporaries, and such presumption W as
46 ALCHEMICAL MFSTICISM.
reckoned, as it ever is, unpardonable. It is only
of late years, indeed, that his position has come to
be appreciated, though some indignation had been
aroused at a much earlier date. Here is an extract,
for instance, from a writer of the seventeenth
century.
<( But such was the stupid ingratitude of Bacon's
age that it almost repented this learned man of
his knowledge. For his own order would scarce
admit his books into their libraries. And great was
this poor man's unhappiness : for being accused of
magick and heresy, and appealing to Pope Nicholas
the Fourth, the Pope liked not his learning, and by
his authority kept him close prisoner a great many
years." *
The stories told about Bacon were, of course, of the
wildest and most extraordinary kind. The best
known of them is embodied in a play of Robert
Greene's (1594), entitled The Honourable History
of Friar Bacon and Friar Bungay. The story is
here told of the famous brazen head, by the enchant-
ments of which the whole of England was to have
been walled with brass. Bacon sent his servant
Miles to watch it while he slept, with exhortations to
waken him if the head should speak. The head
merely uttered the words " Time is," for which Miles
thought it not worth while to waken his master.
The second speech, " Time was," did not suffice to rouse
* Bacon, Roger : His Discoveries of the Miracles of Art, $c. Trans-
lated by T. M. (London, 1659).
ALCHEMICAL MYSTICISM. 47
him, and finally came the fatal words, " Time is past."
Then, as they have it in the play, " a lightning
flashes forth, and a hand appears that breaks down
the head. with a hammer." Miles now roused his
master at once, but it was, of course, too late. In
The Famous Historic of Fryer Bacon, a chap-book
of the year 1527, will be found this and many other
amusing stories. There seems no doubt that Koger
Bacon was one of the several people incorporated
in the old Faust legend. This will be seen by
reference to a curious old book, The Surprizing and
damnable life of Dr. Faustus.*
Of Bacon's works, we must make reference to the
Opus May us, though this is not strictly chemical,
but rather a treatise on the general principles of
science, t But as these principles have a bearing upon
chemistry as well as upon other sciences, and as,
moreover, Bacon insists strenuously upon the value
of experiment a doctrine the acceptance of which
is peculiarly necessary to the advance of chemical
science his work should have interest for every
chemist.
In Part IV. of the Opus Bacon upholds the
value of mathematics. Force, according to him, is
invariably subject to mathematical laws. If we
recollect, and it is certainly difficult to realise it, that
such ideas were promulgated in the thirteenth
* London (1608).
t Roger Bacon: Opus Majus (London, 1733, folio). See also an
interesting paper by Prof. R. Adamson (1876), on The Philosophy of
Science in the Middle Ages.
48 ALCHEMICAL MYSTICISM.
century, while the great Kepler thought the revo-
lutions of the planets might be accounted for by
guiding spirits, we may be able to appreciate Bacon's
pre-eminence. In Part VI., Bacon treats of experi-
ment, and in a way more truly philosophical than
that of his successor Francis Bacon, who is gene-
rally referred to as the founder of the inductive
philosophy. Francis Bacon's system rests wholly
upon induction ; Roger Bacon grants the validity,
indeed, the necessity, of theorising, but the hypothe-
sis must be verified by appeal to observation and
experiment. As he says in Part VI., "Argument
shuts up the question, and makes us shut it up too ;
but it gives no proof, nor does it remove doubt, and
cause the mind to rest in the conscious possession of
truth, unless the truth is discovered by way of
experience."
The strange resemblance in many points between
Roger Bacon's ideas and those of his illustrious
namesake has been noticed by Hal lam in his
History of the Middle Ages. "Whether Lord
Bacon," he says, " ever read the Opus Majus, I
know not, but it is singular that his favourite quaint
expression, prerogatives scientiarum, should be
found in that work ; and whoever reads the sixth
part of the Opus Mo jus upon experimental science,
must be struck by it as the prototype in spirit of
the Novum Organum." But we must not further
discuss the Opus Majus here. So far as it has
bearing upon the general principles of scientific
ALCHEMICAL MYSTICISM. 49
research, it deserves a prominent place in the history
of every science. The practice of spinning wordy
cobwebs without appeal to fact w r as the fashion for
centuries after Bacon's death, and we all owe rever-
ence to the man who so early saw that a theory or
hypothesis cannot stand " unless the truth is dis-
covered by way of experience." But having thus far
glanced at the importance of Bacon's logical work,
we must now turn to more strictly chemical matter.
Bacon has been usually alluded to as the discoverer
of gunpowder, at least as far as Europe is concerned.
That he was acquainted with it is certain from
the following passage in the sixth chapter of his
De secretis operibus artis et naturce.* "Mix together
saltpetre, luru vopo vir conutiret (sic), and sulphur, and
you will make thunder and lightning, if you know
the method of mixing them." By the extraordinary
term "luru vopo vir conutiret," he presumably refers
to charcoal. But it is not certain that he invented this
mixture. On the authority of an Arabic writer in
the Escurial collection, referred to by Hallam, it
seems that gunpowder was introduced by the Sara-
cens into Europe before the middle of the fifteenth
century. Whether Bacon had gathered his informa-
tion at an earlier date from some Eastern source is
uncertain and may be doubted. And, whoever first
prepared this substance, it is difficult to say whether
it has done much credit to its inventor.
Bacon's Mirrour of Alchimy is written in a style
* Hamburg (1618). Also a translation by T. M. : London (1659).
r>
S o ALCHEMICAL MYSTICISM.
similar to that of other alchemistic writing of his and
a later period. In it he adopted Geber's ideas as to
the constitution of the metals : " All metals and
minerals .... are begotten of Argentvive and
sulphur." The book, as a whole, does not seem
worthy of its author.
Raymond Lully's name may perhaps be mentioned
in connection with Roger Bacon (1235 1315).
He wrote a great deal, but for the most part it
was jargon. He had a romantic life, beginning as
a lover of the Lady Eleanor of Castello. She
cured him of his passion by showing him an ulcer
eating away her breast. At her request he con-
secrated himself to God and missionised the Mus-
sulmans. He died in sight of Minorca after being
stoned at Tunis. He was acquainted, it seems, with
nitric acid, Avhich he obtained by distilling saltpetre
with the lower sulphate of iron, and he knew that on
adding potashes to a liquid containing alcohol the
alcohol rose to the surface or was salted out. His
opinion of alcohol seems to have been high, for he
terms it consolatio ultima corporis humani. His
missionising propensities notwithstanding, Lully seems
to have been somewhat of an impostor, and his
chemical opinions are not of much moment.
Bernard of Trevisa spent his whole life in searching
for the secret. In one striking chemical passage he
asserts that the alchemists are mistaken in supposing
that with acids they obtain solutions of the metals as
such, or, as he puts it, as with mercury, for by the
ALCHEMICAL MYSTICISM. 5I
action of these acids the metals are severed or " de-
composed" (aeparalytmtur). The truth, of course,
is that the acid is decomposed, the metal forming a
soluble salt. When we dissolve copper in nitric acid
a chemical change occurs and the metal disappears.
We obtain a blue solution, but this is not a solution
of copper, it contains a salt of copper, viz. copper
nitrate. The writings of this time are romances, and
indeed so far did the writers carry their hyperbole
and mysticism that we find treatises on alchemy
almost unrecognisably disguised in what on the sur-
face seems merely a romantic tale.
But the darkest age of alchemy was now drawing to
a close, and although for a long time the alchemists
held the field, yet more and more of them were
chemists as well. The time of the mere gold- searcher,
the mere alchemist, whose desires consumed them-
selves like his furnace fires to white profitless ashes
which could be rekindled no more, was almost past.
SECOND PERIOD.
CHAPTER III.
SECOND PERIOD : MEDICAL MYSTICISM.
BASIL VALENTINE.
^RANDE rather rashly utters a sweeping con-
demnation of the history of the alchemists
up to the date at which the last chapter
closes : "It presents nothing that the
mind rests upon with satisfaction ; no-
thing that it reverts to with interest or
profit." This is certainly going too far ; for Geber
and Roger Bacon both afford us interest and profit.
But it was a dark age for chemistry to this time. In
the present chapter we shall meet with people who
directed many experiments to the elucidation of
other mysteries than that of the preparation of gold.
It is true- their writings are still written in a very
inflated and often unintelligible style, but we find
a greater tendency to attempt accurate description.
5 6 MEDICAL MYSTICISM.
Basil Valentine is the first of these new chemists
.whom we shall notice. Valentine Avas a native of
Erfurth, and wrote towards the close of the fifteenth
century. He strangely combines the incoherent jar-
gon of the older aViemist with really rational descrip-
tions of experiments. The period which opens with
Valentine is a new one in more than one characteris-
tic. The era of medical chemistry, iatro-chemistry
as it is called, was ushered in by Valentine's Tri-
umphant Chariot of Antimony, in which the medi-
cinal properties of antimony were insisted upon with
strenuous vehemence. The search for transmutation
was to some extent exchanged for the pursuit of the
elixir vitce, which was to cure all the ills of flesh,
and by means of which, even so far back as 1130,
Artephius was said to have lived to the advanced age
of 1,025. The term philosopher's stone has also
been applied to this elixir, and probably some
thought that the same body was to transmute the
metals and prolong life. However, Valentine's pur-
pose was in the main medical, and his work in this
direction led him to important results. Before con-
sidering what services he rendered to science we may
quote a passage from him where the alchemistic taint
i.i pronounced.
The following is from The twelve Keys of Brother
Basil Valentine, of the Benedictine Order. By which
the doors to the ancient stone of our forefathers is
opened, and the unfathomable well-spring of all health
THE KINO AND HIS BEIDE.
From a Woodcut in Die Zivdlf Schlussel
(illustrating the quoted passage).
5 8 MEDICAL MYSTICISM.
is discovered.* " The crown of the king must be of
pure gold, and a chaste bride must be given to him
in marriage. Therefore if you wish to work through
our bodies then take the greedy, grey wolf, so-called
because he is subject to the warlike Mars, but who is
by birth a child of old Saturn, found in the valleys and
hills of the world and possessed by great hunger, and
throw to him the body of the king that he may make
it his food, and when he has devoured the king make
a great fire and throw the wolf into it, that he may
be wholly burned, and by this means will the king be
again released. When this has happened three times
the lion will have conquered the wolf, and will find
nothing more of him to consume, and in this way our
body is made perfect for the beginning of our work."
This is a fair example of the falsely metaphorical
style, and it is a similar passage which is chosen for
satire by Glauber at a later date. If this is indeed
one of the keys to the stone it is itself shut within
what at first seems a keyless lock. If we merely read
the prescription as it stands it is indeed senseless
jargon, but it becomes more intelligible when we make
some attempt to interpret these alchemical terms. The
king signifies sulphur, the ivolf is antimony, Mars is
iron. By thus substituting rational equivalents for
this fanciful nomenclature something may be made of
it, but, as a rule, lejeu ne vaut pas la chandelle.^
* Basilius Valentinug : Chymische Schriften, Hamburg (1677).
t Not content with these fanciful names they represented the metals
by the curious symbols still not entirely obsolete. These symbols are
given below ; each of them is enclosed in a square as they occur in
MEDICAL MYSTICISM.
Valentine's important chemical work is concerned
with the metal antimony, and with ni-
tric, hydrochloric, and sulphuric acids-
Of antimony and its medicinal uses he
writes at length in his best-known work,
The Triumphant Chariot of Antimony.
His other, principal writing is the Halio-
graphia, which appeared in 1644 at
Bologna. It embodies a mass of in-
formation on the mineral, vegetable,
and animal salts. It is scattered through
this and the former work that his refer-
ences to nitric, hydrochloric, and sul-
phuric acids will be found.
Nitric acid is a very old chemical
product. The acid was in common use
among the early alchemists, but we find
in Valentine the first mention of a sim-
ple preparation, according to which a
mixture of three parts of powdered
earthenware with one of nitre is dis-
tilled. The method remained in use for
a long period. Other methods are given
by Valentine and sufficiently clearly
Glauber's Treatise of the Signature of Salts, Metals,
and Plants. The extent to which the symbol
touches the enclosing squares is intended, says
Glauber, to indicate the relative perfection of the
metal. ' ' New if into one of these I put the charac-
ter of the sun or gold, viz., a round circle, it touches
four parts of the square and filleth it up, signify-
ing that among celestial and terrestrial creatures, the snn and gold
do excel all other things in their perfection."
6o MEDICAL MYSTICISM.
described. The method at present in use was
not discovered apparently till the time of Glauber.
It consists in distilling mixed nitre (saltpetre or nitrate
of potash) and sulphuric acid (oil of vitriol), and will be
farther mentioned when Glauber's work is considered.
Valentine termed it water or acid spirit of nitre. It
was afterwards called aquafortis.
Hydrochloric or muriatic acid was known to the
Arabian alchemists, as was its mixture with nitric
acid or aqua regia. But it is in Basil Valentine's work
that we first find mention of the pure acid under the
name spiriius sails, prepared from guter vitriol and
sal commune, that is from the green sulphate of iron
and common salt.
Sulphuric acid was apparently known to Geber, but
its preparation from green vitriol is first fully described
by Valentine. He refers to the product as oil of vitriol
in the Ilaliographia, while the directions for pre-
paring the green vitriol, or lower sulphate of iron, by
dissolving iron filings in dilute oil of vitriol, are also
there given. " The solution, " he says, " when put
aside in a cool place, soon forms beautiful crystals ; "
while elsewhere he states that < this salt is an excel-
lent tonic ; that it comforts weak stomachs ; find
that externally applied it is an admirable styptic."
In references like these we see a distinct desire to
examine chemical products for their own sake, and
not merely because they might lead to the discovery
of the philosopher's stone. Further we see in the
medical tendency which the science was now assum-
From Die Zwolf Schliissel.
62 MEDICAL MYSTICISM.
ing the awakening of a conviction that some every-
day good might be hoped for from its earnest study.
It does not do to love your science any more than to
love a person with an entirely abstract and fanciful
passion. One must love as well
" to the level of every day's
Most quiet need by sun and candlelight; "
and the alchemists were only just realising that their
science must be an every-day science as well as a
beautiful dream.
As the main facts concerning the preparation of
this most important substance, sulphuric acid, were
by this time discovered, we may here find an appro-
priate place for a general sketch of its history. Val-
entine, as just stated, prepared it from ferrous sulphate
by heat. The liquid so obtained fumes in the air,
and is thus distinguished from the acid as ordinarily
prepared by the name of fuming sulphuric acid. It
is also now known as Nordhausen sulphuric acid,
from the fact that it was prepared at Nordhausen,
in the Hartz. It consists really of a solution
of sulphur trioxide in sulphuric acid. It is now
prepared in Bohemia in the works of J. D. StarcJk. It
is a colourless, thick, oily liquid when pure, but is
generally coloured slightly brown from the presence
of organic matter. The oxide of iron left behind in
the retort when the distillation is complete was termed
colcothar or caput -mortuum of vitriol. This last term
arose from the fanciful practice by which the old
chemists symbolised the dregs and last products of
MEDICAL MYSTICISM. 63
substance by the figure of a death's head and cross-
bones. Sulphur trioxide (SO 3 ) is also prepared in
large quantities, near London, by Dr. Messel.
Another and more important method of preparing
sulphuric acid is for the first time described by Basil
Valentine, and it is a modification of this which is
now in general use. It consists in burning a mixture
of sulphur and nitre (nitrate of potash), whereby the
sulphur is oxidised or burnt up by the oxygen of the
nitre, and sulphuric acid is formed. The following
are his words : " Take of antimony,* sulphur, salt nitre,
of each equal parts, fulminate them under a bell, as oil
of sulphur per campanam is made, which way of pre-
paring hath long since been known to the ancients ;
but you will have a better way if instead of a bell
you take an alembic and apply to it a recipient, so
you will obtain more oil, which will indeed be of
the same colour as that made of common sulphur,
but in powers and virtues not a little more excel-
lemV'f
The present method of manulacturing sulphuric
acid was, according to some accounts, introduced into
England from the Continent by Cornelius Drebbel ;
but the first authentic information is that a certain
Dr. Ward obtained a patent for its manufacture. He
employed glass globes of about forty or fifty gallons
capacity. A little water was poured into the globe,
* The antimony forms a sulphide with the sulphur present and is
not essential to the reaction
*" Triumphant Chariot of Antimony.
6 4
MEDICAL MYSTICISM.
a stoneware pot introduced and on this was placed a
red-hot iron ladle. A mixture of sulphur and salt-
petre was then thrown into this ladle, and the vessel
closed to prevent the escape of the copious fumes
evolved. The vapours were absorbed by the water
APPARATUS TO ILLUSTRATE THE MANUFACTURE OF SULPHURIC ACID.
a, flask for boiling water.
l>, flask containing copper and sulphuric acid to evolve sulphuric dioxide,
c, flask containing copper and nitric acid to evolve nitrous fumes. The other
tubes in the large flask are to admit air.
and sulphuric acid thus formed. To distinguish it
from the acid obtained from the iron sulphate it was
termed oil of vitriol made by the bell. It was priced
MEDICAL MYSTICISM. 65
at from Is. 6d. to 2s. Gd. per pound. The next
advance was effected by Dr. Roebuck, a physician of
Birmingham, who replaced the glass globes by leaden
chambers. These chambers were first erected in
Birmingham in 1746, and in 1749 at Preston Pans
in Scotland. As before, the charge of sulphur and
nitre was placed within the chamber, ignited, and
the door closed. After the lapse of time sufficient
for the absorption of the product by the water in the
chamber the doors were opened and the charging
repeated.
The size of the leaden chambers was at first limited
to six feet square, and for many years did not exceed ten
feet- square. By 1783 Messrs. Kingscote and Walker
had erected chambers forty-five feet long and ten feet
wide. Berthollet's application of chlorine to the
bleaching of cotton goods (1788) gave at once an
enormous impulse to the manufacture, and in the fol -
lowing way : Hydrochloric acid is largely used in the
preparation of chlorine, and sulphuric acid in the pre-
paration of hydrochloric. The reaction of the manu-
facture of each upon that of the other is thus readily
seen. The final improvement, chiefly proposed by
Chaptal, resulted in making the process continuous.
To this end the sulphur * is burnt separately to form
sulphur dioxide, and this is sent into the leaden
chambers mixed with steam. Nitre is heated in
separate vessels and the nitrous fumes resulting from
its decomposition also passed into the chambers.
* Iron pyrites, a sulphide of iron, is actually used in practice.
E
66
MEDICAL MYSTICISM.
To show the extent to which the sulphuric acid
industry has developed we must recall that in Dr.
Ward's time the commercial acid was priced at from
Is. 6d. to 2s. 6d. per Ib. It may now be obtained
at the price of Id. per Ib., while the annual product
in Great Britain cannot fall far short of 1,000,000
MANUFACTURE OF SULPHURIC ACID.
Steam passes in from the boiler (i) ; sulphur dioxide and nitrous fumes through
the large pipes (a).
tons. In the South Lancashire district alone the
quantity manufactured some years ago amounted to
3,000 tons per week. Dyeing, bleaching, and the
alkali industry consume enormous quantities of sul-
MEDICAL MYSTICISM. 67
phuric acid, and there are innumerable manufactures
in whick it is more or less employed. Such is the
development presented to us by a single chemical
industry. The figures are impressive enough, and we
are apt to become elated by mere contemplation of a
long succession of noughts when anything commercial
is concerned. Perhaps it may be well, therefore, to
remind ourselves that the mere production of sul-
phuric acid, even to the amount of inland seas, is
in itself no special boon. Chemistry has so far been
applied to manufacture. Good, but how far has
the manufacture increased the happiness of life ?
Having now shown the wider development and
application of some ideas known in all their essential
details so far back as the time of Basil Valentine,
and brought to their present enormous range of ap-
plication by only very slight additions and changes,
we must return to our alchemist. We have discussed
to some extent his position as a chemist, and we need
now only treat of -the work upon which he himself
most strenuously insisted the elucidation of the
properties and virtues of antimony.
This metal occurs native as stibnite or antimony
sulphide, a mineral known in very early times, and
employed by women in the East for painting the eye-
brows. In St. Jerome's translation of the Hebrew of
Ezekiel xxiii., 40, we read " circumlinisti stibio oculos
tuos," "thou hast painted thine eyes around with
stibnite."
The word alcohol was originally used to distinguish
6s MEDICAL MYSTICISM.
this mineral. The Arabic name was " Kohl/' and this
word passed as alcool or alkohol into other languages,
as, for instance Spanish, where the above biblical
passage is rendered "alcoholaste tus ojos." At a
later date the term alcohol was applied to any fine
powder and, finally, spirits of wine. How this last
transition was effected it is difficult to say. We
know that strong alcohol was formerly termed vinum
alcalisatum (wine strengthened with alcohol), and it
has been suggested that by some misunderstanding this
came to be written vinum alcoholisatum, and then
alcohol vini. At best this is a somewhat doubtful
conjecture. Pliny termed the mineral stibium, while
in the Latin translation of Geber the word antimo-
nium is used. The German name spiessglas is first
found in the writings of Basil Valentine.*
How the word antimony was derived it seems
impossible to say. A fanciful story is related to the
effect that Valentine, intent upon discovering the
medicinal properties of this substance, used his
brother monks as " subjects " for his experiments, and
administered it in some form to several, some of whom
succumbed to its powers. Upon this it is said that
Valentine invented for this body the term antimoine,
i.e., " hostile to monks." (!) To dispose of this story it
is only necessary, apart from its inherent absurdity, to
cite Kopp's remark to the effect that this word would
have been invented by a Frenchman, while Valentine
wrote in German.
* This account is taken from Eoscoe and Schorlemmcy's Treatise.
MEDICAL MYSTICISM. 69
Valentine's monograph indicates a really epoch-
making advance on previous chemical writings. It
is a thoroughly earnest attempt to study in detail the
properties of one substance and its derivatives. We
find here the first description of the mode of obtaining
the metal, though this is not mentioned as a new
discovery. Numerous antimonial preparations are
described, and special stress is laid upon their
medicinal properties.
The metal antimony, as already stated, is found in
nature chiefly as the sulphide. It forms with other
metals some important alloys which may here be
mentioned. Valentine alludes to the existence of
alloys of antimony. English type-metal is an alloy
of lead, antimony, and tin. The antimony gives the
alloy the property of expanding as it solidifies. From
this it results that when used to make a cast of a
letter it presses itself into all the interstices, and a
very accurate reproduction is obtained. The tin
gives the metal toughness and coherence. Three
analyses of English type-metal are here given :
I. II. ill.
Lead .... 50 55-0 61-3
Antimony . . .25 22*7 18'8
Tin . . .25 22-1 20'2
German type-metal contains about 15 per cent, of
antimony.
Britannia Metal and Pewter. This is a silver-
white alloy largely used for spoons, tea-pots, and
other " silver" articles.
tin and antimony,
MEDICAL MYSTICISM.
It is mainly composed of
Britannia Metal.
Plate
Pewter.
Ashbury
Metal.
Tin . .
85-7
81-9
89-3
77-8
Antimony . .
Copper . . .
10.4
1-0
16-2
7-1
1-8
19-4
Zinc . .
2-9
1-9
.
2 8
Bismuth . .
1-8
White or anti-friction metal is used for lining the
brasses of various parts of locomotive engines. It is
composed of tin, antimony, and copper. The variety
of this alloy known as Babbit's metal, also contains
a considerable percentage of lead.
Two processes may be used to extract metallic
antimony from the native sulphide. In either case
the sulphide is subjected to the -liquation process. In
this process the mineral is melted in vertical cylinders,
through a hole in the bottom of which it flows out
leaving the gangue behind. The sulphide, thus puri-
fied, is known as crude antimony. By one process the
metal is obtained from it by heating to redness with
scrap iron. The iron takes away the sulphur from
the antimony sulphide, leaving the metal behind.*
The metal is fused with sodium carbonate (pearl-ash)
* Where Fe stands for iron, Sb for antimony, and S for sulphur we
have:
Sb 2 S 3 + 3 Fe = 3 Fe 8 + Sb 8 .
MEDICAL MYSTICISM. 71
to purify it from foreign metals, and poured into
moulds where it is allowed to cool slowly. During
this slow cooling the metal assumes a crystalline
structure and exhibits on its surface very beautiful
fern-leaf markings. It has a white colour and is very
brittle. In the second process the purified sulphide
is roasted in order to convert it into oxide, and the
72 .MEDICAL MYSTICISM.
oxide is "reduced" to metal by melting in a large
earthen crucible with charcoal or crude tartar. The
construction of a common form of liquation furnace
is shown in the illustration on the previous page.
The ore is placed in the cylinders c. c and the molten
sulphide collects in the pots 71, n'.
Both of the above methods were known to Basil
Valentine : " Antimonium is a master in medicine,
and from it by means of cream of tartar and salt a
king (regulus) is made, steel-iron being added to the
spiessglas during fusion. Thus by an artifice a
wonderful star is obtained which the learned before
my time have termed the philosophical signet star."
Again : " Take good Hungarian spiessglas with the
same quantity of crude tartar, and half as much
saltpetre ; rub these small and let them fuse well in a
wind furnace ; afterwards pour out into a mould
and allow to cool, when a regulus is found." The
preparation of the stellated antimony was asserted
by different alchemists to be due to the action of
various occult influences. Valentine thought the
appearance only resulted when iron was employed in
the preparation ; many on the other hand asserted
that the stars were in some way answerable for the
result, and that it was only during some propitious
conjunction that the stellated metal could be ob-
tained. We see here once more an indication of the
parting of the ways between alchemy and chemis-
try. The path of the former, leagued with astrology
MEDICAL MYSTICISM. 73
and other mystic arts, was to tend ever downwards
towards deeper degradation, until it was represented
only by a race of ignorant impostors and a few perplexed
fanatics. That of the latter was to ascend by ways
that were often steep and barren, but became ever
more prosperously fruitful, to the lonely Pisgah heights
beyond which the land of promise stretched no longer
as an unfulfilled dream but as the realisation of
unbaffled hope.
Of Valentine's description of his antimonial pre-
parations we may here give some samples. After a
very lengthy introduction, the greater part of which
is devoted to violent abuse of the doctors of his day,
and during the perusal of which we wait with grow-
ing impatience for matter which is really to the point,
Basil Valentine at last rewards us by describing the
preparation of " antimony-glass " which consists of
the oxide usually coloured by sulphide. " Take Hun-
garian antimony, or any other (the best), grind it upon
a marble into most subtile powder, lay this powder
thin and sparingly in a plain earthen vessel, round
or square, which let be made with rims about the
height of t\vo fingers' breadth ; place this vessel on a
calcining furnace, administer at first a gentle fire of
coals and when the stibium begins to fume, stir it with
a little iron rod to and againe, without ceasing, until
it ceaseth to emit any vapour ; but if in the calcina-
tion the antimony chanceth to melt and run into
balls, take off the vessel from the fire and let the
74 MEDICAL MYSTICISM.
stibium cool, and grind it again, and doe as afore,
which must be so often done, until it neither
fumes nor runs together any more, but remains in
the, form of white ashes, for then is your calcination
perfect.
" Take now this stibium thus calcined, put it into
a goldsmith's crucible, place it at a violent fire, that
the antimony may flow like pure clear water, and
that you may know when the glasse of stibium has
attained a perfect and pellucid colour, put into the
crucible a long cold iron, and the glasse will stick
thereunto, which strike with an hammer, and so sepa-
rate it, and hold it up against the light, which if it
be transparent 'tis good and perfect glasse."*
The above quotation is given to show that the
alchemist's style is here passing into the clear and
accurate language of the chemist. It contrasts
strangely indeed with the language used by the same
writer in Die Zwblff Schlussel.
We must lastly refer to the marked medical ten-
dencies of Basil Valentine's work. We have already
said that with him the era of medical chemistry
opened. His naive enthusiasm for the union of
chemistry and medicine is often irresistibly amusing,
but is at the same time of grave significance. Medi-
cine had indeed up to this date been a very unscien-
tific affair, and, when we recollect that up to this day
we are almost wholly ignorant of the true functions of
such a well-known organ as the spleen, this will not
* Triumphant Chariot of Antimony, London (1661).
MEDICAL MYSTICISM. 75
surprise us. With regard to the chemical changes
which go on in the body we are far more ignorant.
The question of the clotting of blood and its pre-
cise causes is still sub judice, and the common ideas
of yesterday on this matter have been strongly com-
bated of late. We know that phosphorus and
arsenic are both very poisonous bodies, but ivhy
they are so it seems impossible to say. We can
conjecture that phosphorus affects the oxidation pro-
cesses of the body, but when we have said so much
we have not got far and can go no farther.
The case of arsenic is made doubly mysterious by the
fact that people can accustom themselves to take poison
ous doses of the substance without harm. Eoscoe has
contributed to the -Literary and Philosophical Society
of Manchester an interesting paper " On the alleged
practice of arsenic-eating in Styria," from which it
appears that in one case a wood-cutter was seen by a
medical man to eat a piece of arsenious acid (arsenic
trioxide) weighing 4-5 grains, and the next day he
crushed and swallowed another piece weighing 5 '5
grains, and the following morning was in his usual
state of health: A dose of one grain is, with those
who are not of the cult, very dangerous, while one of
two to four grains is almost always fatal. How
individuals can thus by practice withstand fatal doses
it is at present simply impossible to say. When
then on such simple matters we are at the close of the
nineteenth century so ignorant, it is startling to find
any writer at the close of the fifteenth century who could
76 MEDICAL MYSTICISM.
discern any relation between chemistry and medicine,
or could conceive that the latter was to be dealt with
scientifically at all.
Antimony was the substance above all others whose
medicinal properties Valentine was sworn to defend.
In The Triumphant Chariot he approaches his
subject with almost awed devotion : " He that will
write of Antimony needs a great consideration and
most ample minde .... in a word one man's life is
too short to be perfectly acquainted with all its
mysteries. It is to be administered for inward and
outward diseases, which to many moles Avill seem
incredible." Valentine is not given to compliment
those who oppose him. " Whoever, therefore, will
be a true antimonial anatomist, let him first consider
the division or operation of his body." For the
unchemical medicine -man Basil Valentine entertains
the loftiest scorn, and upon such men he pours out
the vials of his wrath. They do not even know how
to prepare their own medicines ; " they know not
whether they be hot or dry, black or white, they only
know them as written in their books, and seek after
nothing but money. Labour is tedious to them, and
they commit all to chance ; they have no conscience,
and coals are outlandish wares with them ; they write
long scrolls of prescriptions, and the apothecary thumps
their medicine in his mortar, and health out of the
patient." Probably Valentine's denunciations might
apply to some medicine men even now, for it is said
MEDICAL MYSTICISM. 77
that they have been known to mix in a prescription
substances which by interaction would lose their
characteristic medicinal properties ; " they only know
them as written in their books."
Valentine finds it difficult to repress his wrath
against these " moles/' and especially such as refuse
to recognise the surpassing value to the human
organism of antimony. Thus we find him breaking
forth in this strain : " So I know that many trifling
wanderers, lazy doctors, empericks, and many other
intruders into physick, will clamour out against
antimony, crying a crucifige, but yet it will endure,
when those ignorant medicasters shall be broken in
pieces." Farther on he gives two ways of extracting
a poison, first by its contrary, second by its like :
"which proudly arrogant medicasters or physicians, by
reason of their sluggish and droanish laziness, are
unacquainted with." A plain-spoken man is this
Basil Valentine.
Again : " Ah, wretched men, unlearned doctors,
unexperienced physicians, who write tedious receipts
on a long paper. ye apothecaries that set over
the fire great cauldrons sufficient to boil the meat of
noblemen's houses, and to hold enough for a hundred
persons, Low long will ye be blind ...?... O
deplorable, putrid and stinking bag of worms . . . '
These vigorous onslaughts are amusing enough now,
but they must have called for some courage when
they were made, and at least their tendency was in
78 MEDICAL MYSTICISM,
the right direction. And this must close our account
of Valentine. He rendered some sterling services to
knowledge by his discoveries, by his advocacy of
really scientific aims, by the dauntless courage of his
attacks upon an effete empiricism, and by his early
inauguration of the union between medicine and
chemistry.
CHAPTER IV.
SECOND PERIOD : MEDICAL MYSTICISM.
PARACELSUS : VAN HELMONT,
>HE scientific sky was now for a moment
illuminated by the flash of an erratic
meteor, which after some moments of
dazzling brilliancy plunged back into
cimmerian gloom, and left behind it only
the feebly glimmering track of light surviv-
ing until now. The name of Paracelsus carries with
it a mysterious suggestion of power. But it was
power for the most part expended in fitful and
unproductive bursts. According to Van Helmont's
account Paracelsus came to Constantinople during
1521 and received there the philosopher's stone.
The adept from whom he received the stone was said
to be a certain Solomon Trismosinus, a countryman
of Paracelsus. This man appears also to have been
So MEDICAL MYSTICISM.
in possession of the Universal Panacea and is said to
have been seen still alive by a French traveller at
the end of the seventeenth century ! * The details
left us of his career are all too few, but as we read
even these scattered fragments we continually expect
some consummation of achievement from so mysteri-
ously isolated a man. But we await in vain ; " we
have a careless and insolent indication of things that
might be not the splendid promise of a grand
impatience, but the scrabbled remnant of a scornfully
abandoned aim."
Phillipus Aureolus Theophrastus Bombastus Para-
celsus von Hohenheim was by birth Philip Hochener,
but he changed his name on commencing his pro-
fessional career. He was the son of a physician and
born in 1493 at Einsiedeln, a small town in the
canton of Schwitz, distant some leagues from Zurich.
At an early age he quitted his native country and
wandered over Europe, visiting the most important
towns. This restless spirit characterizes the whole of
his future career, and was one great reason why so
much of his influence was dissipated and lost.
In 1526 he returned to his native land and was
recommended by CEcolampadius to the chair of physic
at Basle. Here Paracelsus commenced his career by
burning publicly in the hall the works of Avicenna
and Galen. These two physicians were not together
* F. Hartmann : Life of Paracelsus and the Substance of his Teachings ;
a curious work in which the author professes belief in all the mysteries
of alchemy.
MEDICAL MYSTICISM. 8 1
possessed of so much knowledge, he assured his
audience, as were his own shoe-ties ; all the universi-
ties and all the writers united were less instructed
than the hairs of his beard, and he was to be regarded
as the sole monarch of physic.
After such proceedings Basle soon ceased to be able
to contain him. According to some accounts he was
obliged to leave the town owing to his dissolute habits
and the wild extravagance of his life. On the whole
one may fairly incline to doubt some of these worst
stories that were told of him. The force of impact
with which this strange being met the stormy oppo-
sition of his age is sufficient proof of some nobler
aims ; and the blindness of his enemies to these leads
one to suspect that their condemnation was not un-
mingled with spite. Besides, Paracelsus was essentially
of an aggressive nature, he wanted to do things in a
way of his own, and moreover he wanted people to
see that that way of his own was a good one. The
mildest-mannered man would be sure to incur some
hatred as soon as he suggested that things might be
done better than they are, and Paracelsus does not
seem by any means to have bee'n mild or bland.*
Indeed we may fully expect that such a character
would have to take an unusually large share of
envenomed hatred and scorn.
Let us make allowance for the hatred he inspired
* See his works Opera omnia medico- chemico-chirurgica, Geneva
(1658). Some of his chemical writing was translated by R. Turner :
London (1657).
F
82 MEDICAL MYSTICISM.
and consent, to take him at his best. Another
account is given of the reasons which obliged him to
leave Basle and it seerns the more probable story. A
rich canon, it is said, fell sick and offered a hundred
florins to any one who could cure him. Paracelsus,
with characteristic daring, at once offered to cope
with the disease. He administered three pills and
the canon got well. We all know the old rhyme :
" The devil was ill,
The devil a monk would be ;
The devil got well,
The devil a monk was he."
And the Canon of Basle seems to have acted in this
. case after the pattern of one who should not have
been his patron saint. Being so soon restored he felt
too confident to part readily with his money, and he
refused to pay the promised sum.* The matter was
brought before the judicial powers, who decreed that
the physician should only receive his customary fee.
Probably, such a decision was capable of being called
legal ; it was certainly not just. Incensed at his
treatment by the canon, and at the absurd partiality
of the judicial decision, Paracelsus retired in high
dudgeon, declaring he would leave the inhabitants of
Basle to the eternal destruction which they deserved.
In 1527, therefore, he quitted Basle for Strasburg,
then travelled into Hungary, and after wandering all
* Testimonials to his cures of cases of elephantiasis placed under his
care by the City Council of Nuremberg may be found in the archives
of that city. (Hartmann.)
MEDICAL MYSTICISM. 83
over Europe in restless discontent, returned to Salz-
burg to die in poverty in 1541, at forty-eight years of
age.
It is difficult to speak very definitely of the dis-
coveries made by Paracelsus. It was, as already hinted,
by the impact of his masterful personality that he
made the impression that he has left behind. To him
was due the growing closeness of union between
chemistry and medicine. An alchemist, he yet de-
spised the mere search for gold ; a physician, he de-
spised the ordinary rote and rule of his profession ; a
learned professor, he yet determined, in spite of
all precedent, to lecture in the common people's
tongue. He aimed at making knowledge at once
more useful and more widely known. The hide-bound
pedants of his age were all against him, and this the
more because, even making all allowance for ex-
aggeration, we must admit he was most extrava-
gantly aggressive. But, in spite of the pedants, his
work produced a resistlessly expansive impression.
Of the discoveries of Paracelsus as a chemist we
may mention that he was the first to prepare hydro-
gen gas. That alone is sufficient to lend deep inte-
rest to his name. He obtained an inflammable gas by
the action of dilute acids on metals ; this gas was
certainly hydrogen, though its true nature and its
importance lay undiscovered till the time of Caven-
dish in 1766. Paracelsus adopted the views taken by
Basil Valentine as to the universal constituents of
matter, supposing them to be three in number, sul-
84 MEDICAL MFSTICISM.
phur, mercury, and salt. It appears, however, that
these constituents were not regarded as identical with
the common substances recognised by these names,
but that, for instance, salt was taken in the sense of
the principle of saltness, and so on; it was the some-
thing which gave rise to the saltness of salt itself.
But it is difficult to enter into the subtlety of these
views and if we appreciate their general bearing we
may be content.
Paracelsus was the first who included animal and
vegetable bodies in the same classification, and, ac-
cording to his theories, health was supposed to result
from the presence in the organism of the above con-
stituents in their normal proportions, while a dis-
turbance of these relations led to disease.
In his desire for the union of chemistry and medi-
cine Paracelsus introduced a variety of mercurial pre-
parations in certain diseases. The use of mercury
for these purposes is strongly maintained at this
day. Opium also came into general use as a medicine
owing to the influence of Paracelsus. In such ways
he took the initiative in establishing the class of chemi-
cal-physicians which now arose.
These men were of course treated as possessed of
very questionable powers. It was not " the thing" to
administer chemical preparations for medicine ; it was
not done ; and what more condemnation could be
needed of those who should try to do it ? That mer-
cury and antimony should be used as medicines was
certainly too heterodox to be allowed. Their fathers
MEDICAL MYSTICISM. 85
had lived and died without antimony or calomel, and
why should these new-fangled faddists think they
knew better ? And the superior people among them
said it was all very well in theory no doubt ; but in
practice ! and they shook their heads silently and
with infinite wisdom.
This made the introduction of chemical prepara-
tions by no means easy, and so, when the physicians
wanted to administer chemical substances, they dis-
guised them under pretty and fanciful names and their
patients were quite satisfied and happy. If these sub-
terfuges were not resorted to, woe betide the physician.
Towards the end of the fifteenth century the use of
antimony was prohibited at Paris, and Besnier was
expelled from the faculty for having persisted in ad-
ministering it. Chemical medicines came into use in
England in the reign of Charles I., and shortly after
1644 the London College of Surgeons made its appear-
ance. We must be ready to recognise the good done by
the line of medical chemists. As Brande says, " The
foundations of chemical science are to be found in the
medical and pharmaceutical writers of the sixteenth
century, who rescued it from the hands of the alchemical
pretenders, and gave it a place and character of its
own." As time went on and the medical sect grew,
the alchemists were becoming more and more pre-
tenders indeed, and more and more justly typified by
the Subtle of Ben Jonson. The finest talent was
enlisted in the ranks of the medical chemists to
whose work Paracelsus had given such impetus. It
86 MEDICAL MYSTICISM.
is true that Paracelsus had often raved rather than
reasoned, but his ravings, like those of Cassandra,
were at least prophetic, and, unlike hers, were never
doomed to be impotent.*
Van Helrnont, a Dutchman, was one of the fol-
lowers of Paracelsus, and flourished in the early part
of the seventeenth century. He was, it seems, a
conscientious enthusiast, but of his additions to
knowledge nothing very definite can be said. That
the character of the man was of interest is suffi-
ciently shown by the following extract from an
autobiographical fragment which he left : f
"In 1594, being then seventeen years of age, I
finished rny courses of philosophy, but upon seeing
none admitted to examinations at Lou vain who were
not in a gown and hood, as though the garment made
the man, I was struck with the mockery of taking
degrees in arts. I therefore thought it more profit-
able, seriously and conscientiously, to examine myself ;
and then I perceived that I really knew nothing, or,
at least, nothing that was worth knowing. I had, in
fact, merely to talk and to wrangle, and therefore
refused the title of Master of Arts, finding that no-
thing was sound, nothing true, and unwilling to be
declared master of the seven arts, when my conscience
told me I knew not one. The Jesuits, who then
taught philosophy at Louvain, expounded to me the
* Those who wish for an idealised and poetical sketch of the career
ol Paracelsus should of course read Browning's poem, published under
that name.
-f Quoted in Brando's Chemistry (2nd ed., 1821).
MEDICAL MYSTICISM. 87
disquisitions and secrets of magic but these were
empty and unprofitable conceits ; and instead of grain
I reaped stubble. In moral philosophy, when I ex-
pected to grasp the quintessence of truth, the empty and
swollen bubble snapped in my hands. I then turned
my thoughts to medicine, and having seriously read
Galen and Hippocrates, noted all that seemed certain
and incontrovertible ; but was dismayed upon re-
vising my notes, when I found that the pains I had
bestowed, and the years I had spent, were alto-
gether fruitless ; but I learned at least the emptiness
of books and formal discourses and promises of the
schools. I went abroad and there I found the same
sluggishness in study, the same blind obedience to
the doctrines of their forefathers, the same deep-rooted
ignorance."
Van Helmont (15771644) adopted neither the
Aristotelian nor the Paracelsian doctrine as to the
constituents of matter. He admitted that air and
water were elements. Yet he was the first to recog-
nise the existence of different kinds of " air," and was
apparently the inventor of the word " gas." He gave
his attention to the " air " which is given off during
the process of fermentation, and gave to it the name of
gas sikestre, or " the gas that is wild and lives in
out-of-the-way places." Later this gas was called
fixed air, and is of course carbonic acid gas, carbon
dioxide, or the gas which is obtained on burning
charcoal in air. Yan Helmont identified this gas
with that given off during combustion, with that found
88 MEDICAL MYSTICISM.
in the " Grotto del Cane," near Naples, and also with
that obtained by the action of acids on calcareous sub-
stances, such as marble. He mentions a gas pingue
which is evolved from dung, and is inflammable.
This is probably impure ammonia. Van Helmont
also showed that when a metal is dissolved in an
acid it is not destroyed, but may be recovered from
solution in the metallic state by suitable means.
Van Helmont was a representative of a different
sect of the alchemists from any we have yet discussed.
As his ideal and goal he set before himself the dis-
covery, not of transmutation nor of the medicinal
"philosopher's stone" as usually understood, but
of the universal solvent, or alkahest as it was termed,
which at the same time was to serve as the cure of
all diseases.
Apart then from his interest as a man of penetrating
judgment, sufficiently discernible in the short auto-
biographical extract quoted above, Van Helmont's
chief merits lie in his discovery of the existence of
different kinds of gases, which had hitherto been all
generally confused under the one name of " air."
This discovery was indeed one of the very first impor-
tance, and required at that time great keenness of
observation and alertness of attention. If we recall
how in all their superficially observable properties
atmospheric air and carbon dioxide are exactly
similar, we shall be more in a position to appreciate
the talents which, in that condition of knowledge,
could discern the differences. In the first place one
MEDICAL MYSTICISM. 89
cannot see air, and in the ordinary sense cannot feel
it, cannot take it up and inspect it as one does a
mineral ; and these peculiar attributes are characteristic
of most gases. This of course makes the discovery
of their properties a work of quite peculiar delicacy.
Then too such bodies are always tending to escape
from us. If one takes a handful of carbonic acid gas
out of a jar it at once streams away into the surround-
ing air. They will not remain, or at least not remain
PREPARATION OF CARBONIC ACID.
long, in a vessel which is open at top, as water will
do. We cannot pour hydrogen into a basin and then
examine it at leisure, as could be done with a liquid.
Carbonic acid, however, being a very heavy gas, and
thus tending to sink rapidly in the air, will in this
respect to some extent behave like water. If marble,
which is calcium carbonate (carbonate of lime), is
treated with hydrochloric acid, carbon dioxide is
given off and we may conduct the gas so evolved out
go MEDICAL MYSTICISM.
of the evolution flask into a collecting cylinder as
shown. The gas being so much heavier than air it
will lie in the cylinder, and only be disturbed quickly
by a considerable draught. And having got this gas
in the cylinder we may indeed pour it out into
another, much as we should do with water, though
some will certainly be lost in the process. It will
stream downwards into the lower cylinder, and by
simple tests, such as pouring in a little lime water
which will at once be turned milky, we can readily
show that it is there.
Such being the properties of carbonic acid gas it is
readily seen that it presents us with fewer difficulties
than do other gases ; we can more easily get hold
of it and deal with it. And carbonic acid, indeed,
was the first gas distinguished from ordinary atmo-
spheric air, and this work was accomplished by
Van Helmont. In the fermenting vats of breweries
this gas is evolved in large quantities. Being heavy
and not exposed to rapid air- currents it collects
there, and it was there that Van Helmont discovered
it. He found that it extinguishes flame and, when
inhaled for some minutes, is fatal to animal life.*
These properties were at once sufficient to distinguish
it from atmospheric air, and this and others were
sufficient to identify it with the gas obtained by other
processes, such as the action of acid upon marble, and
found by Van Helmont in the Grotto del Cane, the
* It should be noted, however, that this gas taken into the stomach
as in aerated drinks is quite harmless and even beneficial.
MEDICAL MYSTICISM. 9I
mineral waters at Spa, and at other places. Carbon
dioxide is formed during combustion, the carbon of
the burning body, such as a candle, combining with
the oxygen of the air to form the oxide.* It is also
given off in large quantity in the breath of animals,
being formed by the burning up of the waste products
in the tissues. It occurs in chalybeate, and acidulous
waters, and in volcanic districts escapes in large
volumes from the fumeroles and rents in the ground.
The Poison Valley in Java is remarkable for the
evolution of this gas in very large quantities. In
the Grotto del Cane the gas issues from fissures some
two or three feet below the mouth of the cave. Up
to this depth the gas, by reason of its great density,
collects. The cave is thus fatal to small animals
thrown into it, while men breathing the pure air above
this level are unaffected. ,
It is interesting to remind ourselves that carbon
dioxide has now became a commercial article in eve^-
day use. Aerated waters in almost every case hold
carbonic acid gas in solution, t The gas is forced in
under pressure, and in these circumstances the water
will take up more than its usual amount. On opening
a bottle, therefore, of one of these aerated waters, and
thus releasing the pressure, the gas begins to escape,
thereby causing effervescence and the peculiar spark-
ling appearance seen in the liquid. The consumption
* C -\- 62 COz ; or carbon -\- oxygen = carbon dioxide,
t The eau oxygene now somewhat in vogue contains oxygen in place
of carbonic acid.
92 MEDICAL MYSTICISM.
of these drinks is now enormous. Forty years ago
two hundred thousand bottles of aerated waters were
consumed annually in France. Ten years ago two
hundred million bottles were scarcely sufficient to
satisfy the demand. Some natural waters are aerated,
for example, Apollinaris, Carlsbad, and Friedrichshall
waters.
To make the water strongly effervescent the gases
which escape from the Apollinaris Brunnen, and which
contain more than 99 per cent, of carbonic acid, are
condensed into the water by machinery specially
erected at the spring. The Apollinaris spring fur-
nishes a regular supply of water amounting to G,000
quart bottles per hour, or more than forty million
(40,000,000) bottles per annum.*
In manufacturing the artificial water the gas evolved
by treating marble with a mineral acid is first passed
through water in the purifier, then stored in a gas-
holder, and next passed into a machine for mixing it
thoroughly with water. The bottling of the water
is also effected by machinery, and in bottles now
generally used, small glass balls are inserted as a
substitute for corks.
Such then is the importance of carbonic acid gas,
which to Yan Helmont was known as the wild or out-
of-the-way gas, "gas silvestre." It would have seemed
to him strange and even incredible that so subtle and
intangible an essence should be bottled every day for
the use of thousands of quite ordinary mortals at quite
* Spon's Encyclopedia.
MEDICAL MYSTICISM. Q3
ordinary dinner-tables. The wandering, mysterious
gas silvestre sparkling before us on our table of an
evening in the light shed by the burning of a still
more wonderful "gas" than any known to Van
Helmont, that is a strange picture to contrast with
the knowledge of his day.
Van Helmont was bitten with the Paracelsian
spiritualistic madness and was by this led to form
some very curious ideas. The archeus or sentient
soul he conceived as having its seat in the stomach,
where it directs the first digestion ; other digestions
being carried on with the aid of the vital spirits in
different parts of the body. There are in all six
digestions described by him ; the number seven has
been chosen by nature for the state of repose. The
mystical tendency of Van Helmont is sufficiently in-
dicated by the last clause. It permeated his whole
being. He had striven in vain to find any satisfac-
tory knowledge till he secured the works of Thomas
a Kempis and Jonn Tauler. He then thought he
perceived that wisdom is to be obtained only by
humility and prayer. Though a gentleman of means
and lord of Merode, of Royenbock, of Oorschot, and
of Pellines, he gave up all his property to his sister
and renounced all the privileges of his birth. After
this a genius appeared to him in all important cir-
cumstances of life, and in 1633 his own soul ap-
peared to him in the form of a resplendent crystal.
Having followed the ordinary courses of medicine and
discarding their doctrines with disgust, he turned his
94 MEDICAL MYSTICISM.
attention to Paracelsus, of whom he became in most
respects a warm follower. After the year 1599 he
travelled for some time, and on his return married a
rich Brabantine lady and passed the rest of his life
on his estate at Vilvorde.
Van Helmont achieved for himself immortal fame
by his discovery of the gas silvestre, but for a long
period his work sank into obscurity and was forgotten.
Such strange halts are there in the progress of science
that it was left to Dr. Black, in the middle of the
eighteenth century, to rediscover infixed air the for-
gotten gas of Van Helmont.
THIRD PERIOD,
CHAPTER V.
THIKD PERIOD : THE DECLINE OF MYSTICISM.
GLAUBER.
, AN HELMONT as a disciple of Paracelsus was
mentioned immediately after him, but the
name of Agricola, who was a contemporary
(1490 1555) of Paracelsus, must not pass
unnoticed. He was the author of a re-
markable work, De Re Metallica, contain-
ing a complete treatise on metallurgy and mining,
and most clearly written. Many of the processes
described by him are now actually in use.
The next name of importance is that of Glauber
(1G03 1G68), who still shares a somewhat hazy
popular fame as the discoverer of " Glauber's salt,"
or sodium sulphate. This was the piece of work
which seems to have been Glauber's favourite, and
his admiration for this substance certainly led him to
o
9 8 THE DECLINE OF MYSTICISM.
much magnify its value. The hydrated* sodium sul-
phate, known as Glauber's salt, is first mentioned in
his De Natura Salium published in 1658. His col-
lected works were translated into English and pub-
lished in a folio volume " for public good, by the
labour, care, and charge of Christopher Packe, Philo-
Chemico-Medicus, in 1689. In Glauber's works
we find the first clear description of the preparation
of ammonium sulphate (sulphate of ammonia), for-
merly known as sal ammoniacum secretum Glauberi.
This salt is now used for the manufacture of other
ammonia salts, and is also largely employed as a fer-
tiliser in artificial manures. Its conversion into sal
ammoniac, f or ammonium chloride, by distillation
with common salt (sodium chloride), was also first
described by Glauber. Ammonium nitrate, too, was
first prepared by him and known as nitrum flam-
mans. The production of copper sulphate or blue
vitriol by boiling copper with sulphuric acid (oil of
vitriol) was first proved by Glauber in 1648. The
sulphate is now obtained on the manufacturing scale
by roasting the copper ores and digesting with sul-
phuric acid. It is largely used in calico-printing,
and in preparing copper pigments, such as Scheele's
green and emerald green. It is also used in electro-
metallurgy.
The production of vinegar by the distillation of
wood is described by Glauber, but not as a new dis-
* I.e., combined with water.
f Sal ammoniac, the reader may be reminded, was known to Geber.
THE DECLINE OF MYSTICISM. 99
covery. He mentions that the acetum lignorum so
obtained may, by redistillation, be made as virtuous
as the common acetum vini. At a later date his
wood vinegar came to be known as pyroligneous acid,
a name which is indeed preserved still. The method
of preparing this acid and its derivatives is described
by Glauber in great detail and, apparently, with ori-
ginal improvements. He tells us of the power pos-
sessed by wood-tar, or the oily product of the distil-
lation, which is less volatile than the acid, of preserv-
ing wood. "Any wood exposed to the Rain, or
standing in the water, easily rotting, being anointed
with this Oil will be preserved so that it will not so
easily rot." In closing this portion of his discourse
Glauber says : " Nevertheless I easily persuade myself,
that this discourse of mine will not be credited by
many, which I cannot help. It content eth me that
I have written the Truth and lighted a candle to my
neighbour."
But Glauber's chief claim to immortality rests in
his being the first to describe the preparation of
hydrochloric (muriatic) acid, by distilling common
salt with sulphuric acid, and the first to obtain by
this same operation the sodium sulphate so long to
be known to posterity as <c Glauber's salt." The pre-
paration of the hydrochloric acid, or spirit of salt, is
described in the first section of the second part of
the Miraculum Mundi. Here also is given the
method for obtaining the Sal Mirabile, which is, of
course, obtained in the same process and the discovery
THE DECLINE OF MYSTICISM. 101
of which first appeared in Glauber's De Natura
Salium in 1658. To the discussion of the spirit of
salt Glauber acutely adds : " Plainly after the very
same manner as we have taught spirit of salt to be
prepared, so may also be made Aquafortis* ....
Instead of salt take nitre, and you will have Aqua-
fortis"
The present method of preparing nitric acid from
nitre and oil of vitriol (sulphuric acid), would thus
appear to have been first used by Glauber, and,
indeed, for a long time afterwards the acid thus ob-
tained was known as Spiritus nitrifumans Glauberi.
Glauber entertained somewhat grandiose ideas as to
the uses and virtues of his salt. " Husbandmen,
physicians, apothecaries, and chirurgeons are to
receive in it a priceless boon." Again, " I believe
every Artificer and Trading Man when he can per-
form his work with less labour and charge, and
acquire his wares for less trouble and cost, will sell
his commodities to his neighbours at a cheaper rate
than he could before he found the benefit of this
salt." He then goes on to enumerate fifty-nine of
its uses in Medicine, the Arts, and in Alchemy.
As a stage in the manufacture of carbonate of soda
in the alkali works, the sulphate is now produced on
an immense scale. In the year 1876, no less than
* Nitric Acid. This acid is now prepared on the manufacturing
scale from sodium nitrate and oil of vitriol. It is largely employed in
the manufacture of coal-tar colours, nitro-glycerine, gun-cotton, sul-
phuric acid, and nitrate of silver (now much used for photography).
102 THE DECLINE OF MYSTICISM.
700,000 tons were in this way prepared in the United
Kingdom. The pure sulphate is used in the production
of various kinds of glass chiefly bottles ; in certain
medicinal preparations, and to some small extent in
dyeing and printing. Here again, as in the case of
Helmont's gas silvestre, a wonder of the world has
become a commonplace. It is, however, none the less
wonderful for that.
Salt was regarded by Glauber as one of the prin-
ciples of matter, and he assigns more power to it than
to the others. " This known salt I here call (and
not injuriously) the universal treasure, and general
riches." Again, " It is the beginning and end of all
things, and it increases their powers and their virtues."
Glauber invented and improved chemical apparatus
to a large extent, and in his Furni Novi Philosophic
many useful and interesting furnaces may be found
described.
We cannot forbear, before closing our comments
upon Glauber, to quote the following amusing imita-
tion by him of the style adopted by Basil Valentine
in a paragraph already quoted. This passage occurs
in the discussion on concentrating and amending
metals by nitre. " First a man is to be made of iron,
having two noses on his head, and on his crown a
mouth which may be opened and again close shut.
This if it be to be used for the concentration of metals
is to be so inserted into another man made of iron or
stone, that the inward head only may come forth of
the outward man t but the rest of his body or belly
104 THE DECLINE OF MYSTICISM.
may remain hidden in the belly of the exterior man.
And to each nose of the head glass receivers are to be
applied, to receive the vapours ascending from the
hot stomach. When you use this man you must
render him bloody with fire to make him hungry and
greedy of food. When he grows extremely hungry
he is to be fed with a white swan. When that food
shall be given to this iron man, an admirable water
will ascend from his fiery stomach into his head, and
thence by his two noses flow into the appointed
receivers ; a water, I say, which will be a true and
efficacious aqua- vita? ; for the iron man consumeth the
whole swan by digesting it, and changeth it into a
most excellent and profitable food for the king and
queen, by which they are corroborated, augmented,
and grow. But before the swan yieldeth up her spirit
she singe th her swan-like song, which being ended,
her breath expireth with a strong wind, and leaveth
her roasted body for meat for the king, but her
anima or spirit she consecrateth to the gods that thence
may be made a salamander, a wholesome medicament
for men and women." This is a very good imitation
of the style of the older alchemists. It has the advan-
tage, too, of being more humorously absurd. The iron
man with two noses to which receivers are attached is
seen in the illustration which is taken from a woodcut
in Packe's edition of Glauber's collected works.
We may get a further glimpse into the character of
our author from the following quotation taken from a
paragraph on gunpowder ;
THE DECLINE OF MYSTICISM. 105
'' Of this mischievous composition and diabolical
abuse of gunpowder much might be written ; but
because the present world taketh only delight in shed-
ding innocent blood, and cannot endure that un-
righteous things should be reproved, and good things
praised, therefore it is best to be silent, and to let
every one answer for himself when the time cometh
that we shall give an account of our stewardship,
which, perhaps, is not far off ; and then there will be
a separation of good and bad by him that trieth the
heart, even as gold is refined in the fire from dross.
And then it will be seen what Christians we have been.
We do all bear the name, but do not approve our-
selves to be such by our works. Ever one thinketh
himself better than others, and for a word's sake which
one understandeth otherwise, or takes in another sense
than the other (and though it be no point whereon
salvation doth depend), one curseth and condemneth
another, and persecuteth another unto death, which
Christ never taught us to do, but rather did earnestly
command us that we should love one another, reward
evil with good and not good with evil as now-a-days
everywhere they use to do. Every one standeth upon
his own reputation ; but the honour of God and his
commands are in no repute, but are trampled under
foot, and Lucifer's pride, vain ambition, and phari-
saical hypocrisy or show of holiness hath so far got
the upper hand with the learned, that none will leave
his contumacy or stubbornness or recede a little from
his opinion, although the whole world should be turned
106 THE DECLINE OF MYSTICISM.
upside down thereby. Are not these fine Christians ?
By their fruit you shall know them, and not by their
words. Wolves are clothed with sheep's skins, so that
none of them almost are to be found, and yet the
deeds and works of wolves are everywhere extant."
This is not chemistry, it is true : but we are con-
cerned here also with character, and of that the pre-
vious passage gives much indication. What a man visi-
bly does may not be so important as what he is. As
Emerson puts it, " we do not want actions, but men."
So in studying the lives of the workers in any tech-
nical branch of human labour, the study is generally
pleasant in proportion to the space in their hearts
which we find unoccupied by technicality. The quaint
moralizing of Glauber in the foregoing passage and in
other places shows us a man who had a good deal of
earnestness in his heart, and it is all the pleasanter on
that account to read of his chemical work.
Glauber was a truly scientific worker and had a
fertile mind. We see in his work a distinct advance
in method upon that of Basil Valentine. It is cer-
tainly more sane, though not so striking, as that of
Paracelsus. We are indeed approaching, though
sloAvly, to a more quietly scientific age. Mysticism
had received some mortal wounds to which, in spite
of its intense vitality, it must gradually succumb.
Theory was gradually to become more closely insepar-
able from observation and experiment.
An interesting alchemical work may next be re-
ferred to The Brief of the Golden Calf: discover-
THE DECLINE OF MYSTICISM. 107
ing the Rarest Miracle in Nature, how by the smallest
portion of the Philosopher s Stone a great Piece of
common Lead teas totally transmuted into the purest
transplendent Gold, at the Hague in 1C 66. This
work is by Joliann F. Helvetius, and contains one of
the most celebrated records of transmutation, which,
as it is of considerable interest, may be here quoted
at some length : " :
"The 27th day of December, 1666, in the afternoon,
came a stranger to my house at the Hague, in a ple-
beick habit, of honest gravity and serious authority,
of a mean stature and a little long face, black hair and
not at all curled, a beardless chin, and about forty -four
years (as I guess) of age, and born in ^fcrth Holland.
After salutation he beseeched me with great reverence
to pardon his rude accesses, for he was a lover of the
Pyrotechnian art, and having read my treatise against
the sympathetic powder of Sir Kenelm Digby, and
observed my doubt about the philosophic mystery,
induced him to ask me if I really was a disbeliever as
to the existence of a universal medicine which would
care all diseases, unless the principal parts were
perished or the predestinated time of death come. I
replied I never met with an adept, or saw such a
medicine, though I had frequently prayed for it.
" Then I said, ' Surely you are a learned physician.'
' No,' said he, * I am a brass-founder and a lover of
* The original version is, like most of these documents, exceedingly
prolix and abounds in unnecessary details. That here given is from
an abridgment in Brande's Chemistry,
icS THE DECLINE OF MYSTICISM.
chemistry.' He then took from his bosom-pouch a
neat ivory box, and out of it three ponderous lumps
of stone, each about the bigness of a walnut. I
greedily saw and handled for a quarter of an hour this
most noble substance, the value of which might be
somewhere about twenty tons of gold ; and having
drawn from the owner many rare secrets of its admir-
able effects, I returned him this treasure of treasures
with a most sorrowful mind, humbly beseeching him
to bestow a fragment of it upon me in perpetual
memory of him, though but the size of a coriander
seed. ' No, no/ said he, ' that is not lawful, though
thou wouldst give me as many golden ducats as would
fill this room ; for it would have particular conse-
quences, arid, if fire could be burned of fire, I would
at this instant rather cast it all into the fiercest flames.'
He then asked if I had a private chamber whose pro-
spect was from the public street ; so I presently con-
ducted him to my best furnished room backwards,
which he entered without wiping his shoes, which
were full of snow and dirt.
" I now expected he would bestow some great
secret upon me, but in vain. He asked for a piece
of gold, and opening his doublet showed me five
pieces of that precious metal which he wore upon
a green riband, and which very much excelled mine
in flexibility and colour, each being the size of a
small trencher. I now earnestly craved a crumb
of the stone, and at last, out of his philosophical com-
miseration, he gave me a morsel as large as a rape-
THE DECLINE OF MYSTICISM. log
seed ; ( But/ I said, ' this scant portion will scarcely
transmute four grains of lead/ ' Then/ said he, ' de-
liver it me back ; ' which I did in hopes of a greater
parcel ; but he, cutting off half with his nail, said,
' Even this is sufficient for thee/ ' Sir/ said I, with
a dejected countenance, 'what means this?' And he
said, 'Even that will transmute half an ounce of lead/
So I gave him great thanks and said I would try, and
reveal it to no one. He then took his leave and said
he would call again next morning at nine.
" I then confessed that while the mass of his medicine
was in my hand, I had secretly scraped off a bit with my
nail which I projected on lead, but it caused no trans-
mutation, but the whole flew away in fumes. ' Friend/
said he, ' thou art more dexterous in committing a
theft than in applying medicine ; hadst thou wrapped
up thy stolen prey in yellow wax, it would have pene-
trated and transmuted the lead into gold/ I then
asked if the philosophic work cost much or required
long time, for philosophers say that nine or ten
months are required for it. He answered, ' Their
writings are only to be understood by adepts, without
whom no student can prepare his magistery. Fling
not away, therefore, thy money and goods in hunting
out this art, for thou shalt never find it/ To which I
replied, ' As thy master showed it thee, so mayest thou
perchance discover something thereof to me, who
know the rudiments, and therefore it may be easier to
add to a foundation than begin anew/ ' In this art/
said he, ' it is quite otherwise ; for unless thou knowest
no THE DECLINE OF MYSTICISM.
the thing from head to heel, thou canst not break
open the glassy seal of Hermes. But enough ; to-
morrow at the ninth hour, I will show thee the man-
ner of projection.'
" But Elias never came again ; so my wife, who
was curious in the art whereof the worthy man
had discoursed, teased me to make the experiment
with the little spark of bounty the artist had left
me. So I melted half an ounce of lead, upon which
my wife put in the said medicine ; it hissed and
bubbled, and in a quarter of an hour the mass of lead
was transmuted into fine gold, at which we were ex-
ceedingly amazed. I took it to the goldsmith, who
judged it most excellent, and willingly offered fifty
florins for each ounce."
Comment upon this story is needless. If the events
narrated were not very much out-of-the-way we should
believe Helvetius at once, but, of such a very extraor-
dinary occurrence we should probably feel uncertain
on all evidence short of ocular demonstration.
FOURTH PERIOD.
CHAPTER VI.
FOURTH PERIOD: THE BEGINNINGS OF SCIENCE.
,N event of importance belonging to the period
with which we have been dealing may
here be referred to. The Royal Society
was founded by Charles II., and incor-
porated by him in 1662, under a Royal
Charter, for the improvement of natural
knowledge. The first volume of the Philosophical
Transactions of that Society bears date 1665. With
occasional intermissions the Transactions were pub-
lished by the successive secretaries of the Society till
the year 1750. At that date the publication was put
into the hands of a Committee of Papers, and since
1762 a volume has annually appeared.
In 1666 the Royal Academy of Sciences was in-
stituted in Paris under the protection of Louis XIV,
ii4 THE BEGINNINGS OF SCIENCE.
In its early annals we find the names of Homberg,
Geoffrey, and the two Lemerys. Homberg discovered
boracic acid, which he prepared by decomposing
borax by means of a mineral acid, and termed sal
sedativum. Geoffrey made contributions to pharma-
ceutical chemistry, and was probably the first com-
piler of the " Paris Pharmacopoeia." Of the Lem&rys
more will be said in the sequel.
Ever since its foundation the Eoyal Society of
London has been a nucleus round which has clustered
the scientific genius of Great. Britain. In the earlier
years of its infancy it helped to fan the few glowing
sparks of the desire for truth into a broadening blaze.
It brought together those who were in sympathy,
through their devotion to knowledge, and who in
their union found double strength. By the inter-
change of their ideas thought was quickened and the
advance of science aided. By the publication of
original papers new discoveries were placed on record,
and thus preserved from being lost, as had too often
happened before. The discussion of these papers
helped more thoroughly to sift the evidence on which
their conclusions were based, and promoted much
increased accuracy and simplicity of thought and
expression.
Kesearch, too, was stimulated by the increased
definiteness of boundary between the known and the
unknown. Before such societies had existed the
magic-mongers, who then so frequently took the
place of men of science, were accustomed to produce
THE BEGINNINGS OF SCIENCE. 115
their questionable results in mystical folios, or still
stranger manuscripts, the few copies of which became
dispersed and too often lost. It was, therefore, al-
most impossible to tell what subjects were really
uninvestigated, and hence arose much repetition of
already accomplished work, and delay in the real
advancement of learning. Research was also more
directly encouraged by the Royal Society, by award-
ing grants of money to defray the expenses of those
investigations which seemed worthy of such aid.
Having now left Glauber behind us, we are enter-
ing upon a new epoch once more, the period with
which the names of Boyle, Hooke, and Mayow are
indissolubly connected.
But, before passing on to consider Boyle and his
assistant, Hooke, mention must be made of a chemist
whose work, though not of so great importance, is yefc
of considerable interest. Nicholas Lemery (1645
1715) was the well-known author of the GOUTS de
CTiymie (1675). This book embodied his ideas and
teachings, and, being translated into Latin and most
modern languages, enjoyed a wide popularity and
produced great effects upon the progress of the
science. He still retained the belief in salt, mercury
(or spirit), sulphur (or oil), as elements, but to these
were added water (or phlegm), and earth. The for-
mer set were the active, the latter the passive ele-
ments. As already stated these terms when thus
used did not necessarily signify only the bodies more
specially known by those Dames. " Sulphur," although
1 1 6 THE BEGINNINGS OF SCIENCE.
used for brimstone, was also more generally applied
to oils (perhaps from their usually having a yellow
colour), and hence we also find the plural " sulphurs"
in use. The substances included under one of these
names were also supposed to share the same essential
nature exhibited under different forms. It is difficult
to state clearly what these ideas were ; the fact being
that the ideas themselves were not clear. But if we
bear this in mind we shall be able to appreciate the
advances made as the theoretical notions of the
chemists become more intelligible.
Lemery, in his work, defines the aim of chemistry
to be a knowledge of the various substances " qui se
rencontrent dans un mixte " (which meet in a com-
pound), understanding by this term natural products
in general. He classifies the products as mineral,
vegetable, and animal, placing among the first,
metals, minerals, earths, and stones ; among the
second, plants, resins, gums, fungi, fruits, acids, juices,
flowers, mosses, manna, and honey ; and among
the third, the various parts of the animal organism.
Lemery thus established the distinction, now become
so broadly defined, between inorganic and organic
chemistry. The difference between the two realms
of the science was for long a subject of dispute. It
became gradually evident that the chemistry of mine-
rals or unorganized structures obeys certain well-
defined and never abrogated laws. A true inorganic
chemical compound, say, for instance, mercuric oxide,
is found on analysis to have always the same compo-
THE BEGINNINGS OF SCIENCE. 117
sition ; in this case, 100 parts of mercuric oxide
always contain 92 4 6 parts of mercury to 7'4 parts of
oxygen. Now, owing to the difficulty of purifying
substances found in the vegetable and animal king-
doms, it was for a long time considered that these
bodies did not obey those and other laws of com-
bination.
:' As discovery advanced, however, substances, un-
mistakably organic, were found which distinctly
obeyed these laws'; and when finally it was found
possible artificially to prepare compounds previously
known only as existing in the organized structure of
plant or animal, the gulf, hitherto separating the
organic and inorganic realms of the science, was at
last bridged, and the universal reign of consistency
and law became apparent.
But the gulf although -bridged did not cease to
exist, although it has been subsequently narrowed.
Broadly, the distinction is now between compounds
of carbon, and compounds of not-carbon. The ele-
ment carbon is sharply distinguished from the other
elements by the immense number and complexity of
its compounds, while among these compounds nearly
all the substances playing an active part in the life
and decay of an organized structure are to be found.
Becher, in 1669, argued that the same elements occur
in the three natural kingdoms, but more simply
combined in the mineral than in the vegetable or
animal. Stahl, in 1702, asserted that- in vegetable
as well as animal substances a larger proportion of
n8 THE BEGINNINGS OF SCIENCE.
watery and combustible principles is to be found ; a
view in which he was perfectly at one with the more
exact science of a later day, for hydrogen and carbon
are as a rule the main and characteristic constituents
of organic bodies. Van Helinont had held before
Stahl that organic substances can be resolved by
heat into their constituent elements, aqueous and
combustible principles, or water and fire. This idea
was, as we shall see, controverted by Robert Boyle
in his " Sceptical Chemist " (1661). He pointed out
that heat leads to different results under different
conditions. As an example of how near the light
truth may rest hidden for long periods before being
discovered, it is interesting to note that, in spite of
these suggestive discussions regarding the composition
of organic bodies, it was not till 1784 that the exis-
tence of carbon and hydrogen hi alcohol was a proven
fact.
CHAPTER VII.
FOURTH PERIOD. THE BEGINNINGS OF SCIENCE.
THE ACKNOWLEDGMENT OF NESCIENCE.*
t
>E have already observed that the progress of
chemistry was once more carrying it into
a new era far more nearly allied to the
present. Like the dawn of much new
knowledge which the world slowly wins
from darkness, the first brightening touch
on the horizon was to creep upwards in a tremulous
twilight of doubt. It is ever difficult to unsay what
is said, or to combat an error that has become a
habit of thought. Old instincts and old superstitions
when they have ceased to be openly loud in their
insistence, fall back upon whispering persuasion, to
which, because we are often unconscious of its
seductive suggestion, we easily fall a prey, and before
* The term nescience is a convenient one to signify the negation or
absence of knowledge.
izo THE BEGINNINGS OF SCIENCE.
we can dare to openly defy a principle which has
lived long in our hearts, we pass through a time of
half-timid wonderment, and doubt if, after all, it
be infallibly true. Then, after a long period of
lingering doubt, our mind is made up, and we
combat the false thought until we think that we
have slain it. But a false confidence in our victory
often deludes us, and the day comes when we
discover in some fresh bias our old enemy in a new
disguise.
A parallel to this frequent course of progress in
the individual human mind is found in the changes
passed through by the science we are considering.
Alchemy and mysticism had ruled the older chemists,
the latter partially crystallizing in the form of fan-
tastical notions concerning the fundamental principles
of matter. Slowly but surely uncertainty and doubt
was creeping into the minds of the workers as to the
so-called truths of transmutation. For some time
yet the doubt was not to become open denial, and
the idea was to spring up again and again even until
the present century, at the commencement of which
Peter Woulfe lived. The curious mysticism em-
bodied in the notions entertained about the elements
was to prove a phantom even less easily exorcised,
and more powerful to do harm. The period of doubt
was beginning, as will be seen in the discussion of
Robert Boyle, and true ideas concerning the nature
of an " element," and hence of combustion and otlier
important natural phenomena, seemed about to spring
THE BEGINNINGS OF SCIENCE. 121
up. But soon after this the apparently-slain demon
was to be resuscitated as a giant of invulnerable
strength. The phlogistic theory was started, and, as
we shall see, for half a century it held chemistry in
thrall, and caused men of remarkable brilliancy and
power to grope blindly in the darkness for truths
which, except for the baleful shadow that en-
shrouded them, would have been as clear as day.
Chemistry had to wait for the steady lustre of
Lavoisier's talents to dispel the gloom.
In entering upon this period of doubt, we shall
discuss the three chemists, Boyle, Hooke, and Mayow ;
and first of all let us take the man who is most
fitly representative of this era Robert Boyle.
Robert Boyle (1627 1691) was the seventh son
and fourteenth child of Richard, Earl of Cork. He
was born at Lismore, in Munster. At eight years of
age he was sent to Eton, where, says he, a perusal of
" Quintus Curtins" "conjured up in me that un-
satisfied appetite for knowledge that is yet as greedy
as when it was first raised." It is related that while
recovering from a fever at Eton he was induced to
read "Amadis de Gaul" and other romantic books.
The effect of the romance of that period upon him
was to produce an intolerable restlessness and unset-
tlement in his mind, which he determined to end.
To counteract these tendencies, he, therefore, set
himself, .being then ten years old, to extracting
square and cube roots and other laborious and
uninteresting calculations, in order to calm his brain.
122 THE BEGINNINGS OF SCIENCE.
Such strength of mind in one so young was perhaps
to be condemned as dangerously prophetic of too
great austerity. As a matter of fact, however, he
seems through life to have kept his heart readily
open to human sympathies and to have been quite
free from the cynical reserve which has characterized
a few intellectual workers. While at Eton his life
was greatly endangered by the fall of the room in
which he was sleeping, and had he not, with striking
presence of mind, wrapped the sheet of the bed round
his face he would probably have been suffocated with
the dust.
After about four years at Eton, Boyle went to his
father's seat in Dorset, and afterwards travelled
abroad with his brother Francis and tutor. He took
a view of those wild mountains where Bruno, the
first founder of the Carthusian monks, lived in
solitude, and where the first and chief of the
Carthusian abbeys was built. Boyle relates that " the
devil, taking advantage of that deep, raving melan-
choly, so sad a place, his own humour, which was
naturally grave and serious, and the strange stories
and pictures he found there of Bruno, suggested
such strange and distracting doubts of some of the
fundamentals of Christianity that, though his looks
did little betray his thoughts, nothing but the for-
biddenness of self-despatch hindered his acting it."*
He shortly after became fully converted to Christi-
anity, though "the fleeting clouds of doubt and
hic Britannica.
THE BEGINNINGS OF SCIENCE. 123
disbelief did .never after cease to now and then
darken the serenity of his quiet." Boyle was in
Marseilles in 1641 at the outbreak of the Irish
Rebellion. His father transmitted his brother 250,
but it never reached them, and they were left almost
penniless. They made their way to Marcombes, and
then to Geneva, where they lived for two years on
credit, and at length, by the sale of some jewels, got
together enough money to bring them home. They
reached England in the summer of 1644. Their
father was dead, and so confused was the state of the
country that for nearly four months Boyle could not
make his way to the manor of Stalbridge, which he
had inherited.
But through all this turmoil the scientific men were
steadily, though secretly, at work. Through all the
din of conflicting faction and disputed power they
held calmly on towards the goal which to them was
highest and best. There is something perhaps rather
coldly grand about their impenetrable patience, but
grand it certainly is. The " Philosophical Society," or,
as Boyle preferred to call it, the " Invisible Society,"
met secretly in London in 1645, and from these
meetings he derived fresh impulse. " Vulcan has so
transported and bewitched me," he wrote from Stal-
bridge to his sister, Lady Ranelagh (1649), "as to
make me fancy my laboratory a kind of Elysium."
In 1652 3 he visited his Irish estates, and on his
return in 1654 settled at Oxford in the society of
some of his early philosophical associates. Meetings
124
THE BEGINNINGS OF SCIENCE.
were held amongst them and experiments performed
and discussed.
In 1659 Boyle perfected his air-pump, and in
1660, amongst other results, he published "Boyle's
Law," confirmed by Mariotte in 1676. This well-
known law asserts that the volume* of a gas varies
inversely as the pressure. For instance, if a certain
volume of air be contained in the closed end of
the U-shaped tube shown in the illustration, let
us call this volume 1, and the pressure to which it is
at first subjected 1. If we double the pressure we
shall halve the volume. The volume 1 under pres-
sure 1 becomes the volume J under pressure 2, the
* " Volume " means the amount of cubic space occupied by any
substance.
THE BEGINNINGS OF SCIENCE. , 25
volume I under pressure 4, and so on. Similarly
the volume 1 under pressure 1 becomes the volume
2 under a pressure J, the volume 4 under pressure
i &c. Of the two cases shown in the illustration the
first shows the gas at the ordinary pressure of the
atmosphere, the mercury standing at the same height
in each limb of the tube. Now the ordinary pressure
SIMPLEST FORM OF THE BAROMETER.
of the atmosphere, as recorded by the barometer, is
sufficient to support a column of mercury 760 milli-
metres high. If therefore we pour mercury into the
long limb of the bent tube till the height of the
column in it is 760 millimetres higher than the
height of the column in the short limb, the gas
enclosed behind the mercury which was formerly at
126 THE BEGINNINGS OF SCIENCE.
the ordinary atmospheric pressure will now have
to sustain twice that pressure, and its volume is
accordingly halved, as is seen in the second illustra-
tion. This law, though not exactly true for all degrees
of pressure, has yet been of very great service.
It may be objected that this is a question of physics
rather than of chemistry. But it is a law, which
is in every-day use by the chemist in calculating
the amount of a gas the volume of which is not
observed under the normal pressure of 760 mm. A
further complication arises from the fact that these
gases are observed at various temperatures and not
often at the normal temperature, which is taken as
the melting point of ice, or centigrade. Now
gases expand on heating, and it was Gay-Lussac who
at a much later date discovered the laws of their
expansion. Each gas expands for one degree centi-
grade Y -f T of its volume at C. Thus 273jolumes
of gas at C. become at 1 equal to 274 volumes,
and so on. From these laws we can readily reduce
the volume of a gas observed at any given tempera-
ture and pressure to the volume the same weight of
gas would occupy at C. and 760 mm. pressure.
Once this is known the weight of the gas may be very
simply deduced. In this way, if in analysing a
nitrogenous organic body a certain volume of nitrogen
is obtained, the weight of nitrogen contained in the
body is readily calculated.
In 1668 Boyle came to London and was a pro-
minent member of the then newly constituted Royal
THE BEGINNINGS OF SCIENCE. 127
Society. He was elected president in 1680, but
refused to act, owing to a scruple he entertained as to
taking oaths. In 1689 his health began to fail and
he issued an advertisement restricting the visits of
his acquaintances. He also had a board put up out-
side his house announcing when he received visits.
Boyle's health had never been good ; from the age
of twenty-one he suffered from stone, and much feared
that if it forced him to take to his bed the pain of it
would become insupportable. He died, however,
without pain, and almost without serious illness.
Boyle developed talent early, and at twenty-one he
had already written on ethics and published several
moral and religious essays. In 1 6 6 5 he published his
" Occasional Reflection upon Several Subjects," which
procured him the satire of Swift in " A pious Medita-
tion upon a Broomstick, in the style of the Honourable
Mr. Boyle."
Personally Robert Boyle is described as pale,
emaciated, and very delicate, so " that he had divers
sorts of cloaks to put on when he went abroad,
according to the temperature of the air, and in this
he governed himself by his thermometer .... For
almost forty years he laboured under such a feeble-
ness of body and lowness of strength and spirits that
it was astonishing how he could read, meditate, try
experiments and write as he did." To these dis-
abilities was added that of a memory by his own
account so treacherous that he was often tempted to
abandon study in despair.
iz8 THE BEGINNINGS OF SCIENCE.
He " wore the white flower of a blameless life."
Naturally choleric he controlled himself to mildness; he
was unostentatiously liberal, unselfish, and unambitious.
He refused to take orders, excusing himself on the
ground of not having an inner call, though this involved
refusing the provostship of Eton. He also repeatedly
declined a peerage. There is something very attrac-
tively quiet and simple about such a nature. It is
an example of a man who worked quietly and peace-
fully at the problems toward which his nature felt
drawn, undisturbed by feverish unrealities of ambi-
tion and unsullied by the desire of worldly fame.
His work never led him into the bitter controversies
in which others have sometimes too readily engaged,
it did not lead him to forget the claims of human
sympathy and sorrow, or to doubt the existence of
knowledge beyond his own. The work itself has
proved of lasting and notable service, and perhaps
even more serviceable when we read of it, was the
calm, unsullied purity of his soul.
Boyle's principal chemical work was published in
1661, under the title of The Sceptical Chymist ; or
Chemico-physical Doubts and Paradoxes, touching the
Experiments whereby vulgar Spagyrists are wont to
endeavour to evince their Salt, Sulphur, and Mercury
to be the true Principles of Things. We see here
the beginning of the time of doubt. It is in this work
that the first rational notion of an element, and of the
difference between an element and a compound, is con-
tained. The book is written in the form of a discus-
THE BEGINNINGS OF SCIENCE. 129
sion between a party of learned gentlemen, of whom
one, Carneades, plays the part of the Sceptical Chymist.
The earlier portions of the book are devoted to a
demolition of the Aristotelian doctrine of the elements,
which is amusingly and interestingly defended by one
speaker in the following passage :
" I speak thus, Eleutherius (adds Themistius), only
to do right to reason, and not out of diffidence of the
experimental proof I am to allege. For though I shall
name but one, yet it is such a one as will make all
other appear as needless, as itself will be found satis-
factory. For if you but consider a piece of green wood
burning in a- chimney, you will readily discern in the
disbanded parts of it the four elements of which we
teach it and other mixed bodies to be composed. The
fire discovers itself in the flame of its own light ; the
smoke by ascending to the top of the chimney and
there readily vanishing into air like a river losing itself
in the sea, sufficiently manifests to what element it
belongs and gladly returns. The water in its own
form boiling and rising at the ends of the burning
wood betrays itself to more than one of our senses ;
and the ashes by their weight, their firiness, and their
dry ness put it past doubt that they belong to the ele-
ment of earth. If I spoke (continues Themistius) to
less knowing persons I would perhaps make some ex-
cuse for building upon such an obvious and easy
analysis, but 'twould be I fear injurious not to think
such an apology needless to you, who are too judi-
pious either to think it necessary that experiments to
I
130 THE BEGINNINGS OF SCIENCE.
prove obvious truths should be far-fetched, or to
wonder that among so many mixed bodies that are
compounded of the four elements some should, upon
a slight analysis, manifestly exhibit the ingredients they
consist of." There is a delicious naivete about the
concluding portion of this speech, a blind simplicity
that is almost charming. The absurdity of the sup-
positions implied in the experiment are so quietly put
aside, that we become aware of the figure of Boyle
behind Themistius with a satirical smile upon his
face.
Carneades, after some preamble, replies thus : " To
begin then with his experiment of the burning wood,
it seems to me to be obnoxious to not a few consid-
erable exceptions. And first, if I would now deal
rightly with my adversary, I might here make a great
question of the very way of probation which he and
others employ without the least scruple to evince
that the bodies commonly called mixed are made up
of earth, air, water, and fire, which they are pleased
also to call elements ; namely, that upon the supposed
analysis made by fire of the former sort of concretes,
there are wont to emerge bodies resembling those
which they take for the elements. For . . . . i-f I
were disposed to wrangle I might allege that by The-
mistius, his experiments, it would appear rather that
those he calls elements are made up of those he calls
mixed bodies, than mixed bodies of the elements ;
.... it appears .... that which he takes for ele-
mentary fire and water are made out of the concrete,
THE BEGINNINGS OF SCIENCE. 131
but it appears not that the concrete was made up of
fire and water. Nor has .... he .... yet proved
that nothing can be obtained from a body by the fire
that was not pre-existent in it."
There is some very shrewd reasoning here. How,
indeed, are we to know that heat thus applied splits
a body up into its constituent elements ? Besides, the
absurdity of describing the smoke as air when; as Car-
neades points out, the main portion of it descends
as soot, what an odd piece of reasoning it is which
makes the appearance of flame during the combus-
tion prove that fire is one of the principles of the
wood.
In the succeeding discourses Carneades proceeds to
apply his judgment to the other theories of the elements
as well. He states that the so-called elements obtained
by the chemists are not even pure. He is told that
later Aristotelians have undertaken to further purify
these supposed elements (salt, sulphur, and mercury).
Very well, that does not alter the truth of what he
has said as to the ordinary operations. " And as to
the thing itself, I shall freely acknowledge to you that
I love not to be forward in determining things to
be impossible, till I know and have considered the
means by which they are proposed to be effected.
And therefore I shall not peremptorily deny either
the possibility of what these artists promise, or my
assent to any just inference, however destructive to
my conjectures, that may be drawn from their per-
formance. But give me leave to tell you withal,
132 THE BEGINNINGS OF SCIENCE.
that, because such promises are wont (as experience
has more than once informed me) to be much more
easily made than made good by chemists, I must with-
hold my belief from their assertion till their experiments
exact it, and must not be so easy as to expect before-
hand an unlikely thing upon no stronger inducements
than are yet given me."
The extreme and almost amusing caution of Car-
neades is sufficiently evident from the above quota-
tions. He has begun to distrust the old theories and
beliefs, but he is not prepared to dogmatically assert
a new creed of his own. But in the course of the dis-
cussion it becomes more and more clear what defini-
tion of the "element" Carneades is inclined to favour.
The modem view is here for the first time suggested,
that an element is a body which by no -known process
can be split up into two or more different substances.
It is a simple body. It is a whole made up of similar
parts. If we find that we can, by some new analytical
process, split up an apparently simple body, we cease
to regard it as an element ; and it is by no means
improbable that we may in this way cease to regard
as elements many of the substances now so-called.
Boyle was quite aware of the variability of the
number of apparently elemental principles. He thinks
" that it may as yet be doubted whether or no there
be any determinate number of elements ; or, if you
please, whether or no all compound bodies do consist
of the same number of elementary ingredients or
material principles." Finally, in a sequel added to the
THE BEGINNINGS OF SCIENCE. 133
discourses proper to the Sceptical Cliymist, Carneades
goes so far as to say : "I am content ....
to tell you that .... though it may seem extrava-
gant, yet it is not absurd, to doubt whether, for ought
has been proved, there be a necessity to admit any
elements or Hypostatical principles at all." Boyle
had certainly penetrated far into the period of
doubt/"
From these details we see the great credit due to
Boyle for first openly distrusting the curiously vague
and mystical notions, concerning the constitution of
the various kinds of matter, which for so long had
held in bondage the infant science. It was a strangely
deep insight which led him to view the number of so-
called elements as variable, and it may even be that
his suggestion that, after all, there may be no such
thing as a true element, may become the most accepta-
ble hypothesis. Or it may be thought that all the
elements enumerated in our tables are modifications
and combinations of modifications of one primordial
element. Oxygen, hydrogen, nitrogen, iron, copper,
are well-known examples of substances now regarded
as elements. It may well, however, be that, by spec-
troscopical or other mode of research, these substances
may; be found to be made up of still simpler bodies,
* See also the interesting Appendix to the Sceptical Chymist, on the
Produciblcncss of Chemical Principles. In this Boyle discusses the want
of uniformity among bodies supposed to be part of the same principle.
Thus some oils, spirits, and brimstone, were all termed sulphurs,
because inflammable. Boyle looks with disfavour upon so loose a
notion, and thinks it more probable that "sulphur " itself is made up
of the same universal matter as other bodies.
134 THE BEGINNINGS OF SCIENCE.
though of this at present not much can be said. We
have even had suggestions as to the possible ways in
which the elementary bodies may have come into
existence and how also they may cease to be."* At
present much of the work in this region must consist
in speculation, but speculation is ever the forerunner
of discovery.
Besides his really remarkable observations upon the
nature of the elementary bodies, Boyle was the author
of some pregnant work upon that great puzzle of
chemists up to the time of Lavoisier, the phenomenon
of combustion. We all of us now know that what
happens when a candle burns, is that its carbon and
hydrogen combine with the oxygen of the air thus
forming carbonic acid gas and water vapour. But
at the time of Boyle vague notions, such as that
described by Themistius in the Sceptical Chymist
were in vogue. The first step towards clearing up
the difficulty was to find out whether the air had
anything to do with the burning of combustible
materials, and accordingly Boyle experimented with a
view to finding whether they would burn under the
exhausted receiver of his air-pump. There being
under these conditions very little air present Boyle
found that such combustibles as a candle, charcoal,
sulphur, etc., would not light.
On the other hand gunpowder, if strongly heated
under the receiver by means of a burning-glass,
* See the suggestive paper by Prof, Crookes in his presidential
address to the Chemical Society (1888).
THE BEGINNINGS OF SCIENCE. 135
exploded, and from this it was concluded that the
nitre in the gunpowder gave up something capable of
acting as a substitute for air. Nitre, we now know,
contains oxygen and readily parts with it to other
combustible bodies. Boyle's conclusion was therefore
perfectly correct. But in spite of such advance Boyle
still believed in the material nature of flame, and,
owing to bias of this kind, though he was aware that
many metals when heated in air are altered with gain
of weight, he ignored the true explanation. It seems
strange that it should not have occurred to him that
the metals had absorbed a ponderable constituent
(oxygen) of the atmosphere. Instead of this he sup-
posed them to weigh heavier, owing to addition of
11 igneous corpuscles."
To sum up Boyle's work, his discussion of the
qualities proper to an element led to the views con-
cerning those bodies at present entertained ; he was
the first to distinguish definitely between an element
and a compound, and between a compound and a
mixture ; his work upon combustion was accompanied
by very suggestive experiments; he seems to have
introduced vegetable colour tests to distinguish acid
and alkali,* and he developed the law of the compres-
sion of gases now so familiar by his name and so
serviceable alike to chemists and physicists.
His style of writing, as may have been suggested
by the quotations given, though quaintly interesting,
* The every-day test now in use is that of litmus, which is turned red
by acid and blue by alkali.
I 3 6
THE BEGINNINGS OF SCIENCE.
is intolerably prolix, a characteristic in those days
not uncommon.* But we readily forgive his defects
when we find how earnestly painstaking he was.
* The Life and Works of the Honourable Robert Boyle were brought out
in five volumes folio by Thomas Birch in 1744. A curious pamphlet,
by Boyle, -An Historical Account of a Degradation of Gold made by an
Anti-elixir, not mentioned in the text, gives a description of the con-
version of gold into a baser metal.
CHAPTER VIII.
FOURTH PERIOD : THE BEGINNINGS OF SCIENCE.
HOOKE: MAYOW: HALES.
HE next of those to be considered in this
period is Robert Hooke (16351702).
Hooke is naturally associated with Boyle,
as he was for a considerable time his
assistant and aided him in some im-
portant work. But his character is very
much less attractive than that of his employer ; he
wanted the unambitious earnestness which had always
characterized Robert Boyle.
Robert Hooke was born in the Isle of Wight and
was originally intended for the Church, but he was
of a weakly constitution, and much subject to head-
ache, and owing to these causes the idea was finally
abandoned. His leanings were first shown in a con-
siderable aptitude, as a boy, for constructing mechan-
138 THE BEGINNINGS OF SCIENCE.
ical toys. After his father's death Dr. Busby took
him into his house and supported him while at West-
minster School. After leaving school he went to
Christ Church, Oxford, and, in 1G55, he was intro-
duced to the Philosophical Society. Here his talents
were speedily discovered and he was employed to
assist first Dr. Willis and then Mr. Boyle. In 1662
he was made curator of experiments to the Eoyal
Society, and when this body was established by
charter he was one of the first nominated to fellow-
ship. He obtained several professional posts and in
1665 he published in folio his Micrographia, or
some physiological descriptions of minute bodies made
by magnifying glasses, with observations and inquiries
thereupon. The work was dedicated to Charles II.
After the great fire of London Hooke was appointed
one of the city surveyors, and in this capacity seems
to have amassed a considerable sum of money which,
after his death, was found locked up and untouched
in a large iron chest. He seems to have had an
ungovernable tendency to believe that all new dis-
coveries had been anticipated by himself, and when
Newton, in 1686, published his Principia Hooke
claimed priority in the idea of gravitation. There
was enough truth in this to cause Newton to allow
the claim, but the fact is that the idea of gravitation
is a very old one, and Newton's honour was to have
made it a workable theory. When Hooke laid claim
to having originated Newton's views as to gravitation
Newton wrote to Dr. Hal ley : "I intended in this
THE BEGINNINGS OF SCIENCE. 139
letter to let you understand the case fully, but, it
being a frivolous business I shall content myself with
giving you the heads of it." In a postscript he adds,
" Since my writing this letter I am told by one who
had it from another lately present at one of your
meetings how Mr. Hooke should make a great stir,
pretending that I had all from him .... This
carriage towards me is very strange and undeserved
. . . . he has published Borell's hypothesis in his
own name .... Borell did something and wrote
modestly. He has done nothing and yet written in
such a way as if he knew and had sufficiently hinted
all but what remained to be determined by the
drudgery of calculation and observations ....."
But here Hooke was somewhat maligned by report.
The facts were that at a meeting of the Royal Society
a member remarked that Newton had done the work
so thoroughly that no more was to be added. Sir
John Hoskins, the Vice- President, was in the chair,
and replied that the book was the more to be prized ;
the theory was both invented and perfected at the
same time. This gave Hooke offence, " upon which,"
writes Halley, "they two who till then were the
most inseparable cronies have since scarcely seen one
another and are utterly fallen out." A spirit such
as this would cause us to reluctantly withdraw
our reverence from a worker of even the highest
intellectual predominance. Hooke lived the life
of a cynic and recluse, and on the death in 1687
of his niece, Mrs. Grace Hooke, with whom he
140 THE BEGINNINGS OF SCIENCE.
lived, he became more cynical than ever. The tradi-
tion runs that for the two or three last years of
his life he sat night and day at a table engrossed
with his inventions and studies, and never went to
bed or undressed. Wasted and emaciated by his
strange mode of life, and by the denial to himself
of comforts he could readily have gained, he died
in 1702 and was buried in St. Helen's Church,
Bishopsgate Street. He is described as penurious,
melancholy, mistrustful, and jealous. We could more
readily pity his melancholy had it not been so self-
imposed. We must, however, admire his keen in-
sight and penetrative power.
The main interest of Hooke's work centres in his
Micrographia and probably the most remarkable
words he ever uttered are contained, almost paren-
thetically, in a work where, from its title, we should
have no expectation of finding the subject they deal
with treated of at all.'""
Hooke seems in the quietest and most unbiassed
way to have set about observing the facts of combus-
tion, and waited for these facts to work out in his
* To understand Hooke's work thoroughly, the pregnant preface to
the Micrographia should be read. First of all Hooke implores the
reader to observe great caution in accepting the conclusions there set
forth. Caution is naturally the key-note of the period of doubt. But
an over -caution often produces a tendency to cling to a hypothesis
once accepted and an over -reluctance to accept the plunge into the
stream of new ideas. Hooke avoids both Scylla and Chary The
door of the senses, he says, must always be left open. The under-
standing "must watch the irregularities of the senses, but it must not
go before them or prevent their information."
THE BEGINNINGS OF SCIENCE. 141
mind their natural conclusion. He arrives at the
opinion that the combustion of a combustible, or, as
he calls it, " sulphureous," body, for instance, char-
coal, is due to the combination of part of it with a
substance contained in the air, and also in saltpetre.
This resulting body is volatile and flies off, and, of
course, corresponds to carbonic acid gas, together with
water vapour. Another portion of the body uniting
with part of the air is supposed to form an unvolatile
" coagulum " extrac table from soot. Part of the
combustible will often not combine with the air and
is left behind as the ashes. The air is spoken of as
the solvent of inflammable bodies, by a somewhat in-
accurate analogy, so that when charcoal burns, it is
viewed as an analogous action to that of dissolving a
solid in alcohol. The air is viewed as containing but
a little of the true solvent ; a view quite correct, as
four-fifths of the atmosphere consist of nitrogen ; and
the solvent is therefore easily exhausted. Thus, for
instance, air must be continually admitted into a
vessel in which we are burning a large piece of char-
coal, or the charcoal will cease to burn. Just as heat
is sometimes generated by dissolving substances in a
liquid, so, says Hooke, heat is produced during the
solution or combustion of a body in air, and this heat
shows itself as flame, and is not an element, but a
phenomenon resulting from the violent agitation of
the particles of the burning body. Saltpetre contains
more of this supporter of combustion and hence burns
more rapidly. Altogether, this is a very wonder-
H2 THE BEGINNINGS OF SCIENCE.
ful anticipation of the present ideas about combus-
tion. So far as it goes it is accurate, and if it
could have been followed up farther in the same
spirit, chemistry might have advanced more rapidly
than it did. The passage from Micrographia above
described is so interesting and deals with so immensely
important a subject that we shall not hesitate here
to quote at some length therefrom :
" Thirdly, from the experiment of the charring of
coals (whereby we see that notwithstanding the great
heat, and the duration of it % the solid parts of the
wood remain, whilst they are preserved from the free
access of air, undissipated), we may learn that which
has not, that I know of, been published or hinted,
nay, not so much as thought of, by any ; and that, in
short, is this.
<( First, that the Air in which we live, move, and
breathe, and which encompasses very many^ and
cherishes most bodies it encompasses, that this Air
is the menstruum, or universal dissolvent of all sul-
phureous bodies.
" Secondly, that this action it performs not till the
body be sufficiently heated, as we find requisite also
to the dissolution of many other bodies by several
other menstruums.
" Thirdly, that this action of dissolution produces or
generates a very great heat, and that which we call
fire ; and this is common also to many dissolutions
of other bodies, made by menstruums, of which I
could give multitudes of instances.
THE BEGINNINGS OF SCIENCE. 143
"Fourthly, that this action is performed with so
great a violence and does so minutely act, and
rapidly agitate the smallest parts of the combustible
matter, that it produces in the diaphanous medium
of the air the action or pulse of light, which what it
is I have elsewhere already shown.
"Fifthly, that the dissolution of sulphureous bodies
is made by a substance inherent and mixed with the
air, that is like, if not the very same with that which
is fixed in saltpetre,* which by multitudes of experi-
ments that may be made with saltpetre, will, I think,
most evidently be demonstrated.
" Sixthly, that in this dissolution of bodies by the
air a certain part is united and mixed, or dissolved
and turned into ike air and made to fly up and down
with it* in the same manner as a metalline or other
body dissolved in any menstruum does follow the
motions and progresses of that menstruum till it be
precipitated.
" Seventhly, that as there is one part that is dis-
soluble by the air, so are there other parts with
which the parts of the air uniting do make a coagulum
or precipitation, as one may call it, which causes it
to be separated from the air, but this precipitate is
so light and in so small and rarefied or porous clusters
that it is very voluble and is easily carried up by the
motion of the air, though afterwards, Avhen the heat
and agitation that kept it rarefied ceases, it easily
condenses and, commixt with other indissoluble
* Italics not in the original.
H4 THE BEGINNINGS OF SCIENCE.
parts, it sticks and adheres to the next bodies it
meets withal, and this is a certain salt that may be
extracted out of soot.
" Eighthly, that many indissoluble parts being very
apt and prompt to be rarefied and so, whilst they
continue in that heat and agitation, are lighter than the
ambient air, are thereby thrust and carried upwards
with great violence and, by that means, carry along
with them not only the saline concrete I mentioned
before, but many terrestrial or indissoluble and irrare-
fiable parts, nay many parts also which are dissoluble
but are not suffered to stay long enough in a suffi-
cient heat to mate them prompt and apt for that
action. And therefore we find in soot, not only
a part that being continued longer in a competent
heat will be dissolved by the air or take fire and
burn, but a part also which is fixed, terrestrial and
irrarefiable.
" Ninthly, that as there are these several parts that
will rarefy and fly or be driven up by the heat, so
are there many others that, as they are indissoluble
by the aerial menstruum, so are they of such sluggish
and gross parts that they are not easily rarefied by
heat and therefore cannot be raised by it ; the
volubility or fixtness of a body seeming to consist
only in this, that the one is of a texture or has
component parts that will be easily rarefied into the
form of air, and the other that it has such as will not
without much ado be brought to such a constitution ;
and this is that part which remains behind in a white
THE BEGINNINGS OF SCIENCE. 145
body called ashes, which contains a substance or salt
which chemists call alkali. What the particular
nature of each of these bodies is I shall not here
examine, intending it in another place, but shall
rather add that this hypothesis does so exactly agree
with alf phenomena of fire and so genuinely explicate
each particular circumstance that I have hitherto
observed that it is more than probable that this
cause which I have assigned is the true, adequate,
real and only cause of those phenomena, and there-
fore I shall proceed a little further to show the
nature and use of the air.
" Tenthly, therefore, the dissolving parts of the air
are but few, that is it seems of the nature of those
saline menstruums or spirits that have very much
phlegm mixed with the spirit, and therefore a small
parcel of it is quickly glutted, and will dissolve no
more ; and therefore unless some fresh part of this
menstruum be applied to the body to be dissolved
the action ceases and the body leaves to be dissolved
and to shine, which is the indication of it, though
placed or kept in the greatest heat; whereas, salt-
petre is a menstruum, when melted and red hot, that
abounds more with those dissolvent particles, and
therefore as a small quantity of it will dissolve a
great sulphureous body, so will the dissolution be
very quick and violent.
" Therefore, in the eleventh place, ifc is observable
that, as in other solutions, if a copious and quick
supply of fresh menstruum, though but weak, be
K
1 4 6 THE BEGINNINGS OF SCIENCE.
poured on or applied to the dissoluble body, it
quickly consumes it : so this menstruum of the air,
if by bellows or any such contrivance it be copiously
applied to the shining body, is found to dissolve it
as soon and as violently as the more strong men-
struum of dissolved nitre.
"Therefore, twelfthly, it seems reasonable to think
that there is no such iliing as an Element of fire that
should attract or draw up the flame, or towards
which the flame should endeavour to ascend out of a
desire or appetite of uniting with that as its homo-
geneal, primitive and generating Element ; but that
that shining transient body, which we call flame, is
nothing but a mixture of air and volatile sulphureous
parts of dissoluble or combustible bodies which are
acting upon each other whilst they ascend ; that is
flame seems to be a mixture of air and the combustible
volatile parts of any body, which parts the encom-
passing air does dissolve or work upon, which, action,
as it does intend the heat of the aerial parts of the
dissolvent, so does it thereby further rarefy those
parts that are acting or that are very near them,
whereby they, growing much lighter than the heavy
parts of that menstruum that are more remote, are
thereby protruded and driven upward ; and this may
bo easily observed also in dissolutions made by any
other menstruum, especially such as either create heat
or bubbles. Now this action of the menstruum or air
on the dissoluble part is made with such violence or
is such that it imparts such a motion or pulse to the
THE BEGINNINGS OF SCIENCE. 147
diaphonous parts of the air as I have elsewhere shown
is requisite to produce light."
This hypothesis, Hooke says, is the result of " an
infinite of observations and experiments." He holds
out the prospect of a much larger discourse on the
same subject, " the air being a subject which (although
all the world have hitherto lived and breathed in
and been conversant about) has yet been so little
truly examined or explained that a diligent inquirer
will be able to find but very little information from
what has been (till of late) written of it."
John Mayow (1645 1679) was born in Cornwall
and became a student of medicine. He practised
chiefly at Bath in the summer.
Mayow carried on investigations into the nature
of combustion, published in 1674 in his Tracts on
various Philosophical Subjects* which, apparently
unknown to himself, had been to some extent antici-
pated in Hooke's Micrographia (1665). He burned
a candle under a bell-glass over water, observed
that the air diminished in volume, and that the
gas left was a little lighter than air and had no
longer the power of supporting combustion or life.
This gas was, of course, nitrogen, the other constituent
of the atmosphere. The carbonic acid gas formed
had been slowly absorbed by the water. He recog-
nised that the portion of the air necessary to com-
bustion and to life (i.e. oxygen) was contained also
* Mayow's first paper, however, De Sale Nitro et Spiritu Nitro-
aereo, was published ia 1669,
i 4 8 THE BEGINNINGS OF SCIENCE.
in saltpetre (potassium nitrate, KNO 3 ). The nitre
or saltpetre he said contains fire-air (oxygen) and no
sulphureous (combustible) particles. For combustion
he asserted that fire-air and sulphureous particles
were needed.
Mayow seems to have been the first to use the
pneumatic trough for collecting gases, and the use of
this alone makes possible the examination of most
gases. An example of it is given farther on in the
sketch of Priestley's apparatus.
In the course of his investigations Mayow was, by
his medical leanings, induced to consider the chemical
meaning of breathing. He ascertained, as already
stated, that one part only of the atmosphere is the
supporter of life, but he did not wish to stop there.
The idea of his time was that respiration cooled the
blood. Mayow, on the other hand, seeing the part
played by these " nitre-aerial particles" or oxygen in
combustion, concluded that this gas was connected
with the heating of the blood.* He showed the
existence of gases in the blood by subjecting it to
the action of the air-pump, which extracts them.
Mayow was quite right in thinking that the " fire-
air" had to do with supplying the heat of the
blood.
On the subject of chemical affinity Mayow made
remarks of some moment. It may be as well to
explain here shortly what the term chemical affinity
is supposed to convey. There is no doubt that
* ChemischpJiysiologisclteSchriftcn. Jena (1799),
THE BEGINNINGS OF SCIENCE. 149
strictly speaking affinity should mean similarity to or
relation to ; but the word has been diverted from
its proper significance and is now generally, used
to denote the tendency exhibited by substances to
combine with each other. Thus we say that phos-
phorus has a great affinity for oxygen, thereby
intending to convey the fact that phosphorus and
oxygen have a strong tendency to combine to-
gether. This is brought home to us by observing
that phosphorus when exposed at ordinary tempe-
ratures to the air burns slowly away, without a dis-
tinct flame, but giving off light fumes of phosphorus
pentoxide (anhydrous phosphoric acid) and emitting
a pale glow when observed in the dark. If slightly
heated, as, for instance, by the sudden pressure of a
blow, the phosphorus at once bursts into flame. Again,
if sufficiently finely divided the phosphorus will in-
flame, as we say, spontaneously and without applica-
tion of heat. Thus if a small piece of white phosphorus
be dissolved in some carbon disulphide (a highly
refracting liquid usually possessing an atrocious smell)
and a little of the solution be poured upon blotting
paper, the volatile carbon disulphide v r ery rapidly
evaporates and leaves the phosphorus on the paper
in a very fine state of division. Directly the paper
has become thoroughly dry the outer edges of the
phosphorus disc left by the carbon disulphide begin
to fume strongly, the heat developed by the combina-
tion rapidly increases, the paper begins to char, and
the next instant the whole mass bursts into flame.
I5 o THE BEGINNINGS OF SCIENCE.
Such facts as these teach us that phosphorus and
oxygen are very eager to become united, and we
express the general result of our observations in the
statement that phosphorus and oxygen have a strong
affinity for each other.
The cause of the luminosity of phosphorus when
exposed to the air was not for some time decided.
The obvious suggestion would be that the light arose
from combination with the oxygen of the air. On
the other hand it was stated that phosphorus became
luminous when exposed in an atmosphere upon which
it would exert no chemical action, for instance, hydro-
gen or nitrogen gas. The luminosity in these cases
was, however, found to be due to the presence of
traces of oxygen gas, and it seems at last decided
that these phenomena of phosphorescence are to be
seen only in the presence of oxygen gas. From these
facts we should naturally expect phosphorus to be
more luminous in pure oxygen than in air. But now
comes a curious surprise for our expectations ; in
pure oxygen phosphorus exhibits no luminosity at all.
If the temperature be raised or the gas be rarefied,
the phenomenon of phosphorescence is observed, but
below 20 C., and at atmospheric pressure, phos-
phorus may be preserved for many weeks in this
gas without undergoing the slightest oxidation. If
the oxygen be diluted with an indifferent gas, as
hydrogen, or be rarefied, the luminosity is once more
seen. If a stick of phosphorus be introduced into a
tube filled with oxygen, closed above and connected
THE BEGINNINGS OF SCIENCE, 151
below with a mercury reservoir, by raising or lower-
ing the latter we may alternately increase or lower the
pressure in the tube, and at the same time extinguish
or revive the phosphorescence. Certain gases and
vapours such as sulphuretted hydrogen, ether, turpen-
tine, permanently put out the luminosity.
Kobert Boyle had made some remarks upon these
tendencies of bodies to combination, and held that
combination consists of an approximation, a bringing
close together of the smallest particles of matter.
Previous to this time it was thought that the sub-
stances entering into a compound were annihilated by
the act of combination. Mayow strongly combated
this error. The views advocated by him would lead
us to say that when phosphorus and oxygen combine,
both bodies are still present in the compound, and
could by suitable means be obtained from it. Mayow
supported his argument by a somewhat ambiguous
example ; that of the combination between hydro-
chloric acid and ammonia. For although it may in
a certain way be said that hydrochloric acid and
ammonia exist together in sal-ammoniac, yet it by no
means follows that each of them exists as suck,
Hydrochloric acid consists of hydrogen and chlorine
combined togetber in a certain way ; it is perfectly
true that the hydrogen and the chlorine occur in the
sal-ammoniac but probably not combined in the same
way ; there may, in the sal-ammoniac, be a re-arrange -
nient of the constituents of the gas.
The phenomena of double decomposition were also
1 52 THE BEGINNINGS OF SCIENCE.
studied by Mayow. We may illustrate these by the
action of sulphuric acid upon potassium nitrate (nitre)
from which result nitric acid and potassium sulphate.
In this case the group of elements attached to the
hydrogen of the sulphuric acid exchange this bondage
for a union with the potassium of the nitre, the group
attached to the potassium combining at the same time
with the hydrogen to form nitric acid. In chemical
symbols this is expressed thus :
2 KNO :i -f H 3 S0 4 = K 2 S0 4 + 2 HNO 3 .
Nitre -f- sulphuric potassium -j- nitric acid
acid sulphate.
Mayow's comments upon this reaction correctly express
this exchange, though their explanation of why it
occurs is somewhat erroneous.
Mayow, like the medical chemists of an earlier
school, offers a timely warning to the physicians who
may be ignorant of the mutual affinities and decom-
positions of bodies. He reminds them that the dif-
ferent substances in their prescriptions may act upon
each other with surprising results ; " one substance
may destroy the efficacy of another, and something
perfectly different from the original may result."
Mayow's work was almost wholly forgotten, as was
the fate of so much other work previous to this time.
At the close of the eighteenth century his fame was
revived chiefly through the agency of Drs. Beddoes*
and Yeats. There was indeed then a tendency to
overrate his discoveries in the spirit of those who
* Chemical Experiments, $c., from Mayow. Edited by Beddoes.
Oxford (1790).
THE BEGINNINGS OF SCIENCE. I53
are fond of exclaiming that there is nothing new
under the sun. Beddoes attributed to Mayow the
discovery of, " if not the whole, certainly many of those
splendid truths which adorn the writings of Priestley,
Scheele, Lavoisier, Crawford, Goodwin, and other
philosophers."
Certainly Mayow was remarkably lucid and far-
sighted in some of his expositions, but it must be
allowed that such judgment as that quoted much
overrates his achievements.
Before leaving this period of the science, mention
may be made of Dr. Stephen Hales (1677 -1761),
an ingenious and able experimenter, though one
who was too much engrossed in the details of
his experiments to consider sufficiently their pur-
pose.
He was the grandson of Sir Kobert Hales, and,
after leaving Cambridge, resided till the time of
his death at Teddington. Offered a canonry at
Windsor, he showed unusual wisdom by refusing
it, preferring to continue to devote himself to the
parochial duties and scientific pursuits engaged in
which he felt perfectly content. He published in
1727 his Statical Essays .... also a Specimen
of an Attempt to analyse the Air, ly a great variety
of Chymico- Statical Experiments. Hales made a
number of experiments on the "air" produced by
heating bodies, by fermentation, etc. He collected
his gases in ingeniously-devised apparatus, but think-
ing they were all modifications of common air he
i 5 4 THE BEGINNINGS OF SCIENCE,
appears never to have examined them systematically,
and thus a whole series of discoveries eluded his
grasp. He obtained "air" by distilling wood, and
found it fatal to animals (carbonic acid), from nitre
(oxygen), etc., and he details the amount of air ob-
tained by distilling hogs' blood, tallow, sal-ammoniac,
Indian wheat, peas, mustard seed, amber, tobacco,
sugar, by fermenting sheeps' blood, by the action of
vinegar on oyster shells, &c., but with the mass of
undigested facts so obtained he seemed content. He
found that iron filings and strong sulphuric acid pro-
duced scarcely any air, he observed that on adding
water a gas is abundantly evolved. This gas was
hydrogen, but including all gases as "air" he did not
stop to examine it.
Dr. Hales also made a number of investigations
into the movement of sap in vegetables. In his
experiments, directed to ascertain the force with
which trees imbibe moisture, he obtained some strik-
ing results. Thus, after cutting across the root of a
pear-tree, the section being half an inch diameter, he
cemented this into a tube, twenty-six inches long,
filled with water, and dipping at its lower end into
mercury. So vigorously was the water absorbed that
in six minutes the mercury rose eight inches in the
tube. The experiment was made in August. Eight
inches of mercury would be about equal to 109 inches
or about nine feet of water. Thus the absorption of
the root would be sufficiently powerful to raise or sup-
port a column of water nine feet high.
FIFTH PERIOD.
CHAPTER IX.
FIFTH PERIOD: THE CHILDHOOD OF TRUTH.
CULLEN, BLACK.
,Y those readers acquainted with some of the
chief characteristics of modern science it
will have been observed that up to the
date we have now reached very little
notice had been taken of the quantitative
aspect -of phenomena. Weight Avas not
yet considered an all-important factor in chemical
investigations ; and, indeed, it could not be so until,
at least to some extent, the fact of the indestructibi-
lity of matter was recognised. It is true that in the
directions given by such men as Basil Valentine and
Glauber, for the preparation of various bodies, men-
tion is often made of the quantities of the different
ingredients intended to be mixed together. But
there is no precise attempt to connect the quantity of
the product with the quantities of the substances em-
ployed to produce it, nor to elucidate in this way its
composition,
158 THE CHILDHOOD OF TRUTH.
When we reflect how often a portion at least of
the product of a reaction is gaseous and would there-
fore seem to be destroyed, we shall not wonder
that the value of weight in chemical science was lost
sight of. When a candle burns, all that we are
directly aware of is that light is given out and the
candle slowly disappears ; and what more natural
than to conclude that where there is disappearance
there is destruction ? As a matter of fact we now
know that in this process no particle of the candle
has ceased to exist ; all the matter that composed it
is there, but the candle is no longer there as such.
But so long as chemists could not collect the carbon
dioxide and measure or weigh it, what could they
suggest, but that matter was now and again in the
habit of evanescing, or, so to say, " going to coloured
cob-web " and becoming inappreciable. While these
views prevailed no great depths could be reached by
science ; it was held back, as it were, by the want of
weight.
But we are now entering upon the period when
quantitative chemistry really begins. It is true that
many of the experiments of Dr. Hales included mea-
surement of gases ; but he was not sufficiently aware
of any definite purpose in what he did. It has, in-
deed, been very shrewdly remarked that Hales had
learnt how to question Nature, but not how to cross-
examine her.* The cross-examination was to be con^
ducted, in part, by the well-known chemist, Dr.
* F. H. Butler, Encye. rit. Art. Chemistry.
THE CHILDHOOD OF TRUTH. 159
Black, and it has been continued with increasing
skill and penetration to this day.
Before, however, we proceed to sketch Black's life
and work it is only just that some reference should
be made to his instructor, Dr. Cullen, of Edinburgh.
Dr. Cullen was a man who engaged in remarkably
little original work, and yet such was the charm of
his character, and so wide-spread was the elevating
influence of his enthusiasm, that, after we have got to
know his life, we are almost glad that the brilliance
of original achievement should not be there to distract
us from the calm of his energy and the loving-kind-
ness of his toil. Cullen* was essentially a man who
influenced others. Not striving after his own fame
he was content that others should reap the benefits
of his knowledge, and that to them should pass the
glory of penetrating those problems which his con-
scientious enthusiasm as. a teacher left him no time
to solve. He was an example of the few teachers
who follow closely the mental unfolding of their
pupils, and of the still fewer who aim at influence
upon character as well as upon brain. He was
uniformly attentive to his students, while his cordiality
and warmth of heart took them by storm.
He made himself personally known to all his pupils.
He used to invite them to his house, two, three,
and sometimes four at a time, and he would place
himself on terms of the easiest intimacy with those
* William Cullen, M.D., born at Hamilton in Scotland (1710
1790\
160 THE CHILDHOOD OF TRUTH.
of whose character he formed high opinion. He
would talk with them upon any topic to which they
chose to refer, and by the complete confidence with
which he spoke to them would win from them con-
fession as to all their plans and difficulties in life.
He became their friend, and by the individuality of
his contact with them won a high place in their hearts.
Caring little for the emoluments of office he succeeded
by the most delicate tact in evading payment for his
courses where he thought his students pecuniarily
unable to afford it. In such a case, for instance, he
might invite the student to attend certain lectures, as
he would be glad of his opinion on certain parts of
the course. Or, again, he would press books from
his own library upon them. As persons in such
positions are often peculiarly sensitive he was. here
again obliged to resort to little schemes in order to
make the offer agreeable. He would point out some
particular passage of importance in the book that he
wished the student to borrow, and use his professional
authority to desire him to take the book home at
once and study this passage as a matter of immediate
importance.
By such winning generosity and insight Cullen
acquired a quite exceptional popularity with his
pupils, and as a result a quite exceptional bitter-
ness of jealousy on the part of his colleagues. But
to this jealousy he gave no heed, and went on his way
without appearing to hear the sneers uttered at his
expense. As an instance of his deserved popularity
THE CHILDHOOD OF TRUTH. 161
it may be mentioned that when the professor of
Materia Medica, Dr. Alston, died in 1763, Cullen was
invited to continue his course. Alston had opened
the lectures with ten students. When Cullen con-
sented to continue them one hundred new students
instantly enrolled themselves. That is sufficiently
indicative of the position he had attained.
Among those thus taught by him was one pupil
whose name was to be remembered for many long
years as a true son of science, Dr. Joseph Black. It
was well for Black to have obtained his instruction at
the hands of such a man, for Cullen saw chemistry,
not as a curious and useful art, but as a division of
the vast science of nature.
Dr. Black* had, as a man, about him much of the
charm that attached to Cullen. There is a quiet and
dignified simplicity about his character that clings
round his name to this day. He was so gentle, so
unassuming, and so sincere, that it is reassuring to find
that in this brawling world his voice could yet be
heard above the tumult. Black obtained the chemical
chair at Glasgow. Thomson says of him that he
" constituted the most complete model of a chemical
lecturer that I ever had an opportunity of witnessing."
He was not a mere chemist but a cultivated man.
He had considerable aesthetic taste, as shown in his
love of music and painting. Even a retort or cruci-
ble was to his eye an example of beauty or deformity.
He was also warm-hearted and affectionate, and with
* Joseph Black, 17281799.
L
1 62 THE CHILDHOOD OF TRUTH.
Dr. Hutton he formed an unusually close friendship,
imparting to him every one of his speculations and
receiving the same confidence in return. The two
friends were seldom asunder for two days together.
Black always suffered from delicate health, and
towards the end of his life this became so pronounced
that he had to give up all professional work. He
did not attempt to achieve what his strength would
not allow : " he spun his thread of life to the very
last fibre." Careless of his own fame he did not
torment himself by restlessness or eagerness, but
happily resigned work which he felt himself unable
to fulfil. Thus his life was always tranquil and at
peace. The manner of his death was curiously sudden
and calm. He was sitting alone at table with some
bread, primes, and milk before him. It seems that
he had the cup of milk raised to his lips when, feel-
ing some sensation of approaching weakness, he set
it down on his knees and held it there between his
two hands ; and so, without a single tremor or
struggle, he died. It might almost have been an
experiment designed by him to show how quietly he
could pass away, for the cup was not displaced nor
was a drop of the milk spilt. His servant, coming
in and seeing him sitting still in so easy an attitude,
thought he had dropped into a doze. When the man
had left the room, however, he had some unaccount-
able misgivings and went gently back into the room
once more. Still, however, the pose seemed so easy
and natural that he went out reassured. Coming
THE CHILDHOOD OF TRUTH. 163
back a third time, and finding Dr. Black still seated
in the same posture, he at last went up to waken
him and found him dead.
The two great pieces of work for which Black is
renowned are his investigation of the alkalies and
his discovery of latent heat. The former is con-
tained in his Experiments on Magnesia Alba,* of
which some account must now be given. The reader
may here be reminded of the chemical reactions,
called double decompositions, examined by Mayow.
One of the first experiments that strike us in Black's
paper has an interesting bearing on these reactions.
He distilled together in a retort magnesium car-
bonate, ammonium chloride, and water, and found
some magnesium chloride left behind in the retort.
Magnesium chloride is, of course, made up out of the
metal magnesium and the "negative" element chlorine,
or, as it was then less accurately expressed, it con-
contains a base and acid for its constituents. "When
ammonium hydratef is added to its solution the
ammonium combines with the chlorine to form am-
monium chloride, whilst magnesium hydrate separates
out as a white precipitate. This Black expressed by
saying that " the attraction of the volatile alkali
(ammonia) for acids is stronger than that of mag-
nesia."
But the reaction observed by him in the experi-
*- Edinburgh (1777).
t Ammonium hydrate is tho ordinary ammonia solution expressed
as a derivative of the metallic radical ammonium. The formula for
the hydrate isNH 4 (OH), the NH 4 group being ammonium.
j6 4 THE CHILDHOOD OF TRUTH.
ment first referred to is the very reverse of this. The
ammonia is already combined with the strong hydro-
chloric acid to form, ammonium chloride, yet it gives
up its " negative," or " acid," element which becomes
combined with the magnesium. Thus Black re-
marks : " But it also appears that a gentle heat is
capable of overcoming this superiority of attraction,"
The truth was beginning to appear that the final
arrangement of the elements in a mixture of various
bodies is not simply dependent upon superiority of
attraction ; for under different circumstances totally
different arrangements will result. The view now
generally held is that in a mixed solution all possible
combinations of the negative and positive elements
occur. Thus, suppose we have a mixture in solution
of sodium carbonate and magnesium chloride. Then
the following bodies will all actually at first occur :
sodium carbonate, magnesium chloride, sodium chlo-
ride, and magnesium carbonate. But magnesium
carbonate (the "magnesia alba" of Black) is insoluble,
and hence is precipitated at once. Being thus with-
drawn from solution it is at the same time withdrawn
from the sphere of action of the other ingredients.
Those ingredients now consist of sodium carbonate,
magnesium chloride, and sodium chloride, and there
being one possible combination now absent more mag-
nesium carbonate is at once formed. This again goes
out of solution, and so on until there is left in the
solution sodium chloride, and the precipitate con-
sists of magnesium carbonate. It is not that the
THE CHILDHOOD OF TRUTH. 165
magnesia has a superior attraction for carbonic acid,
but it is simply the fact of the insolubility of the
magnesium carbonate which brings about the re-
action. Other considerations enter into the study of
chemical reactions which we cannot go into now.
Before Black's time it was known that ordinary
lime is quickened by heat. Black experimented with
a view to finding out whether magnesia would form
" a quicklime." An ounce of magnesia alba was
heated for an hour to the melting point of copper.
When it came out of the furnace it had lost seven-
twelfths of its weight. After being thus treated
Black found it would still dissolve in acids to form
salts, but laid stress on the fact that it did so " with-
out any the least degree of effervescence."
The question was, what had happened to the mag-
nesia alba (magnesium carbonate) in this process of
quickening? To elucidate this he distilled magnesia*
in a retort, and, as it was evident from the previous
experiment, that the magnesia lost something while
being quickened, he expected to condense this vola-
tile body in his receiver. To his surprise, however,
all he could condense was a little water (a substance
only present as an impurity in this reaction) the
weight of which was not nearly equivalent to the loss
of weight sustained by the magnesia. Now this use
of weight to assist in unravelling the knots of the
problem is exceedingly important. It might have
* In the course of this passage the terra magnesia is used, as it was
used by Black, to signify magnesia alba.
i66 THE CHILDHOOD OF TRUTH.
been thought that some matter had merely been de-
stroyed in the reaction, but it does not seem to have
occurred to Black to accept such a view of the matter
as rational. His conclusion therefore was that some-
thing had gone off in a non-visible form, and the
question now was what ?
His view was that the volatile matter lost in cal-
cination was mostly air. He next calcined two
drams of magnesia alba, dissolved the resulting
quick magnesia in dilute sulphuric acid and reprecipi-
tated the magnesia alba from this solution by means
of a " mild " alkali. The weight of substance thus
obtained was one dram fifty grains, from which it is
seen that the magnesia had in this process very
nearly recovered its original weight. Obviously part
of the addition must be "air," that is gaseous matter,
for it could be again driven off as " air " by heat.
Furthermore this " air " must have come from the
mild alkali by means of which the magnesia alba
was reproduced.
Further Black's argument is this : Stephen Hales
had already shown that the mild alkalies contain a large
quantity of air which they emit when joined to an
acid. Thus if ordinary washing soda be treated with
hydrochloric acid there is copious effervescence and
evolution of gas. In the case before us, when the
quick magnesia dissolved by acids is reprecipitated as
magnesia alba by alkali, the alkali, Black argues,
really becomes joined to the acid to form a salt, but
without visible emission of air. Yet the air is not
THE CHILDHOOD OF TRUTH. 167
retained by the alkali, for the alkaline salt obtained
is the same in quantity as if pure add and not mag-
nesium salt had been used to obtain it. That is to
say, the weight'of sodium sulphate obtained by adding
one ounce of sodium carbonate to magnesium sulphate
is the same as that resulting from the solution of one
ounce of sodium carbonate in sulphuric acid, no "air"
having attached itself to the sodium sulphate in either
case. What then has become of this air which was
in the mild alkali to start with, and is there no
longer ?
Obviously, concludes Black, forced from the alkali
by the acid this air has lodged itself in the magnesia,
and it is the presence of this air that distinguishes
magnesia alba from quick or calcined magnesia.
In our way of stating it the first is magnesium car-
bonate, the second is magnesium oxide. Carbonic
acid added to the latter produces the former.
The whole course of this inductive reasoning as
pursued by Black is peculiarly thorough and scien-
tific, and in itself would make him well worthy of
the place he has won. He went on to apply these
views to the calcareous earths (such as chalk) and the
mild alkalies in general. They are distinguished from
the calcined earths and the caustic alkalies by the pre-
sence of this air, which the latter tend to reabsorb. *
Previously to his time the causticity of quicklime was
supposed to be occasioned by its combination with
igneous particles.
* That is, in modern language, they are carbonates.
168 THE CHILDHOOD OF TRUTH.
Black collected the gas evolved by treating mag-
nesia alba with acid, and distinguished it from atmo-
spheric and other " airs." In this he was repeating
the discovery made by Van Helmont more than a
century before, but then entirely forgotten. He dis-
tinguished this peculiar body by the name ^i fixed
air.
Black's researches upon these subjects afford a very
instructive example of work conducted in a truly
scientific spirit. Certain phenomena afforded interest-
ing matter for investigation, and Black proceeded by
endeavouring first of all to multiply facts. The
quickening of lime by heat was already known.
Would other analogous bodies, such as magnesia alba,
give similar results ? These were found to occur, and
the next point was to observe accurately and in detail
what took place during the calcination. The observed
facts were loss of weight and loss of power of efferves-
cence with acid. Could these losses be restored ? By
the processes above described he found that they
could, use being made of mild alkali which in the
reaction lost its "air." In regaining its weight and
power of effervescence the magnesia then has taken
up " fixed air/' a definite gas found to be common
to the calcareous earths and the mild alkalies, and
conspicuous by its absence from the calcined earths
and the caustic alkalies. In these steps Black aimed
consistently at the cross-examination of nature. He
did not allow himself to be led astray by any precon-
ceived theory or to be turned aside by any apparent
THE CHILDHOOD OF TRUTH. 169
improbability. This case is only illustrative of the
singularly unbiassed character of Black's mind, for he
was the only chemist of his day who, in the great
phlogiston controversy which will be dealt with in
the next chapter, definitely avowed his conversion to
the Lavoisierian doctrine of combustion.
The other research of Black's, which must be briefly
sketched in order to appreciate the later development
of the science, was his discovery of latent heat.
It may not be out of place to here refer first to
the construction of the ordinary thermometer. It
consists of a glass tube of fine bore, having a bulb at
one end. This bulb and part of the stem is filled
\vith mercury, and before the fine end of the tube is
sealed oft" all air is expelled by boiling the mercury.
When the end is closed the mercury, as its tempera-
ture is lowered, falls in the table. To graduate the
thermometer the bulb is plunged into melting ice
when the mercury becomes stationary at a definite
point, which is then marked by the scratch of a
file on the glass. This " freezing-point " is in the
centigrade scale and 32 in Fahrenheit's scale. The
next operation is to immerse the bulb and stem in
steam at the boiling point of water. The mercury,
of course, rises, and this time another mark is made
where it becomes stationary. Two fixed points are
thus obtained, and all that remains is to divide the
interval into the required number of degrees. On
the centigrade scale the melting point will be and
the boiling point 100. On the Fahrenheit scale the
1 7 o THE CHILDHOOD OF TRUTH.
melting point will be 32 and the boiling point
212.
Now, the ascertainment of these points is only made
possible by the fact that ice while melting and water
while boiling remain at a uniform temperature. If
some pounded ice be placed in a basin and a centi-
grade thermometer immersed therein it will be found
to indicate a temperature of 0. As time passes the
ice gradually melts and a good deal of water collects
in the basin, but the mercury still stands at 0.
Later on only a few pieces of ice are left floating on
the water, but the thermometer still marks the melt-
ing point of ice. Moreover, suppose we apply heat
to the vessel containing it ; the ice melts faster but
it does not grow any warmer ; the temperature is still
zero (32 F.). In the same way if water be boiled in
an open vessel, the more heat is applied the faster
the water boils, but its temperature remains at 100 C.
(212R).
It was these phenomena which led Black to con-
clude that an amount of heat was used up or rendered
latent in converting the ice into water and the water
into steam. Thus, if we start with a vessel full of
hard frozen ice at a temperature below the freezing
point, and apply heat by means of a small flame, the
mercury of a centigrade thermometer immersed in
the ice will gradually rise up to arid then will
come to a standstill. The first quantity of heat
raises the temperature of the ice ; when that has
reached its melting point the whole of the rest of the
THE CHILDHOOD OF TRUTH. 171
heat is used in melting the ice. When the whole of
the ice is melted the water so formed begins to rise
in temperature once more till the boiling point is
reached, when again the mercury becomes stationary.
At this stage all the heat is used in converting the
water into steam. The steam may be superheated to
any desired temperature.
Black determined the latent heat of water to be
7 9 '4 4, and in order to explain how this is done we
must use some very simple mathematics. A certain
weight of ice M at 0, is immersed in a weight of
water m at a temperature t more than sufficient to
melt the ice. As soon as the ice has melted the
final temperature is noted, say 6. In cooling from
t to the water has parted with a quantity of heat,
QII (t 0). If x be the latent heat of ice it absorbs
in liquefying heat M#, but besides this the water
formed from the ice has risen to 6 and has thus
absorbed the heat M0. We have :
= w* (t-9).
from which x t the latent heat of water, is deduced. It
is about 79-2.
The latent heat of steam, arrived at in a very
similar way, is about 538, that is to say, a pound of
water at 100 C. absorbs during vaporisation enough
heat to raise the temperature of 538 Ibs. of water by
1 centigrade.
SIXTH PERIOD.
CHAPTER X.
SIXTH PERIOD : THE CONFLICT WITH ERROR.
THE BIRTH OF ERROR.
is now time to discuss the development
and meaning of a theory which for many
long years was the object of blind idolatry
to the chemists of the time. In pre-
vious pages some examples have been
given of the attempts made to conjecture
(for it was little more than conjecture) the nature of
the fundamental principles of matter. We have seen
how salt, sulphur, and mercury had their turn with
air, earth, water and fire, and how in the advanced
writings of Robert Boyle all dogmatism regarding the
elements was eyed askance. Among subsequent
theories only two need be mentioned. The first was
propounded by a German chemist, Becher (1635
1682), who held that the primary ingredients of
176 THE CONFLICT WITH ERROR.
matter were water and earth, and that from these
were produced three earths the fusible or strong,
the fatty, and the fluid earths improperly called salt,
sulphur, and mercury. The second was the phlogiston
theory of Stahl.
George Ernest Stahl was born at Anspach in 1660,
and studied medicine at Jena.* In 1694 he was
named second professor of medicine to the University
of Halle to which post he was helped by Frederick
Hoffmann. In 1716 he was made physician to the
King of Prussia, and went to Berlin, where he died in
1734. In his medical views Stahl to some extent
followed Van Helmont. "The body as such has
no power to move itself, and it must always be put
in motion by immaterial spirits ; all movement is a
spiritual act." His dissertations, pamphlets, etc.,
number four or five hundred. His theory of the
elements lasted half a century.
Stahl developed the doctrines of Becher and
enumerated four elements, viz : water, acid, earth, and
phlogiston. Metals on heating for the most part
become oxidised, and this calcination was explained
by Becher on the supposition that they consisted of
an earth and something of -which they became
deprived on ignition ; the burning of brimstone
(sulphur) was, in like manner, thought to be its
* Some account of Stahl is given in the Biographic Universette, where
his unbounded arrogance is commented, upon. ' ' La lecture atten-
tive de ses ecrits prouve une grande disposition a la melancolie, un
orgueil sans bornes, et un profond mepris pour tous ceux qui ne
pensaient pas comme lui."
THE CONFLICT WITH ERROR. 177
resolution into an acid and a true sulphur, or that
combustible part which was dispelled by heat. It
was this supposed combustible body to which Stahl
gave the name of phlogiston (cfrXoyiarov, combustible).
The " phlogiston " of Stahl is in many ways analogous
to the souls and spirits assigned to metals and salts
by the alchyrnists, or to what Geber called the
" humidity " and Cardan the " celestial heat " of
metals.
To illustrate this curious theory let us take the
simple case of the burning of a piece of coal. The
question is, what is happening while the coal
burns ? We have seen how Hooke would have
answered this question more than a hundred years
before the overthrow of the Stahlian views. Accord-
ing to him a certain part of the coal unites with a
part of the air and is "made to fly up and down
with it," and moreover the part of the air causing
this action is contained, ''fixed," in saltpetre. This
comes very near to an account of the production of
carbonic acid during combustion, but owing to his
unfortunate analogy between the action of the
"substance inherent and mixed with the air" and
the action of a liquid solvent there was a loophole of
escape. Had his ideas been only a little more
matured the victory of phlogiston might have been
averted. His facts were good, so far as they went,
and he did not allow his creeds to outrun his facts
The Stahlians, on the contrary, took a different
method with the undeniable gaps in the ranks of
M
178 THE CONFLICT WITH ERROR.
their facts. They filled up the vacancies with fictions.
Their fictions were the creations of clever minds
whose facile ingenuity only led them farther astray.
To the problem above propounded viz., what
is happening while coal burns the Stahlian answer
was that the combustion of the coal was due to
the loss of phlogiston which was given up to the
air. The more perfectly combustible a body was the
greater the amount of phlogiston it contained, so that
charcoal and lamp-black, and other reducing agents,
came in time to be regarded as nearly pure phlogiston.
When by carbon a metallic calx was reduced, or a
compound containing sulphur was obtained from fused
sodium sulphate, phlogiston was supposed to be
absorbs 1 from the charcoal. Incombustible bodies
were upposed to have already parted with their
phlogiston. As most combustible bodies were insol-
uble phlogiston itself came to be regarded as a dry and
earthy body, capable of receiving a motion of great
velocity the motus rcrticittaris manifested when
ignition or flame was produced.*
Mayow had stated that the "nitre air" of the
atmosphere caused fermentation and souring of wines,
produced sulphuric acid from sulphur, and effected
the calcination of metals.
As early as 1630, John Key had noticed that
metals grew heavier when calcined, as he thought,
by the absorption of " thickened air," but they
had given no general theory of combustion, nor
* Encyc. Eritannica. ait. "Stahl,"
THE CONFLICT WITH ERROR. 179
explained why some bodies grow lighter on heating.
Boyle, also, had observed the increase in weight of
metals, but attributed it to combination with heat
particles or "igneous corpuscles."* The bearing of
these observations upon the hypothesis of phlogiston
was quickly perceived. If calcination results in the
loss of a material principle, phlogiston, how, at the
same time, can it be accompanied by a gain in weight ?
This was the apparently unanswerable paradox. But
with exquisite ingenuity the Stahlians surmounted
the difficulty and retorted that phlogiston was the
principle of levity or of negative weight. Such slippery
opponents could readily elude one's grasp.
Frederick Hoffmann (1660 1742), who contri-
buted to analytical chemistry in Germany, held with
Stahl that sulphur consisted of acid and phlogiston,
and that combustible bodies contained a principle
describable as phlogiston ; but he thought it possible
that the calces of metals were formed, not by the
subtraction of phlogiston, but by the combination of
the metals with an acid material. Boerhaave, too,
cast doubt on the assumption of the existence of an
earth and a combustible principle in metals. Neu-
mann (16831737), J. H. Pott (16921777),
Marggraf (1709 1782), and Macquer (17181784),
the discoverer of arsenic acid, supported Stahl, and fur
many years his doctrine held its ground against all
opponents.
Let us now examine a few chemical facts 1/y the
* See ante, p. 135.
i8o THE CONFLICT WITH ERROR.
light of the phlogistic hypothesis and see what is the
explanation it affords us.
When lead is heated it undergoes characteristic
changes of colour, becoming first yellow and then red.
What is happening to it ? It is losing more and more
phlogiston. The yellow substance (massicot) is the
partially dephlogisticated calx of lead. When the
metal is wholly deprived of phlogiston it is converted
into the red substance (red lead). But the yellow sub-
stance weighs more than the metal. That is because
the metal has been losing "the principle of levity."
And the red substance weighs more than the yellow
from which it is obtained. That, too, is because
the yellow substance has been losing more of " the
principle of levity."
But here is another fact for the Stahlians to explain.
Some charcoal is mixed with a little massicot and
the mixture heated. A malleable globule of metallic
lead is formed. What has occurred ? The charcoal
has given up phlogiston to the partially phlogisticated
calx, and this, by complete phlogistication has become
converted into metal. So too red lead may be
reduced to the metallic state, only more phlogiston
is needed.
An interesting phenomenon observable in this
experiment if carried on in a closed vessel is the evolu-
tion of a considerable amount of an incombustible
gas. Does not this suggest that the calx has been
losing something during reduction ? So far tho
ingenuity of the Stahlians is fairly successful. But
THE CONFLICT WITH ERROR, 181
next let us ask them, how is it that lamp-black, consist-
ing of very nearly pure phlogiston, weighs anything
at all ? Or at least, why is it not lighter than air ?
Probably they would reply that it does not contain
enough phlogiston for that. There is no need to
dwell on this trifle, so we will next point out an
interesting experiment.
Here is a small porcelain crucible. The cru-
cible on trial does not alter in weight after heating.
A small piece of charcoal is placed in it, and crucible
and charcoal are heated over a Bunsen burner.
The charcoal enters upon a \igorous combustion.
On withdrawing the flame the mass is seen to be
losing its dense black colour, and presently there
is left in the bottom of the crucible only a little
grey ash. The charcoal has been in combustion ; it
has therefore been losing phlogiston ; phlogiston is
the principle of levit} T , therefore obviously the char-
coal, since it contained so large a proportion of this
principle, should now weigh far more than before it was
burnt. Surely that is a correct Stahlian argument.
Now let us weigh the crucible with the ash in it. To
our astonishment it weighs much Jess. This loss is
not due to the crucible, for that, we have already
shown, is unchanged by heat, and if now cleaned and
weighed will be found to have undergone no altera-
tion. The loss, then, is due to the charcoal, and
amounts to considerably more than 90 per cent, of its
weight. How would the Stahlians answer that ?
But it would be very easy to puzzle the Stahlians
1 82 THE CONFLICT WITH ERROR.
with an examination of this kind, and perhaps it
would be hardly fair to make use of our increased
knowledge to do so.
The ideas of Scheele upon this subject illustrate
the confusion of mind produced by these doctrines.
He found that when air was phlogisticated by com-
bustion the residual gas (nitrogen) occupied less bulk.
Thinking it to be a compound of phlogiston with air
he expected it to be heavier than common air. To
his surprise he found it to be actually lighter. He
concluded that one constituent of the air remained
while another, united to phlogiston in some way,
disappeared. In his endeavours to find out what
had become of it, he finally came to the conclusion
that the compound of air with phlogiston was heat or
fire, which escaped through the glass. With these
views present to his mind he heated nitre in a retort
over a charcoal fire with sulphuric acid. In addition
to a fuming acid he obtained a colourless air (oxygen).
His explanation was that the charcoal in burning
united with fire-air (oxygen) to form heat. This heat
passed into the retort and was there decomposed,
giving rise to red nitrous fumes and pure fire air.*
When Priestley discovered oxygen gas he tried to
suit it to the phlogiston hypothesis. It supported
combustion more readily than common air, that is
it could take up more phlogiston. Thus in his
opinion it contained less phlogiston than common
air. It was therefore termed dephlogisticated air.
* Roscoe and Schorlemmer, Treatise, Hist. Introduction.
THE CONFLICT WITH ERROR. 183
Nitrogen, not supporting combustion, was on the
other hand termed phlogisticated air. It was already
saturated with phlogiston and could not take up more.
Hydrogen was looked upon as either pure phlogiston
or phlogisticated water.
When we see such a man as Scheele drawn into
fanciful assertions of the kind described above we can
the better estimate the havoc played by the hypothesis
of Stahl in the minds of his followers.
But it is inexpressibly strange to find such men as
Priestley and Cavendish, the one clinging to this idea
as though it were the soul of science, and the other
unwilling to recognise its absurdity. That they might
have been blinded to the meaning of their own dis-
coveries we can to some extent understand, but that
when this meaning was pointed out they should still
have refused to see it, would be incredible were not
the facts so certain. Priestley insisted that the effect
of combustion was to load dephlogisticated air (oxygen)
with the combustible principle phlogiston, in spite of
Lavoisier's proof that the only product of the reaction
was the incombustible gas fixed air. Cavendish, more
unaccountably still, in spite of his own accurate ex-
periments, regarded it as most probable that inflam-
mable air (hydrogen) was "phlogisticated water."
Harmful, however, as we cannot but think that the
Stahlian hypothesis was, we must recognise that it
contained in it at least an element of truth. The
supposed loss of phlogiston was really a loss of poten-
tial energy. The attraction of oxygen for another
i8 4
THE CONFLICT WITH ERROR.
element, so long as they are not combined, is capable
of being converted into a certain amount of work or
heat. Once the combination takes place the heat is
evolved and the capacity for work is destroyed. The
acting forces have been brought to a state of equi-
librium. The potential energy is lost.
CHAPTER XL
SIXTH PERIOD : THE CONFLICT WITH ERROR.
THE FIRST OF AUGUST, 1774.
ITH this apparatus, after a variety of other
experiments, an account of which will be
found in its proper place, on the 1st of
August, 1774, I endeavoured to extract
air from mercurius calcinatus pev se * ;
and I presently found that by means of
this lens, air was expelled from it very readily.
Having got about three or four times as much as the
bulk of my materials I admitted water to it and found
it was not imbibed by it". But what surprised me more
than I can well express, was that a candle burned in
this air with a remarkably vigorous flame, very much
* I,e. mercuric oxide (HgO) obtained by heating- mercury in presence
186 THE CONFLICT WITH ERROR.
like that enlarged flame with which a candle burns
in nitrous air, exposed to iron or liver of sulphur ;
.... I was utterly at a loss to account for it."
In these words Priestley announces his discovery of
oxygen gas. It may be said without qualification
that here was the most important chemical fact
discovered up to that time.
The rare cheerfulness which characterized Priestley's
temperament had very serious difficulties to contend
with in his early days. His father, Joseph Priestley,
was a cloth-dresser by trade, living in Birstall, near
Leeds. His son Joseph, the subject of this chapter,
was born in 1733. As a boy, Priestley was of a
weakly and consumptive habit, and his early educa-
tion was, in consequence, somewhat desultory. His
mother died early, and the strict Calvinism in which
he was brought up by his aunt, Mrs. Keighley, of
whom he speaks with much affection, threw an occa-
sional deep gloom over his boyish life. " I felt occa-
sionally such distress of mind as it is not in my power
to describe, and which I still look back upon with
horror." It must indeed have been a deep mental
distress to be so vividly recalled in after life. His
continued ill-health interfered for some time with
his purpose of entering the ministry. But so inclined
was Priestley to look at the bright side of all things
that of these drawbacks he wrote : " I even think it
an advantage to me, and I am truly thankful for it,
that my health received the check that it did when I
was young ; since a muscular habit from high health
THE CONFLICT WITH ERROR. 187
and strong spirits are not, I think, in general,
accompanied with that sensibility of mind which is
both favourable to piety and to speculative pursuits."
Eventually he went to the Dissenting Academy at
Daventry and studied under Dr. Doddridge.
Priestley's first charge on leaving Daventry was
Needham Market, in Surrey. He had a marked
defect in his speech, and his stuttering manner not
suiting his congregation they left him almost penni-
less. After resorting to many unsuccessful experi-
ments for the purpose of earning his bread and cheese
he was finally obliged to leave. Years after he came
down to preach at the same chapel when better
known. His delivery was much the same and the
same congregation attended the chapel; but this time
they flocked to hear him, and pretended to admire
the utterance they had formerly despised. After
other vicissitudes Priestley went, in 1761, to War-
rington as " tutor in the languages " to a dissenting
academy. Here he taught Latin, Greek, Hebrew,
French, and Italian, and lectured on Logic, on Elocu-
tion, on the Theory of Language and Universal
Grammar, on Oratory and Criticism, on History and
General Policy, on Civil Law, and on Anatomy.*
Here also he found time to marry a daughter of
Mr. Isaac Wilkinson, an ironmaster near Wrexham,
in Wales. At Warrington, too, he got to know
* For a view of Priestley's versatility see the catalogue of his books
published in 1794. An interesting lecture on Piiestley was delivered
at Manchester by Professor Thorpe, Science Lectures (Series 6).
i88 THE CONFLICT WITH ERROR.
Benjamin Franklin, but for whose influence most of
Priestley's scientific work might have been left un-
done. It was about this time that he gave some
attention to the study of Electricity and, in spite of
all his other business, brought out a history of the
subject, which was very favourably received. At the
Academy he and the tutors lived together in unusual
harmony. " \Ye drank tea together every Saturday, and
our conversation was equally instructive and pleasing."
In 1767 Priestley removed to Leeds. " At Leeds I
continued six. years very happy, with a liberal, friendly,
and harmonious congregation." Here he made ex-
periments on impregnating water with " fixed air "
to prevent scurvy, and was to have accompanied an
expedition, then sailing, as chaplain, but that his
heretical tendencies were discovered in time. But
the event at Leeds, of which he speaks with most
warmth, is his meeting Thomas Lindsay, then of
Catterick. " A correspondence and intimacy com-
menced, which has been the source of more real satis-
faction to me than any other circumstance in my
whole life."* His theological writings were never
published without Lindsay's advice and approval.
With Lindsay he kept up a very frequent and con-
stant correspondence, while with other friends he
corresponded very freely, though, as he remarks in a
letter to Lindsay, his literary labours often obliged
him to write till he could hardly hold the pen.
* In a much later letter to the same he says, " If I have been any
use in the world you are the cause of it,"
STATUE OF PSIE3TLEY, AT BIRMINGHAM.
THE CONFLICT WITH ERROR. 191
From Leeds Priestley went into the family of the
Earl of Shelburne, afterwards Marquis of Lansdowne,
who had his country seat at Bowood, in Wiltshire.
His office was nominally that of librarian, for which
he received a house and 250 a year, with a certain
annuity for life. He had little employment, he says,
attaching to his post, and was thus free to prosecute
his own inquiries. When he went to his lordship he
had materials for his volume, Experiments and
Observations on different Kinds of Air, which he soon
afterwards published.
In his winter residence in London, while with
Shelburne, he saw much of Lindsay and of Franklin.
This was just before the American war; and their con-
versation was chiefly of a political nature. Franklin
was very pacifically inclined. He thought that if
war broke out it would last ten years, and was sure
that America would be finally victorious. As a fact
the war lasted eight years, and she was victorious. In
March, 1775, Franklin left England ; his last day in
the country he and Priestley spent together alone.
They read some accounts of the reception of the
Boston Port Bill in America, " and as he read the
addresses to the inhabitants of Boston from the places
in the neighbourhood the tears trickled iloun his
cheeks."
With Shelburne Priestley continued for seven
years, when a coolness sprang up between them, which ;
however, at a later date passed away. He was not
very greatly pleased with this mode of life, and does
-i 9 3 THE CONFLICT WITH ERROR.
not seem to have envied persons in high station.
He believed much more happiness was to he found
in the life of the middle classes. But he adds that
wealth may be of immense value when in the hands
of a good man, and that when a person is born to
affluence and not hurt by it, "it produces a godlike
character unattainable otherwise." After leaving Lord
Shelburne he settled in Birmingham. Here, on 14th
of July, 1791, riots in favour of " Church and King "
broke out in consequence of a meeting to celebrate
the anniversary of the French Eevolution. Priestley's
opinions being considered heretical and violent, the
mob marched upon his house, where he was unsus-
pectingly sitting with his wife and family. Friends
hastened to warn him ; at first their news seemed to
him incredible, but finally he consented to regard his
own safety and left the house. He retired to Mr.
Hawkes's in the neighbourhood, and from there saw
his house, with library, manuscripts, and philosophical
instruments, burnt to the ground. At this destruc-
tion of his property and labour he looked on with
perfect calm, and afterwards fled in disguise to
Worcester and thence to London. " Persons in the
habit of gentlemen" were found secreting his papers
with a view to discover incriminating details.* He
was appointed successor to his friend Dr. Price at
the dissenting meeting in Hackney, but still suspicion
pursued him. His political opinions gave offence to
* Curry, Life of Joseph Priestley, a pamphlet. Birmingham
(1804).
THE CONFLICT WITH ERROR. 1 93
men in power, and he was finally obliged to quit the
country.
.-.; He embarked in 1794, a victim to popular igno-
rance and ingratitude. Before leaving Priestley placed
on record the following remarkable words : "I can-
not refrain from repeating again that I leave my
native country with real regret, never expecting to
find anywhere else society so suited to my disposition
and habit, such friends as I have here (whose attach-
ment has been more than an even balance to all the
abuse I have met with from others), and especially
to replace one particular Christian friend, in whose
absence I shall, for some time at least, find all the
world a blank I can, however, truly say that
I leave without resentment or ill-will. On the con-
trary, I sincerely wish my countrymen all happiness,
and when the time for the reflection (which my
absence may accelerate) shall come, they will, I am
confident, do me more justice." It is hardly possible
to do justice after a victim's death, but, so far as
slow growth of somewhat wider views is equivalent
to repentance for past narrowness, to that extent
justice has tardily been done to Priestley, among
others whose heroism was then considered no mitiga-
tion of their heresy. Heresy, not merely in religion
but in political views and in social life, has ever been
to the ordinary man the one unpardonable sin.
Priestley settled near his sons on the Susquehanna,
and there died. His end was very calm. His mind
was perfectly clear and tranquil. He dictated some
N
194 THE CONFLICT WITH ERROR.
last words, and then had the manuscript read to him.
After making some needful corrections he said quietly,
" That is right ; I have done," and after a few hours
he passed away.
He had reason, he said, to be thankful for a happy
temperament of body and mind, and certainly a more
cheerful mortal it is difficult to conceive of. His
constitution had been far from robust, but with ex-
quisite felicity he remarks, " excellently adapted to
that studious life which has fallen to my lot." He
always slept well, and, when fatigued, could sit down
and sleep ; " and whatever cause of anxiety I have had,
I have almost always lost sight of it when I have got
to bed, and I have generally fallen asleep as soon as I
have been warm." His spirits after momentary depres-
sion always recovered their level, and, indeed, he had
found that after trouble they would rise beyond their
former height without any change in the circum-
stances.
He spoke of having a very failing memory which
made his old writings, when re-read, seem perfectly
new to him. One instance is mentioned by him
in his autobiographical sketch, where his loss of
memory went so far that he had serious fears of his
mental powers totally failing. * In writing a prefatory
dissertation to one of his books he had occasion to
refer to some point (he forgets what) connected with
the Jewish passover. He had to consult and com-
pare several writers, and he digested the results in a
few paragraphs. For a fortnight his attention was
THE CONFLICT WITH ERROR. 195
drawn to other things, and at the end of this time it
suddenly occurred to him that he had still to examine
the point of the Jewish passover. Without any
recollection that he had already done the work he
proceeded to consult the same authorities, and to
write out the opinions thus arrived at. He would
never have remembered the former paper but that he
accidentally discovered the manuscript, " which," says
he, " I viewed with a degree of terror." Yet even
this defect of memory he thought was, on the whole,
probably a boon, being very likely compensated by
greater inventive power.*
Priestley's manner of work was quiet and methodical.
He could do nothing if hurried, but could work
quickly if he felt that he had ample time. He wrote
in the presence of wife and children, occasionally
speaking to them ; but could not write during read-
ing aloud or uninterrupted conversation.
Certainly few characters afford us more varied
and interesting material for study. Essentially, and
from first to last, Priestley was a brilliant man, a
man of splendid talents, wonderfully acute, and quick
in perception, inventive and industrious. But his
work was not that of a genius, it had hardly its ease
or its accuracy. His versatility was amazing, but it
was more the outcome of patience than of power, and
to some extent he lacked the expansive capacity of
a really great mind. In the latter part of his life, at
least, he found it difficult to accommodate himself to
* $. T. Butt, Priestley's Life and Correspondence (1831).
196 THE CONFLICT WITH ERROR.
new ideas, and although his own discoveries were in
themselves ruinous to the phlogistic theory yet he
never could be got to see it. His last publication
was The Theory of Phlogiston Established. We
may say then that Priestley was a man of exceptional
acuteness and versatility who made full use of his
powers.
Such an estimate will fairly account for the work
accomplished by his life. It is not necessary to say
that he was a genius. Indeed, remarkably few
scientific men would be worthy of such a title. The
career has not as yet attracted many representa-
tives of the highest order of mind. At the same time
it will not do to lay too much stress upon Priest-
ley's blunders over the phlogistic theory. We must
bear in mind the great ascendency it had obtained
over the minds of all chemists, and we must remem-
ber that only in rare cases is the scientific mind free
from bias. Priestley's in this case was certainly not.
The honour of acknowledging conversion belongs to
Dr. Black, as we have already remarked. But the
honour of a brilliant and eminently useful career, a
life full of wide sympathies and noble unselfishness,
a fame unsullied by jealousy or ambition, and a heart
cheerfully hopeful through all misfortune belong to
Joseph Priestley, whom the English people drove
from their shores as their only tribute to his zeal.
The phlogiston theory is rather fully exemplified
in some of the work undertaken by Priestley. When
he found that a candle confined in a close vessel ig
igS THE CONFLICT WITH ERROR.
after a while extinguished, he concluded that this
was due to the limited amount of air becoming satu-
rated with phlogiston. The candle burned while it
could give off phlogiston, but the impulse to this
evolution of phlogiston was to be found in the capacity
the atmosphere had for combining with or absorbing
phlogiston. As soon as this capacity was exhausted
and the air could take up no more phlogiston the
burning of the candle ceased.
Priestley experimented upon the action of hydrogen
(rediscovered by his contemporary, Cavendish) on
metallic calxes (oxides) heated by a burning-glass.
The method was to heat the oxides in a cylinder of
hydrogen inverted over water or mercury. In this
way it was found that the hydrogen was absorbed and
the calx converted into metal. We now know that
what occurs in such a case is simply that the hydro-
gen abstracts the oxygen from the metallic oxide or
"calx," combines with this oxygen to form water,
and leaves the metal in a free state reduced from its
oxide. Now Priestley observed that a small quantity
of water was formed in these experiments, but he was
bent upon explaining all things by means of phlogis-
ton. He therefore neglected this item in the account
and concluded that phlogiston was the same thing as
inflammable air and existed in a combined state in
metals ; just as fixed air was contained in chalk and
other calcareous substances, both being equally ca-
pable of being expelled again in the form of air.
Priestley seems to have been the first to substitute
THE CONFLICT WITH ERROR. 199
mercury for water in the pneumatic trough, and thus
succeeded in obtaining gases, the collection of which
had baffled the endeavours of previous experimenters.
Cavendish had tried to get " inflammable air " from
a mixture of copper and " spirits of salt" (hydrochloric
acid). He obtained an air that "lost its elasticity,"
that is, was absorbed on contact with water. Priestley
was " exceedingly desirous " of becoming further ac-
quainted with this gas. He therefore began the experi-
ment, replacing the water by quicksilver, as, he says, he
never failed to do where he suspected that a gas would
be in any way affected by water. He in this way
collected a gas which, he went on to show, was
derived entirely from the acid, and might be equally
well obtained by merely boiling common "spirit of
salt " per sc. In short Priestley obtained the true
hydrochloric acid, which is a gas and had not before
been isolated. Ordinary aqueous hydrochloric acid is
merely a solution of this gas in water.*
This method of using quicksilver was of great
service to Priestley ; for by means of it too he showed
that ordinary " spirits of hartshorn," or spirit its
volatilis salts ammoniaci, is a solution of ammonia gas
in water. Stephen Hales, in 1727, had heated lime
with sal-ammoniac in a vessel closed by water, and he
observed that no air was given out, but that, on the
contrary, water was drawn into the apparatus.
Using a mercury trough Priestley, by this same old
method, obtained ammonia gas and showed that the
* Observations on different Kinds of Air, 1772.
200 THE CONFLICT WITH ERROR.
ordinary aqueous ammonia, or " volatile spirit of sal-
ammoniac/' is a solution of this gas in water.*
(1774.)
Priestley followed up these discoveries by endeavour-
ing to obtain an "air" from oil of vitriol (sulphuric
acid). He heated the acid for a long period without
any result beyond the production of some white
fumes which condensed in the upper part of his flask.
The tube leading from the flask of course dipped
under mercury. The end of this experiment is worth
giving in his own words. " Despairing to get any air
from the longer application of my candles I with-
drew them ; but before I could disengage the phial
from the vessel of quicksilver a little of it passed
through the tube into the hot acid ;t when, instantly
it was all filled with dense white fumes, a prodigious
quantity of air was generated, the tube through
which it was transmitted was broken into many
pieces (I suppose by the heat that was suddenly
produced), and part of the hot acid being spilled
upon my hand, burned it terribly, so that the effect
of it is visible to this day. The inside of the phial
was coated with a white substance, and the smell
that issued from it was extremely suffocating." In
this way Priestley found out (1775) how to prepare
pure sulphur dioxide. Stahl had shown that the
fumes of burning sulphur are altogether different
from sulphuric acid and are only partially on the
* Observations on different Kinds of Air, 1772.
f Being sucked up by the condensation,
THE CONFLICT WITH ERROR. 201
way to it, but it was Priestley who first isolated tho
gas.
The next passage is characteristic both of Priestley's
good spirits and of his obstinacy : " This accident
taught me what I am surprised I should not have
suspected before, viz. : that some metals will part
with their phlogiston to hot oil of vitriol and thereby
convert it into a permanent elastic air, producing the
very same effect with oil, charcoal, or any other
substance." The reaction may be most simply stated
as follows : taking copper, which is the metal
usually employed, in place of mercury. First, the
sulphuric acid is a compound of hydrogen, sulphur,
and oxygen hydrogen sulphate. The copper dis-
places the hydrogen of the acid, forming copper-
sulphate and free hydrogen. This hydrogen is of
course liberated in the presence of another portion of
sulphuric acid which we may for convenience repre-
sent as composed of water and sulphur trioxide.
The free hydrogen takes away a third of the oxygen
from the trioxide, forming more water and sulphur
dioxide, which is evolved as a gas.* Priestley was
successful in producing this gas with copper, mercury,
silver, iron, and sulphuric acid, the reaction being
similar in the different cases. When carbon is used
* After reading the discussion of chemical symbols the reader may
be able to appreciate this reaction when expressed in the more
mathematical form of chemical equations :
(i.) Cu -f H-SO Cu SO 4 + H 2 .
(ii.) H 2 SO 3 -f H 2 = 2H 2 + SO 2 ,
202 THE CONFLICT WITH ERROR.
carbon dioxide (the fixed air of Priestley and Black)
is evolved. * Sulphur itself may be heated with
sulphuric acid, the products in this case being only
sulphur dioxide and water, j- Priestley found that
gold and sulphuric acid gave no result.
Sulphur dioxide is a colourless gas of suffocating
odour like that of burning sulphur, and during this
combustion it is formed. It will not support the
combustion of a candle any more than will carbon
dioxide. It combines with metallic oxides to form
the salts termed sulphites. The moist gas bleaches
vegetable colouring matter, such as litmus. The gas
is readily soluble in water and its solution is known
as sulphurous acid. The dry gas may be condensed
to a liquid by being passed through a spiral tube
surrounded by a freezing mixture.
Lastly we come to Priestley's supreme discovery,
that of oxygen, or, as he termed it, dephlogisttcated
air. To some extent we may attribute such a dis-
covery to chance ; but chance as a rule will only assist
men of rare intelligence and insight. Opportunities
for good work of one kind or another occur con-
tinually to all, but the large majority of us are too
blind to see them. Most good work is too near us
for us to think it worth doing. All honour to those
who have lent us their spectacles and shown us how
easy their discoveries were!
Priestley was by no means definitely in search of
* C + 2 H 2 SO 2 H 2 -{- CO 3 -f 2 SO 2 .
f S -f 2 H 2 S0 4 = 3 SO 2 -}- 2 H 2 0.
THE CONFLICT WITH ERROR. 203
oxygen when he found it. The conditions of scien-
tific work then did not admit of such an attitude.
Chemistry was not far enough on her uphill path to
see the tracts of country crossed by her future
advance. We can predict now what compounds and
even what elements ought to occur in nature and can
often tell how to search for them. If we do not
always find them that is because either we or nature
are not what we ought to be. In Priestley's time
prediction in science, to have any chance of fulfilment,
must be as vague as utterances of the Delphic sibyl.
In most cases the only course was to " prospect
around " and see what turned up. After showing,
as he did by experiments with a candle similar to
those employed by Mayow, that air would support
only a limited amount of combustion, Priestley went
on to prove that it could be renovated and made fit
once more for respiration by the action of growing
plants. Thus on the 17th of August, 1771, he first
burned out a wax candle in a confined portion of air
and then introduced into it a sprig of mint. On the
27th of the same month he found that another
candle burned perfectly well in it. The mint had
restored to the air its original virtues. To make
assurance doubly sure he divided the used-up air
into two parts. One he left standing alone over
water ; into the other he put the sprig of mint.
After some days had elapsed he always found that a
candle would burn in the latter but not in the
former.
204 THE CONFLICT WITH ERROR.
The true explanation of these phenomena is that
the carbon dioxide formed by the combustion is
absorbed by the plant and, in the presence of chloro-
phyll and sunlight, split up into carbon and oxygen,
the plant retaining the carbon and giving the oxygen
back to the air. Priestley did not recognise the full
bearing of his discovery on the composition of the
atmosphere. In 1772, however, Dr. Rutherford,
Professor of Botany in the University of Edinburgh,
showed definitely that common or atmospheric air
contains a gas differing from fixed air, and yet, like it,
incapable of supporting combustion. This he showed
by treating air in which animals had breathed with
caustic potash. The potash in this case absorbed the
fixed air (forming the mild alkali or carbonate), yet
when this absorption was complete a residual gas
still remained and in this a candle would not burn.
It was nitrogen gas.
In the same year Priestley found that combustion
in a bell-glass over water gave rise to fixed air absorb-
able by milk of lime. The residual (phlogiscated)
air, he found, would not support combustion, but he
did not then consider it as a constituent of the at-
mosphere.* He showed that " nitrous gas " (nitrogen
dioxide) when mixed with " phlogisticated air"
* At the time of the 1790 edition of his Experiments and Observation,
Priestley seems to have been rather doubtful as to the correct way of
regarding the composition of the air. He was inclined to reg-ard air
as a simple gas in a certain state of phlogistication, but the same
nomenclature, he says, will suffice if it be regarded as composed of
two distinct gases.
TffE CONFLICT WITH ERROR. $05
(nitrogen), occasioned no diminution in volume. If
mixed with dephlogisticated air (oxygen), on the other
hand, in due proportion, the whole of the resultant
mixture was absorbed over water. This, indeed,
was the method used by Priestley for the analysis of
air, or of ascertaining what was termed the good-
ness of atmospheric air. The results of these analyses
varied, and thus suggested the notion that the com-
position of the air varied, but this idea was exploded
by Cavendish.
Interested as he became in his researches on gas-
eous bodies in general, Priestley proceeded somewhat
as Hales had done before him, but with much more
alertness of observation, to investigate the air obtain-
able from different bodies. In the course of these
labours mercuriits cakinatus per se, or mercuric oxide
(red precipitate), was one of the bodies experimented
on. From the important paper on this subject we
may quote his own words : " For my own part I will
frankly acknowledge that, at the commencement of
the experiments recited in this section I was so far
from having formed any hypothesis that led to the
discoveries I made in pursuing them, that they would
have appeared very improbable to me had I been
told of them ; and when the decisive facts did at
length obtrude themselves upon my notice it was
very slowly, and with great hesitation, that I yielded
to the evidence of my senses. And yet, when I con-
sider the matter, and compare my last discoveries
relating to the constitution of the atmosphere with
206 THE CONFLICT WITH ERROR,
the first, I see the closest and easiest connection in
the world between them, so as to wonder that I
should not have been immediately led from the one to
the other. That this was not the case I attribute to
the force of prejudice, which, unknown to ourselves,
biases, not only our judgments, properly so-called,
but even the perceptions of our senses : for we may
take a maxim so strongly for granted that the plain-
est evidence of sense will not entirely change, and
often hardly modify, our persuasions ; and the more
ingenious a man is the more effectually he is en-
tangled in his errors ; his ingenuity only helping
him to deceive himself by evading the force of
truth."
How pointedly these latter remarks applied to
Priestley himself it is scarcely necessary to say.
Having discovered the supporter of combustion in
oxygen gas, having seen its relation to combustion very
fully discussed by others, how could he, except at the
impulse of bias, continue fixed in his belief that com-
bustion essentially means loss of phlogiston. He was
aware that metals gained in weight by calcination,
but still held to the idea that this gain was consis-
tent with the loss of a constituent element. Lavoisier
showed him that the only product resulting from
combustion in dephlogisticated air was fixed air,
but still Priestley held that the result of combus-
tion was to load the air with phlogiston. And so,
whatever difficulties and inconsistencies grew out of
the Stahlian hypothesis, Priestley defended it, im-
THE CONFLICT WITH ERROR, 207
pervious to sense and reason. Yet the grim tyranny
of a false idea is ever in the end overcome. " No-
thing," said the old chemist, Glauber, " can extin-
quish truth it may be prest, but cannot be overcome ;
like the sun's light it may be hidden, but not extin-
guished ; " and when we see the distorting power of
bias we need his faith to believe in the final van-
quishing of error.
In the pursuit of his inquiries Priestley ( ' proceeded
to examine by the help of a burning-glass what kind
of air a great variety of substances, natural and facti-
tious, would yield, putting them in vessels filled
with quicksilver and kept inverted in a basin of the
same
" With this apparatus, .... on the 1st of August,
I endeavoured to extract air from mercurius calci-
natus per se : and I presently found that, by means of
this lens, air was expelled from it very readily."
With true caution Priestley suspected that this result
might be due to some peculiarity or impurity in his
individual specimen of mercuric oxide. But other
specimens obtained by him gave precisely similar
results. He proceeded to test this gas with " nitrous
air" (nitrogen dioxide), and, to his astonishment,
found that it was better than common air, that is to
say, the product was more completely absorbed by
water. Now the nitrous air test is, according to
Priestley's ideas, the fitness of air for respiration,
and he naturally next experimented directly upon the
respirability of the new gas, Placing a mouse in a
208 THE CONFLICT WITH ERROR.
jar of the dephlogisticated air he found that it would
live for an hour. In the same bulk of atmospheric
air it lived only a fourth of the time. L.^
breathed it himself. " The feeling of it to my lungs
was not sensibly different from that of common air ;
THE CONFLICT WITH ERROR. 209
but I fancied that my heart felt peculiarly light and
easy for some time afterwards. Who can tell but that
in time this pure air may become a fashionable article
of luxury ? Hitherto, only two mice and myself have
had the privilege of breathing it."*
The conclusion deducible from the experiments
related in the paper from which several extracts
COMBUSTION OF PHOSPHORUS IN OXYGEN.
above are made is, that the atmosphere is, on an
average, made up of four volumes of phlogisticated
air (nitrogen) to one volume of this new gas, de-
phlogisticated air, or, as Lavoisier termed it, oxygen,
Priestley, however, did not directly assert these con-
clusions himself, though we may so interpret his
experiments. The analyses made by him and others of
air gave somewhat varying results, and it was thought
* Experiments and Observations on different Kinds of Air. London
(1774-75), 2 vols. Another edition in 3 vols. was published at Bir-
mingham in 1790.
O
210 THE CONFLICT WITH ERROR.
that the proportion of the two chief constituent gases
was actually different at different places and seasons.
It was left to Cavendish to show that this was not
the case, but that the proportion of these consti-
tuents was, on the other hand, remarkably constant.
We have glanced rapidly at the more striking of
Priestley's discoveries, and we can readily see that
they were interesting and important. He had an
admirable knack of finding out new things ; but he
hardly ever followed up sufficiently the discoveries he
had made. Others had to show the bearing of his
work upon the general theory of chemistry and to
draw from his experiments conclusions he would
not stop to deduce. Happily there was at least
one man then living fit for the task, pre-eminent in
the power of combining scattered ideas into an
orderly whole, a man in intellectual power and grip
surpassing any chemist before his time. That man
was the great French chemist, Lavoisier. Before pro-
ceeding to the discussion of his work we must say
something about the accurate and acute English
worker, Cavendish. Next we shall pass on to Lavoi-
sier, and with him the dawn of modern chemistry
begins.
CHAPTER XII
SIXTH PERIOD : THE CONFLICT WITH ERROR.
TRUTH IN DISGUISE.
FTER Priestley's work the material, at least,
for the solution of great chemical problems
was at hand. The solution of one of the
principal of these was afforded by Caven-
dish, whose other work also threw much
light upon the path of chemical progress,
though his eyes were too blinded by the dust of the
phlogiston theory to fully discern what lay before
him.
As a man Cavendish was certainly one of the most
extraordinary of the chemists with whom we have
had to deal. In fact, in no real or full significance
of the word, was Cavendish a man at all. He was a
well-arranged intellectual machine, a thing without
enthusiasm, sympathy, or happiness. The questions
212 THE CONFLICT WITH ERROR.
coming before him were apparently answered with
absence of emotion as complete as that of the logical
machine invented by Professor Jevons when it draws
conclusions from data which are given it. To irse
this machine a key is pressed for each term of the
propositions forming the data from which conclusions
are to be drawn. The proper series of keys having
been pressed the correct deductions from those data
are at once presented to view. This is apparently
representative of the action of Cavendish's mind.
Various facts struck different keys in his mind, and
in consequence of its internal mechanical construction
these facts were at once sorted out and arranged so
as to make evident the conclusions derivable from
them. He was more wonderful than the machine, in
that he was able to vary the relations of external
facts ; he was less wonderful than it, in that his
conclusions were not wholly accurate. Mechanical
as he was, he was not free from bias.
Cavendish's family traces back its origin to Sir
John Cavendish, Lord Chief Justice of the King's
Bench in the reign of Edward III., while other
genealogists have carried it back to Robert de Gernon,
a famous Norman who assisted William the Conqueror
in his invasion. The Honourable Henry Cavendish,
son of Lord Charles Cavendish, -was born at Nice, on
the 10th of October, 1731. His mother died when he
was about two years old, and of his early years
nothing is known. In 1749 he went to Cambridge
and remained there till 1753) but did not graduate.
THE CONFLICT WITH ERROR. 213
For the next ten years his history is a blank. His
intellect was gathering strength. His first contribu-
tion to the Koyal Society was made in 1766, On
Factitious Airs. Cavendish had training in many
sciences, electricity, geology, chemistry and mathe-
matics. His chief work was purely chemical. He
was not at all eager to publish his researches. Two
lengthy investigations, Experiments on Arsenic
and Experiments on Heat, were written before
1766 and discovered for the first time after his
death. They were apparently written out for some
friend whose name never transpired, and the reason
of their remaining unpublished Avas never known.
His Experiments on Air were published in the
Philosophical Transactions for 1784.
His father, Lord Charles Cavendish, allowed his
son 500 a year during his lifetime, and it was
argued, but with not much appearance of truth, that
the smallness of this allowance led Cavendish into
the too economical habits afterwards characteristic of
him. Cuvier states that Cavendish was left a very
large fortune by his uncle about the year 1773. At
his father's death, in 1783, he also had a fortune
left him. The details as to how he came by his
wealth are somewhat contradictory, but however that
may be, he died in 1810, leaving 700,000 in the
funds and a landed estate producing an income of
6,000 a year. None of this great wealth went to
the help of science.
Cavendish's London residence was close to the
2i4 THE CONFLICT WITH ERROR,
British Museum, at the corner of Montague Place
and Gower Street. Those who passed its portals
reported that books and apparatus were its chief
furniture. Latterly he had a separate house for
books in Dean Street, Soho. It is one of the few
indications that he might have been capable of
interest in human affairs that he allowed books from
this library to be lent to scientific men on recom-
mendation. It is characteristic also of the extremes
to which he carried his methodical habits that when
he thus took a book from his own library he entered
his name as an ordinary borrower. His favourite
residence was a suburban house at Clapham, after-
wards known as Cavendish House, the draAving-room
of which was converted into a laboratory.
Many stories are told illustrative of Cavendish's
extreme reserve, and his apparent freedom from all
human sympathy.* He constantly attended the
meetings of the Royal Society, and as a rule avoided
all conversation. An F.R.S. wrote : " We used to
dine at the Crown and Anchor and Cavendish often
dined with us. He came slouching in, one hand
behind his back, and, taking off his hat (which by-
the-bye he always hung up on one particular peg)
he sat down without taking notice of anybody. If
you attempted to draw him into conversation he
always fought shy. Dr. Wollaston's directions I
found to succeed best. He said, ' The way to talk to
Cavendish is never to look at him, but to talk as it
* See G. Wilson : Life of the Honourable H. C. Cavendish (1848).
.THE CONFLICT WITH ERROR, 215
were into vacancy, and then it is not unlikely but
you may set him going.'" T. G. Children relates
how, when he first became a member of the Crown
and Anchor club he saw Cavendish talking very
earnestly to Marsden, Davy and Hatchett. Children
went up and joined the group. His eye caught that
of Cavendish and the latter instantly became silent
and would not say another word. He had seen a
strange face.
Lord Brougham remarks : " He entered diffidently
into any conversation and then seemed to dislike
being spoken to. He would often leave the place
when he was addressed, and leave it abruptly with a
kind of cry or ejaculation, as if scared and disturbed."
On one occasion, it is related, Cavendish was present
at some reception when a foreigner was introduced to
him. The latter began expatiating upon his talents
to Cavendish's great annoyance. Growing more
and more embarrassed he at length darted from the
room and left the house.
His horror of females was extreme. He ordered
his dinner by a note left on the hall table, and would
not allow any maidservant to show herself on pain of
instant dismissal. The person whom he had made
his heir he saw only once a year, and then for about
ten minutes. He lived by himself and no one was
known to be his friend. One single letter written to
him, and discovered after his death, signed " Your
most affectionate," brings Cavendish nearer to ordinary
human sympathies than anything else in his career.
216 THE CONFLICT WITH ERROR.
In the journals kept by him of his travels about the
country there is, except in one solitary spot, no
reference to the beauties of scenery passed through,
no suggestion that he was capable of being cheered
by nature's brightness or made pensive by her
gloom. In the one exceptional passage referred to
he does mention the bald fact that from a certain
place a fine view of the surrounding country is to be
obtained. Otherwise the pages are untinged, in their
dreary preciseness, by the warmth of a single emotion.
It should, however, be stated that according to the
journal recording his visit to his rival Watt at
Birmingham in 1785, he seems to have felt quite a
considerable interest in his inventions, if not in the
man. Numerous references occur to the explanations
Watt had given him,
For scientific purposes Cavendish would very occa-
sionally invite Fellows of the Eoyal Society to his
house, and his few guests were always treated to a leg
of mutton. An F.R.S. is responsible for the follow-
ing statement : " Cavendish seldom has company at
his house ; but, on one occasion, three or four scientific
men were to dine with him, and when his house-
keeper came to ask what was to be got for dinner
he said ' a leg of mutton.' ' Sir, that will not be
enough for five.' 'Well, then, get two,' was the
reply."
In spite of his wealth Cavendish hardly over gave
pecuniary aid to science. It is amusing to find him,
when an enlarged voltaic battery was desired at the
THE CONFLICT WITH ERROR. 217
Royal Institution, joining in the complaints of illibe-
rality in the patrons and himself doing nothing. He
had apparently an objection to be considered liberal,
or rather, perhaps, he was not sufficiently awake to
the ordinary affairs of life to recollect that a liberal
course was open to him. On one occasion he was
induced to allow a gentleman of small means and
considerable talents to reside in his London library in
order to rearrange it. The man finished this work
and left London. Some time after, when Cavendish
was dining at the Royal Society's Club, the gentle-
man's name was mentioned. "Ah! poor fellow,"
said Cavendish, " how does he do, how does he get
on ? " "I fear very indifferently." " I am sorry for
it." " We had hoped you would have done some-
thing for him, sir." " Me, me, me ? what could I
do ? " "A little annuity for his life ; he is not in
the best of health." " Well, well, well, a cheque for
ten thousand pounds, would that do ? " " Oh, sir,
more than sufficient, more than sufficient." And the
cheque was accordingly written.
In person Cavendish was tall and rather thin, his
face in the portrait prefixed to his life looking wizened
and pinched. His dress was old-fashioned and some-
times a little neglected.
This is almost all that can be said of Cavendish
apart from his scientific work. Occasional gleams
of wider sympathy suggest that his nature held
within it possibilities of a far higher order ; there
was a spark of fire buried deep in the ice. But no
218 THE CONFLICT WITH ERROR.
influence he encountered had power to develop the
possibilities, or break down the ice-barriers. And so
at last he became what we have seen him to be, a
passively selfish cynic, aware only of monotonous
existence, not of life, ignorant of laughter and of
tears. Morally his character was a blank. There
was not apparently a human soul with which he had
relations other than those of business and science.
He was interested in no one and in nothing outside
his scientific work. His life was, in regard to all
human sympathy, one of the most sadly wasted that
history records. Through it all he was alone. For
him no human face was rich in the beauty of affec-
tion, no voice was welcomed with gladness, no caress
could soothe pain. To him was unknown the power
of unselfish sympathy, the joy of helpful pity, or
exultation in the redress of wrong. To him life
brought only its morning of labour and its night of
sleep, work without happiness, quiescence without
rest. To him sky and earth were silent, and heaven
was without hope. He understood the voices neither
of joy nor sorrow. Life to him was an ashen desert
of speculation and proof. Through it all he was
loveless and alone. It is a saddening life to con-
template, and still sadder is it to think of what
can have induced so chilling a frost. Whether defi-
nite sorrow and disappointment, or only absence of
surrounding warmth of sympathy was its cause, it
will now never be possible to say. With his sorrows,
if his heart ever felt human pain, and with his errors,
THE CONFLICT WITH ERROR, 219
his life has passed out into the darkness, and of him.
there is left with us the best that he could leave us,
the germ of nobleness that was in him, the work, in
these latter days, so full in fruit.
The work done by Cavendish was small in amount,
but what remains of it is excellent. Considering the
power shown in what he did accomplish and the
advantages he possessed it is only surprising that he
did not do more. We are tempted to wonder how
his time was employed. But when we recollect how
withdrawn he was from the impulse of every-day con-
tact with other men, a stimulus quickening and in-
vigorating alike to heart and brain, we can readily
believe that much of his intellectual life must have
lain dormant and never wakened into activity of
thought.
The first communication made by Cavendish to the
Royal Society was, as already mentioned, in 1766,
under the title of Factitious Airs. The research
is divided into four papers and deals with hydrogen,
carbon dioxide, and the gases evolved by fermenta-
tion, putrefaction, and destructive distillation. It is
true that hydrogen had been obtained so far back as
the time of Paracelsus, that Mayo\v had collected it,
and that Hales had shown it to be combustible ; but
the phenomena of its production and its properties
were first distinctly studied and clearly set forth by
Cavendish. He showed that different metals yield
different quantities of the gas, but that the same
weight of the same metal evolved a like amount of
220 THE CONFLICT WITH ERROR,
gas from different acids.* He observed that, though
itself inflammable, hydrogen extinguished flame and
also destroyed life. He also proved it to be lighter
than air, and as a result of this the gas was subse-
quently used in balloons instead of heated air.
In the same papers referred to above Cavendish
COMBUSTION OF HYDEOGEN.
6* vessel in which the water vapour formed is condensed.
S, dish to receive the water.
discussed the properties of carbon dioxide, or fixed
air, more fully than had previously been done, and
showed the fixed air obtained from marble to be
identical with the air produced during fermentation.
His next paper (1767) consists merely of an analysis
of the water in Rathbone Place. It is interesting as
showing the results obtainable at that time. In the
same paper he seems to have been the first to notice
* The suggest! ven ess of this discovery will appear in the sequel,
when we see that a certain weight of any metal is equivalent to a
definite quantity of hydrogen, and will therefore always replace and
set free the same amount of it in any acid.
THE CONFLICT WITH ERROR. 221
that the liine, existing in water as carbonate, is,
though insoluble in pure water, held in solution by
the excess of free carbon dioxide present. This
carbonic acid can be removed by boiling the water,
whereupon the calcium carbonate is deposited as the
fur lining kettles and boilers.
In 1781 Cavendish accurately investigated by
Priestley's method the composition of atmospheric
air. Contrary to previous ideas he showed it to be
of unvarying composition.
The paper, Experiments on Air, in the Philo-
sophical Transactions for 1784,* con tains his greatest
work. He here relates experiments made on explod-
ing together air and hydrogen " to find out what
becomes of the air lost by phlogistication." Accord-
ing to some observations of Priestley's friend, Waltire,
it appeared that this explosion was accompanied by
loss of weight. Cavendish repeated these experiments
with the result that in most cases there was no loss
of weight and it never exceeded the fifth of a grain,
an amount ascribable to errors of experiment. Wal-
tire and Priestley had observed the production of
water during the experiment, but, just as Priestley
had done before in the case of the reduction of
metallic calxes, they neglected it, and it was leffe for
Cavendish to discover its meaning.
In his paper, Experiments on Air, in the Philo-
sophical Transactions for 1784, we find the follow-
ing epoch-making passage.
* Philosophical Transactions, 1784, p. 719.
222 THE CONFLICT WITH ERROR.
"From the fourth experiment it appears that 423
measures of inflammable air are nearly sufficient to
completely phlogisticate 1,000 of common air, and
that the bulk of the air remaining after the explosion
is then very little more than four-fifths of the common
air employed, so that, as common air cannot be
reduced to a much less bulk than that by any method
of phlogistication, we may safely conclude that when
they are mixed in this proportion and exploded,
almost all the inflammable air and about one-fifth
part of the common air lose their elasticity and
are condensed into the deiv ivhich lines the
glass."
Now, 1,000 volumes of air actually contain 210
volumes of oxygen, and these need 420 volumes of
hydrogen to combine with them. Cavendish's ex-
periments, therefore, for that date, were remarkably
exact.
The next point was to ascertain without doubt
what was the nature of the " dew " so obtained. To
this end he led oxygen and hydrogen gases into a
long cylinder measuring eight feet by three-quarters
of an inch, and there burnt them together. The
dew condensed in the further part of the tube. " By
this means upwards of 135 grains of water were
condensed in the cylinder, which had no taste nor
smell, and which left no sensible sediment when
evaporated to dryness, neither did it yield any pungent
smell during the evaporation ; in short, it seemed pure
water."
THE CONFLICT WITH ERROR, 223
His conclusions are set forth in the following
sentence :
. " By the experiments with the globe it appeared
that when inflammable and common air are exploded
in a proportion, almost all the inflammable air, and near
one-fifth of the common air, lose their elasticity and
are condensed into dew. And by this experiment it
appears that this dew is plain water, and, conse-
quently that almost all the inflammable air, and about
one-fifth of the common air, are turned into pure
water."
In another experiment Cavendish admitted the gases
mixed in proper proportion into a vacuous globe,
exploded them and found that the condensation was
complete, so that repeated charges were admitted into
the globe without any need for re- exhaustion.
The paper appearing in 1785 is also of great
importance as containing the first account of the
composition of nitric acid. Priestley had observed
that some nitric acid was always present in the water
obtained by the union of its constituent gases. Caven-
dish made a long and very careful series of experi-
ments with the object of explaining the occurrence
of this acid. After much trouble he was able to
show that pure dephlogisticated air (oxygen), when
combined with pure inflammable air (hydrogen),
formed only pure water. He found that the addition
of phlogisticated air (nitrogen) increased the amount
of nitric acid formed, and finally concluded that its
formation in ordinary cases was due to the presence
224 THE CONFLICT WITH ERROR.
of traces of atmospheric air, the phlogisticated air
(nitrogen) of which went to form the acid.
In spite of the prolonged and accurate attention
given by Cavendish to the composition of water he
seems to have never clearly conceived that it was a
compound of dephlogisticated and inflammable airs.
It is strange, considering how obvious and simple a
solution this afforded of the phenomenon that the
two gases when exploded together produce water,
that this plain notion should never have found favour
with him. James Watt, the engineer, had already,
in 1783, in a letter to Black thrown out the sugges-
tion that " water is composed of dephlogisticated and
inflammable air." In this opinion he anticipated and
made a distinct advance upon Cavendish, and much
has been written as to their rival claims to be con-
sidered as discoverers of the composition of water.
Cavendish certainly first established the facts proving
its composition, although he was so blind to their
meaning as to write in 1784 the following words :
" From what has been said there seems the utmost
reason to think that dephlogisticated air is only water
deprived of its phlogiston, and that inflammable air,
as was before said, is either phlogisticated water or else
pure phlogiston, but in all probability the former."
But although Cavendish remained to the last a
believer in phlogiston, and was thus, like Priestley,
precluded from seeing the full importance of his own
work, yet he was by no means so bigoted in his
partisanship as the latter chemist. He recognised
THE CONFLICT WITH ERROR. 225
in a passage net sufficiently noticed that many facts
could be explained as well by the Lavoisierian method,*
and although he never became a convert he was not
an ungracious opponent. His aberration on the
subject of phlogiston should not detract much from
our opinion of his intellectual power, when we recog-
nise how universal a sway that notion possessed over
the minds of men. It is indeed an annoyance to find
his acute and accurate papers reduced sometimes by
its means, like all the work of his day, to an incohe-
rence not unworthy of the jargon of the early alche-
mists; but our appreciation of his merit becomes
more unalloyed as we become accustomed to the
peculiar intellectual atmosphere in which he lived.
And considering the power of one false idea over the
minds of that day we gain an increased appreciation
of the singular fairness and freedom from bias of Dr.
Joseph Black, the one chemist who was converted to
truth. But though Cavendish could not discern the
widening dawn, his. work did much to produce its
light.
Two Swiss chemists of renown, Bergman and Scheele,
were at work about this time. Bergman (1735
1784) was one of the pioneers of analytical chemistry,
but of his work it is impossible to speak here in
detail. Scheele (1742 178G) is famous as the dis-
coverer of chlorine and as one of the first workers in
the field of organic chemistry. Another discovery
redounds much to his credit, though in it he had
* See p 246.,
P
226 THE CONFLICT WITH ERROR.
probably been anticipated by Priestley the discovery
of oxygen. Scheele obtained the gas by the decom-
position of nitric acid by heat, and gave it the name
of empyreal air. His discovery of chlorine gas was
made in 1774, and this element was termed by him
dephlogisticated marine acid gas.'"" He prepared it
TREPANATION OF CHLORINE,
w, wash-bottle containing water.
by the action of hydrochloric acid upon manganese
dioxide. On mixing the black oxide with the acid
a greenish mass is obtained which rapidly begins to
evolve chlorine. The first part of the operation may
be conducted at the ordinary temperature of the air,
unless the weather is very cold, but heat is needed
to drive off the latter portions of the gas. This is
passed through a small wash-bottle containing water
to remove hydrochloric acid, and if needed dry is
* Marine acid = muriatic acid = hydrochloric acid.
THE CONFLICT WITH ERROR. 227
further passed through sulphuric acid or other re-
agent capable of absorbing its water.
It seems also that Scheele was the first to carefully
investigate sulphuretted hydrogen, a gas invaluable
to the analytical chemist, as by its means different
metals are under different conditions thrown out of
solution as insoluble sulphides by the action of the
gas. Furthermore it was Scheele's announcement of
the existence of calcium phosphate in bones (a dis-
covery made first by Gahn in 1769), which led to
the manufacture of phosphorus from bone-ash, a
source from which all the phosphorus of commerce is
still obtained.*
Scheele's investigations of Prussian blue led him to
the discovery of prussic acid which he made in 1782.
This substance if? still prepared by his process of
acting on potassium ferrocyanide (yellow prussiate of
potash) with sulphuric acid. The pure acid is a
mobile liquid and one of the most powerful of known
poisons. A few drops produce death in a dog in
thirty seconds.
He first showed baryta to be a distinct earth,
and proved the separate existence of molybdic and
tungstic acids.
Some of Scheele's best-known discoveries lay in the
domain of organic chemistry. A number of organic
acids tartaric, oxalic, citric, malic, gallic, uric, lactic,
and mucic were either first prepared or first identi-
* Phosphorus was probably first prepared by the alchemist Brand,
of Hamburg, in the 17th century,
228 THE CONFLICT WITH ERROR.
fied by him. But even this does not complete the
long list of his discoveries, for he was the first to
obtain the valuable substance glycerine, to which he
gave the name of " the sweet principle of fats," and
which afterwards bore the name of Scheele's sweet
principle or oil-sugar. Scheele obtained his glycerine
by the action of litharge on olive oil. Oils and fats
contain glycerine or, more strictly, " glyceryl," com-
bined with acids. If these be heated with potash or
litharge the metal takes the acid and glycerine is
set free. The name glycerine was first given to the
body by Chevreul in his " Recherches sur les Corps
gras," etc. He also determined its composition.
Many workers were engaged upon this body before
an accurate knowledge of its constitution was obtained,
and these include Pelouze, Berzelius, Liebig, Berthelot,
De Luca, and Wurtz.
The number of Scheele's discoveries is surprising,
and he was the first to pay any accurate attention to
the phenomena of organic chemistry. He, too, was
blinded by his bias on the phlogiston theory, but his
work contributed greatly to the building up of the
modern science.*
* Some of Scheele's papers are translated by Beddoes under the title
of Scheele's Chemical Essay* (1786)4
SEVENTH PERIOD.
CHAPTER XIIL
SEVENTH PERIOD: THE TRIUMPH OF TRUTH.
LAVOISIER,
HE greater chemists of this period repre-
sented three different types of mind ;
Priestley, brilliant and rapid in discovery,
but somewhat inaccurate in experiment,
and insufficient in theoretical grasp ; Ca-
vendish, slow but thorough in discovery,
accurate and painstaking in experiment, but not
directly influencing the theoretical ideas of his time :
Lavoisier, who discovered no new fact, but was ori-
ginal and exact in his experiments, and exerted, by
his marvellous intellectual grasp, incalculable in-
fluence upon the theoretical progress of his science.
He was not one who dealt with isolated facts, his
mind had something of the philosopher's taste for
classification and general principles. There is, perhaps,
232 THE TRIUMPH OF TRUTH,
come tendency in experimental work to arrest the
imagination, to deter from speculation, to dull the
worker's appreciation of what is not presentable to
sense. But this tendency is indulged at the peril of
the worker and his science. It produces a conserva-
tism often delaying scientific advance. The conser-
vative tendency was strong in Lavoisier's time,
but he escaped it and rescued his science from its
grasp.
Antoine Laurent Lavoisier (1743 1794) was born
at Paris in 1743. His father, a wealthy tradesman,
educated him at the College Mazarin, and encouraged
him in his scientific tendencies. Lavoisier was re-
lieved from the necessity of earning his bread, and
was thus able to devote his time and energy to science.
On leaving college he worked with extraordinary
ardour, and a devotion greater than most would have
exhibited had their work been forced upon them by
want. His latter work was for the most part devoted
to science for its own sake, but among his early ex-
periments were some made in the hope of a prize
offered for the best mode of lighting the streets of
Paris. He experimented with various lamps, and it
is indicative of the depth of his enthusiasm that, to
increase the sensitiveness of his eyes while thus en-
gaged, he lived for six weeks in a room deprived of
all light and hung with black. Not long after this
he refuted the belief, entertained by many, that water
by distillation could be converted into earth.
Lavoisier availed himself, as much as possible, of
THE TRIUMPH OF TRUTH. 233
the benefits of discussion and criticism. One day a
week he threw open his laboratory to a select company
of friends, communicated his results, and invited
comment or criticism.
In 1772 he recorded the results of his experiments
on the calcination of metals. These led him to aban-
don the theories of the phlogiston school. In 1778
he broached his theory that oxygen was the uni-
versal acidifying or oxygenizing principle. In 1783
he completed the proof of the composition of water.
In 1792 the Lavoisierian doctrines received recogni-
tion in Berlin, and in 1789 he published his remark-
able Traite elemental de Chimie.
Lavoisier's abandonment of the old chemical creed
brought upon him much obloquy and odium. At the
height of his unpopularity he was burnt in effigy at
Berlin on account of his antiphlogistic ideas ; yet
Berlin only a few years later was converted to his
views. But it was not his independence as a chemist
which was to cause his ruin. His overflowing energy
had engaged him also in political work. He was a pro-
minent member of the body of" Farmers-General " of
the revenue, and in this administrative capacity is
said to have done some good work. " Lavoisier,"
said Lalande, " was to be found everywhere."*
'' Francois de Fourcroy speaks indignantly of Lavoisier's fate.
" L'homme qui auroit illustre son siecle par ses talens, qui auroit
repandu ses lumieres sur la societe, dont les travaux auroicnt eu pour
but d'instruire, de rend re meilleurs et plus heureux les homines, seroii
place dans un meme tombeau avec celui qui en auroit fait le tourment
ou qui en auroit etc la honte ! " Notice sur la vie de Lavoisier. Paris
(1796). Lalande's notice is given by Scherer in his Nachtrage.
234 THE TRIUMPH OF TRUTH,
But in May, 1792, the year 2 of the Republic
and at the height of the revolution, the arrest of all
the Farmers-General was ordered. All were to give
account of their moneys and incomings, and die " for
putting water in the tobacco they sold." The charges
were brought against the whole body on the 2nd of
May by Dupin, a member of the Convention. Lavoi-
sier found a hiding-place in the deserted rooms of the
Academy. Hearing, however, that his action would
tend to prejudice his colleagues he gave himself up
and awaited his fate. He expected the confiscation
of his property, and announced his intention if this
sentence was passed of earning his bread as an
apothecary, the trade most nearly suited to his tastes.
But on the 6th of May he, with twenty-seven others,
was condemned to the guillotine.
The death of a man of such peaceful eminence did
not pass without some protest. Petitions for commu-
tation of the sentence, in consideration of his high
services to knowledge and the state, were presented in
vain. He himself looked on calmly, and might have
met his death without a word had he not been inter-
rupted in some investigations. But to be snatched away
just before an interesting research was completed, just
when nature was in a mood to bring him more confi-
dences that, at its best, was annoying. So he peti-
tioned for a fortnight's delay to get done with his expe-
riments ; then he would be at their service. But the
petitions were all alike refused. The Republic had "no
need of savants." And on the 4th of May, with the
THE TRIUMPH OF TRUTH. 235
experiments unfinished, the guillotine reeeiv in him
one of her most illustrious victims. We can only be
thankful that his doom did not descend in time to
rob us of the work, the results of which we are still
permitted to inherit.
It is a very unfortunate circumstance that our
admiration for Lavoisier is to some extent restricted
by the too clearly proved fact that he laid claim to
discoveries to which he had no right. His Opus-
cules Physiques et Ghymiques contain discoveries of
Joseph Black, put forward as if they were his own,
while his claim to the simultaneous discovery of
oxygen has been the occasion of many disputes,
finally ending by an invalidation of the claim. It is
much to be regretted that our warm admiration
for the splendid talents and services of so great
a worker should have to encounter the chill of dis-
appointment we must experience in the character of
the man.
Lavoisier claims our attention chiefly on account of
his being the first to distinctly and clearly enunciate
the great principle of the indestructibility of matter*
The belief in this pervades, and indeed alone makes
possible, the whole of his work. He showed that
chemistry could not exist without the chemical
balance.
It is true that quantitative experiments in the
* As a philosophic principle this had been taught ages before : e.g.
by Lucretius, who followed Greek masters. But as a scientific truth
it had never been proved, and indeed was not generally held. .
236 THE TRIUMPH OF TRUTH.
science had already been performed, and that Black
and Cavendish had raised these to a high degree of
exactitude. There was necessarily in these experi-
ments a tacit assumption that at least in the case
under investigation matter was not expected to be
destroyed. If he had expected the destruction of
matter how could Black have inferred that because
magnesia alba lost weight on heating some thing was
given off, and when he found out that the thing could
not be condensed, further concluded that it was a
gas ? Or how could Cavendish have determined the
relative amounts of oxygen and hydrogen condensing
to form water, had he thought that during the ex-
plosion some of either gas might cease to exist ?
Clearly these experiments had an underlying disbelief
in the destruction of matter in the course of these
particular experiments. But such vague previsions
were widely different from any assertion of a general
law. It is the difference between the unscientific
industry of his contemporaries and the far-sighted
precision of Lavoisier. According to him every
chemical change is accompanied only by transfer and
exchange of matter, not by destruction. His doc-
trine is, " Rien ne se cree, rien ne se perde de la
nature." The total weight of the reacting bodies
remains the same from beginning to end of the
reaction. We see here the first attempt at a chemical
equation.
The theory was propounded in regard to fermenta-
tion, Lavoisier having tried to make out what became of
THE TRIUMPH OF TRUTH. 237
the sugar during the process. After investigating the
matter he came to the conclusion that, starting with
a certain weight of sugar, there were obtained as a
result of the fermentation certain weights of alcohol
and carbonic acid gas, which together were equal to
the weight of sugar present when the reaction began.
N othing, said Lavoisier, is lost ; but instead of our
sugar we have an equivalent quantity of carbonic acid
and alcohol.
Strangely enough this argument, forming one of
the bases of "the great theory, was founded upon an
experimental error. The carbonic acid and alcohol
produced by the fermentation are not together equal
in weight to the sugar made use of. What then is
the final conclusion ? Not that matter has been
destroyed, but that, as shown by the eminent French-
man, Pasteur, other substances besides alcohol and
carbonic acid are formed. What Lavoisier said was
quite true for about 95 per cent, of the sugar used,
but the remaining 5 per cent., or thereabouts, is con-
verted partly into glycerine and succinic acid, and
partly used up for developing the growth of the
ferment. But even this is not a full list of the pro-
ducts which include other " alcohols " differing from
common alcohol (higher homologues of it, as they are
called), organic acids of the fatty series and ethereal
salts, from which the spirit derives a peculiar smell.
All these bodies have a higher boiling point than
common alcohol, and are classed together under the
name of fusel-oil. The fusel-oil is got rid of by rectifi-
2 3 8 THE TRIUMPH OF TRUTH.
cation, and if present forms a very deleterious im-
purity.*
Lavoisier then was not quite accurate in the
example most immediately connected with his bril-
liant thought. But the theory need happily never
be wanting in support. All the thousands of opera-
tions carried on daily in the laboratories eastward
from San Francisco to Pekin are so many confirma-
tions of its truth. The balance is the first requisite
of the laboratory, and did we not believe in the
indestructibility of matter the use of the balance
would be meaningless and absurd.
It may be as well here to illustrate from every-
day life the full force and truth of this great idea.
When a candle has burnt out what has become of
it? This is the chemist's riddle, and like most
riddles we must give it up and ask our questioner
for the answer. First of all the riddle was asked by
nature and the chemist had to find out the answer
for himself ; for nature is not so lenient as the chemist,
and would not allow us to give it up. The chemist
knows her principles in these matters well, so that
he at once sets to work to puzzle the matter out,
and, as the result of his puzzling, this is what lie
would tell us to do, to find out what has happened to
the candle.
We have already been introduced to many of the
* The reader wishing to follow the interesting subject of fermenta-
tion in more detail should consult Schiitzenberger's admirable book On,
Fermentation, Intern. Scientific Series.
THE TRIUMPH OF TRUTH. 239
facts destined to overthrow the Stahlian hypothesis,
and need not therefore start from the beginning in
our reasoning. Suppose we burn a candle under a
glass jar* as Priestley did long ago. Its flame is soon
extinguished, and after any fumes may have subsided
a clear gas is left in the bell-jar not differing in sight
from ordinary atmospheric air. Now let us light
another candle and plunge it, as the chemists say,
into this innocent-looking gas. The flame at once
goes out, and if we were cruel enough to put a
mouse into the jar the flame of its life would go
out too. Evidently something is now in the air
which was not there before.
If our gas-jar is appropriately constructed, open at
both ends with the lower end placed in water and
the neck closed by a wide glass stopper, we may do
something further with the gas we have got. If we
introduce some caustic potash into the water in
which the jar is standing we shall soon have evidence
that the potash is taking up or absorbing some of the
gas in the jar, for the level of the water in it will rise.
Repeating this experiment with the potash with a jar
of air in which a candle has not been burnt we shall
obtain no alteration of level ; there is nothing here
absorbable by the potash, f Evidently the combus-
tion of the candle has produced a gas absorbable by
potash.
* Any common glass bottle with a neck wide enough to admit a
candle may serve for this purpose.
t Of course a little carbonic acid gas is present in ordinary air, "but
it will be very much too little to be, in this way, perceived,
2 4 o THE TRIUMPH OF TRUTH.
If we repeat these experiments with a jar filled
with pure oxygen instead of air we should obtain
the following results. With the unaltered gas
potash would effect no absorption. After the com-
bustion of a candle therein potash would effect far
more absorption than in the same circumstances
with common air. Any gas left after absorption will
be either nitrogen, an impurity derived from atmo-
spheric air, or unused oxygen gas further reducible
by repeated combustion. From these experiments we
may conclude that part of the candle (its carbon)
combines with part of the air (its oxygen) to form
a gas (carbon dioxide) not supporting combustion
and absorbable by caustic potash. The presence of
carbon dioxide may be readily and simply shown by
merely pouring a little clear limewater into a glass
bottle in which a candle has been burnt. The lime-
water is at once turned milky. This phenomenon
will not occur with ordinary air and is characteristic
of carbon dioxide, the " fixed air " of Black.
One product of the combustion, then, is carbon
dioxide. That another product results may be
very readily shown by merely holding a common
tumbler over a burning candle. A misty appearance
is at once seen on the interior of the glass, soon
gathering into drops of dew. If instead of using
such primitive apparatus we suck the products of
combustion through a cooled tube or condenser, we
may collect enough of the drops formed to find out
that they are pure water, Wo should find that it
THE TRIUMPH OF TRUTH. 241
was tasteless, boiled at 100 C,, and evaporated with-
out leaving any residue.
The products of the combustion of a candle then
are carbonic acid and water. The carbonic acid is
derived from the carbon contained in a combined
form in the candle. We may obtain the same gas
by the combustion of charcoal, and, as Lavoisier
showed, by the combustion of the diamond. The
water must be obtained from the hydrogen of the
candle, for as the facts of Cavendish showed, water is
composed of hydrogen and oxygen. The matter of
the candle has not, then, been wholly destroyed as
appearances would at first suggest. By appropriate
arrangements we may show that the products of
combustion actually weigh more than did the candle
itself or the part of it that has been burnt away.
A wide tube is suspended from one arm of a balance.
A cork having a candle fixed upon its upper surface
and pierced with holes to admit of the passage of a
current of air, is fitted into the lower end of the
tube. Its upper end is connected by a piece of
caoutchouc tubing with a second glass tube bent
into the form of a U. The bent tube is filled with
fragments of solid caustic potash, a substance, as we
just now learned, capable of absorbing carbonic acid
gas, and at the same time very hygroscopic, or taking
up water with great activity. The two tubes having
been exactly counterpoised on the balance, are con-
nected finally with an aspirator. By allowing the
water to flow out from this last a current of air is
242
THE TRIUMPH OF TRUTH.
drawn through the whole apparatus. The candle
being lighted the aspirator is set to work, care being
taken that the current is not too rapid, lest some
carbonic acid or water vapour should be drawn past
the caustic potash unabsorbed. When an appreciable
amount of the candle has been burnt the apparatus
is disconnected from the aspirator and the balance
once more allowed to vibrate freely. It will now be
found that the index point oscillates farther on the
side of the counterpoise than on the side of the tubes.
XT-TUBE.
The tubes now weigh more than the counterpoise.
But when the experiment began the tubes and their
counterpoise were equivalent. They have therefore
gained in weight. Thus in spite of the apparent
disappearance of some of the matter composing the
candle, not only has none of it been destroyed but
it has actually gained in weight, owing to the addition
to it of oxygen from the air during the process of
combustion.
We have thus been able to catch the invisible
THE TRIUMPH OF TRUTH. 243
products of the combustion and render their existence
evident to the eye. We may further show that the
amount of carbon and hydrogen in the products is
just the same amount as that contained in the burnt
portion of the candle, but the inquiry here would be
somewhat more complicated. We know the propor-
tions of hydrogen and oxygen in water, we know also
the proportions of oxygen and carbon in carbonic
acid, we know lastly, from individual experiments
and by reason of the law of constant proportions first
definitely recognised by Lavoisier, that the composi-
tion of these compounds is constant. If then we
knew the amount of water and carbonic acid generated
we could calculate the amount of carbon and hydrogen
in the candle. But to do this we must collect the
water and carbonic acid separately.
Let us make use of a pure paraffin candle contain-
ing nothing but hydrogen and carbon. Let us pass
its products of combustion first through a U tube,
containing fragments of pumice soaked in sulphuric
acid. This will absorb the water. The carbonic
acid escaping from this tube may then be collected
by passing the gases through bulbs containing
caustic potash solution. We have thus got the
means of collecting the two products separately. But,
if we are to be at all accurate, we must make further
provision against error ; for water vapour and car-
bonic acid are present in the common air used to
burn our candle, and will, of course, add their weight
to the result, To obviate this, we may first pass the
244 THE TRIUMPH OF TRUTH.
air through soda-lime and sulphuric acid to free it from
carbonic acid and water, and then over the burning
candle. If we were to weigh the tube containing the
candle before and after the experiment, the loss of
weight would give us the weight of candle burnt.
The gain in weight of the U tube containing sul-
phuric acid, would give us the weight of water
formed, while the gain in the potash bulbs would
represent the carbonic acid evolved. Knowing the
composition of water and carbonic acid, we could
calculate the weight of hydrogen and carbon these
gains respectively represented. Added together, we
should find these very nearly the same as the weight
of candle burnt. None of the matter composing it
is lost during combustion. We might thus account
for the matter composing the candle, and determine
its composition.
The method is not quite the same as that at
present in use for determinations of carbon and
hydrogen in organic bodies, but it is substantially
that used by Lavoisier in some of his attempts at
organic analysis made by him just before his exe-
cution. We may refer to these experiments again
in a chapter on the development of organic chemis-
try, a subject which can only, in a work of this kind,
be very briefly sketched, and is more conveniently
treated separately.
Finally, we must remember that the doctrine of
the indestructibility of matter includes also a dis-
belief of its creatability. Just as it cannot be
THE TRIUMPH OF TRUTH. 245
destroyed, so neither can it be created. The products
of a reaction contain the same amount of matter as
the substances taking part in it. They do not
contain less, and they do not contain more. This
belief is distinctly contained in Lavoisier's own
words on the subject of fermentation : " We may
consider the substances submitted to fermentation
and the products resulting from that operation as
forming an algebraic equation, and, by successively
supposing each of the elements in this equation
unknown, we can calculate their values in succession,
and then verify our experiments by calculation, and
our calculations by experiment, reciprocally. I
have often successfully employed this method for
correcting the first results of my experiments, and so
to direct me in the proper road for repeating them
with advantage."*
Lavoisier, in his mission of evolving order from
incoherence, was also the first to openly acknowledge
the law of combination in constant proportions.
Bergman (1735 1784) tacitly acknowledged the
truth in his numerous analytical researches. For
what is the use of analysing a compound, if different
specimens of it have varying composition ? How can
its composition be stated if it be indefinite ? But
this is not the first time in the history of science in
which a great principle has been acted on before it
was realised. Lavoisier distinctly stated that in
* Lavoisier: Elements of Chemistry (1787). Kerr's Translation,
p. 197.
246 THE TRIUMPH OF TRUTH,
every oxide and every acid, the relation of oxygen to
the metal is constant. He also refers to the different
oxides of nitrogen exhibiting different, but in each
individual compound definite, degrees of oxidation.
He had, indeed, only just escaped discovering the
law of multiple proportions. Had not his execution
terminated his career, he might have followed up
this among several others of his uncompleted trains
of thought.
His first important research (1770) depended
upon the use of the balance, and thus early indicated
the tendency of his mind. In it he refuted the
notion, at the time a moot point, that water, by being
heated, may be converted into earth. He found
that previous observers had been deceived by the
use of impure water, or by the water having taken
up some matter from the vessel in which it was
heated.
Lavoisier's work on combustion and his combat
with the Stahlian hypothesis began with some
experiments first recorded in 1772, and not pub-
lished till 1774, on the calcinations of the metals.
His open rejection of phlogiston was not announced
till 1777, and it is interesting to note that before
this date, at least one other worker had seen reason
to distrust the theory. Bayen, in 1774, had
supposed calcination due to the absorption of an
aerial fluid. He had found that calx of mercury
(mercuric oxide) on heating loses weight, evolving
a gas equal in weight to what is lost. From this he
THE TRIUMPH OF TRUTH. 247
concluded that either the phlogiston theory was in-
correct, or that this particular calx could be reduced
without addition of phlogiston. But the phlogistians
with their principles of levity and the like, were well
capable of preventing these simple facts from dis-
pelling the clouds which befogged the minds of the
chemists in 1774.
Lavoisier's conclusions on the subject of the cal-
cination of metals were first placed in the hands of the
French Academy as a sealed paper in 1772, the final
publication not taking place till 1774. His reason for
first depositing the inquiry in its unfinished state in
the hands of the Academy, was the desire to have
proof of priority should another worker anticipate
him before his investigation was complete. "I was
young, I had just entered upon the career of science,
I was eager for glory, and I believed I ought to take
some care to protect the. ownership of my discovery."
In his first work on the subject Lavoisier finds that
sulphur and phosphorus not only do not lose but
actually gain in weight. His attention is thus
directed to the calcination of metals with the idea
that the combustion has in the previous cases been
accompanied by an absorption of air, and that similar
results may be expected from calcination. To eluci-
date his point he reduces the calx of lead or litharge
with charcoal, and finds that a large quantity of gas
is liberated. We see at once the point at which this
meets the phlogistic theory. According to this last
the addition of phlogiston to the calx was alone
2 48 THE TRIUMPH OF TRUTH.
needed to produce the metal. But Lavoisier did not
grasp these relations at once, though he saw that the
discovery was important. " Experience has entirely
justified my suspicions ; I have effected the reduction
of litharge in closed vessels with the apparatus of
Hales, and I have observed that at the moment of
the transition of calx into metal a large quantity of
air was set free, and that this air had a volume at
least a thousand times that of the litharge used. This
discovery appears to me one of the most interesting
made since Stahl, and I have thought it right to
secure my property in it."
In 1774 Lavoisier made experiments on the calci-
nation of lead and tin. These metals he, like Boyle,
heated in closed glass globes. The globes did not alter
in weight, proving that the amount of air absorbed
was the same as that taken up by the metal. When
the globes were opened air rushed in and the weight
increased. In a paper on calcination, first read before
the Academy in 1775, occurs his first reference to
oxygen gas under the name of Vair pur or Vair vital.
In 1777 Lavoisier combated Priestley's assertion that
combustion loaded air with phlogiston. He showed
that air, after the combustion of a candle in it, con-
tained " fixed air," and, moreover, that if for common
atmospheric air dephlogisticated air (oxygen) were
substituted, the gas left after combustion was almost
wholly composed of fixed air. The phlogiston war
was now raging, and in 1778 he broached his theory
that oxygen (as he now called the gas : 6i;?, sour, and
THE TRIUMPH OF TRUTH. 249
aw, I produce) was the universal acidifying or
oxygenizing principle.
Two memoirs contain the chief portion of Lavoi-
sier's views on combustion, one read before the
Academy in 1775, Sur la Combustion en general,
and another, Reflexions sur le Phlogistique, published
by the Academy in 1783. The second paper con-
tains the full development of his theory, and in it
he denies the existence of phlogiston, upholds the
elementary character of the metals and such substances
as carbon, sulphur, etc., and states emphatically that
when these bodies are burnt all that occurs is their
combination with oxygen.* The simple truth of these
views was possessed of a resistless force which in the
end carried all before it.
After Cavendish's experiments in 1783 Lavoisier
completed the proof that water was a compound of
oxygen and hydrogen. He repeated, in conjunction
with Laplace, the experiments of Cavendish and added
a further confirmation of his own. In this case water
was allowed to drop slowly into a gun-barrel heated
to redness in a furnace. Here part of the water was
decomposed, any that escaped being condensed in a
worm through which the gases passed after leaving
the furnace. The oxygen combined with the metallic
iron in the gun-barrel, and the gas finally collected
under the bell-jar was found to be pure hydrogen.
This completed the proof now resting upon both
* Lavoisier was thus the first to ascertain the composition of " fixed
air " or carbonic acid, as also of sulphur dioxide,
250
THE TRIUMPH OF TRUTH.
analytical and synthetical foundations. The exact
composition of water has since been most accurately
determined both by endiometric synthesis or explosion
of the mixed gases in a carefully graduated tube, and
by gravimetric synthesis by passing perfectly pure
hydrogen over a known weight of copper oxide.
Lavoisier was not slow to appreciate the full im-
port of these discoveries. Kopp has concisely set
LAVOISIER'S APPARATUS FOE THE ANALYSIS OF WATER.
forth the steps leading to a clear knowledge of the
composition of water ; Cavendish first ascertained
the facts; Watt first argued from them as to the com-
pound nature of water ; Lavoisier first clearly recog-
nised its compound nature and the nature and
amounts of its components.
Before closing the account of Lavoisier's work
mention must be made of his very remarkable Traite
El&nentaire de Chimie. It is a work remarkable
THE TRIUMPH OF TRUTH. 251
for its arrangement and lucidity, for scientific accu-
racy, and for the originality of the ideas it contains.
"It is a very constant principle, and one of which
the general application is well recognised in mathe-
matics as in all kinds of sciences, that we can, for our
instruction, proceed only from the known to the un-
known When we enter for the first time
upon the study of a science we are, with regard to
this science, in a state very similar to that in which
children are, and the course that we have to follow is
precisely that which nature follows in the formation
of their ideas. Just as in the child the idea is the
result of sensation, and it is sensation which causes
the idea, in the same way too, for him who begins to
devote himself to the study of the physical sciences,
ideas should only be a consequence, an immediate
result of an experiment or of an observation." *
It is in his " Traite" that he gives the very clear
proof devised by him of the presence of oxygen in
the air. He heated mercury in a retort connected
by its bent neck with air confined under a bell glass
over mercury. After heating for twelve days the air
had been reduced from 50 to 42 or 43 cubic inches,
while red particles appeared on the surface of the
mercury. These last, which consisted of mercuric
oxide, were carefully collected, and on heating yielded
411 grains of mercury, and 7 to 8 cubic inches of
pure oxygen. The whole of the oxygen was thus
recovered from the mercury.
* (Etivres da Lavoisier (1862), torn. i. Introduction to the Trails.
2 5 2 THE TRIUMPH OF TRUTH.
He gives a table of thirty-three simple substances,
among which he still includes heat or caloric and
light. He also gives tables of the combinations of
the various elements, and in these he looks upon the
gaseous elements as combinations of a ponderable
substance, the true element, with heat. Thus the
combination of " 1'hydrogene avec le calorique = gas
hydrogens."* So too the combination of sulphur
with caloric gives rise to sulphur gas. After all,
though incorrect, these views only veil a great truth,
for in these gases heat is rendered latent. Black, the
discoverer of latent heat, had himself regarded the
phenomenon as an act of combination. Of combus-
tion Lavoisier here remarks,! " Combustion is nothing
but the decomposition of oxygen gas acted upon by
a combustible body. The oxygen which forms the
base of this gas is absorbed, the caloric and light
become free and are liberated (deviennent libres ei se
degagent). All combustion then carries with it the
idea of oxygenation. . . '
The view of combustion here set forth is now,
perhaps, somewhat modified, and combustion is
regarded as " an act of chemical union accompanied
by the evolution of light and heat."
This same work contains a prediction of the com-
pound nature of the alkaline earths (soda and potash)
previously thought to be simple bodies. From their
ready combination with acids he concludes that
"they may very possibly be metallic oxides with
* (Eui-res, torn. i. f (Em-res, i. 338. -,
THE TRIUMPH OF TRUTH. 253
which oxygen has a stronger affinity than with
carbon, and consequently are not reducible by any
known means." This was a prediction of Sir
Humphrey Davy's discoveries on this point.
Quite enough has been said to account for the
enormous and resistless influence exerted by Lavoisier
on the progress of the science, but one more achieve-
ment must be recorded of him, and that is, that he
entirely revised its nomenclature. He devised the
term oxide for those combinations of oxygen which
SPECIMEN OF DIAMOND. THE KOH-I-NOOB.
were not acids. When more than one oxide or acid
was known the one containing less oxygen was dis-
tinguished by the termination ons, as nitrous oxide,
the one containing more by ic, as nitric oxide. He
devised the term hydrogen (vcwp, water ; <yevvcua> I
produce) in place of inflammable air, and carbonic
acid as a substitute for fixed air. The meaning of
the term acid has somewhat changed since Lavoisier's
day, and it is now used for substances containing
hydrogen replaceable by a metal. Lavoisier was the
first to show that the combustion of diamond gives
254. THE TRIUMPH OF TRUTH.
rise to carbonic acid, and thus to show the identity
of the diamond with common charcoal. The diamond
may readily be burnt when heated in air or oxygen.
The formation of carbonic acid in the process may be
readily shown by igniting a diamond, encircled in
platinum wire, by means of an electric current from
a few Grove's cells. A little lime-water contained in
the jar will, after the combustion, become turbid.
It is difficult to over-estimate the influence of
Lavoisier, and after seeing for ourselves what he did,
and what precision and simplicity he introduced
where so much before was only inaccuracy and
incoherence, time would be wasted in panegyric.
Liebig's summary of his achievements is as follows :
" He discovered no new body, no new property, no
new natural phenomenon previously unknown ; but
all the facts established by him were the necessary
consequences of the labours of those who preceded
him. His merit, his immortal glory, consisted in
this that he infused into the body of science a
new spirit."*
* Letters on Chemistry, ii=
EIGHTH PERIOD.
CHAPTER XIV.
EIGHTH TElilOD : THE ATOMIC THEORY.
DALTON'S IDEA.
,Y the atomic theory the older chemistry has
been transformed into the modern science.
It will be our business in the two succeed-
ing chapters to trace its growth. Lavoisier
had asserted the law of constant propor-
tions. He recognised that, for example, a
given weight of mercuric oxide always contained the
same weights of mercury and of oxygen. This was a
great advance upon the older ideas of chemical com-
binations. But so simple and true a doctrine was
not to remain uncontested. It was assailed by Ber-
thollet, a pupil of Lavoisier's, in a memoir read before
the Egyptian Institute at Cairo. Berthollet ascribed
the composition of compounds to physical causes.
ll
2 5 8 THE ATOMIC THEORY.
He showed that varying results could be obtained in
the neutralisation of an acid by a base. S. L. Proust
enlisted himself on the side of the Lavoisierian theory,
and the battle was converted into a duel between
these two opponents. The contest was continued for
a period of seven years with varying fortune, but
Proust finally came off victor. He had rendered a
lasting service to science. " The discussion," says
Wurtz, " was maintained on both sides with a power
of reasoning, and a respect for truth and propriety,
which have never been surpassed."*
Proust found that on dissolving carbonate of copper
in acid and reprecipitating by alkaline carbonate, the
same weight of carbonate as that originally dissolved
was obtained. This is an example of his work, and
by it he was led to conclude that copper carbonate
Avas of unvarying composition. Subsequent work led
to similar conclusions about other compounds. The
varying composition attributed by Berthollet to salts
was explained by showing that although two or more
salts may be formed by different quantitative combi-
nations between a given acid and given base, yet for
these salts the proportions are constant. Thus mercury
forms two different chlorides, one containing twice as
much chlorine as the other. There is only a differ-
ence in the proportion of chlorine present, yet the
properties of the two substances are wholly distinct,
* The Atomic Theory (International Scientific Series) ; to which book
is owing much of the material of these chapters. Those who wish to
follow more closely the development of the theory cannot do better
than consult this very ably and lucidly written work.
THE ATOMIC THEORY. 259
and for each of the two salts the composition is con-
stant. The lower chloride, mercurous chloride (Hg 2
Cl 2 ), is a white insoluble powder, used as a non-poi-
sonous medicine, and, in this capacity, known as
calomel*
The next step was the discovery of the law of defi-
nite proportions by the German chemist, J. D. Bichter,
of Berlin. He was much possessed with the idea of
applying mathematics to chemistry. He followed
his hobby too far, and by many ingenious manoeuvres
attempted to show that the quantities of bases satu-
rating a given weight of acid represent the terms of
an arithmetical progression, while the quantities of
acids combining with a given weight of base, form the
terms of a geometrical progression. His reasoning
on these points broke down, but he did succeed in
showingf that definite, but different, amounts of
bases are needed to saturate and neutralise a given
weight of a given acid. The weights of bases saturat-
ing a given amount of a given acid bear to each other
a definite ratio. Thus 60 grammes of acetic acid
are saturated by 40 grammes of caustic soda, and by
56 grammes of caustic potash, the proportions being
as 5 to 7. Further, a certain weight, 3 6 '5 grammes,
of hydrochloric acid will be neutralised by exactly
these same weights of soda and potash, they have
the same relative capability of saturating the two
* From KaXo/xtXac, a fine black colour, because it turns black when
acted upon by an alkali.
. t -Anfanpsffrunds der Stiichiometrie, oder Hesskunst chemlscher Ele-
mente.
260
THE ATOMIC THEORY.
different acids. Considerations such as these led
Bichter to draw up a table showing the equivalent
quantities of different bases saturating 1000 parts of
different acids. The numbers, though of course in-
accurate, contained a great truth more clearly ex-
hibited by G. E. Fischer, in a note to his translation
of Berthollet's Chemical Statics.
The following is part of Fischer's table, and it shows
at a glance the equivalent quantities of bases and
acids. Thus it states that 859 parts of soda are
equivalent in neutralising power to 1,605 parts of
potash; further, that 712 parts of muriatic acid
(hydrochloric) are equivalent to 1,480 parts of acetic
acid. It also contains the assertion that 859 parts
of soda will neutralise 712 parts of muriatic acid, or
1,480 parts of acetic acid, and that 1,605 parts
of potash, the equivalent of the foregoing amount
of soda, will neutralize the same weights of these
acids.
BASES.
Alumina .
Magnesia
Ammonia
Lime
Soda
Strontia
Potash
Baryta
525
Fluoric aci
A
a
415
Carbonic
572
Muriatic
793
Oxalic
859
Phosphoric
1,329
Sulphuric
1,605
Nitric
2,222
Acetic
i
Citric ,
>
AdD9.
427
577
712
755
979
1,000
1,405
1,480
1,583
The precise bearing of these results upon the atomic
theory will be presently seen. Had the weights here
given been those of elements, instead of acids and
THE ATOMIC THEORY. 261
bases, they would be analogous to the chemical equi-
valents of a later date.
We have said that with Lavoisier came the triumph
of truth over fanciful error. But it was a hard-won
fight, and her fit weapons had yet to be forged. The
evil power had been driven from her own land, but
she. had need of added strength before attempting the
conquest of his kingdom. Her trustiest sword was
to be forged by John Dalton and tempered by the
workers that came after him.
John Dalton was born in 1766, at Eaglesfield, two
miles and three-quarters south-west of Cockermouth,
in Cumberland.
" The township of Eaglesfield, situated on the undu-
lating limestone formation of West Cumberland, pre-
-vious to the enclosure of the waste lands and the in-
troduction of good husbandry, about half a century
ago, would offer little more than herbage for rough
kine, and hard lines of life to the scattered inhabi-
tants. Bucolic life of the boorish* sort prevailed in
the hamlet, in which farmers of small holdings, their
clodhopping service, and common craftsmen, laboured
for a subsistence of a vegetative or earthy sort. The
village consisted, and its features are not much altered
to-day, of old-fashioned grey-stone dwellings, regular
in their irregularity of position, and in structure
dilapidated ; straggling manure heaps, a bit of dirty
common or village green, and dirtier duck-pond, backed
* Boorish is perhaps an unfortunate word. The race that produced
Dalton can hardly have been boorish.
262 THE ATOMIC THEORY.
by a dingy ' smiddy/ to which the loungers with
their gossip and tittle-tattle daily gravitated to dis-
cuss the news of the district Eaglesfield
folk were a stiff race of countrymen, presenting stal-
wart forms in a coarse woollen garb of home-make,
and the horny hands and sweating brows of labour,
rejoicing in hamlet isolation, and heedless of the con-
tentions and turmoil of the world."*
i This vivid description helps us to clearly realise the
surroundings of Dalton' s early life. The one light of
the village was quakerism, and this the Daltons well
represented.
" The house in which Dalton was born has been
altered and much improved since his days ; its low
thatched roof has been raised and slated ; the par-
tially boarded loft converted into upper rooms ; its
small leaden windows displaced by large panes of
glass ; and the grey-stone facing of the building white-
washed. Still the general features of the interior of
the humble dwelling remain pretty much as when
occupied by weaver Joseph Dalton and his active
spouse Deborah."
"By a small porch, showing quaint recesses for pots
and pans, you enter the kitchen or general sitting and
business room of the family, where probably, Joseph
had his loom placed ; from this apartment, by a
narrow passage, you reach a smaller room immedi-
ately adjacent, in height and width six feet, and in
length fifteen feet. The recess to the left of the
* Lonsdale's Life of Dalton [Cumberland Worthies].
THE ATOMIC THEORY. 263
doorway was occupied by a chaff bed, upon which
Joseph and Deborah slept, and there John Dalton,
the chemist, first saw the light of day, on or about
September 6th, 1766." When Dalton afterwards
showed friends his birthplace he used to point with a
smile to the corner cupboard, where, in his early
boyhood, the sweets were kept. Having a great
longing for these, when his mother was one day out,
he tried to reach the door-handle, but was too small.
To effect his purpose he, regardless of consequences,
kicked a hole in the plaster of the wall below the
cupboard, and in this way gained a footing. Detec-
tion was, alas, inevitably certain, and his feat was
followed by an interview with an angry mother ter-
minated by a sound whipping.
All Dal ton's ancestors were real " sons of toil,"
but some of them must surely have had latent intel-
lectual power, or else whence did his wonderful in-
sight arise. His father, Joseph, showed no special
ability, or at least none is recorded of him. He
earned small wages by his shuttle, and had six chil-
dren, three of whom, Jonathan, Mary, and John,
grew to maturity. No record occurs of John's birth,
and the date of it is a matter of hearsay and guess-
work. He was sent to Pardshaw Hall school, two
and a half miles off, and placed under Mr. John
Fletcher. John was by no means a quick boy, either
at work or play. But he was steady-going and
thoughtful, and fond of his books. At ten or eleven
years old, Dalton delivered his first lecture to some
264 THE ATOMIC THEORY.
of his schoolfellows from the top of a hedge. The
audience was enthusiastic, and received his demon-
strations with loud applause. Mr. Fletcher was wise
enough to discern the boy's latent power, and led him
to begin the study of mathematics. Later on, Elihu
Eobinson, a Quaker gentleman of the neighbourhood,
helped him in his studies. Another youth, Alderson,
and he would puzzle together over a problem. Al-
derson was more ready to seek Robinson's help than
was Dalton. " Yan med deu't,"* John would say.
Such a dialogue as the following would sometimes take
place between Eobinson and Dalton :
. "Well, John, hast thou done that question ? "
" No ; yan med deu't," and then later, t( I can't
deu't to-neet, but mebby to-morn I will."
In 1785 he, with his cousin and brother, became
joint-managers of a school at Kendal. The school
was not a great success. He continued at Kendal till
1793, when he obtained a post of teacher of mathe-
matics and natural philosophy at New College, Mosley
Street, Manchester. In 1792 he made his first visit
to London, (( a surprising place," but " the most dis-
agreeable place on earth for one of a contemplative
turn of mind." In 1794 he first described colour-
blindness, being himself an instance of it. His dis-
covery of his own defect arose through the purchase
of a pair of stockings as a present for his mother.
His mother was somewhat startled by their appear-
ance, their colour being a brilliant red, unfit for any
* (Me might do it."
THE ATOMIC THEORY. 265
Quaker to wear. To Dalton they seemed a bluish
dark drab.
New College was removed in 1799 to York and,
unwilling to leave Manchester, where he evidently
formed close associations, Dalton became a private
tutor. In 1805 he took up his abode with the Kev.
\V. Johns, and lived with him in a very delightful
harmony. The way in which it came about was
characteristic of Dalton' s childlike simplicity. Johns'
wife met Dalton one morning :
" Mr. Dalton, how is it that you so seldom come
to see us ? "
" Why, I don't know, but I have a mind to come
and live with you."
At first the wife doubted whether he was serious,
but finding that he was so, she consulted with her
husband who had a true attachment for Dalton, and
the arrangements were made. Dalton came and
remained with them for the following twenty-six
years. " During the long period," says Johns'
daughter, " he and my father never, on any occasion,
exchanged one angry word."
Dalton was robust and muscular, and of a simple
and open countenance, his profile in old age striking
us with a certain strange beauty of enduring patience.
He stooped slightly, his height being about five feet
seven inches. His health, compared with that of
most of the chemists of whom we have spoken, was
exceptionally good. It is related that on one occasion,
when he had an attack of catarrh, his physician pre-
266 THE ATOMIC THEORY.
scribed James's powder. Next day, finding Dalton
better, he naturally put the cure down to his medi-
cine. "I do not well see how that can be," said
Dalton, "as I kept the powder until I could have an
opportunity of analysing it." In general company
Dalton was silent, and on religious topics extremely
reticent. He was fond of tobacco, and of Davy he
said, " the principal failing in his character as a
philosopher is that he does not smoke." He did not
marry ; he had never, he said, had time. The truth
of this statement may be doubted, but possibly the
smallness of his pecuniary resources may have helped
to prevent it. With growing age his capacity to
receive new truths seems to have become somewhat
narrowed, but he always preserved the genuine sim-
plicity of heart which lends an added charm to his
name.
It was in 1802 that Dalton conceived his theory.
The facts influencing him were such as these. He
noticed that nitric oxide would combine with two
different amounts of oxygen to form two distinct
more highly oxygenated compounds. These two
distinct compounds could be formed by combining
the nitric oxide (or nitrous air, as it was still called)
with a lesser or greater amount of oxygen. But
between these no definite compound could be ob-
tained. A compound of nitric oxide with either one
volume or two volumes of oxygen gas could be
got, but not between nitric oxide and one and a half
volumes of oxygen or one and three-quarters.
THE ATOMIC THEORY. 267
Again Dalton observed that marsh gas* contains
just double as much hydrogen as olefiant gas.t It
was these facts, as we learn from Thomson in his
History of Chemistry, which formed the foundations
of Dalton's theory. Meditating upon such facts as
these, Dalton asked himself why nitrogen will com-
bine with oxygen only in quantities which are simple
multiples of a certain number ? or why carbon will
similarly combine with hydrogen only in like definite
proportions ? Then came the brilliant hypothesis won
from this apparently barren fact.
It had been supposed by others long before Dal-
ton's time, by Democritus, Epicurus, and Lucretius,
that matter is made up of minute indivisible particles
or atoms. Just before Dalton's hypothesis was de-
veloped, Kirwan (1783) and Higgins (1789) had
suggested that chemical combination is due to the
approximation of these unlike particles. Higgins
represented certain compounds as formed by the
union of particles or atoms of the same weight, but
united in different proportions. So far had specula-
tion gone before Dalton's turn came, and so far spe-
culation was barren.
In spite of the efforts of other workers the concep-
tion remained until Dalton's time, wanting in cohe-
* Marsh gas is a hydrocarbon given off, as its name implies, in
marshes and forming the fire-damp of mines. It is evolved with
petroleum in petroleum springs, and the gas of the mud volcanoes at
Bulganak, in the Crimea, consists, according to Bunsen, of pure
marsh gas or methane. It exists in large quantities in coal gas.
t Bicarburetted hydrogen, olefiant gas, or ethylene, is formed by the
action of sulphuric acid on common alcohol.
2 63 THE A TOM 1C THEORY,
rence and consistency. But Dalton's keen intuitive
insight readily saw where the error lay. The hypo-
thesis was reasonable enough, but one fatal mistake
deprived it of influence upon science. The atoms or
different elements are not of equal weight, and Dai-
ton set about weighing them. It is not certain how
in some cases his results were arrived at. His first
table of atomic weights is introduced casually at the
close of a paper read before the Manchester Literary
and Philosophical Society, October 23rd, 1803, on
the absorption of gases by liquids. He applies his
theory, and wrongly, to the particular subject in
hand.
" The inquiry," he says, " into the relative weights
of the ultimate particles of bodies is a subject, as far
as I know, entirely new ; I have lately been prosecu-
cuting this inquiry with remarkable success. The
principle cannot be entered upon in this paper, but I
shall subjoin the results, as far as they appear, ascer-
tained by my experiments." He then gives a table of
the relative weights of atoms, starting with hydrogen
as unity. It is of special interest as being the first
table of atomic weights ; but as a table given at a later
date is less inaccurate, we shall quote that instead.
Before, however, proceeding farther we must notice
that three distinct ideas lie embedded in this atomic
theory of Dalton's. It includes the law of constant
proportions of Lavoisier and Proust, the law of de-
finite proportions of Richter* and others, and the law
* Wurtz terms Richter's law the law of proportionality.
THE ATOMIC THEORY. 269
of multiple proportions of Thomson, Wollaston, and
Dalton himself. Let us briefly consider what each of
these laws states.
The law of constant proportions asserts that in
every individual compound there is a fixed relation
between the weights of the elements composing it.
Thus. 216 grammes of mercuric oxide always contains
200 grammes of mercury and 1G grammes of oxygen.
It has a constant composition.
The law of definite proportions asserts something-
more than this. It asserts that there is a definable
relation between the proportions in which different
bodies unite. It is really a law of equivalence.
As an illustration we may take the following facts :
One part by weight of hydrogen combines with 35-5 parts of chlorine,
with 80 parts of bromine with l'26'o of iodine, or with 19 parts of
fluorine.*
Now 39 parts of potassium combine with 3 5 '5
parts of chlorine to form potassium chloride. 39
parts of potassium therefore combine with the same
amount of chlorine as does 1 part of hydrogen. We
naturally inquire farther, with how many parts of
the other elements just named will this quantity of
potassium combine ?
We find that
39 parts by weight of potassium combine with 35 5 parts of chlorine,
with 80 parts of bromine, with 126-5 parts of iodine, and with 19 parts
of fluorine.
39 parts of potassium therefore combine with the same amount of
chlorine, bromine, iodine, or fluorine, as does 1 part of hydrogen.
* To form the corresponding acids, hydrochloric, hydrobromic acids,
&o.
2 70 THE ATOMIC THEORY.
This is a striking relation. From these state-
ments it appears that 39 parts of potassium are
equivalent to 1 part of hydrogen. If we suppose the
compounds formed to be, in Dalton's nomenclature,
binary compounds, containing one atom of each ele-
ment, one of hydrogen to one of chlorine, one of
potassium to one of chlorine, and so on, we must
conclude that the atom of potassium is equivalent in
combining power to the atom of hydrogen, but weighs
39 times as much As a matter of fact the modern
atomic weight of potassium is approximately 39.
The law of multiple proportions contains an addi-
tional truth. It asserts that in a series of compounds
of the same elements, these are always combined
together in the proportion of simple multiples of
certain definite weights, the combining weights of the
elements combined. Thus, to take an example in the
series of hydro-carbons known as the paraffins, we
observe the following relations :
In the first of the series methane or marsh gas
12 parts of carbon are combined with 4x1 = 4 parts of hydrogen.
In the second, ethane
2 x 12 = 24 parts of carbon are combined with 6x1=6 parts of
hydrogen.
In the third, propane
3 x 12 = 36 parts of carbon are combined with 8x1=8 parts of
hydrogen.
In the fourth, butane
4 x 12 = 48 parts of carbon are combined with 10 x 1 =*10 parts
of hydrogen.
Starting with 1 6 parts of methane we cannot add
THE ATOMIC THEORY. 271
less than 12 parts of carbon* to get the next higher
compound. We could not, for instance, obtain a
compound containing 20 parts of carbon to 5 J parts
of hydrogen.
Again, in the case of the nitrogen oxides, already
united, we have a series of five compounds
The first containing 28 parts of nitrogen to 16 of oxygen (nitrous
oxide).
The second containing 28 parts of nitrogen to 2 x 16 = 32 of oxy-
gen (nitric oxide).
The third containing 28 parts of nitrogen to3x 16 = 48 of oxygen
(nitrogen trioxide).
The fourth containing 28 parts of nitrogen to 4 x 16 = 64 of oxygen
(nitric peroxide).
The fifth containing 28 parts of nitrogen to 5x16 = 80 of oxygen
(nitrogen pentoxide).f
Now, if we consider these facts in the light of the
atomic theory how can we explain them ? Very
simply ; thus : we cannot add less than 1 2 parts of
carbon at a time, because we cannot add less than
one atom of carbon at a time. The atom of carbon
we have reason to believe weighs twelve times as much
as the atom of hydrogen. In the first compound
one atom of carbon weighing 12 combines with four
atoms of hydrogen, weighing altogether 4, to form a
molecule of methane. The composition of the whole
volume of the gas is of course the same as the com-
position of each molecule, 1 2 parts of carbon to 4 of
h} 7 drogen. To get the next higher compound we add
* The reader must understand that the addition of carbon cannot be
made directly ; all that is meant is that no intermediate compound is
obtainable.
t The older formulae for these gases are, for present convenience
adopted.
272 THE ATOMIC THEORY.
one atom of carbon to each molecule of methane, and
the atom being indivisible we cannot add less. We
also add two atoms of hydrogen. Each molecule of
the gas (ethane) will now contain two atoms of car-
bon to six atoms of hydrogen, that is 24 parts by
weight of carbon to 6 of hydrogen, and the gas as
a whole, possessing the composition of each of its
own molcules, contains 24 parts of carbon to G of
hydrogen. In the case of the nitrogen oxides we may
picture the relation as simpler still, one atom of oxy-
gen being added at each step. Unfortunately, how-
ever, matters are here somewhat complicated by other
changes.
The law of combination in multiple proportions
may now be more shortly stated thus : The elements
unite in the proportion of simple multiples of certain
definite ^veights, called their combining weights.
It is easy to see how readily these laws fall into
their places under the atomic theory. Indeed, it
would be impossible to fully express them without
its aid. In the cruder form assumed by them in
Dalton's day, they led him to his great conception.
He conceived of each element as made up of minute
indivisible particles or atoms. These atoms for each
element had a definite weight of their own. How
did he arrive at this weight? To answer this question
we must form some idea of the different kinds of
combination possible among these atoms. In Dal-
ton's New System of Chemical Philosophy we find the
following : -
THE ATOMIC THEORY. 273
" If there are two bodies, A and B, which are dis-
posed to combine, the following is the order in which
the combinations may take place, beginning with the
most simple, namely :
1 atom of A + 1 atom of B = 1 atom of c, binary.*
1 ,, -f 2 ,, =1 ,, D, ternary.
2 ,, +1 , b =1 ,, B, ternary.
1 ,, + 3 ,, = 1 ,, F, quaternary."
arid so on. The left hand side of the equation re-
presents the elements combining, the right hand side
the compound formed. Dal ton applied the term
atom to the smallest particles of the resulting com-
bination where we now should use the word molecule.
Having formed this conception of the possible com-
binations, Dalton was further guided by the following
set of arbitrary rules. f
" 1st. When only one combination of two bodies can be obtained,
it must be presumed to be a binary one, unless some cause appear to
the contrary.
"2nd. When two combinations are observed they must be pre-
sumed to be a Unary and a ternary.
" 3rd. When three combinations are obtained we may expect one
to be a binary and the other two ternary.
"4th. When four combinations are observed we should expect
one binary, two ternary, and one quarternary.
" 5th. A binary compound should be specifically heavier than the
mere mixture of its two ingredients.
" 6th. A ternary compound should be specifically heavier than the
mixture of a binary, and a simple, which would, if combined, con-
stitute it.
" 7th. The above rules and observations equally apply when two
bodies, such as c and D, D and E, &c., are combined."
* That is, containing 1 one atom of each element ; a ternary com-
pound contains two atoms of one element, one of the other,
f New System of Chemieal Philosophy, pt. i.
274 THE ATOMIC THEORY.
From rule 1, Dalton deduced that water was a
binary compound. Water thus contained, according
to Dalton, one atom of hydrogen to every atom of
oxygen. Further, it contained, by weight, he said, 1
part of hydrogen to 7 parts of oxygen. Taking the
hydrogen atom as the unit of weight this meant that
the oxygen atom weighed seven times as much as the
lydrogen atom, the atomic iveight of oxygen was 7.
In his assumption that water was a binary compound
Dalton was wrong, but it was the best possible as-
sumption under the circumstances. Moreover, the
proportion of oxygen to hydrogen is not 7 to 1, but
very nearly 8 to 1 ; but this inaccuracy was necessary
to the determinations of that time. Ammonia, Dal-
ton also supposed to be binary, containing one atom
of nitrogen to every atom of hydrogen. By weight it
consisted, according to him, of 1 part of hydrogen to
5 of nitrogen. This meant that the nitrogen atom
weighed five times as much as the hydrogen atom,
the atomic weight of nitrogen was 5. " Nitrous gas"
(nitric oxide) he considered to be binary, containing
one atom of nitrogen to one of oxygen, 5 parts by
weight of nitrogen to 7 of oxygen, in accordance with
the atomic weights.
By steps such as these Dalton arrived at his table
of the atomic weights of the elements. Moreover, he
adopted a characteristic symbol for the atom of each
element, and combined these to symbolise the "atom"
of compounds. A few of his atomic weights are here
given. Had his determinations been correct they
THE ATOMIC THEORY.
2 75
should have been simple submultiples of the weights
now in use. The numbers he would have obtained
by accurate experiment appear in the second column.
Elements.
Dalton's atomic
weights.
Corrected
numbers.
Symbol.
Hydrogen
1
1
o
Nitrogen
4-66
CD
Carbon ....
5
6
Oxygen ....
7
8
O
Iron
38
28
O
Silver ....
100
108
OF COMPOUNDS.
Compound.
Dalton's atomic
weights.
Corrected
numbers.
Symbol.
Water ....
8
9
00
Carbonic oxide
12
14
00
Carbon dioxide
19
22
O0O
In Dalton's first table there are some curious inac-
curacies which it is difficult to explain. Thus the
" atomic " weight of nitric oxide should be the sum
of the weights of nitrogen and oxygen ; these in the
first table, are 4'2 and 5'5, giving 97. But 9'3 is the
number in the table. These discrepancies are difficult
of explanation.*
The symbols adopted at a somewhat later date
were analogous to those now in use, For these in
* See Roscoe on Dalton's first table of atomic weights, Nature,
1874.
27 6 THE ATOMIC THEORY.
most cases the first letter of the name of the element
is taken to represent the atom. Thus on the Dal-
tonian hypothesis that water is a binary compound,
containing one atom of hydrogen to one of oxygen, its
symbol will be HO, H representing the hydrogen
atom and the oxygen atom. Ammonia will be NH,
sulphuretted hydrogen HS, olefiant gas HC, carbonic
oxide CO, and carbonic acid CO 2 .
One word more must be said before closing this
account of Dalton's work. The fact of the inaccuracy
of his determinations should not be allowed to detract
from the grandeur of his conception. It should
rather enhance and elevate our admiration for his
talent, that with means so imperfect he could achieve
so much. It is easy from our modern laboratories to
lock back with a smile upon the crude methods in
use at Dalton's time. It is easy to suggest that
determinations so inaccurate could never alone have
given the atomic weights their true value and posi-
tion in ihe science. That may be, but it was Dalton's
intuitive penetration and patient thought which trans-
formed the old atomic theory from a baseless fancy
into ij resistless truth.*
* It is legitimate to term the atomic theory a truth, and one of a
high order, so long as we regard it as only expressing an analogy
between the actual constitution of matter and our conception of it. It
was by sifting the truth of the conception from the falsehood that
fche theory became capable of serving its science.
CHAPTER XV.
EIGHTH PERIOD: THE ATOMIC THEOEY.
THE DEVELOPMENT OF D ALTON'S IDEA.
HEN we wish to estimate the quantity of
anything we describe it in measures of
weight or of volume. Dalton described
the quantity of his individual atoms by
weight. The introduction of their mea-
sure by volume was to complete the
power of the atomic theory as a weapon
of science.
Gay-Lussac found that the relations existing
between the volume of one gas and that of another
with which it will combine, and that of the com-
pound formed, are very simple. The starting-
point was the determination of the volumetric com-
position of water by Gay-Lussac and Humboldt in
1805.
2 volumes of hydrogen unite with 1 volume of
oxygen to form 2 volumes of aqueous vapour,
278 THE ATOMIC THEORY.
2 volumes of nitrogen unite with one volume of
oxygen to form 2 volumes of nitrogen protoxide.
1 volume of chlorine unites with 1 volume of
hydrogen to form 2 volumes of hydrochloric acid.
1 volume of nitrogen unites with 3 volumes of
hydrogen to form 2 volumes of ammonia.
1 volume of carbonic oxide unites with 2 volumes
of chlorine to form 2 volumes of carbonyl chloride.*
Carbonic oxide is a compound gas, and therefore
not on quite the same footing as the rest of the
bodies mentioned in this table.
In 1808 Gay-Lussac stated his general law of gas-
eous volumes : The iveights of the combining volumes
of the gaseous elements bear a simple ratio to their
atomic weights. He suggested that the relative
weights of the gaseous volumes entering into combi-
nation exactly represent the relative weight of the
atoms. The specific gravities of the elementary
gases, i.e. their weight in terms of the weight of an
equal volume of hydrogen as unity, are therefore the
same as their atomic weights. Thus, taking the
unit volume of hydrogen to weigh 1, we find that
the unit volume of nitrogen weighs fourteen times as
much ;f the specific gravity of nitrogen is 14 and its
atomic weight is 1 4. This is the outcome of Gay-
Lussac' s theory, and establishes an intimate relation
between the volumes of the elementary gases and
their atomic weights.
t According to modern determinations.
THE ATOMIC THEORY. 279
The Italian chemist, Amedeo Avogadro, in 1811,
explained the relation between the volumes and the
combining weights by the supposition of a simple
relation between the volumes of gases and the number
of ultimate particles they contain. The hypothesis
put forward by Avogadro was that equal volumes of
all gases contain always equal numbers of these ulti-
mate particles.*
Let us consider the case of a compound, and, to
choose a simple case, take water. The volume of the
atom is necessarily taken as the unit volume. Now,
to use the language of the chemists of Gay-Lussac's
time : 2 volumes of hydrogen, i.e. 2 atoms of hydrogen,
unite with 1 volume of oxygen, i.e. 1 atom of oxygen,
to form 2 volumes of water, i.e. two atoms of water.
2 volumes of water thus contain 2 volumes of hydro-
gen and 1 volume of oxygen. Then comes the
difficulty, for it follows from this that 1 volume of
water, i.e. I atom of water, must contain 1 volume of
hydrogen, i.e. I atom of hydrogen and \ volume of
oxygen, i.e. \ atom of oxygen. T>y similar reasoning
we should find that 1 atom of hydrochloric acid gas
contains J atom of hydrogen and J atom of chlorine.
Obviously as we have started with the atom as the
ultimate particle and the indivisible unit, it is a con-
tradiction of our own theory to introduce J atoms
into it.
This difficulty was seen by Avogadro, and it seemed
* What these ultimate particles are will appear in the sequel.
Also see p. 271.
280 THE ATOMIC THEORY.
likely to invalidate his hypothesis about the relation
between the number of the ultimate particles and the
volumes of the gases. If the atom of water vapour
occupied twice the volume occupied by the atom
of oxygen the relation became less simple. But
Avogadro brought a subtle and, the same time, essen-
tial distinction to the aid of the theory. The ulti-
mate particle of water occupies the same volume as
two atoms of oxygen or of hydrogen, &c. The ulti-
mate particle of water consists of more than one
atom. It becomes in the end most simple to assume
that there similarly exists an ultimate particle of
oxygen gas made up of more than one atom. This it
is which occupies the same volume as the smallest
particle of water, and in modern language we call it a
molecule. But the molecule of water occupies the
same volume as two atoms of oxygen.
The molecule of oxygen is thus composed of two
atoms.
The chemical definition of an atom is :
An atom is the smallest portion of matter which
can enter into a chemical compound.
A molecule is the smallest quantity of an element
or of a compound which can exist in the free
state.
To illustrate these definitions, the smallest portion
of oxygen, represented by the symbol 0, can be trans-
ferred from one compound to another, but cannot
exist alone. Directly the atom is set free it tends to
combine with another atom either of its own kind
THE ATOMIC THEORY. 28 1
or not. The molecule of oxygen, consisting of two
atoms, and represented by the symbol 2 , can exist
free.
In the production of water by the combination of
oxygen and hydrogen, each molecule of oxygen is
acted on by two molecules of hydrogen. We may
represent this as an equation by the use of chemical
symbols. The first letter of the name is taken to
represent the atom, of the element, thus represents
an atom of oxygen occupying 1 volume and weighing
16.* To represent two atoms a small numeral is
placed below or above the symbol, 2 . The molecule
of water composed of two atoms of hydrogen to one
atom of oxygen, or of two volumes of hydrogen to
one volume of oxygen, or of two parts by weight of
hydrogen to 16 parts by weight of oxygen, is repre-
sented by the symbol H 2 ; two molecules of water
will be represented by 2H 2 0. Now we are ready to
express symbolically the formation of two molecules
of water from one molecule of oxygen and two mole-
cules of hydrogen.
2 + 2H 2 = 2H 2 0.
In this reaction the molecule of oxygen is separated
into its two constituent atoms, one of which goes to
each molecule of water. The atom of oxygen can
exist in the compound, water, but cannot exist by
itself.
Having now got some idea of what is the chemist's
* That ia 16 times the weight of an atom of hydrogen, the atom
of hydrogen, the lightest element known, being always taken as unity.
282 THE ATOMIC THEORY.
conception of atom and molecule we can give a clear
and concise statement of Avogadro's law :*
Equal volumes of gases and vapours at equal
temperature and under the same pressure, contain
the same number of molecules, and consequently the
relative weights of these molecules are proportional fo
the densities of the gases or vapours.
This is often termed the law of Avogadro and Am-
pere, for the latter, in 1814, propounded ideas similar
to those of the Italian chemist. He drew a distinction
between particles and molecules, the molecule pf Am-
pere corresponding to the modern atom. According
to Ampere the distances between the individual (< par-
ticles " of gases, or, as we should say, their molecules,
''depends entire upon the heat to which the gas is
subjected." Under equal pressure and temperature
the molecules of all gases are equidistant from each
other. From these suppositions the fact, already
noticed, of the equal expansibility of all gasesby equal
rise of temperature or fall of pressure follows as a
simple deduction. The fact that all gases have- the
same co-efficient of expansion as air was first dis-
covered by Charles. This co-efficient is independent
of pressure. These two laws were arrived at indepen-
dently by Dalton and Gay-Lussac, and it was the
latter chemist who first accurately determined the
co-efficient of expansion of gases. They are in
complete harmony with the hypothesis of Avogadro
and Ampere.
* Journal de Physique, xxxiii. 58.
THE ATOMIC THEORY. 283
The great achievement of Avogadro and Ampere
was not, however, well received by chemists. Its
simplifying power was not acknowledged, and other
and more confused ideas were for many years pre-
ferred to it. This is only one of the many instances
of a great scientific truth being ignored by the men
of science themselves. Contradictions were found to
occur in the rigorous application of the hypothesis,
a*hd it was too readily concluded that a speculation
not immediately and in every detail commendable to
the average scientific mind must for ever remain
barren. The simplicity and truth of Avogadro's
hypothesis were indeed too far in advance of the time.
The great Swedish chemist, Berzelius, attempted a
union between the atomic hypothesis and the law of
volumes. His views were first stated in 1813, but
were more perfectly presented in 1818. He con-
ceived that equal volumes of the simple gases contain
not only, as Avogadro and Ampere had stated, equal
numbers of molecules, but equal numbers of atoms, so
that to compare densities was to determine not merely
the relative weights of the molecules but the relative
weights of the atoms. Thus if we find that a litre of
chlorine weighs 35*5 times as much as a litre of
hydrogen, we may, according to Avogadro, conclude
that the molecule of chlorine is 3 5 '5 times as heavy
as the molecule of hydrogen. But if the molecules
of hydrogen and of chlorine may contain any numbers
of atoms, this tells us nothing about the atomic
weight. Now if we suppose that each molecule of
284 THE ATOMIC THEORY.
hydrogen contains two atoms, and each molecule of
chlorine the same number, the comparison of mole-
cules comes to the same thing as the comparison of
atoms. 3 5 '5 may now be taken as the atomic weight
of chlorine.
This was the view taken by Berzelius. In general
it holds good, but in some cases there are marked
exceptions. Thus the vapours of liquids at a tem-
perature not far removed from their boiling points
often exhibit very anomalous densities. Taking the
atomic weight of sulphur as 32, its vapour density, 90,
not far above its boiling point, shows that the mole-
cule at that temperature must consist of six atoms."""
Above 860 its vapour density (32) corresponds to
its atomic weight. The molecule of six atoms is
broken up into 3 molecules of two atoms each.
The hypothesis of Prout was set forth about this
time (1816), to the effect that the atomic weights of
the elements were integral multiples of that of hy-
drogen. One of the advantages claimed for such a
system of weights was that it would enable us to con-
ceive of hydrogen as the primordial element, from
which the others were formed by successive con-
densations. The J or J of the atomic weight of
hydrogen has been suggested as the atomic weight of
this fundamental element, but even then the weights
cannot be reduced to integral multiples of it. The
* Sulphur boils, according to Regnault, under normal pressure at
44S-4 centigrade, its vapour density being, according- to Dumas, 35-55
at 524.
THE ATOMIC THEORY. 285
suggested hypothesis of a single primordial element
is not, however, to be lightly set aside. It is a pro-
found speculation, and viewed rightly, may afford
valuable guidance to future research.
Two important principles were at this time formu-
lated and incorporated by Berzelius in his table of
atomic weights. The first was the law of specific
heats of Dulong and Petit. We must first offer some
explanation of what is to be understood by the term
specific heat. Shortly, then, it is found that equal
weights of different bodies require different amounts
of heat to raise them through the same number of
degrees of temperature. The unit of heat or thermal
unit may be taken as the quantity of heat necessary
to raise 1 gram of water through 1 centigrade. It
takes less heat to raise a gram of nickel one degree
than to raise a gram of water through the same
temperature.
Now a body will give out on cooling through
a certain number of degrees the same amount of heat
as would be needed to raise it through the same
number of degrees. To find how much is needed
we may therefore mix a certain weight of the heated
substance with a certain weight of cold water. Thus
suppose we mix 100 grams of metallic nickel at
100C. with 100 grams of water at 10C. When
the heat of the nickel has become equally diffused
through the water we find the temperature to have
risen to 18*9. The nickel has cooled through
81-1, and has in so doing heated an equal weight of
286 THE ATOMIC THEORY.
water through 8 -9. 100 grams of nickel thus re-
quires 890 units of heat to raise it through 8 1-1.
But 100 grams of water requires 8110 units of heat
to raise it through 81 '1, since 1 gram needs 1 unit
to raise it through 1. Thus the 100 grams of nickel
takes g-WV times as much heat to raise it through a
given temperature as does the same quantity of
of water. Its specific heat is -g- 8 T 9 T o- = '1097.
The quantity of heat which would raise the tempera-
ture of a given weight of nickel through 1 C. would
raise the temperature of a given weight of water
through only "1097 C. In actual experiments of the
kind just described, the specific heat of the calori-
meter or vessel in which the water is contained must
be taken into account. It of course becomes heated
at the same time as the water, but to understand
the bearing of Dulong and Petit's law, it is unneces-
sary here to enter into further detail.
In 1819 these chemists gave the specific heats of
many solid bodies, particularly metals, and made the
observation that in most cases they were inversely
proportional to the atomic weights. The specific
heat gives the capacity of each gram of the substance
for heat. If we multiply this number therefore by
the atomic weights we shall get the capacities of the
atoms for heat, or, as it is termed, the atomic heat of
the elements. On performing this multiplication we
see that with the greater number of the solid elements
the atomic heat is a nearly constant quantity. The
atomic heats of most of the elements are found to lie
THE ATOMIC THEORY.
287
near 6*4. Dulong and Petit's law then states that
the atomic heat of the elements is a constant quantity ;
or that the atoms of all simple bodies have precisely
the same capacity for heat*
It is readily seen that this generalisation must be
of great service in controlling the atomic weights.
In the case of these metals a very close adherence to
the law is observed, so that Dulong and Petit corrected
by its means the atomic weights of zinc, iron, nickel,
copper, lead, tin, and gold. In the case of these
metals the atomic weight attributed by Berzelius had
been just double that which was in accordance with
the law of specific heats. Their weight was therefore
halved and the formulae of the oxides changed from
Zn0 2 , Fe0 2 , Ni0 2J Cu0 2> &c., to ZnO, FeO, NiO,
CuO, &c.t
A few of the specific and atomic heats are given
below :
Element.
Specific heat.
Temperature of
observation.
Atomic
weight.
Atomic heat.
Zinc .
0-0955
+ 55
64-9
62
Cadmium
0-0567
+ 55
111-6
6-3
Lead .
0-0315
+ 34
206-4
6-5
Mercury
0-0319
59
199-8 6-4
Iron
0-1140
+ 58
55-9 6-4
Among the non-metals carbon has an atomic heat
which is far too low. In the form of diamond its
atomic heat at 45 is 1*8. It is found, however, that
* Annalcsde Chimie, 1819.
t Fe iron (ferrum), Cu copper (cuprum), Zn zinc.
2 88 THE ATOMIC THEORY.
its atomic heat rises with the temperature and at
985 is 5-51.
Another generalisation destined to exercise consi-
derable influence upon the development of the atomic
theory was the law of isomorphism made known
by the German chemist, Mitscherlich, in December,,
1819. Mitscherlich observed that similarity of con-
stitution in salts tended to produce similarity of
crystalline form. Thus potassium chloride is isomor-
phous with sodium chloride ; magnesium sulphate is
isomorphous* with the sulphate of zinc and nickel.
Ordinary sodium phosphate is isomorphous with the
corresponding sodium arsenate. The similarity of
constitution is exhibited in the following formulae,
the water of crystallization being united by a plus
sign to the formula of the salt. Ordinary sodium
phosphate is phosphoric acid, H 3 P0 4 , in which 2
atoms of hydrogen are replaced by sodium, Na 2 HP0 4 ;
and it crystallizes with 12 molecules of water,
Na 2 HP0 4 + 12H 2 0. The corresponding arsenate is
similarly derived from arsenic acid, H 3 As0 4 , and is
thus represented by the formula Na 2 HAs0 4 +
12H 2 0.f As a last instance we may take the case
of sodium nitrate isomorphous with calc-spar (calcium
carbonate), the formulae being respectively NaNO 3 and
CaCO 3 . Upon the older view of the constitution of me-
tallic salts, the view held down to the time of Gerhardt,
* i.e. built up or constructed on the same lines ; from isos, equal ;
and morphe, shape.
t For explanation of any of these symbols see the table of modern
atomic weights given below.
THE ATOMIC THEORY. 289
that they were formed by the union of an acid with
a basic oxide, the formulas of these salts would be-
come N 2 5 + Na 2 and CO 2 + CaO ; the similarity
of constitution would be obscured and the fact of
their isomorphism remain unexplained.
Mitscherlich's law of isomorphism was stated by
him as follows : The same number of elementary
atoms, combined in the same manner, produce the
same crystalline form, and this form is independent of
the chemical nature of the atoms, and determined
solely by their number and arrangement. The
statement so made is somewhat too wide, and impor-
tant restrictions and exceptions have to be allowed.
Nevertheless, the law is an important one, and had
considerable influence with Berzelius in his deter-
mination of atomic weights. Chromium oxide being
Cr 2 3 the isomorphism of chrome alum and iron
alum led to the adoption of Fe 2 3 as formula for
ferric oxide and FeO for ferrous oxide. The adoption
of the last formula led, by chemical analogy and
isomorphism, to similar formulas for lime (calcium
oxide), magnesia (magnesium oxide), and zinc oxide.
Thus this law as well as the law of specific heats
could only be recognised by halving the atomic
weights of a number of metals, and the weights were
accordingly halved.
Guided by these considerations Berzelius adopted
the atomic weights given by him in 1826. His
weights are referred to oxygen as 100. On calcula-
ting them for the atomic weight of hydrogen as the
T
290
THE ATOMIC THEORY.
unit we are struck by the very remarkable accuracy
of the results lie had arrived at. All the accurate
appliances of modern chemistry and the labour of
"workers of unexampled patience and skill have only
in the more important cases succeeded in effecting
alterations in the decimal places of his atomic
weights. A few examples from his table may here
be given.
Element.
Symbol.
Atomic weights
referred to
Oxygen as 100.
Atomic weights
referred to
Hydrogen as 1.
Modern
atomic weights.
Oxygen
Carbon
c
100
76-44
16-02
12-26
15-96
Phosphorus
Sulphur
Selenium
p
s
Se
196-14
201-17
494-58
31-44
32-24
79-26
30-96
31-98
79-0
Iodine
I
789-75
126-56
126-53
Chlorine
Cl
221-33
35-48
35-37
Calcium
Ca
256-02
41-04
39-9
Aluminium
Al
171-17
27-44
27-3
Zinc
Zn
403-23
64-62
64-9
Up to this point the atomic theory had progressed
rapidly, but the chemists began to repent of their
rapid adoption of the new ideas. Atomic weights
had at their first start been regarded as expressive of
what quantities of the different elements were equi-
valent to each other. Upon this idea the theory had
been founded, it was difficult to change its foundations,
it was difficult to admit that additional facts must be
contained in the formulae adopted. Gay-Lussac,
Wollaston, and Gmelin used their influence in favour
of atomic weights founded only upon equivalence, and
THE ATOMIC THEORY. 291
Berzelius was obliged in some points to give way.
He did not, however, readily yield, and, driven back
to the older formula), he adopted HO, H6i and H 3 ^,
as formulae for water, hydrochloric acid and ammonia,
regarding H as a double atom of hydrogen represent-
ing the equivalent of other chemists.
Any inaccuracies in the conceptions of Berzelius
now came rapidly to light. We have seen how he
considered the vapour densities of the elements,
where obtainable, as identical with their atomic
weight. Avogadro had stated that equal volumes of
gases or vapours contained equal numbers of molecules.
Berzelius, in the case of the elements at least, held
that they contained equal numbers of atoms. In
some cases this idea proved to be erroneous. Thus
we are obliged to adopt 200 as the atomic weight of
mercury. The laws of Dulong and Petit, the vapour
densities of its volatile compounds, and purely
chemical considerations necessitate the adoption of
this weight. But, as first pointed out by the French
chemist Dumas, the vapour density of mercury
vapour compared with that of hydrogen is very
nearly 100. It is only half what, according to the
ideas of Berzelius, it should be. There is not the
same number of atoms in a litre of hydrogen and of
mercury vapour. The atom of mercury occupies
twice the space that the atom of hydrogen does. If
the molecule of hydrogen consists of two atoms,
the molecule of mercury vapour consists of one.
Anomalous vapour densities were also found by
292 THE ATOMIC THEORY.
Dumas, in 1832, in the cases of phosphorus and
sulphur. In the case of sulphur the molecule is
disintegrated at a high temperature, but phosphorus
preserves a four-atom molecule at 1040 (Deville and
Troost), Avhile the molecule of arsenic consists of four
atoms at 860 (Deville and Troost).
In consequence of this and other actual or
supposed flaws in the theory of Berzelius the system
of chemical equivalents, as distinguished from the
true atomic weights, gradually gained ground. The
attempt to represent as equivalent molecules not
really comparable led to great complication and
difficulty. Into this labyrinth it is unnecessary here
to attempt to follow chemical theory. An emergence
began with the work of Laurent and Gerhardt* but
the influence of these chemists like that of A.vogadro
was unrecognised and unrewarded till they passed
beyond gratitude or condemnation.
* For the work of these two chemists Laurent's Chemical Method
(Cavendish Society) may be consulted.
CHAPTER XVI.
EIGHTH PERIOD: THE ATOMIC THEORY.
THE ATOMIC THEORY OF TO-DAY.
,HERE are a number of reactions in organic
chemistry as a result of which carbonic
acid, water, or ammonia is produced.
Gerhard t noticed a curious point with
regard to these reactions when written out
as equations in the formula in use in his
day. The equations were observed never to con-
tain formula} for single molecules of water or car-
bonic acid, while they did contain single molecules
of ammonia. The acute mind of Gerhardt sought
for a cause of this strange fact. Representing the
molecules of carbonic acid and water by CO 2 and HO,
never less than two molecules of either occurred in the
representation of these reactions. It appeared to Ger-
hardt an unwarrantable supposition to conclude that
these substances were never liberated in less than two
294 THE ATOMIC THEORY .
molecules at a time. For example, let us take oxida-
tion of alcohol to aldehyde. On the old system of
atomic weights this is formulated :
<7*# 6 o 2 -f o 3 = 2HO -f CWCP
alcohol + oxygen = water + aldehyde.
Again, take the action of any acid upon alcohol :
CH*(P -f HCl = C*H*Cl -f 2HO.
We here see two molecules of water always liberated,
and on this system it was possible always to represent
the water taking part in a reaction as a whole multi-
ple of H 2 2 . The use of the formula HO seemed to
Gerhardt to be therefore in a large measure gone. So
too with the formula CO 2 , and both were accordingly
doubled, becoming H 2 2 and C 2 4 . These formulae
were the true equivalents of the formulas then in use
for ammonia, NH 3 . So too S 2 4 and C 2 2 represented,
according to Gerhardt's equivalents of sulphur, dioxide
and carbonic oxide.* The same equivalent, might,
however, be obtained by simpler means, and instead
of using these double formulae, Gerhardt concluded
that the atomic weights of carbon, sulphur, and
oxygen should be doubled. The school of equivalent
chemists had assigned to these elements the weights
6, 16, and 8 ; Gerhardt adopted the atomic weights
12, 32, and 16. C 2 , representing two atoms of car-
bon weighing 1 2 times as much as the atom hydrogen,
is thus replaced by C representing one atom weighing
the same amount. In this way the double formulae
are halved and become CO 2 , H 2 0, SO 2 , and CO. These
* The molecules represented by these formulae would occupy four
volumes, if the molecule of hydrogen, H 2 , be taken as occupying two.
THE ATOMIC THEORY, 295
formulae possess the great advantage of being in ac-
cordance with Avagadro's law of volumes. The older
formulae were not comparable in this respect. Thus the
molecule of ether vapour, C 4 H 5 0, would occupy two
volumes, while that of alcohol vapour, C 4 H 6 2 , would
occupy four. Williamson showed, by purely chemical
reasoning, that the old formula of ether must be
doubled. It then becomes simpler to use the new
atomic weights, and the molecular formulae of ether
and alcohol then become C 4 H 10 and C 2 H 6 0, each
occupying two volumes.
After adopting the new atomic weights, Gerhardt
saw that it would be necessary to halve the organic
formulae so obtained, if single molecules of water or
carbonic acid were to appear in the equations, and if
the formulae were to be brought into accordance with
the law of volumes. But here he was met by a diffi-
culty. Silver acetate under his new system had the
formula C 4 H 6 Ag0 4 . How could this be halved, seeing
that it contained only one atom of silver ? Gerhardt
solved this problem by halving the atomic weight of
silver. The formula then became G 4 H 6 Ag 2 4 , and
when halved, C 2 H 3 2 Ag. Oxide of silver then became
Ag 2 0, analogous to water H 2 0. In following out his
analogy, Gerhardt halved the atomic weights of a
number of metals. He went too far, but in many
cases the idea was a correct one.
The reforms of Gerhardt necessitated a change in
the conception of the constitution of salts. Previously
salts were considered as combinations of an acid oxide
with a basic oxide. Silver nitrate was, for instance,
29 6 THE ATOMIC THEORY.
regarded as a combination of silver oxide with nitrogen
pentoxide, AgO.NO 5 . Under the new regime such
formulae became simplified, and silver nitrate became
Ag 2 N 2 6 and thus AgNO 3 . The old ideas as to the
constitution of salts thus became untenable, and we
now define a salt as an acid having the whole or part
of its hydrogen replaced by a metal.
Laurent adopted and extended the notions of Ger-
hardt. He pointed out that the hydrates cannot be
considered as compounds of oxide and water, any
more than the salts could be considered as compounds
of oxide with oxide. A hydrate, said Laurent, is an
intermediate stage between water and oxide.
Water is H 2 0; when one hydrogen atom is re-
placed by potassium it becomes KHO, caustic potash ;
when two atoms are replaced it becomes K 2 0, potas-
sium oxide. There is a close analogy here between
the organic and inorganic compounds. Replacing
one hydrogen atom by the organic radical ethyl
(C 2 II 5 ) we obtain ordinary alcohol. Replacing both
hydrogen atoms we obtain ordinary ether.
H 2 0, water. H 2 0, water.
KHO, potassium hydrate. (C 2 H 5 ) HO, alcohol.
K 2 0, potassium oxide. (C 2 H 5 ) 2 0, ether.
Cannizzaro (1858) doubled the atomic weight of a
number of metals once more in accordance with the
law of specific heats, and by a series of gradually
narrowing oscillations the opinions of chemists at
length gravitated to an almost stationary point, and
the table of atomic weights and system of formulae
now adopted is the result of their agreement.
THE ATOMIC THEORY.
297
The following is a table of the atomic weights now
in use.*
Element.
Atomic
Weight.
Sym-
bol.
Element.
Atomic
Weight.
Sym-
bol.
Aluminium . .
27-3
Al
Molybdenum
95-8
Mo
Antimony . .
120-0
Sb
Nickel. . . .
58-6
Ni
Arsenic . . .
74-9
As
Niobium . . .
94-0
Nb
Barium . . .
136-8
Ba
Nitrogen . . .
14-01
N
Beryllium . .
9-2
Be
Osmium . . .
198-6
Os
Bismuth . .
210-0
Bi
Oxygen . . .
15-96
Boron ....
11-0
B
Palladium . .
106-2
Pd
Bromine % .
79.75
Br
Phosphorus . .
30-96
P
Cadmium . .
111-6
Cd
Platinum . . .
196-7
Pfc
Caesium . . .
132-5
Cs
Potassium . .
39-04
K
Calcium . . \
39-9
Ca
Rhodium . . .
104-1
Rh
Carbon . . .
11-97
C
Rubidium . .
85-2
Rb
Chlorine . .
35-37
Cl
Ruthenium . .
103-5
Ru
Cerium . . .
141-2
Ce
Scandium . .
44-0
So
Chromium
52-4
Cr
Selenium .
79-0
Se
Cobalt. . . .
58-6
Co
Silver ....
107-66
Ag
Copper . . .
63-1
Cu
Silicon ....
28-0
Si
Didymium . .
147-0
Di
Sodium . . .
22-99
Na
Erbium . . .
169-0
Er
Strontium . .
87-2
Sr
Fluorine .
19-1
F.
Sulphur .
31-98
S
Gallium . . .
69.8
Ga
Tantalum . .
182-0
Ta
Gold ....
196-2
Au
Tellurium . . .
128-0
Te
Hydrogtn . . .
1-0
II
Terbium . . .
148-5
Tr
Indium . . .
113-4
In
Thallium . . .
203-6
Tl
Iodine ....
126-53
I
Thorium . .
231-5
Th
Iridium . . .
192-7
Ir
Tin
117-8
Sn
Iron ....
55-9
Fe
Titanium . . .
48-0
Ti
Lanthanum . .
139-0
La
Tungsten . . .
183-5
W
Lead ....
206-4
Pb
Uranium . . .
240-0
u
Lithium . . .
7-01
Li
Vanadium . .
51-2
V
Magnesium .
23-94
Mg
Yttrium . . .
92-5
Y
Manganese . .
54-8
Mn
Zinc ....
64-9
Zn
Mercury . . .
199-8
Hg
Zirconium
90-0
Zr
* Some of the symbols are derived from the Latin names of the
elements, e.g., Potassium, K (Kalium] ; Silver, Ag (Argentum) ;
Sodium, Na (Natrium], ; Mercury, Hg (Hydrargyrum], &c,
298 THE ATOMIC THEORY,
In the above table the non-metallic elements are
printed in italics. The distinction between metals
and non-metals is a convenient one, but the two
classes are not sharply separated from each other.
It is in Geber's writing that the first definition of a
metal occurs: "Metallumest corpus miscibile, fusibile,
et sub malleo ex omni dimensione extendibile."* The
discovery of the brittle metals (antimony, bismuth,
and zinc) destroyed the completeness of this defini-
tion. There is no attempt now at a sharply drawn
distinction, but the metals are, as a rule, distinguished
by their peculiar lustre. The metals are also cha-
racterized by the formation of basic oxides. These
basic oxides unite with acid oxides, the oxides of the
non-metallic elements, to form salts. Thus copper
oxide, CuO, unites with sulphur trioxide, S0 3 , to
form copper sulphate, CuSO 4 . If now an electric
current be passed through a solution of this salt it is
decomposed, and the copper is deposited at the nega-
tive pole. Copper is thus positive as compared with
the other group SO 4 , and its oxide is termed positive
or basic. The non-metals have a special tendency
to form negative oxides. Thus sulphur forms two
oxides, S0 2 and S0 3 ; both are negative, and com-
bined with water form respectively sulphurous and
sulphuric acids, H 2 S0 3 and H 2 S0 4 . The hydrogen
in these acids may be replaced by a metal to form a
salt, and, indeed, the acids themselves may be re-
* " A metal is a fusible body susceptible to combination, and wbich
may be extended in all directions under the hammer."
THE ATOMIC THEORY. 299
gar Jed as hydrogen salts (hydrogen sulphite and sul-
phate), and hydrogen itself considered as a metal
owing to its numerous chemical resemblances to that
class of bodies. We already know a liquid metal,
and there is no a priori objection to the existence of
one which is gaseous at ordinary temperatures. On
January 10th, 1878, Raoul Pictet, of Geneva, suc-
ceeded in liquefying hydrogen under a pressure of G 5
atmospheres and at a temperature of -140. When
the stopcock was opened a steel-blue coloured, opaque
jet of liquid hydrogen rushed out, and particles of
solid hydrogen fell with a rattle upon the floor. If
this solid hydrogen could be examined it would per-
haps agree with ordinary ideas of a metal.
This table of the atomic weights is based upon the
great laws of the atomic theory already discussed.
It is founded on the laws of constant, definite,
and multiple proportions. Its supporting pillars
are the laws of volume, of specific heat, and of
isomorphism.
Take the symbol of any individual element and
ask what does it tell us ? is the symbol for the
atom of oxygen weighing 15 '9 6 and occupying one
volume. Further, as in most cases the density of a
gaseous element corresponds with its atomic weight,
we learn that the density of oxygen as compared
with hydrogen at the same temperature and pressure
is about 16. But this is not all; if we express the
atomic weight in grams instead of in hydrogen units
15*96 grams of oxygen occupy 11 -2 litres, aod in
300 THE ATOMIC THEORY.
the same way 1 gram of hydrogen occupies 11*2 litres,
All this is contained in the symbol 0.
Take now the symbol of a metal, lead, Pb. This
represents an atom of lead weighing 20 6 '4, and if
this atomic weight be correct we must assume that
this amount of lead in the gaseous state would occupy
one volume. We also know that the atomic weight
multiplied by the specific heat of lead must give a
result approximating to 6 '4, and we can thus calcu-
late the approximate specific heat of the metal.
Let us now pass to the case of compounds. What
do we learn from the symbol CO 2 ? It represents
one molecule of carbon dioxide containing 1 atom of
carbon and 2 atoms of oxygen, that is 12 parts of
carbon* and 2 X 16 32 parts of oxygen. This
molecule we know will occupy 2 volumes, and con-
tains its own volume of oxygen. It occupies the
same volume as 2 atoms of hydrogen, weighing 2.
Its density compared with hydrogen is therefore
32 -1-12
= 22, or half its molecular weight. If the
molecular weight of carbon dioxide were unknown we
could deduce it from its density. The molecular
weight of a gaseous compound is always equal to twice
its specific gravity compared with hydrogen. If the
molecular weight of carbon dioxide be expressed in
grams we see that 44 grams of the gas occupy 2 2 '4
litres (i.e. 2X11 -2), and contain 2 2 '4 litres of oxygen.
* In ordinary use decimal places in the atomic weights smaller or
greater than '5 may be disregarded.
THE ATOMIC THEORY. 301
When a substance, as ordinary quick-lime (calcium
oxide), CaO, cannot be volatilised, we cannot defi-
nitely say that the true molecular formula has been
determined. Indeed, it is probable that in the solid
state most bodies have complicated molecules consist-
ing of aggregations of many molecules of the same
substance when gaseous.
Lastly, let us see what is contained in an ordinary
chemical equation,
2 Ho -f 2 2H 2 0.
Interpreted, this means that two molecules of hydro-
gen, weighing 4 and occupying 4 volumes, combine
with one molecule of oxygen, weighing 32 and occu-
pying 2 volumes, to form two molecules of water
weighing 2 x 18 = 36 and occupying 4 volumes.
Also we see that 4 grams of hydrogen, occupying
4 X 11-2 = 44-8 litres, combine with 2 X 16 = 32
grams of oxygen, occupying 22*4 litres, to form 36
grams of water vapour occupying 2 2 '4 litres.
Other equations representing interchanges may be
similarly interpreted, though in many cases the volume
relations cannot be so fully given. As a case take
the following:
Bad 2 -f- CuSO 4 = BaSO 4 + CuCi 2 .
* If we add a solution of barium chloride to one of
copper sulphate a precipitate of baric sulphate is
obtained, and cupric chloride remains in solution.
The chlorine is here transferred from the barium to
the copper, and the SO 4 group from the copper to the
qarium. By consulting the table of atomic weights
302 THE ATOMIC THEORY.
the reader may follow out this reaction quantita-
tively.
It will not be difficult now to sec the immense
advantage conferred upon chemistry by this concise
and accurate method of recording and generalising its
facts. The coping-stone has yet, however, to be put
in place. This is the idea of valency or atomicity
developed by the aid of .a large number of workers,
among whom were Dumas, Williamson, Odling, Kekule',
and many others. We have seen that a certain school
of chemists, disdaining the use of Avogadro's hypo-
thesis or Dulong and Pe tit's law, wished to restrict
chemical symbols to a representation of the equivalent
weights of the elements, or those quantities which were
of the same value. When the real atomic weights
came to be adopted it was, however, seen that the
true atoms of the elements were not really equivalent
to each other, they had not all the same capacity for
combination. Some elements would combine together
only in single atoms, one with one ; they were termed
monads, and said to be monovalent. Other elements
could combine with two atoms of a monad element,
and were thus termed diads, or said to be divalent or
diatomic. As an illustration, hydrogen, chlorine,
bromine, iodine, fluorine, potassium, sodium, are taken
to be monovalent. Their atoms combine together in
pairs, one atom of hydrogen with one of chlorine,
forming a molecule of hydrochloric acid, and so on.
The fact that the molecule of hydrogen consists of
two atoms explains why the molecular weight of a
THE ATOMIC THEORY. 303
compound is equal to tivice its vapour density com-
pared with hydrogen. Taking hydrogen, fluorine,
chlorine, bromine, iodine, as monovalent, we gain
insight into the valency of other elements from a
survey of the following compounds :
HgCl 2 , Hgl 2 ; OH 2 , OC1 2 ; SH? ; SeH? ; ZnCl 2 ; NH 3 ; PCI 3 ;
AsH 3 , AsCl 3 , Asl 3 ; CH 4 , CC1* ; SiF 1 ; PF* ; NbCl 3 ; WCP ; WC1 6 .
Oxygen is here seen to be divalent (OH 2 ), arsenic
trivalent (AsH 3 ), and carbon tretravalent (CH 4 ).* The
valency of an element was formerly regarded as defi-
nitely fixed. As a matter of fact, however, many
elements are capable of exhibiting different valencies
in different compounds. Thus, phosphorus is triva-
lent in the trichloride, PCI 3 , and pentavalent in the
pentafluoride, PF 5 .
Combining power runs parallel to replacing power.
An element capable of combining with two monovalent
atoms will be capable of replacing two also. Each
zinc atom combines with two chlorine atoms in the
chloride, ZnCl 2 ; each zinc atom replaces two hydro-
gen atoms of sulphuric acid, H 2 S0 4 , in the sulphate,
ZnSO 4 .
Valency or " atomicity " is variable, but the con-
ception does not on this account lose its significance.
In some elements it is much more strictly marked
than in others, and the very variability of it is char-
acteristic of certain elements (e.g. tungsten) and there-
fore useful. What has yet to be done is to find out
* The prefixes mono, di, tri, tetra, penta, sex, hepta, octo, must be
understood to stand respectively for one, two, three, four, five, six,
seven, eight.
304 THE ATOMIC THEORY. . .
the laws of the variation of valency, to determine the
conditions under which it varies.
While upon the subject of valency a word must be
said with regard to the structural formulae of com-
pounds, a subject now of the highest importance.
Can we tell in what manner the atoms are combined
together in the molecule ? Take such a simple case
as water, H 2 0. How are the atoms combined together ?
In the molecule of free hydrogen, H 2 , we must suppose
each hydrogen atom directly united to the other, and,
representing direct union by a straight line, our
structural formula becomes H H. Similarly the
molecule of hydrochloric acid, where monovalent
hydrogen is combined with monovalent chlorine, is
H Cl, and the most natural conclusion is that the
structural formula for the molecule of water, where
monovalent hydrogen is combined with divalent oxy-
gen, is H H. This formula is entirely supported
by chemical facts. The two hydrogen atoms in this
molecule being similarly united to the oxygen atom
would be expected to play a similar role, and this is
actually found to be the case. The compound
obtained by replacing one hydrogen atom by potas-
sium is always the same substance. But if the two
hydrogen atoms were differently combined we should
expect them to play different parts, and to give rise
to two distinct compounds according as one or the
other was replaced by potassium or other metal.
Furthermore both atoms may be so replaced, a common
property further accentuating their similarity. In
THE ATOMIC THEORY. 305
the same way either or both atoms may be replaced
by an organic radical, as in alcohol C 2 H 5 OH and ether
C 2 H 5 .O.C 2 H 5 , and we thus become convinced of the
similarity of the two hydrogen atoms in water which
we consider as each directly united to the oxygen
atom. Other and far more complicated structural
formulae are built up by similar reasoning. It is
obvious that in building up such formulae considera-
tions of valency will often be useful, enabling us to
detect which arrangement is in accordance with the
prevalent valency of the elements, and therefore which
arrangement is most probable.
It may be asked what purpose do such structural
formulae serve ? They enable us, in the first place, to
express the internal molecular structure of a com-
pound, so that we may see at a glance what are its
chief observed chemical properties and relationships,
what is the way of obtaining it, and how it may be
named ; in the ' second place, they enable us to
predict what will be the chemical properties which
have not yet been observed. In most cases we may
condense these structural formula^ writing together
the atoms forming a group or radical which acts as a
whole. Thus the full structural formula of sulphuric
O\ /O H
acid may be written I s I but this may be advan-
o/ \0^-H,
tageously condensed to SO 2 ^^ The use of structural
formulae is at present most markedly evident in the
region of organic chemistry* but as an inorganic
* See p. 369.
V
306 THE ATOMIC THEORY.
example of it we may take the formula of pyrophos-
phoric acid, H 4 P 2 7 . From this empirical formula
we learn very little. We cannot even tell how many
hydrogen atoms of the acid are replaceable by a
metal, for usually in oxygen acids only those hydrogens
occurring as hydroxyl (OH) can be so replaced. But
if we expand the formula the properties and relation-
ships of the acid appear at once. So expanded the
/OH H0\
formula becomes o=P OH HO_P=O ; and we see that
the acid contains four hydroxylic hydrogens, that is
four hydrogen atoms replaceable by a metal, and
further that it is obviously obtained from orthophos-
/OH
phoric acid o=P OH by the withdrawal of water from
\OH
two of its molecules thus :
/OH H0\ /OH R\
O=P OH + HO P=0 = H*0 4- O~P OH HO P=O.
\OH HO/ \0^
Two molecules of phosphoric acid rr water -f- one molecule of
pyrophosphoric acid.
In these formula phosphorus is represented as
pentavalent, the union with the divalent oxygen
atom being represented by a double line. This is
merely a convention, and is not to be taken as
implying a stronger union. The two " units of
saturation" of the oxygen atom are supposed to be
satisfied by the two " units of saturation" of the
phosphorus atom.*
* W. Lossen would do away with these double bonds and any
adherence to the idea of distinct valencies for each element. He
regards the valency of an element in any particular compound as
represented by the number of atoms with which each atom of the
THE ATOMIC THEORY.
3<>7
The following table gives the valency of a number
of elements :
Monovalent.
Divalent.
Trivalent.
Tetravalent.
I
Pentavalent.
Hexava-
lent.
Bromine
Barium
Antimony
Carbon
Antimony
Platinum
Chlorine
Calcium
Arsenic
Chro-
Arsenic
Tung-
Gold
Carbon
Bismuth
mium
Bismuth
sten
Hydrogen
Chromium
Gold
Iron
Molybde-
Iodine
Iron
Nitrogen
Molybde-
num
Lithium
Magnesium
Phospho-
num
Nitrogen
Potassium
Silver
Manganese
Molybde-
rus
Potassium
Platinum
Selenium
Phosphorus
Tungsten
Sodium
num
Silver
Silicon
Thallium
Oxygen
Sodium
Sulphur
Platinum
Thallium
Tellurium
Selenium
Tin
Sulphur
Titanium
Tellurium
Tungsten
Tin
Zirconium
Titanium
Tungsten
Zinc
Zirconium
element is in. that compound combined. Thus he "would regard
carbon in carbonic oxide, CO, as monovalent [C-O] and in carbon
dioxide, C02, as divalent, being combined with two oxygen atoms
[0-C-O or O-C-0]. There is direct action and reaction between the
carbon atom and one oxygen atom in the first case, and between the
carbon atom and two oxygen atoms in the second. Lossen's views
are the outcome of an attempt to give greater precision to our
conceptions of valency. The desirability of such an attempt cannot
be exaggerated, and Lossen's ideas are important and suggestive. It
must, however, be remembered that, in the present state of our
knowledge the conceptions of valency cannot by any ingenuity be
made very precise, and that theories in a state of unperfected evolu-
tion must lose their possibilities of development with loss of mobility.
( Ueber die Ycrllieihuuj der d. tome in der Molekel ; Annalcn dsr chonie,
cciv. 265.) His reasoning is'.followel and adopted by Pattison Muir
in his Principles of Chemistry (1884).
3 o8 THE ATOMIC THEORY.
The question as to whether the valency of chlorine,
bromine, and iodine varies has yet to be solved.
Thus, one of the compounds discovered by Prinvault,
Cl\ / Cl wliprp
PC1 6 I, may be represented as P i=CP
Cl/ \ci
phosphorus is pentavalent and iodine trivalent.
Platinum must be supposed to be octovalent in the
double chloride (KCl) 2 PtCl 4 , unless WQ allow that
this is a molecular as distinguished from an atomic
compound.
The present system of atomic weights has received
much confirmation from the views developed by
Newlands and Mendelejeff. These chemists found
that the elements may be arranged in periods accord-
ing to their atomic weight, each period repeating the
gradation of properties observed in each of them to
accompany the rise of their atomic weights. This
generalisation was first made by Newlands, and
independently originated by the Kussian chemist,
Mendelejeff, who more developed the theory which is
known as the periodic law.
That there is a relation between atomic weight and
chemical properties is readily seen by a study of the
following table. It gives some of the principal pro-
perties of the Nitrogen family of the fifth natural
group of the elements.
THE ATOMIC THEORY.
39
N=14-01
P=30-96
As = 74-9
Sb = 122
Bi=210
Physical State
gas
M.P.*44-3.
Sublimes
M.P. 425
M.P. 270B.
B.P. 290.
abt. 180.
white heat.
Specific gra-
vity of Solid
?
1-83
673
6-75
9-82
Atomic
Volume
?
16-92
13-07
18-07
21-38
Metallic
Properties
umnetallic
unmetallic
feebly me-
decidedly
very per-
tallic
metallic
fect metal.
brittle
brittle
brittle
brittle.
Hydrogen
Compounds
NH 3
PH 3
AsH 3
SbH 3
NH 3 , am-
PH 3 ,phos-
AsH 3 , ar-
Antimoni-
BiH 3 is un-
monia, is a
phuretted
seniuretted
uretted hy-
known.
very stable
hydrogen, is
hydrogen, is
drogen de-
body. It is
stable, but
readily de-
composes
only with
more read-
composedby
with great
great diffi-
ily decom-
heat. Is al-
ease. Is only
culty decom-
posed by
posed by the
electric
w a y s o b-
tainedmixed
obtained
mixed with
heat.
spark.
with hydro-
gen-
96 per cent,
of H.
It has
Less strong-
No basic
-
strongly
ly basic.
properties.
basic pro-
perties.
It burns
Burns above
Readily in-
Very read-
with diffi-
100.
flammable.
ily inflam-
culty.
mable.
Oxygen Com-
pounds
N 2 is the
P 2 3 and
As 8 3 and
Sb'O 3 has
BisO 3 is
most stable.
P 2 5 are
As 2 5 are
very feeble
strongly
NaO 3 is un-
stable, as is
very stable
and for well-
both stable.
As^O 3 is
acid proper-
ties. It is
basic.
Bi 2 5 is
N*0 5 .
defined phos-
less acid than
also basic.
very u n-
Both N 2 3
phorous and
P 2 3 but
Sb 2 5 is
stable and
and N*0 5
phosphoric
As*0 5 is
somewhat
only very
have strong-
acids.
strongly
more strong-
feebly acid.
ly acid pro-
acid.
ly acid.
preties.
* M.P. = melting point ; B.P. = boiling point.
3io 77/# ATOMIC THEORY,
In the above table we see a very well-marked
gradation of properties as the atomic weights of the
elements rise. Beginning with unmetallic nitrogen,
we end with perfectly metallic bismuth ; and begin-
ning with very stable and strongly basic ammonia,
we end with very unstable and non-basic antimoni-
uretted hydrogen, and finally with the unknown
bismuthamine. There is also much similarity among
the different members of the family, as is shown by
the formation of analogous hydrides and oxides.
The following is Mendelejeff's table. The vertical
column (Roman numerals) constitutes a group, each
group corresponding, for the most part, with a
natural family. The horizontal column (Arabic
numerals) constitutes a series. In the groups the
members present striking similarities, in the series
they present still more striking gradations. The
properties of any member of a series may be taken
as standing between those of the members imme-
diately preceding and succeeding it.
THE ATOMIC THEORY.
rt
fjl
.... 10 VQ ^
d
6
1
1 1
P4
"
,
l
- OD OJ O r-i
3i2 THE ATOMIC THEORY.
In the horizontal series of the elements thus
arranged we observe periodical gradations of pro-
perties. The periodicity may be shown by reference
to the densities of third series of elements which
increase towards the centre of the series and diminish
towards the ends. The atomic volume, on the con-
trary, that is, the specific gravity divided by atomic
weight, diminishes towards the centre and increases
towards the ends.
Xa Mg Al Si P S Cl
Densities .... 0-97 1'75 2-67 2'42 1-84 2'06 1-38
Atomic Volumes . . 24 14 10 11 16 16 27
The capacity of combination with monovalent ele-
ments or the valency also undergoes modification.
Thus, taking the first two series we have :
LiCl BeCi 3 BOP CC1 4 ; CH 4 NIP OH 2 FH
NaCl MgCP A1CP SiCl 4 ; SiH* PH* SH 3 C1H
What we now observe is that the second series
repeats the changes observed in the first, so that the
elements in the vertical groups are closely connected
in their properties.
When we come to the fourth series a certain change
in this arrangement, so far as physical properties are
concerned, is observed. From potassium the specific
gravity increases steadily up to nickel and decreases
again down to rubidium, the oscillation in this case
including two groups. The atomic volume, on the
contrary, decreases down to nickel and rises again up
to rubidium. If we arrange the elements upon a
curve which rises and falls according to increase and
THE ATOMIC THEORY. 313
decrease of atomic volume, as was done by Lothar
Meyer, lithium, sodium, potassium, and rubidium
occupy summits on this curve. The properties of
the elements are found to be characteristically different
according as they occupy portions on the descending,
ascending, or lowest portions of these curves.
We cannot examine more closely here into the
interesting relations between properties and combin-
ing weights. But the most interesting point of all
still remains to be touched upon. In a first glance
at MendelejefF's table we cannot but be struck by the
fact that gaps occur in it in which no element is
placed. These places have yet to be filled. They
represent the elements remaining to be discovered
in the future. How far the gaps may be filled it is
impossible to say, but that many of the absent ele-
ments will yet be found we cannot doubt. By means
of this table Mendelejeff has been able to prophesy
the discovery of unknown elements, and even to
describe with exactness their chief properties. In
three remarkable cases his prophesies have already
been fulfilled. Before 1875 the place now filled by
gallium in the fifth series was vacant. Mendelejeff
suggested that the place belonged to a hypothetical
element, eka-aluminium, the properties of which he
proceeded to define. In the year 1875 Lecoq de Bois-
baudran announced the discovery of a new element
by means of spectrum analysis, termed by him gallium.
On comparison of their properties it became clear
that Lecoq de Boisbaudran's gallium and Mendelej eft's
THE ATOMIC THEORY.
eka-aluminium were one and the same element. The
following is the comparison of the predicted and
actual properties :
[Eka-aluminium. Gallium.
Readily obtained by reduction.
Melting point low. Sp. gr.
5-9.
Not acted on by air.
Will decompose water at red
heat ; slowly attacked by acids
or alkalis.
Will form a potassium alum.
Oxide, EFO 3 . Chloride, EFC1 6 .
Atomic weight about 69.
Readily obtained by electrolysing
alkaline solutions.
M.P. = 30-15. Sp. gr. = 5-93.
Non-volatile and but superficially
acted on by air at bright red
heat.
Decomposes water at high tem-
peratures. Soluble in hot hy-
drochloric acid, scarcely at-
tacked by cold nitric acid ;
soluble in caustic potash.
Forms a well-defined alum.
Chloride, Ga 2 Cl 6 . Oxide, Ga 2 3 .
Atomic weight 69 '7.
So, too, the metal scandium discovered by Nilson
in 1870 is identical with the hypothetical eka-boron
of Mendelejeff with atomic weight about 44. Lastly,
the germanium of Winkler (1885) is identical with
the eka-silicon of Mendelejeff with atomic weight 72.
The greatness of a generalisation enabling us to
predict what elements will be discovered in the future,
and what their chief properties will be, as well as to
systematise the varying properties of the elements
now known, needs no discussion to make its impor-
tance evident. Since Mendelejeff 's discovery chemistry
has seen no greater generalisation.
DAVY.
CHAPTER XVII
DAVY AND FARADAY.
;HE foundations of the science have now been
laid, and we must next glance at what the
workers of to-day have built upon those
foundations.
Sir Humphry Davy's work comes next
in order. His name has become almost a
household word, and there are very few who have
never heard of Davy's safety lamp. Davy* came of
an old but not wealthy family. After the death of
his father he was apprenticed to a trade, and was
soon regarded as rather an idle fellow. He used to
be continually occasioning explosions and other dis-
turbing phenomena in the house of the gentleman
* Dr. J. A. Paris: Life of Sir Humphry Davy (1831). Dr. J.
Davy : Works of Sir H. Davy (1839), Born at Penzance in Cornwall,
31778. Died at Geneva, 1829.
3 1 8 DAVY AND FARAD A Y.
who helped him after his father's death, and who had
not quite the keenness of sight necessary to see what
the boy might become. But his talents were not to
be cheated of their destiny, and in good time he be-
came the great original worker, immortal as the dis-
coverer of the alkali metals and cf the safety lamp,
and the great lecturer of whom Coleridge said, " I
attend Davy's lectures to increase my stock of meta-
phors."
In 1799 Davy discovered the anesthetic properties
of nitrous oxide (N 2 0). This gas is usually prepared
by decomposing ammonium nitrate by heat.
(NH 4 )N0 3 = N 2 -f- 2H 2 0.
It is a colourless gas which, like oxygen, supports
ordinary combustion. A red-hot splinter of wood
rekindles when brought into the gas just as it would
do in oxygen. In these reactions the nitrogen of the
gas is set free ; 4N 2 + C 2 = 2C0 2 + 4N 2 .* But
the most remarkable property of nitrous oxide is its
effect upon animal life. If nitrous oxide be inhaled
by the human subject the first effects are singing in
the ears. Insensibility then follows and, if the gas
be persistently inhaled, death through suffocation.
If air be allowed to enter the lungs when the phase
of insensibility has set in, the effects pass off and no
evil result follows. A certain amount of excitement
* The reason for not halving this and other equations is that so
manipulated they would contain expressions for single atoms (as, in
this instance, C), which have already been defined as not existing
separately.
320 DA VY AND FARADAY.
is sometimes observed after inhalation, whence has
arisen the popular name of laughing gas.
The great discovery of the compound nature of the
alkalis "was made by Davy in 1808."* His method
was to place a small piece of pure potash "upon a disc
of platinum, connecting this with the negative pole of
a galvanic battery, while the upper surface was joined
by a platinum wire to the positive pole. Small
lustrous metallic globules collected on the lower sur-
face of the potash, some of which burnt off while
others became tarnished, and so preserved from further
action of the air. The globules were metallic potas-
sium. At the same time that the metal was being
liberated a violent effervescence, due to liberation of
gases from the caustic potash, occurred at the positive
pole. Davy was unable to obtain the metal in large
quantities but he succeeded in demonstrating its chief
properties. It rapidly absorbs oxygen, t being con-
verted into the oxide (K 2 0), and the oxide is extremely
hygroscopic, and when combined with water forms, as
Davy showed, ordinary caustic potash. Represented
by modern equations these reactions become :
2K 3 + O 3 = 2K 2 0. K?0 + H 2 = 2KOH.
Davy found that when thrown upon water metallic
potassium swam upon its surface, exciting a violent
reaction, and dissolved with formation of caustic potash.
* "On some new phenomena of chemical changes produced by
electricity, particularly the decomposition of the fixed alkalies," c.
Philosophical Transactions of the Royal Society (1808).
f In perfectly dry and pure air potassium, at the ordinary tempe-
rature, remains unchanged.
DAVY AND FARADAY. 321
In this reaction he found that hydrogen was evolved
and, at the high temperature produced, burst into
flame.
K 2 + 2H 2 = 2KHO + H 2 .
The compounds of sodium had been of importance
earlier than those of potash. We have already, in
the second chapter, seen that sodium carbonate was
known to the ancients. The " nitre " mentioned in
Proverbs xxv. 20,* is native carbonate of soda, and is
given as a translation of the Hebrew nether, the same
substance being known as v^rpov in Greek, and nitrum
in Latin.
The discovery of metallic sodium is announced by
Davy in the same memoir, and it was obtained by him
by exactly the same process. Davy observed the for-
mation of the oxide (Na 2 0), and the action of the metal
upon water, and further stated erroneously that sodium
took fire in chlorine gas.
Some of the knowledge relating to these elements
obtained since Davy's discovery may here be briefly
sketched. Gay-Lussac t and Thenard heated iron
turnings in a gun-barrel, and allowed melted caustic
potash to flow slowly on to the hot iron. The iron
took the oxygen of the hydrate while hydrogen gas
was evolved, and metallic potassium distilled over and
was collected in a bent copper tube. The method at
present in use was proposed by Curadau and has been
* " As he that taketh away a garment in cold weather, and as vinegar
upon nitre, so is he that singeth songs to an heavy heart."
t Louis Joseph Gay-Lussac (1778-1850).
X
322 DAVY AND FARADAY.
improved by Brunner, Wohler, and especially by
Donny and Mareska. It consists in the reduction,
at a white heat, of potassium carbonate by carbon :
K 2 C0 3 4- 20 = K 3 -f 3CO.
The ignition of crude tartar (hydrogen potassium
tartrate) provides us with an intimate mixture of
charcoal and potassium carbonate. The mixture is
heated in iron cylinders coated with clay, and the
metal collected in the flat iron condensers suggested
by Donny and Mareska. The rapid cooling of the
vapour insured by these flat and shallow condensers
prevents the formation of the explosive compound,
K 6 C 6 6 5 produced by the union of the potassium va-
pour with carbon monoxide (CO).
The specific gravity of potassium at 13C. com-
pared with water is 0'875 (Baumhauer). The only
metal lighter than potassium unless hydrogen be
included is lithium. At the ordinary temperature
the metal is soft and may easily be cut with a knife.
The fresh surfaces rapidly oxidise and the metal
should be kept under naphtha. Potassium melts at
6 2 4 5 (Bunsen). It boils at a red heat* and the
vapour density suggests a molecule composed of two
atoms.
One or two of its compounds may be mentioned.
Potassium hydrate or caustic potash, KOH, may be
obtained pure by the action of the metal on water,
* E. P. Perman {Journal of the Chemical Society, vol. lv., p. 326,
(1889)] lias quite recently determined the boiling- points of potassium
and sodium. That of potassium he finds to be about 667 C., that of
eoJium 742" C.
DA VY AND FAR AD A Y. 323
It is usually prepared by decomposing potassium
carbonate with slaked lime, Ca(OH) 2 (calcium hy-
drate).
Ca(OH) 3 -f K 2 C0 3 = 2KOH + CaCO 3 .
If the solution be too concentrated the reverse
action sets in and potassium carbonate is produced.
This is an interesting example of the fact that
chemical reactions depend upon other conditions
besides that of the simple affinity of one element for
another.
Potassium hydrate is a hard, Avhite, brittle sub-
stance. It is used for absorbing carbonic acid in
analysis, for surgical purposes, and in the manufacture
of soft soap. The last-named article consists of the
potassium salts of organic acids.
Potassium chloride is found in the Stassfurt potash
beds, and is used in artificial manures, while the
bromide and iodide are extensively used in medicine.
The tri-iodide KI 3 is a somewhat inexplicable com-
pound on the ordinary ideas of valency.* Oxygen
is usually prepared by heating potassium chlorate,
KC10 3 . It decomposes, leaving a residue of chlo-
ride.
2KC10 3 = 2KC1 + 30 3 .
The salt is used in the manufacture of lucifer
matches, for pyrotechnic purposes, and as a medicine.
* It may, however, be regarded as a molecular compound of KI
with P, but the usefulness of any distinction between molecular and
atomic compounds is at present a moot point.
3 2 4 DAVY AND FARAD A T.
Potassium nitrato (saltpetre), KNO 3 , occurs as an
efflorescence on the soil in various hot countries.
It is used in medicine, but most largely in the manu-
facture of gunpowder. Gunpowder consists of a mix-
ture of charcoal, sulphur, and nitre, the proportion
being, approximately, 75 per cent, of saltpetre (nitre),
15 per cent, of charcoal, and 10 per cent, of sulphur,
The simplest expression for the reaction occurring when
gunpowder is fired js : *
2KNO 3 + S -f 30 = K 2 S + N 2 + 3C0 3 .
Nitre + Sulphur + carbon = P$-tam + nitrogen + d ^
This simple expression cannot, however, be taken
as accurately representing what occurs. The first
thorough investigation of the decompositions taking
place was made by Bunsen and Schischkoff. Abel and
Noble have, more recently (1874), published an ela-
borate series of results on the same subject. Among
other results they find that the tension produced on
firing powder in a space which it completely fills
amounts to 6,400 atmospheres, or 42 tons per square
inch. The temperature of the] explosion is about
2,200 C.
Potassium carbonate is obtained by extracting with
water, or lixiviating as it is termed, the ashes of
wood. The name potashes arose from this extraction
being made in pots. By dissolving it in appropriate
* For the sake of simplicity many equations may be written with
single atoms. But the reader must not take this as implying the
separate existence of single atoms,
DAVY AND FARADAY. 325
acids the other potassium salts may be formed. It>
is used in the manufacture of soft soap.
Sodium was obtained by Gay-Lussac and The'nard
by heating caustic soda with metallic iron. At the
present time it is manufactured in considerable quan-
tities by heating to whiteness a mixture of caustic
soda, slack, or small coal, and chalk. Sodium is of
more commercial importance than potassium, being
used in the manufacture of aluminium. When me-
tallic sodium is thrown into water it evolves hydro-
gen, but the heat is insufficient to ignite the gas.
Caustic soda may be formed similarly to the potas-
sium compound.
Sodium chloride, or common salt, is an article of
great commercial importance. The total salt pro-
duced in England amounted in 187G to 1,676,000
tons, of which 1,500,000 tons were obtained by
evaporating brine and 176,000 were raised as rock-
salt.
Sodium carbonate is an article of great commercial
importance. It is obtained from common salt by first
converting into sulphate by means of sulphuric acid
and then acting upon this with coal and chalk. Na 2 S0 4
+ 40= Na 2 S + 4CO : Na 2 S = +CaC0 3 = Na 2 C0 3
-f CaS. This is Leblanc's process (1 794). To him we
owe cheap soap and cheap glass. He died in a French
asylum for paupers. The ammonia soda process con-
sists in passing carbonic acid into an ammoniacal solu-
tion of common salt.
The importance of Davy's discovery becomes very
3-26 DAVY AND FARADAY.
apparent when we thus see the extensive use to which
the compounds of these nietals are put. From these
researches Davy concludes : " Oxygen then may be
considered as existing in, and as forming an element
in all the true alkalies ; and the principle of acidity
of the French nomenclature might now likewise be
called the principle of alkalescence."* From analogy
alone Davy thinks it reasonable to expect that the
alkaline earths (lime, baryta, &c.,) are similarly com-
posed of metallic bases united to oxygen. " I have
tried some experiments upon barytes and strontites,
and they go far towards proving that this must be
the case."
His first attempts to electrolyse barytaf (BaO),
i.e. to analyse it by electricity, were not very success-
ful. Berzelius and Pontin obtained the metal by
electrolysis in presence of mercury, whereby an
amalgam of the metal with mercury was formed.
The amalgam was then heated in absence of air
when the mercury distilled off. Berzelius and
Pontin communicated their results to Davy, who
repeated their experiments and electrolysed baryta,
barium chloride (Bad 2 ) and other barium salts.
* Phil Trans. (1808),
f The compound of barium first observed was the natural sulphate,
heavy spar (BaSO 4 ). It was examined in 1G02 by a Bolognese shoe-
maker, V. Casciorolus. For a long time it baffled analysis. The
presence of a new earth was detected by Scheele in an ore of mangan-
ese and Gahn recognised it ae the basis of heavy-spar. Guyton de
Morveau, a disciple of Lavoisier, proposed in 1779 to name this earth
barote (/3apvs, heavy) and this name was altered by Lavoisier to
baryta.
DAVY AND FARADAY. 327
The metal is best obtained by electrolysis of the
fused chloride.
Calcium was obtained by Davy and by Berzelius and
Pontin by electrolysis of calcium chloride. Matthies-
sen first prepared it as a coherent metallic mass in
1856. Calcium plays an important part in nature.
The carbonate occurs in enormous quantities in its
various forms of calc-spar, arragonite, chalk, marble,
limestone, coral, &c., and united with magnesium
carbonate as magnesium limestone or dolomite.
Quicklime is the oxide, CaO ; slaked lime the hy-
droxide, Ca(OH) 2 . Bleaching powder is formed by
the action of chlorine on dry slaked lime. Calcium
sulphate in different states is known as gypsum,
alabaster, and plaster of Paris.
Strontium was first obtained by Davy in the
same year (1808) by electrolysis of the moistened
hydroxide and of the chloride. It is a yellow metal.
It occurs in nature as the sulphate (SrSO 4 , celes-
tine) isomorphous with heavy-spar and the carbo-
nate (SrCO 3 , strontianite isomorphous) with arrago-
nite.
The discovery of metallic magnesium was an-
nounced by Davy in the same paper. It was first
obtained as a coherent metal by Bussy. The method
proposed by Caron and Deville for its manufacture
is now used on the large scale. The method consists
essentially in decomposing the anhydrous chloride by
metallic sodium, Magnesium is a silver-white metal.
The ribbon, in which form it is usually seen, burns
$23 DAV AND FARADAY.
when lit by a flame with a light of dazzling brilliancy.
It has been observed at sea at a distance of twenty-
eight miles. Bunsen and Roscoe have shown that
this light is rich in chemically active rays, and have
determined its chemical value compared with the
light of the sun.
DAVY S SAFETY LAMP.
Davy attempted unsuccessfully to decompose alu-
mina (APO 3 ), silica (SiO 2 ) and zirconia (ZrO 2 ). In
1809 he published his important paper on chlorine.*
This gas was not then recognised to be an element,
* Phil. Trans. (1809): "Researches on the oxymurlatic acid," &c.
DA VY AND FARADAY. 329
but was known as oxymuriatic acid, and supposed
to contain oxygen. Davy heated the gas with carbon,
and obtaining no action was led to doubt the pre-
sence of oxygen in it. Tin he found to absorb
the gas but the body so formed did not contain
oxygen. By a number of negative proofs of this kind
Davy established the elementary nature of chlorine.*
In 1815 Davy invented his safety -lamp, and it is
to his credit that he took out no patent for it,
preferring to make the discovery a free gift. The
principle of the lamp depends upon the fact that
flame will not pass through fine wire gauze, owing to
the rapid conduction of the heat away from the
point of contact and the consequent cooling down the
gases below their ignition point.
The work of Davy has enriched his science with a
number of brilliant discoveries, but the best of them
all, as he himself said, was his discovery of Faraday.
Michael Faraday Avas born in Newington Butts on
September 22nd, 1791. t His father was a journey-
man blacksmith, and the family afterwards lived in
Jacob's Well Mews, near Manchester Square. Fara-
day himself became errand boy at a bookseller's shop
and \vas afterwards taken on as apprentice. During
* The following 1 passage in this paper is worth quoting : * ' The
vivid combustion of bodies in oxymuriatic acid gas at first view
appears a reason why oxygene should be admitted in it, but heat and
light are merely results of the intense agency of combination." Cf t
HooJcc.
t Michael Faraday : a Biography. By J. H. Gladstone (1872). See
also Tyndall's Faraday as a Discoverer (1870).
330 DA Vr AND FARAD A Y.
his apprenticeship he was sometimes engaged in
book-binding, and books bound by him are now
preserved at the Royal Institution, The first chemical
lectures he attended were paid for by his brother
Robert, who was thus doing more than he could have
been conscious of in aid of science. From his shop
Faraday was taken to hear Davy lecture at the Royal
Institution. Afterwards he was introduced to Davy,
and when the latter was injured in the eyes by his
investigations of nitrogen chloride he became for a
short time his amanuensis. " My desire," says
Faraday, " to escape from trade, which I thought
vicious and selfish, and to enter into the service of
a science which I imagined made its pursuers amia-
ble and liberal, induced me at last to take the bold
step of writing to Sir H. Davy expressing my wishes."
Davy soon after made him his laboratory assistant,
but not till he had earnestly tried to dissuade him
from following a scientific career. It would mean
poverty, ingratitude, and unrewarded toil. But
Faraday was not to be dissuaded.
Faraday married in 1821, though from his posi-
tion at the Royal Institution he obtained up to 1833
besides a house, coal and candles, only 100 per
annum. He had no children. If he had a family
he would probably have been deprived of much of
his work, for it did not pay. He presents us with
the spectacle of a man giving up all for his devotion
to pure, as distinguished from applied, science. In
his earlier years he undertook, commercial analyses
FARADAY.
DA VY AND FARAD A F. 3 3 3
which paid him far better, and in 1830 he made
XI, 000 by these means, and in 1831 considerably
more. But his researches in pure science multiplied
around him, and he at last found that he must
choose between making money and adding to know-
ledge. He did not hesitate in his choice, he did not
try to combine both. He deliberately chose to
abandon treasure for truth. In the following year,
(1832), his total income amounted to 155 Os.
Ever after it was even less than that.
Faraday gave up all in order to follow the
particular work that he felt he was meant to do.
His mind was essentially cast for that of an explorer
into the undiscovered countries of knowledge, and he
determined to be only what he was. In pursuit of
this he refused all other invitations. Thus he was
offered the professorship of chemistry at the London
University (now University College), but tke offer
was declined.
The picture drawn of him by Dr. Gladstone, work-
ing quietly in his laboratory in the morning with
his little niece beside him, never forgetting to please
her by conversation or amuse her with some pretty
experiment, and all the while engaged upon work of
the gravest moment, is charming indeed. If some
one called in and his work was interrupted he was
never put out or otherwise than pleased to see his
visitor. At half-past two he dined, and the after-
noon was spent in writing to friends, of whom he had
many. Then perhaps he would attend a council
3 3 1 DA VY AND FARAD A Y.
meeting, come back for a short time to his laboratory
and then spend the evening very happily at home,
probably reading aloud to his wife or some intimate
friends.
In religion Faraday belonged to the small sect of
the Sandemanians, and at their meetings on Sunday
he sometimes preached. As he approached his
seventieth year the strain of his work became too
great for him, and in 1861 he resigned part of his
duties at the Koyal Institution. His energies slowly
waned, and on August 25th, 1867 he passed away.
Faraday's character took the hearts of all who
knew him with joy. He was so simple and gentle
and self-less, and yet beneath his gentleness lay
hidden a cavern of volcanic fire, ready to blaze out
at sight of injustice or cruelty. He had a fund of
playful, boyish humour which lent added charm to
his presence. Thus Gladstone relates how Faraday
came down unexpectedly to visit him at Hastings
and knocked at the door while he was dressing.
" Who's there ? " cried Gladstone, but the only reply
Faraday would volunteer Avas " Guess," and the
discomfited chemist was forced to go through a
long list of names containing all but the right one
before Faraday would reveal himself, His kindliness
is exemplified by the fact that he would listen with
great interest to the chemical lectures of a boy friend
of his, aged 13, and applauded the experiments
heartily.
As a lecturer Faraday's equal could with difficulty
DA VY AND FARADAY. 335
be found. He contrived by his own earnestness and
enthusiasm to bring out new beauties in the most
commonplace facts. In his enthusiasm over facts of
singular beauty he forgot everything except his own
delight in the knowledge. He was raised into a
state almost of ecstasy, by force of which lie and his
audience were alike carried away.
The most prominent results achieved by Faraday
were electrical, and of these his demonstrations of
the theory of electrical induction are the chief. But
we cannot discuss this part of his work here, and
must pass on to consider his chemical discoveries,
also of great importance. In conjunction with Davy,
Faraday experimented upon the very dangerous com-
pound chloride of nitrogen. This body is formed by
the action of chlorine upon a solution of sal-ammoniac.
It collects as a yellowish oil, the composition of which
has only recently been determined.*
Faraday was the first to effect the union between
carbon and chlorine. Ethylene, or olefiant gas
(C 2 H 4 ), is obtained by treating alcohol with sul-
* This substance was discovered by Dulong in 1811, who continued
his work upon it after it had caused him the loss of three fingers and
one eye. During Faraday's and Davy's investigation it repeatedly
exploded without warning, and sometimes with such violence as to
stun the operators. Dr. Gattermann, of Gottingen, has recently
(1888) continued the investigation of this subsiance. He finds that it
consists of the trichloride (NCI 3 ) together with other chlorides. By
allowing the chlorine to act for some time, washing the resulting oil
free of sal-ammoniac, and again chlorinating, he has obtained per-
fectly pure NCI 3 . He finds that light is a powerful cause of the
explosions of this substance. Dr. Gattermann unfortunately states
that his eyes and nerves have been so affected as to oblige him to tem-
porarily abandon work on the subject.
33b DA VY AND FARADAY.
phuric acid. This gas treated with great excess of
chlorine in presence of light gave rise to a white
solid termed by Faraday perchloride of carbon.
Expressed according to our present equations this
reaction becomes : C 2 H 4 + 5C1 2 = C 2 C1 6 + 4HC1.
When this body was passed through a red-hot tube
Faraday found that it lost chlorine and formed pro-
tochloride of carbon. The reaction may be expressed
thus : * C 2 C1 6 = C 2 C1 4 + Cl 2 . The chloride so
obtained is a liquid. Faraday also combined iodine
with carbon by acting with iodine upon ethylene
(carburetted hydrogen) in sunlight. Ethylene dio-
elide, (C 2 H 4 I 2 ) is thus obtained.
In 1823 Faraday analysed the hydrate of chlorine
(Cl 2 + 10H 2 0) obtained by the action of ice-cold
water upon chlorine, and by use of this compound he
liquefied chlorine gas.
In 1825, Faraday discovered benzene in the oil
obtained from portable gas prepared by Taylor in
1815 by strongly heating fats. His analysis of the
new liquid led him to name it bicarburet of hydro-
gen, its empirical formula being taken as C 2 H where
C = 6. Adopting modern weights (C = 12) this
becomes CH, The vapour density of the body is,
however, six times what this formula would allow and
furthermore the hydrogen of the compound can be
replaced by chlorine in six stages, so that it must be
supposed to contain at least six atoms of hydrogen
* These expressions were, of course, not made use of by Faraday.
They are the interpretations now given of his facts.
DAVY AND FARADAY. 337
in the molecule. Taking this evidence into account
the formula becomes C 6 H 6 . At the present day this
hydrocarbon is obtained by the distillation of coal-
tar. The numberless multitude of the aromatic
compounds (as they are called) are all derivatives
of this body. The department of aromatic chemistry
now far exceeds in area the other combined provinces
of the science. It is difficult to realise that in 1821
at the publication of the second edition of Brande's
Manual of Chemistry, benzene was yet undiscovered.
In the same liquid Faraday obtained a new gaseous
hydrocarbon butylene (C 4 H 8 ).
Some of Faraday's chief chemical work was con-
cerned with condensation of the gases. His experi-
ments established the high probability that the ordi-
nary gases were only liquids with a very low boiling
point. To appreciate this we may recall that liquids
tend to give off vapour at all temperatures. If a
little water be introduced into a barometer tube with
the mercury standing at 760 mm. and at the ordinary
temperature the column is instantly depressed a cer-
tain distance. At a certain temperature this depres-
sion will amount to half the barometric height.
The vapour tension of the water now amounts to
half an atmosphere, or 380 mm. of mercury. If the
temperature of the water in the tube be at last raised
to its boiling point (100 C.) the mercury will be
driven down to the same level as that outside the
tube. The vapour tension now amounts to one
atmosphere. In other words a liquid boils when its
Y
338 DAVY AND FARADAY.
vapour tension is equal to the superincumbent atmos-
pheric pressure. If the pressure upon it be increased
its boiling point will be raised. This at once
suggests a method for liquefying the gases by
pressure. Supposing them to be liquids with low
boiling points their boiling points will thus be raised
and as the pressure increases will ultimately rise
above the temperature at which the experiment is
being performed. The gas will then condense to a
liquid.
The subject was fully investigated by Faraday,*
who succeeded in liquefying a number of gases, t
By sealing up chlorine hydrate in a strong bent glass
tube, warming the compound, and placing the other
limb of the tube in a freezing mixture, Faraday
obtained liquid chlorine which condensed in the cold
limb. The tubes used for these purposes must be
prepared with care and, properly
made, withstand an internal pres-
sure of many tons per square inch.
The application by these means of
FARADAY'S TUBE. pressure and cold succeeded with a
number of gases. Thus, in the case
of sulphuretted hydrogen (hydrogen sulphide, H 2 S),
Faraday brought the material, iron sulphide (FeS)
and sulphuric acid, J into the closed limb of the tube,
the former being separated from the latter by plati-
* Phil. Trans. 1823, p. 160. Ibid, 1823, p. 189.
f The first gas liquefied was chlorine by Northmore in 1806.
J H a SO* 4- FeS = IPS -f- FeSO*.
\ DAVY AND FARADAY. 339
num foil. The open end of the tube was then
sealed and the sulphide shaken down into the
acid. The gas then condensed as the pressure
increased. The gases liquefied by Faraday include :
sulphur dioxide (SO 2 ), carbon dioxide (CO 2 ), nitrous
oxide (N 2 0), cyanogen (CN), ammonia (NH 3 ), hydro-
chloric acid (HC1), hydrobromic acid (HBr), and
hydriodic acid (HI), besides those already mentioned.
Other gases, the so-called permanent gases, resisted
his attempts. He endeavoured in vain to liquefy
hydrogen, oxygen, nitrogen, nitric oxide, marsh-gas,
and carbon monoxide. Natterer and Andrews
though employing very high pressures both failed
in the same attempts, but in 1877 Cailletet and
Pictet * succeeded in liquefying oxygen, carbon
monoxide, and hydrogen. Oxygen liquefies under
a pressure of 475 atmospheres at - 140 C., hydrogen
at 650 atmospheres. Cailletet liquefied ethylene
(C 2 H 4 ), acetylene (C 2 H 2 ), nitric oxide (NO), and
marsh gas (CH 4 ).
Before concluding, mention must be made of Fara-
day's important discovery of the electro-chemical
equivalents of the elements. The same strength of
current, he found, would in equal times liberate
equivalent quantities of the elements. Thus if a
current passing for a given time through a solution
of copper sulphate liberated 63 grains of copper, it
would, under similar conditions, liberate 65 grains
of zinc, 63 and 65 being the respective atomic
* See page 299.
340
DA VY AND FARAD A F.
weights of these metals. It would similarly liberate
216 grains of silver, or twice its atomic weight ; the
equivalent weight of silver, compared with zinc and
copper, being twice its atomic weight, owing to the
fact that silver is monovalent, while zinc and copper
are divalent.
NINTH PERIOD.
r
CHAPTER XVIII,
NINTH PERIOD : THE MODERN SCIENCE.
MODERN INORGANIC CHEMISTRY,
N treating of Davy, Faraday, and Dalton,
the later developments of their greater
discoveries have been shortly discussed.
It has seemed clearer and more intelli-
gible to observe strictly chronological
order only in the case of the main and
fundamental discoveries of the science and those
associated with great and illustrious names. In most
cases, therefore, the later development has been
treated together with the main idea. The chief part
of what remains in this chapter will therefore consist
in briefly summarizing any omitted results of modern
research.
The following table contains the names of elements
discovered since the close of last century. The name
344
THE MODERN SCIENCE.
of the observer by whom the element was first isolated
is printed in ITALICISED CAPITALS. In many cases,
however, compounds were recognised as containing
a new element before the element was obtained
in a free and uncombined state. Names of workers
Observing and recognising such compounds are printed
in italics. The name of the principal worker upon
an element, other than its discoverer, is printed in
CAPITALS, and any other workers in ordinary type.
SGregor ....
1789
Titanium . .
Klaproth. ...
1795
BERZELIUS .
1825
Uranium . .
(Klaproth. ...
( PELIGOT ...
1789
1842
Chromium . .
VAUQUELIN .
1797
Tellurium . .
KLAPROTH
1798
Tantalum . .
( Hatchett . .
\Ekeberg ....
1801
1802
[Del Rio ....
1801
Vanadium . .
) Selfstrom
JBERZELIUS ....
1830
1831
\ROSCOE .
1867
Cerium . . .
(Klaproth
\MOSANDER
1803
1839
Palladium .
WOLLASTON ....
1803
Potassium . .
/ Stahl
\DAVY
1736
1808
Sodium . . .
f Stahl
\DAVY
1736
1808
Barium . . .
( BERZELIUS % PONTIN .
\DAVY
1808
1808
(DAVY
1808
Boron . . .
\ GAY-LUS. $ THENAED .
1808
(DAVY
1808
Calcium . .
BEBZELIUS $ PONTIN .
1808
( Matthiessen
1856
Magnesium
DAVY
1808
Strontium . .
DAVY
1808
Chlorine . .
( SCHEELE
(DAVY
1774
1810
Iodine .
COI7RTOIS
1811
Lithium . .
/ Arfvedson .....
t B UNSEN 4- MA TTHIESSEN
1817
1855
THE MODERN SCIENCE.
345
Selenium . .
BERZELIUS
1817
Cadmium . .
( Hermann
\STROMEYER ....
1817
1818
Silicon . . .
BERZELIUS
1823
Bromine . .
BALARD
1826
Aluminium
( Marggraf .....
\ W(EKLER
1754
1827
Beryllium . .
j Vauquelin
\ WCEHLER
1798
1828
Thorium . .
BERZELIUS
1828
1794
Yttrium. . .
J Eckeberg
1797
(MOSANDER
1839
Didymium . .
( Mosander .....
\MARIGNAC
1841
1853
Lanthanum .
MOSANDER
1841
Erbium . . .
( Mosander .....
( CLEVE & HOEGLUND .
1843
1872
(Rose
1844
Niobium . .
< Blomstrand .....
1866
(ROSCOE
1879
Ruthenium .
CLA US
1844
Caesium . .
Xirchhoff $ Bunsen ....
1860
Rubidium . .
BUNSEN
1861
Thallium . .
( CROOKES
\LAMY
1861
1862
Indium . . .
Reich $ Richter ....
1863
Gallium. . .
LECOQ de BOISBA UDRAN
1875
{Scheele . . .
1771
Fluorine . .
AMPERE
Gore
1810
1870
MOISSAN
1887
( Mosander .....
1843
Terbium .
\ DELAEONTAINE & MARIGNAC
1878
Ytterbium
Marignac
1878
Decipium
Philippium
Delafontaine .....
Delafontaine
1878
1878
Scandium
Nilson
1879
Samarium
Lecoq de Boisbaudran
1879
Thulium .
Cleve
1879
Germanium
Winlcler
1885
i
The existence of others is as yet somewhat doubt-
ful, such as the Yttrium a and Yttrium /? of Marignac
(1879). Ytterbium to Thulium inclusive were all dis-
covered by spectrum analysis.
Of one or two of these bodies some further mention
346 THE MODERN SCIENCE.
must be made. Metallic iodides are found in the ash
of sea-weed, and by treatment with sulphuric acid and
manganese dioxide (MnO 2 ) free iodine is obtained from
this source. Bromine may be obtained from the same
source. It was first discovered by Balard in the salts
obtained by the evaporation of sea-water. Cadmium
occurs as an impurity in most ores of zinc. Silicon
QTJAETZ CEYSTAL9.
is, next to oxygen, the chief constituent of the earth's
solid crust. It occurs always as the dioxide, SiO 2 .
This combined with the metallic oxides gives rise to
the large class of silicates, compounds which play a
very prominent part in geological formations. Clays
consist largely of aluminium silicate. Emerald is a
silicate of aluminium and beryllium. Felspar is a
potassium aluminium silicate. Talc is a magnesium
THE MODERN SCIENCE. 347
silicate. Serpentine, mica, topaz, &c., are complicated
silicates. Pure silica (SiO 2 ) occurs in crystals as quartz
and tridymite. The amorphous * varieties include
opal, flint, sand, &c. Davy's discoveries led to the
suggestion that silica, like baryta and lime, was the
oxide of an unisolated element. Berzelius,f whose
immense services to chemistry are but feebly indicated
by his prominence in the foregoing table, first isolated
the element in 1810, and obtained it in a pure state
in 1823. % It forms a dark brown powder.
The interesting metal aluminium is next to oxy-
gen and silicon in importance as a constituent of the
earth's crust. Its presence in clay and felspar has
been referred to. Felspar forms the chief constituent
of granite, gneiss, porphyry, &c. The oxide, A1 2 3 ,
occurs as the mineral corundum. Of this mineral
the ruby and sapphire are varieties. Wohler obtained
the metal by acting on the chloride with sodium.
The mineral bauxite, a hydroxide of aluminium and
iron, is the usual source of the element. From this
mineral pure aluminium hydrate is prepared. The
dried powder is mixed with common salt and char-
coal and made up into balls. These are heated
and a stream of dry chlorine led over them. A
double chloride of aluminium and sodium distils off
* That is, having no regular rorm.
f 17791848.
% The process used by Berzelius was to treat potassium silicofluoride,
a compound of potassium, silicon, and fluorine, K 2 SiF 6 with metallic
potassium. Potassium fluoride (KF) is formed and silicon liberated.
K 2 SiF 6 -f 4K = 6KF -f Si.
3 48 THE MODERN SCIENCE.
and is condensed in a receiver. The double chloride
is then treated with sodium. The metal is thus
separated, fused, and cast into moulds.
Aluminium is now prepared in this way on a large
scale. Its lightness, malleability, ductility, and fusi-
bility render it highly serviceable. Its white colour,
its susceptibility to high polish, and its unsuscepti-
bility to aerial action enhance its value and render it
an almost ideal metal. Its tensile strength is high,
much higher than that of cast iron, and it is exceed-
ingly sonorous. In spite of these manifold advan-
tages and its universal occurrence it has proved im-
possible to prepare aluminium at a rate enabling it to
compete with other metals. Improvements have,
however, lately been effected which promise to bring
it more into the market. *
Caesium and Kubidium were discovered by Bun-
sen by means of spectrum analysis, a subject to which
we shall briefly refer in the sequel. The spectrum of
the salts of Diirkheim water contained two splendid
blue lines not before observed. They proved to
belong to a new element, the first discovered by
spectrum analysis. The delicacy of the spectroscopic
test is indicated by the fact that it was necessary to
evaporate forty tons of the water to obtain enough
caesium for investigation. Rubidium was similarly
discovered in the mineral lepidolite.
Scheele observed that fluor-spar (CaF 2 ) was the salt
* See a recent discourse of Sir Henry Roscoe's " On Aluminium; "
Nature, 1889.
SIB, HEXRY ROSCOE.
350 THE MODERN SCIENCE,
of a new acid. Ampere in 1810 determined the con-
stitution of, this acid, HF. But the element itself re-
sisted all attempts at isolation. Davy tried the action
of chlorine on silver fluoride (AgF). He expected the
chlorine to replace the fluorine thus : AgF + Cl =s
AgCl -I- F. This reaction actually occurred, but the
fluorine as soon as liberated attacked the vessels in
which the experiments were carried on, and formed
fresh compounds. It appeared incapable of remain-
ing free in the presence of any other element. In
1887 the French chemist, Moissan* succeeded by the
electrolysis of hydrofluoric acid containing potassium
fluoride in obtaining a colourless gas, attacking metals
and other substances with formation of fluorides and
proved to be elementary fluorine. Owing to its ex-
tremely energetic properties it was at first impossible
to collect the gas, but more recently it has been col-
lected and its specific gravity ascertained.
Some points of importance still remain to be
noticed. By modern observation Cavendish's deter-
mination of the composition of atmospheric air has
been confirmed. Approximately one-fifth is oxygen
and four-fifths nitrogen. This may be illustrated by
a simple experiment. A tube closed at one end and
graduated is inverted over water, and a certain volume
of air enclosed within it. A piece of ordinary phos-
phorus is now pushed up into the tube on the end of
a wire. If left for some time this will gradually
absorb the oxygen of the air, and nitrogen will be left
* An. de Chim.
THE MODERN SCIENCE. 35 1
behind. If the air measured originally 20 divisions
from the top it will now measure 16. One-fifth, or
the amount occupying the space between 4 divisions
of the tube, has been absorbed by the phosphorus.
The actual method of analysis used by modern che-
mists is the eudiometric one discussed below.
Besides nitrogen and oxygen air contains traces
of other gases, notably carbonic acid and ammonia.
The normal amount of the former gas is 4 volumes
in 10,000 volumes of air.
The analysis of the air by weight was conducted in
1841 by Dumas and Boussingault. They found
2 2- 9 2 per cent, oxygen to 77*08 per cent, nitrogen.
The analysis of water has been frequently repeated
since Cavendish's time.* According to the volumetric
method a graduated tube is filled with mercury and
inverted over a mercury trough. The tube used for
such a purpose is termed an eudiometer.^ Some pure
oxygen gas is next passed up into the tube and its vol-
ume carefully measured. The height of the mercurial
column in the tube above the mercurial surface in the
trough must also be noted, as this by its downward
tendency diminishes the pressure upon the gas. The
height of the thermometer and barometer must also be
carefully observed. A large excess of hydrogen is next
admitted, but the total quantity of both gases must not
* Nicholson and Carlisle, in 1800, first decomposed water by elec-
tricity.
t From evdia, clear weather, and ptrpov, a measure, i.e. a measure
of the purity of air, or of the quantity of oxygen which it contains.
3 S 2 THE MODERN SCIENCE.
be more than sufficient to fill about one-sixth of the
tube. The tube is now pressed securely down upon
a plate of caoutchouc (india-rubber) placed under the
mercury, and by means of two platinum wires passing
through the glass in the upper part of the tube a spark
is sent through the mixed gases. A flame is seen to
pass through the gases and combination occurs, the
water forming, as Cavendish observed, a dew upon the
side of the tube. On releasing the eudiometer from the
caoutchouc pad the mercury rises and the volume is
found to be considerably diminished. The residual gas
is carefully measured, and the observation of the
mercury column, thermometer and barometer repeated.
The volumes of the gas before and after the explosion
must next be reduced by calculation to what they
would be at identical pressure and temperature.*
The customary pressure and temperature are 760
millimetres of mercury and 0C. The following
numbers are those of an actual experiment; f the
volumes being reduced to and a barometric height
of one metre.
Volume of oxygen 95*45
V" Volume of oxygen + hydrogen . . . 55 7 '26
Volume after explosion 271 '06
Thus with the explosion 286 - 2 volumes J dis-
appeared.
* See ante p. 126.
t As given in Roscoe and Schorlemmer's Treatise.
J The volumes here spoken of may be taken as cubic centimetres,
cubic inches, or multiples of any other unit. The actual graduations
of the tube are usually in millimetres (measures of length] and their
THE MODERN SCIENCE. 353
As a large excess of hydrogen was present we
know that the whole of the oxygen will have been
used in the production of water. Thus of the 286*2
volumes 95*45 are oxygen; the rest, 286*2 95*45
= 190*75, consists therefore of hydrogen. Now the
cause of the disappearance of these 286*2 volumes is
their condensation to form a very small bulk of water.*
Thus we must conclude that 95*45 volumes of oxygen
combine with 19075 volumes of hydrogen to form
water, or that 1 volume of oxygen combines with
1*9963, i.e. very nearly 2 volumes of hydrogen to
form water. The relations of the volumes are thus,
1 : 2, as expressed in the formula OH 2 . By explod-
ing his gases in a eudiometer, heated by the vapour
of arnyl alcohol, Gay-Lussac showed that the volume
of steam formed was identical with the volume of
hydrogen used. In accordance with Avogadro's law
2 volumes of hydrogen combine with 1 volume of
oxygen to form 2 volumes of water vapour.
II 2 -f = IPO.
2 vols. -f- 1 vol. = 2 vols.
Careful gravimetric analyses, or analyses by weight,
of water were carried out first by Berzelius and
Dulong, and afterwards in 1843 by Dumas and Stas.
The method adopted was to pass hydrogen over
capacity will thus depend on the "width of the tube. This in no way
affects the proportions between them. The numbers refer to divisions
of the tube.
* In very accurate experiments allowance must be made for the
volume occupied by the condensed water, but compared with the
volume of the gases it is a negligeable amount.
Z
354 THE MODERN SCIENCE.
heated copper oxide and collect the water formed by
its reduction. The experiments of the two latter
chemists were conducted with very many precautions.
The hydrogen was passed through a series of 8 U
tubes containing substances which freed it from every
trace of impurity and moisture. It then passed over
a weighed quantity of copper oxide and the water
formed was condensed in a small weighed bulb, the
last traces being absorbed by hygroscopic substances
in weighed tubes. The loss of weight of the copper
oxide gives the weight of oxygen used, the gain in
weight of the second bulb and tube gives the weight
of water formed. The difference between the two
weights gives the weight of hydrogen in that quantity
of water. From these experiments it was found that
two parts by weight of hydrogen combine with 15*9608
parts of oxygen. The composition by weight deduced
by calculation from the composition by volume coin-
cides with these results.*
The properties of water it is unnecessary to enu-
merate. It may, however, be well to remind the
reader that the density of water increases with a
cold till the point of 4 is reached on the Centigrade
scale. Water below 4 is lighter than that at 4 and
therefore floats upon the warmer water, as does the
ice formed from it. In this way the rapid circulation
of the water as it cools is stopped, and our lakes and
* The exact composition of water and hence the exact atomic weight
of oxygen is still the subject of experiment. Thomsen, Scott, Cooke
and Richards, Keiser and Rayleigh are the recent workers in this
field.
B. VT. BTTN'SEN',
356 THE MODERN SCIENCE.
rivers prevented from becoming a mass of ice. Other
substances, such as grey cast-iron, expand similarly
on solidification. The beautiful forms assumed by
water during crystallisation are sufficiently well known
in the phenonema of snow-crystals.
Lastly, we must refer to the great invention of the
spectroscope, an instrument of increasing importance
to the chemist. Roscoe says, " The spectroscope,
next to the balance, is the most useful and important
instrument which the chemist possesses." Crookes
has remarked, "If I name the spectroscope as the
most important scientific invention of the latter half
of this century I shall not fear to be accused of exag-
geration," The very importance of the subject pre-
vents us from entering into any long discussion of it
here. It has come to form a distinct branch of
chemical science. In the hands of men like Bunsen
and Crookes it has explored the recesses of the rocks
for minute traces of hidden treasures, while with it
workers like Miller, Huggins, and Lockyer have
fathomed the abysses of space and determined the
constitution of the stars.
It was first observed by Newton that white light
when passed through a prism is split up into coloured
rays. Some of the rays are bent more sharply out
of their course by the prism than others, and thus
if these be received upon a screen they form a band
or spectrum in which the colours follow the order :
violet, indigo, blue, green, yellow, orange, red. Using
the light of the sun we obtain in this way the solar
THE MODERN SCIENCE. 357
spectrum. Dark lines in the solar spectrum were
first observed by Wollaston in 1802 and mapped by
Fraunhofer, an optician of Munich. Herschel and
Talbot observed that bright lines in the spectrum
might be obtained by heating certain substances in
the flame, but it is to Kirchhoff and Bunsen that the
BOLAE SPECTEUM.
interpretation and utilisation of the phenomena of the
spectrum are due. Different substances when volati-
lised in a colourless flame colour it in various ways.
Thus, if a little common salt be held in the flame of
a spirit lamp it colours it an intense yellow. The
sodium compound is capable when thus heated of
emitting light rays of a particular refrangibility.
The spectrum obtained from this flame is very dif-
358
THE MODERN SCIENCE.
ferent from the continuous spectrum described above.
It consists of two bright yellow lines. Moreover, if
pure white light (lime-light, for instance) be made to
pass through such a sodium flame before being ana-
lysed it will be found that its continuous spectrum is
interrupted by a double black line occupying a definite
position in the yellow.
Kirchhoff and-Bunsen invented their spectroscope
SPECTEOSCOPE.
for observing these phenomena. The light is received
through a very fine slit and by an arrangement of
lenses the rays are rendered parallel before reaching
the prism where the light is split up. It then enters
the observing telescope where, by means of another
lens, an image of the spectrum is obtained, and this
is observed through a magnifying glass. An incan-
THE MODERN SCIENCE. 359
descent solid or liquid gives only a continuous spec-
trum, but where the substance is capable of being
ever so slightly volatilised it is found that each
element gives a spectrum of characteristic bright
lines. So delicate is the test that u o~owo~o ^ a m ^^~
gram of sodium salt can be detected with certainty.
The dark lines in the solar spectrum are due to
the absorption of certain portions of the solar light
by upper incandescent vapours. Each vapour absorbs
in this way the same light that it emits. Thus the
sodium line is in the sun represented by a black line
in the yellow. But the interesting facts of spectro-
scopy and stellar chemistry cannot be gone into here.
These few words have only been inserted to remind
readers that these discoveries are among the most im-
portant of the modern science.
I
CHAPTER XIX,
NINTH PERIOD : THE MODERN SCIENCE,
ORGANIC CHEMISTRY TO-DAY.
OME short reference must now be made to
the immense strides made by organic
chemistry since the time of Scheele.
Lavoisier was the first to attempt the
ultimate analysis of organic bodies. In
his later form of apparatus for the deter-
mination of carbon and hydrogen in these bodies,
Lavoisier burnt his oil or other organic substance in
a stream of oxygen and collected the water and car-
bonic acid formed, employing eight or nine absorp-
tion bulbs for the latter purpose. The substantial
features of this method have already been described.
From his analyses he drew the correct conclusion
that vegetable bodies are composed mainly of carbon,
hydrogen, and oxygen, while animal bodies contain
in addition nitrogen and sometimes phosphorus.
Guyton de Morveau, one of Lavoisier's disciples,
THE MODERN SCIENCE. 361
suggested the term of la base or le radical for that
portion of a substance which combines with oxygen.
This radical might be either elementary as carbon,
or compound as the radical of tartaric acid. The
radicals of the vegetable and animal kingdom La-
voisier regarded as usually complex. His researches
on fermentation have been referred to. He did not
make any wide distinction between inorganic and
organic chemistry, but he was an illustrious pioneer
in the latter branch of the science.
Berzelius, in 1814, began important investigations
into the composition of organic bodies. His method
of analysis for carbon and hydrogen depended upon
treating the substance with potassium chlorate and
collecting the water and carbonic acid formed. Ber-
zelius followed Lavoisier in a belief in the existence
of compound radicals. In 1815 Gay-Lussac dis-
covered cyanogen gas (CN).
The belief prevailed at this time that organic
bodies could not be artificially prepared. This was
the view adopted by the German chemist, Gmelin, in
his great Handbuch. But the belief in mysterious
vital forces alone capable of giving rise to organic
products was rudely shaken by the synthesis of urea
effected by Wohler in 1828. Urea is a highly
important animal product and is excreted regularly
in the urine.* Ammonium cyanate is an artificial
* The quantity excreted by an adult man amounts to from 30 to
40 grams daily (a little over 1 oz.). The formation of the various
constituents of the urine forms one of the most interesting chapters in
physiological chemistry.
362 THE MODERN SCIENCE.
product of the laboratory and may be obtained by
acting with an ammo-
nium salt upon potassium
cyanate. Now, this salt
when heated to 100 C.
becomes rapidly converted
into urea. Here, then, is
the first case of an organic
j product synthesised from
oj J inorganic sources.
In 1823 the great Ger-
,J man chemist, Liebig,* be-
& gan to perfect the me-
| I thods of organic analysis.
I | His labours on this point
S | culminated in the develop-
*rh CJ
8 | ment of the process actu-
* I ally in use at the present
* day for determining the
carbon and hydrogen in or-
ganic bodies. His method
consists essentially in heat-
ing a mixture of the car-
bon compound with copper
oxide in a long glass tube.
The carbon and hydrogen of
the substance are oxidised; the water formed is absorbed
* Justus Liebig (18031873) was born at Darmstadt. He was
made professor at Giessen, and founded its laboratory. He remained
at Giessen for twenty-six years, during which time he published 200
THE MODERN SCIENCE. 363
in a tube filled either with calcium chloride or with
pumice moistened with sulphuric acid, while the carbon
dioxide is absorbed by potash solu-
tion contained in the bulbs devised
byLiebig. The method customarily
in use at the present day differs
from that of Liebig in only a few
particulars. The combustion is now
usually carried on in a current of
oxygen gas, the substance analysed POTASH
being placed in a porcelain boat
behind a long column of copper oxide. * Gas has
replaced charcoal as a .means of heating the combus-
tion tube. The perfection of this method of ana-
lysis took Liebig many years to accomplish, but the
results of its use amply rewarded the labour bestowed
upon it.
In 1832 Liebig and Wohler published their cele-
brated research upon the radical of benzoic acid-
These chemists found that bitter almond oil, benzoio
acid and their derivatives all contained a particular
group of atoms, or compound radical, involving
oxygen as well as carbon and hydrogen, and termed
papers, 20 of them joint works chiefly with Wohler. He also pub-
lished works on organic analysis, organic chemistry, physiological
and agricultural chemistry, his chemical letters, &c., and edited several
journals. His discoveries include those of aldehyde, chloral, and,
simultaneously with Souberain, chloroform.
* To estimate nitrogen in nitrogenous bodies with this apparatus all
that is necessary is to mix the substance with copper oxide and substi-
tute, a current of carbon dioxide for one of oxygen. The nitrogen of
the substance escapes as such and is collected over potash solution.
THE MODERN SCIENCE. 365
by them benzoy.l* (C 7 H 6 0). Liebig gave great sup-
port to the radical theory by the development of
his true idea that both ether and common alcohol
contain the same radical ethyl, the former being the
oxide (O i H 5 0), while the latter is its hydrate f
(C*H*0, HO). The work of Liebig, Berzelius, and
Dumas further developed this theory, the central
idea of which is that the elements of inorganic
chemistry are represented in organic chemistry by
combinations of elements, or compound radicals,
which play the part of elementary bodies. We
term cyanogen a radical, says Liebig, 1, because it
is an unchanging constituent in a series of com-
pounds ; 2, because it may be replaced in these
compounds by simple bodies ; and, 3, because in its
compounds with elementary bodies these latter can
be set free and replaced by their equivalents of
other simple bodies. At least two of these condi-
tions must be fulfilled if the radical is to be con-
sidered a true one.
The work of Dumas and Laurent led to the
publication, in 1839, of Dumas's theory of chemical
types. Dumas observed that the elements of a
compound could often be replaced by their equi-
valents of other elements or compound radicals.
Laurent added the observation that when such
substitution was made the compound still retained
* " Yl " from the Greek v\?i, matter.
f In our present formulae the relation between the compounds is
expressed by ether (C 2 H 5 ) 2 O. alcohol C 2 H 5 OH.
366 THE MODERN SCIENCE.
its essential chemical properties or its^ehemical type.
As an example we may take the case of acetic acid,
C 2 H 4 2 . By the action of chlorine one of the atoms
of hydrogen may be replaced, and we obtain mono-
chloracetic acid, C 2 H 3 C10 2 , in which the chlorine
plays the part of the hydrogen replaced. The views
of Dumas and Laurent were strongly combated, but
they held their ground. The observation of reverse
substitution in the conversion of a chlorinated body
back again into its hydrogen derivative much
strengthened their position (Melsens, 1842). The
facts of replacement had an interesting bearing upon
the development of the atomic theory. The fact
that in these substitutions never less than two atoms
of chlorine react was one of those which led Lau-
rent to the conclusion that the molecule of chlorine
must consist of two atoms.*
The older radical theory was modified by Gerhardt
(1839) and assimilated to the theory of chemical
types. The older theory regarded the radicals as
closed groups of atoms, while Gerhardt, though not
abandoning the belief in a cc residue," which was the
equivalent of the radical, regarded the whole com-
pound as forming the chemical unit. Thus, accord-
ing to Laurent and Gerhardt j* alcohol is represented
* As examples take the action of chlorine upon acetic acid above
mentioned :
Cl 2 -f C 2 H 4 2 = HC1 -f C 2 H 3 C10 3
or upon marsh gas :
CH* -f CF = CH 3 C1 + HC1,
t See ante p. 296.
THE MODERN SCIENCE. 367
by the formula C 2 H 5 OH, containing the residue OH.
The action of hydrochloric acid upon alcohol will be
represented as C 2 H 5 OH + HC1 = C 2 H 5 C1 + HOH,
or C 2 H 5 |OH H| Cl, forming ethyl chloride, C 2 H 5 C1,
a body first prepared by Basil Valentine and known
as sweet spirit of salt.
The classical researches of Bunsen upon the caco-
dyl compounds were of weighty service to the true
radical theory. The source of these interesting com-
pounds is Cadet's fuming liquid obtained by distilling
arsenious acid (As 2 3 ) with potassium acetate. In a
series of researches which are models of penetration
and skill, Bunsen investigated the composition of
this liquid and its derivatives. " If we examine this
group of bodies," says he, " we recognise in them an
unchangeable member (Glied), the composition of
which is represented by the formula C 4 H 12 As 2 "*
[C 2 H 6 As]. To this radical Bunsen gives the name
cacodyl (ATCU- &>?/?, stinking), from the frightful smell
possessed by most of its compounds. Bunsen finally
succeeded in preparing the free radical by the action
of zinc on cacodyl chloride [(CH 3 ) 2 AsjCl. Taking
the group (CH 3 ) 2 As, as analogous to the atom of an
element, the molecule of free cacodyl contains tivo
such atoms (CH 3 ) 2 As As (CH 3 ) 2 , and it has there-
fore been termed dicacodyl. Soon after this Kolbe
and Frankland succeeded in similarly isolating the
radicals of the alcohol series.
* Annalen xxxvii. 1. (1841),
3 68 THE MODERN SCIENCE.
In 1849 Wurtz discovered the compound ammonias,
the existence of which was predicted by Liebig. They
consist of ammonia, NH 3 , in which one or more of the
hydrogen atoms is replaced by an organic radical.
Thus if the radical ethyl, C 2 H 5 , be substituted for one
hydrogen atom, the compound NH 2 C 2 H 5 termed ethy-
lamine is obtained. The replacement of two atoms
produces diethylamine NH(C 2 H 5 ) 2 , and so on. The
new theory of types initiated by Laurent and whix;h
regarded organic compounds as formed upon the type
of the simple inorganic ones, was much aided by these
discoveries. The compound ammonias may be con-
ceived as built upon the ammonia type. Again,
Williamson's classical research on etherification in
1850 proved that the alcohols and ethers must be
considered as built up on the water type. We thus
have
Water ^ J ethyl alcohol G ^ J ethyl ether ^HS } O
Substituting the hydrogen atoms of water by other
radicals we obtain other alcohols and ethers, as for
instance,
Propyl alcohol C3 ^ ? j O propyl ether ^^j j and mixed ethers as
P2TT9 *)
ethyl propyl ether 3jj 7 j O
and so on.
The subsequent discoveries of Williamson and others
did much to develop the new theory. The theory must
not be pressed too far, the same substance can be
arranged on a variety of types, and the formulae are
less advanced than true structural formula?, inasmuch
THE MODERN SCIENCE. 369
as they only suggest a certain number of reactions of
the compound. -%/
Since 1850 the researches of innumerable workers
have completely transformed the science, and the best
course to adopt in closing this chapter seems to be to
sketch, in what must of necessity be very bare outline,
the system of organic chemistry to-day.
First, let us define the range of organic chemistry.*
The simplest and truest way of stating the pro-
vince of organic chemistry is to say that it is the
chemistry of the hydrocarbons and their derivatives.
Let us also start with the assumption that carbon is
tetravalent (a fact first pointed out by the great
German chemist Kekule'). The primary hydrocarbon
thus becomes marsh gas or methane CH 4 . Its struc-
tural formula is
H
H-C H
A .
all the hydrogen atoms playing a chemically similar
part. By the action of chlorine upon this substance
we can replace the hydrogen atom by atom, obtaining
successively CH 4 , methane ; CH 3 Cl,f methyl chloride ;
CH 2 C1 2 , dichloromethane ; CHOP, chloroform J or
* For- a discussion of the distinction between the organic an!
inorganic departments of the science vide Chapter VI., p. 116.
t CH 3 is an organic radical termed methyl ; see p. 365.
J This invaluable compound was first introduced into medicine by
Sir James Simpson of Edinburgh in 1848.
A A
37 o THE MODERN SCIENCE.
trichloromethane ; CC1 4 , tetrachloromethane or car-
bon tetrachloride. In a similar way we can replace
the hydrogen atoms of the hydrocarbon by bromine
and iodine, obtaining corresponding compounds as, for
instance, CH 3 I, methyl iodide. The action of caustic
potash upon methyl chloride gives rise to methyl
alcohol } the term alcohol being applied to hydrocarbons
having one or more of their hydrogen atoms replaced
by hydroxyl (OH) :
CH 3 C1 + KOH = CH 3 OH -f KC1.
Methyl alcohol is a convenient source of a number of
methyl compounds. The first action of sulphuric acid
gives us hydrogen methyl sulphate CH 8 HS0 4 . The
remaining hydrogen atom of sulphuric acid may be
replaced by a metal. By various other means, such
as the action of an acid on the alcohol or of a metallic
salt on an haloid ether (CH 3 I, Br or Cl), many other
methyl salts may be obtained, as the nitrate, nitrite
sulphide, sulphite, silicate, &c. Where an acid is
dibasic, as sulphuric acid, we may obtain two salts,
for instance CH 3 HS0 4 and (CH 3 ) 2 S0 4 according as one
or both hydrogens are replaced. On oxidising methyl
alcohol the first product is termed formic aldehyde.
H H
H-C OH + = H 2 -f H C=Q*
OHO being 1 the characteristic aldehyde group.
THE MODERN SCIENCE. 371
Further oxidation converts it into formic acid,
H OH
H C = + = H C = 0.
OH
The group c or, as it is shortly written C0 2 H,
^o
is termed carboxyl, and is characteristic of the organic
acids.
It has already been observed that the first product
of the action of sulphuric acid upon methyl alcohol is
methyl hydrogen sulphate, CH 3 HS0 4 ; another product
formed under suitable conditions is methyl oxide, or
CH 3 ^
dimethyl ether, /-
CH 3//
When methyl iodide (CH 3 I), is treated with silver
nitrite (AgNO 2 ), nitromethane (CH 3 N0 2 ) is obtained,
being methane (CH 4 ) in which one hydrogen atom is
replaced by the group NO 2 .
H H
I ^ I /
H-C I + AgN ! = Agl + H-C-N |
I M) I X
H H
By appropriate means we can replace further hydro-
gen atoms in methane by the nitroxyl group (NO 2 ),
obtaining, for instance, trinitromethane or nitroform
CH (NO 2 ) 3 . Furthermore we can, as might be expected,
replace different hydrogen atoms at one and the same
time by different groups, obtaining, for instance, bromo-
trinitromethane, C(N0 2 ) 3 Br, and so on. It is obvious
therefore, that from the single hydrocarbon methane
372 THE MODERN SCIENCE.
a large number of direct derivatives may be obtained,
for there is no theoretical reason why we should not
introduce into the molecule of methane these various
substituting groups in every kind of combination.
Some important classes of bodies still remain to be
mentioned. If we reduce nitromethane by nascent
hydrogen the nitroxyl group becomes converted into
amidogen NH 2
CH 3 N0 2 -f 3H 2 ^CI1 3 NH 2 -f- 2H 3 0.
The substance so formed may indeed be regarded as
ammonia, NH 3 , in which one hydrogen atom has
been replaced by methyl, CH 3 . It is termed methy-
lamine. The two remaining hydrogen atoms of
ammonia may be similarly replaced with production
of di- and tri- methylamine ((CH 3 ) 2 NH & (CH 3 ) 3 N).
Here again we may effect a double substitution, obtain-
ing, for instance, di-iodomethylamine CH 3 NI 2 , where
one hydrogen atom of ammonia, NH 3 , is replaced by
methyl and the two others by iodine. Bodies of a
similar nature may be derived from arseniuretted
hydrogen, AsH 3 , giving respectively monomethyl,
dimethyl, and trimethyl arsine, &c. So too from
phosphuretted hydrogen, PH 3 , analogous phosphines
are obtainable. Amines, arsines, and phosphines
are all of them basic bodies, and, like ammonia,
combine with acids to form a variety of salts. By a
very superficial glance we are thus able to see how
rapidly the number of compounds derivable from
even one hydrocarbon swells. But if we take methyl
THE MODERN SCIENCE. 373
iodide and heat it with zinc the following reaction
occurs
CH 3 1 1 1 1 CH 3
I Zn I
that is to say, the zinc takes away the iodine from
two molecules forming zinc iodide, Znl 2 , and the two
methyl groups are left. They cannot exist separately ;
each carbon being combined with only three hydrogen
atoms has yet power of combining with another
atom. The two carbons thus become directly united
and H 3 C CH 3 , or ethane, is the result. It is
methane in which one hydrogen atom is replaced by
the methyl group, CH 3 . Graphically its formula is
H H
H-b C-H, and from it a whole series of compounds
H H
analogous to those obtainable from methane may be
produced. The only difference is that there being
more hydrogen atoms to replace, the number of
derivatives is considerably larger in number. Thus
we may obtain two hydroxyl derivatives ; the first,
CH 3 .CH 2 OH, is common alcohol, or ethyl alcohol,
as it is distinctly termed, the group, CH 3 .CH 2
or C 2 H 5 , constituting the radical ethyl. The
second is CH 2 OH.CH 2 OH, having one hydroxyl
in each methyl (CH 3 ) group* and known as ethylene
* At first sight it would seem that we might obtain a body
H
I
CH 3 .C OH containing its two hydroxyls attached to the same
OH
carbon atom. Such bodies, however, cannot be obtained, losing
water at once and becoming monohydroxylic.
374 THE MODERN SCIENCE.
glycol.* The acid corresponding to ethyl alcohol is
of course acetic acid, CH 3 .C0 2 H, Mono-, di- and
tri-ehloroacetic acids (CH 2 C1.C0 2 H : CHC1 2 .C0 2 H :
CCP. C0 2 H) and other such derivations are known.
Acetic aldehyde is CH 3 .CHO. Trichloracetaldehyde,
CCP.CHO, is usually known as chloral.
The hydrocarbon next above ethane, C 2 H 6 , is
propane C 3 H 8 . These hydrocarbons are said to form
a homologous series, the higher being obtained from
the next lower one by the addition of CH 2 . Their
derivatives are also homologous.
From propane, C 3 H 8 , analogous derivatives may be
obtained, but here some complications occur. Writ-
ing out the formula of propane more fully we have
CH 3 .CH 2 .CH 3 . Now it makes all the difference
whether we substitute a hydrogen atom in the
methyl (CH 3 ) groups at the end of the chain or an
atom in the CH 2 group at the centre. Suppose, for
instance, that we introduce iodine into the methyl
group. The formula becomes CH 3 .CH 2 .CH 2 I. The
carbon atom with which the iodine is combined is
attached to one other carbon atom and two hydrogen
atoms. It moreover plays a certain part in respect
to the rest o the molecule. The introduction of the
iodine atom alters its relation to the rest of the
molecule. But now suppose the iodine atom in
the central group. The formula becomes CH 3 .
CHI.CH 3 . The carbon atom with which the
* Dibasic acids, &c., can of course be obtained, corresponding to
the alcohols.
THE MODERN SCIENCE. 375
iodine is now combined is attached to two other
carbon atoms and one hydrogen atom. It plays
a part in the molecular whole quite distinct from
that of the terminal carbon atoms. The intro-
duction of the iodine atom now alters its relation to
the rest of the molecule. The change produced in
the molecule by the introduction of the Jodine atom
in the one case is therefore quite distinct from that
produced in the other. The two compounds are
therefore quite distinct. The first is termed primary,
the second, secondary propyl iodide.* It may be
well to observe that the two terminal carbon atoms
play an exactly similar part in the molecule and that
therefore the compound CH 3 .CH 2 .CH 2 I is identical
with the compound CH 2 LCH 2 .CH 3 ; indeed these
formulas must never be taken as representing the
relation of the atoms in space but merely as indicat-
ing which atoms are directly united to each other.
Obviously these modes of substitution in the propane
molecule may be repeated with other substituting
groups, giving us, for instance, CH 3 .CH 2 .CH 2 OH,
primary propyl alcohol (C 3 H 5 .OH) and CH 3 .CHOH,
CH 3 , secondary propyl alcohol (C 3 H 5 OH). It is
noticeable that the empirical formulae (C 3 H 6 0) of the
secondary and primary derivatives are identical.
The substances are only distinguishable when their
rational or structural formulae are given. Bodies thus
* When there is a long chain a large number of isomers may be
obtained as CHICHI. CH 2 .CH 3 . CH 2 . CH 3 ; CH 3 . CH 2 . CHI. (CH 2 ) 2 .
CH 3 and so on.
376 THE MODERN SCIENCE.
containing in their molecules the same number of
the same molecules are said to be isomeric* From
propane, then, we may not only obtain a series of
derivatives strictly analogous to those obtainable
from, ethane, but the number of derivatives is also
much increased by the possibility of forming such
isomeric bodies. Proceeding up the series of hydro-
carbons we have
4 , C 2 H 6 , C 3 H 8 , C 4 H 10 .
The last hydrocarbon, butane, has not yet been
mentioned. In this case the hydrocarbon itself may
exist in two isomeric modifications and each of these
gives rise to a long series of derivatives.
The first modification where all the carbon atoms
may be written out in a chain is termed normal
butane, CH 3 .CH 2 .CH 2 .CH 3 , the second, isobutane,
CH 3 CH(g3 or trimethyl methane. Each of these is
capable of forming two mono-substitution products.
The alcohol, CH 3 COH(gis, is termed a tertiary al-
cohol, the substituting group being in primary com-
pounds united to CH 2 , in secondary compounds to
CH, and in tertiary compounds to C. The primary
alcohols when oxidised give rise to acids as we have
seen. The secondary alcohols on the other hand form
a new class of bodies termed ketones. Thus with
secondary propyl alcohol,
CIF.CIP.CHOH.CH3 + O = CH 3 .CH 2 .CO.CH3 + H 2 O,
the product being known as ethylmethyl ketone.
* Tliis name was given by Berzelius (taog, equal ; ftepof, a share)*
THE MODERN SCIENCE. 377
Tertiary alcohols split up on oxidation. We have
then
CH 3 .CH 2 .CH 2 .CH*
CH 3 .CH 2 .CHOH.CH 3 CIP.CH 2 .CH 2 .CH 2 OH.
/CB?
CH3.CH 7
X CH3
, CH 3 , CH 3
CIF.COH' CH 2 OH.CH /
and by introducing various substituting groups we
may theoretically obtain chlorine substitution pro-
ducts, alcohols, aldehydes, ethers, acids, ketones,
amines, and so forth, in almost any number.
Butane exists in two modifications ; of the next
higher paraffin, C 5 H 12 , there are three modifications ;
of the next, C 6 H U , five are possible and four known ;
of the next, C 7 H 16 , nine are possible, and when we
reach the hydrocarbon, C 13 H 28 , it has been calculated
by Professor Cayley that no less than 799 modifica-
tions should exist. Each of these modifications should
give rise to several complete series of derivatives of its
own.
But this is by no means the only series of hydro-
carbons known to the chemist. Another series
begins with the term C 2 H 4 , ethylene, and like the
other proceeds upwards by increments of CH 2 . The
structural formula of ethylene is
CH 3
(U
where we see that two of the units of saturation of
carbon are engaged with each other. The series of
378 THE MODERN SCIENCE.
the defines, as they are termed, is characterised by
this constitution. Its members tend to combine
directly with chlorine and other elements. Thus
ethylene produces the dichloride, CH 2 C1.CH 2 C1, which
is identical with symmetrical dichloroethane. We can
also substitute hydrogen in ethylene, obtaining for
instance, monochlorethylene, CH 2 :CHC1. and so on.
The hydrocarbons form the series C 2 H 4 , C 3 H 6 , C 4 H 8 ,
C 5 H 10 , and so on. We may obtain from them a large
number of derivatives similar to those obtained from
the paraffins, except for the peculiar union of two
of the carbon atoms and the unsaturated character or
proneness to combination resulting from that union.
An example of this group is afforded by the following
compounds :
CH 2 : CH.CH 3 , CH 2 : CH.CH 2 OH, CH 2 : CH.C0 2 H,
CH 2 : CH.CH 2 !.
Another important series of hydrocarbons is the
acetylene series commencing with the term ClfeCH,
a gas capable of combining with four atoms of chlo-
rine to form CHCP.CHCl 2 . Far fewer compounds
of this series are, however, known.
Other series of hydrocarbons are known, but need
not be referred to here with the exception of one,
which has become of greater importance than all the
rest, the benzene series. All the hydrogen atoms of
benzene (C 6 H 6 ) are proved to be of equal value in
the molecule, and the only way of representing this
structurally is by the ring formula proposed by
Kekule:
THE MODERN SCIENCE. 379
iic CH
or, perhaps preferably Ladenburg's modification.
We may obtain from it substitution products much
in the same way as from other hydrocarbons. But
there are special laws regulating this substitution.
Representing the benzene molecule as is commonly
done by a simple hexagon we see that we can obtain
only one monosubstitution product, all the hydrogens
being similar, and three disubstitution products, e.g.
ci
V
\J
Fara-
known as ortho-, meta-, and para-dichlorobenzene.
C 6 H 4 C1 2 1 : 6 is identical with C 6 H 4 C1 2 1 : 2, the
chlorine in both cases being combined with adjacent
carbon atoms. Where three hydrogen atoms are re-
placed by the same element three isomeric modifica-
tions may be obtained, but where there is more than
one substituting element there is a larger number
of isomers.
We may thus replace hydrogen in the benzene ring
by a variety of groups just as in the case of the
paraffins, and may produce higher hydrocarbons by
380 THE MODERN SCIENCE.
introducing alkyl radicals, as, for instance, CH 3 . We
thus obtain C 6 H 5 .CH 3 where CH 3 is termed a side
chain. On oxidising such derivatives the side chain
becomes converted into carboxyl and thus we here
obtain C 6 H 5 .C0 2 H, benzoic acid. Where there are
two side chains as in C 6 H 4 (cJp[J), orthoxylene, oxida-
tion produces a dibasic acid as C G H 4 (co*H[Jj, ortho-
phthalic acid. By substitutions of this kind we may
obtain an enormous number of benzene derivatives, and
the reader may at will construct large numbers on paper
for himself. It is easy with the constitutional formula
now in use to predict the existence of numerous
compounds as yet undiscovered, and to describe their
chief properties, for these undergo a gradual modifica-
tion of properties as we pass up a homologous series
just as properties of the elements become modified
with rise of atomic weight.
In many compounds two or three benzene rings
may be combined, either indirectly, as in rosaniline,
or directly, as in naphthalene
I II I
which body is again the source of a large series of
compounds. We cannot do more here than thus
indicate how in the modern system of organic chernis-
THE MODERN SCIENCE. 381
try the vast numbers of its compounds diverge from
a few simple hydrocarbons like the branches of an
enormous genealogical tree. The system is so far
perfected that the character of the undiscovered com-
pouuds is in many cases as plain to the chemists as
the character of the elements destined to fill the
blanks in Mendelejeff's table. Modifications of pro-
perties occur along with rise of molecular weight and
change of structure. Thus, as an instance of the
former truth, boiling points rise, and often very regu-
larly, as we pass up a homologous series. As an
instance of the latter normal compounds have a higher
boiling-point than iso-compound. Similarity of struc-
ture on the other hand always goes hand in hand
with similarity of properties, and thus it happens that
all the paraffin hydrocarbons have great chemical
similarity, for instance, in allowing their hydrogen to
be replaced by chlorine, and that all the primary
alcohols form acids on oxidation. It is these strictly
defined relations which make it possible to direct
research in this department upon such definite lines
and make organic chemistry so perfect a science.
CONCLUSION.
may seem to some that science becomes
less interesting and less beautiful as it
advances. This, however, is but a one-
sided view to take. The mere facts of
science may be dry enough, but the facts
have to be interpreted, and so arise deep
truths through which we seem to peer
into the great heart of nature. There is a poetical
side to this, and the poetry of it becomes more obvious
as the truths become more deep. Again, the truths
which Ave are able to see and the conjectures we are able
to frame only bring us more closely into contact with
the vast regions of mystery where knowledge fades
into speculation, and speculation into awe. We need
fear no loss of the mysterious by the achievements of
THE MODERN SCIENCE. 3 S 3
science, though, we exchange a lesser mystery for a
greater. The wonder with which in ignorance we
look up through the branches of a forest beech and see
the giant boughs spread upwards in moveless strength
and the floating tresses of sunlit leaves curved back
towards us, the wonder with which we watch in its
cool nooks the softness of the shadow, or through
its recesses the changeful play of palpitating light
this wonder is great. But that is still greater and
of more enduring worth with which, by higher know-
ledge, we watch the same wondrous beauty and see
beyond it how, through the myriad cells of leaf and
branch and trunk, minute by minute, the life cur-
rents of protoplasm ebb and flow, making the green
grace of the tree possible by their swift mysterious
power : or again, how the gleaming spears of sun-
light that shiver into soft glow of colour upon
those tiny wind-lifted shields have sped unstayed in
their few moments of dazzling life through depths of
space, so vast and desolate that before them the mind
of man can only wonder in impotence, or recoil in
dread, to be stayed at last and fall in fragments at
the light touch of one trembling leaf. No need is
here to complain that science will leave us with
nothing to wonder at. It is only morbid conceit which
can forget the great truth uttered by a man who com-
bined the keen observance of science with the lofty
insight of the poet " Poetry is the impassioned ex-
pression which is in the face of all science."
In our review of the progress of our science we have
384 THE HfODERN SCIENCE.
soon it at first advancing slowly through the darkness
of ignorance and error. In this darkness it was
difficult to go forward, but it was more difficult to
go back. After a while the darkness hero and there
lightened a little, but the first gleams of brightness
were too often alluring marsh-lights beckoning to
impenetrable morass ; the false guides were more
treacherous than the night. But as the twilight of
doubt broadened into the day of knowledge it re-
vealed ever wider and wider tracts of hill and hollow
for us to explore. At last the daylight has flooded
mountain rock, and valley mist, and we stand in
wonderment before the vision of the newly revealed
realm as it stretches before us, from the gold of the
sunrise to where hastening night has dropped his
purple mantle on the hills. It is a splendid kingdom,
but great is the task of mastering it, and great our
responsibility if we err. We must have regard to its
beauty and not merely to its wealth. We must
not forget the beauty of its mountains in our search
for the treasure of its mines. Wo must see the
countenance but not forget its expression.
INDEX;
Acid, Acetic, 98, .374
Hydrochloric, CO, 99, 199
Nitric, 39, 59, 00, 101,
W.I
Organic, 227, 371
PniBBic, 227
Sulphuric, 00, 02
Affinity, 148, 163
Agricola, 1)7
AlbertuB Magnus, 38, 43
Alcohol, 33, 118, 237
Alkalies, 105, 252, 320
Aluminium, 328, 347
Ammonia, 88, 199
Ampere, 282
Antimony, 07, 85
Aquafortis, 00
Aqua regia, 39
Atmosphere, 33, 203, 209, 221,
251, 351
Atomic theory, 257
Avogadro, 279
Bacon, It., 24, 40
Barium, 227, :'2
Bayen, 240
Bechcr, 117, 175
Benzene, 330, 378
Bergman, 225, 245
Bernard of Trevimi, 50
Berth elot, 228
Berthollet, 257
BerzdiuH, 228, 283, 289, 326,
353, 301
lilack, Dr., 94, 101
Boerhaavc, 179
U
INDEX.
Boyle, 121,151, 179,243.
Bunsen, 348, 358, 367
Calcium, 327
Carbonate, 89, 167
Carbon dioxide, 89, 141, 219,
241
Cavendish, 33,83, 183, 211
Chaptal, 65
Chevreul, 228
Chlorine, 225, 328, 336, 338
Chloroform, 369
Combustion, . 134, 140, 147,
246, 252
Condensation, 337
Constant proportions, 245, 257,
269
Copper sulphate, 98
Crookes, 134, 345, 356
Cullen, 159
Dalton, 261
Davy, 317
Dulong and Petit, 285
Dumas, 351, 353, 365
Electro-chemical equivalents,
339
Elements, 40, 50, 83, 87, 102,
115, 128, 146, 176, 252, 297,
344
Faraday, 320
Fats, 228
Fermentation, 34, 287
Fusel-oil, 237
Gas, 87
Gay-Lussac, 278, 325, 353, 361
Geber, 15, 38, 298
Geoffrey, 114
Gerliarclt, 293
Glass, 27
Glauber, 58, 97
Glycerine, 228
Gunpowder, 49, 105, 134
Hales, 153, 199
Helmont, Van, 86
Hermes Trismegistus, 38
Higgins, 267
Hoffmann, F., 179
Hooke, 137
Hydrogen, 83, 89, 219
Sulphide, 227
Indestructibility, 157,235
Iron sulphate, 39, 50, 60
Isomers, 374
Isomorphism, 289
Latent heat, 169
Laurent, 296
Lavoisier, 183, 231, 360
INDEX.
Lead oxides, 180
Lemery, 114
Liebig, 30, 228, 254, 362, 368
Lessen, 306
Lully, Raymond, 34, 50
Macquer, 179
Magnesium, 327
Marsh gas, 267
Mayow, 147, 178
Mendelejeff, 308
Metals and non-metals, 298
Metals known to ancients, 25
Molybdenum 227
Newlands, 308
Newton, 138, 356
Nitrogen, 204
Nomenclature, 253
Northmore, 338
Olefiant gas, 267
Opium, 84
Organic chemistry, 116, 225,
360
Oxygen, 147, 185, 202, 226,
248
Palissy, Bernard, 30
Paracelsus, 79, 94
Phlogiston, 169, 176, 206
Phosphorus, 150, 227
Pliny, 27, 32, 68 .
Pneumatic trough, 143, 198
Porcelain, 29
Pott, 29, 179
Priestley, 182, 1C5
Proust, 258
Prout, 284
Radical, 361, 363
Reactions, 163
Reaumur, 30
Rey, John, 178
Richter, 259
Roscoe, 75, 276, 344
Royal Society, 113
Rutherford, 204
Sal-ammoniac, 98
Salt-petre, 49, 101, 131, 145
Salts, 50, 151, 295
Scheele, 182, 225, 326
Silicon, 27, 346
Soap, 30
Sodium sulphate, 98
Spectroscope, 356
Stahl, 117, 176,200
Starch, 28
Stas, 353
Strontium, 326
Structural formula?, 304
Suidas, 37
Sulphur dioxide, 200
Sulphurs, 116
Symbols, 59, 275, 299
INDEX.
Valentine, 55, 83, 367
Tractatus A.ureus, 40
Transmutation, 19, 40, 107
Tungsten, 227
Valency, 302
Ward, 63
Water, 33, 221, 233, 246, 351
Watt, 224
Williamson, 268, 302
Wohler, 361
Wood tar, 99
Wurtz, 228, 368
THE END.
PRINTED BY J. 8. VIRTUE AND CO., LIMITED, CITY ROAD, LONDON.
2 5 2 5 6