SUMMARY AND CONCLUSION.
We have thus traced some of the main paths along which Chemistry has
advanced since the day when, ceasing to be guided by the dreams of men who
toiled with but a single idea in the midst of a world of strange and
complex phenomena, she began to recognize that Nature is complex but
orderly, and so began to be a branch of true knowledge.
In this review we have, I think, found that the remark made at the
beginning of the introductory chapter is, on the whole, a just one. That
the views of the alchemists, although sometimes very noble, were "vague and
fanciful" is surely borne out by the quotations from their writings given
in the first chapter. This period was followed by that wherein the
accurate, but necessarily somewhat narrow conception of the Lavoisierian
chemistry prevailed. Founded for the most part on the careful,
painstaking, and quantitative study of one phenomenon--a very wide and
far-reaching phenomenon, it is true--it was impossible that the
classification introduced by the father of chemical science should be broad
enough to include all the discoveries of those who came after him. But
although this classification had of necessity to be revised and recast, the
genius of Lavoisier enunciated certain truths which have remained the
common possession of every chemical system. By proving that however the
forms of matter may be changed the mass remains unaltered, he for the first
time made a science of chemistry possible. He defined "element" once for
all, and thus swept away the fabric of dreams raised by the alchemists on
the visionary foundation of _earth_, _air_, _fire_ and _water_, or of
_mercury_, _sulphur_ and _salt_. By his example, he taught that weighings
and measurements must be made before accurate knowledge of chemical
reactions can be hoped for; and by his teaching about oxygen being _the
acidifier_--although we know that this teaching was erroneous in many
details--he showed the possibility of a system of classification of
chemical substances being founded on the actually observed properties and
composition of those substances.
Lavoisier gained these most important results by concentrating his
attention on a few subjects of inquiry. That chemistry might become broad
it was necessary that it should first of all become narrower.
The period when the objects of the science were defined and some of its
fundamental facts and conceptions were established, was succeeded, as we
saw in our sketch, by that in which Dalton departed somewhat from the
method of investigation adopted by most masters in science, and by
concentrating his great mental powers on facts belonging to one branch of
natural knowledge, elaborated a simple but very comprehensive theory, which
he applied to explain the facts belonging to another branch of science.
Chemistry was thus endowed with a grand and far-reaching conception, which
has been developed and applied by successive generations of investigators:
but we must not forget that it was the thorough, detailed work of Black and
Lavoisier which made possible the great theory of Dalton.
At the time when Dalton was thinking out his theory of atoms, Davy was
advancing as a conqueror through the rich domain which the discovery of
Volta had opened to chemistry. Dalton, trained to rely on himself,
surrounded from his youth by an atmosphere in which "sweetness and light"
did not predominate, thrown on the world at an early age, and obliged to
support himself by the drudgery of teaching when he would fain have been
engaged in research, and at the same time--if we may judge from his life as
recorded by his biographers--without the sustaining presence of such an
ideal as could support the emotional part of his nature during this time of
struggle,--Dalton, we found, withdrew in great part from contact with
other scientific workers, and communing only with himself, developed a
theory which, while it showed him to be one in the chain of thinkers that
begins in Democritus and Leucippus, was nevertheless stamped with the
undeniable marks of his own individuality and genius, and at the same time
was untouched by any of the hopes or fears, and unaffected by any of the
passions, of our common humanity.
Davy, on the other hand, was surrounded from childhood by scenes of great
natural beauty and variety, by contact with which he was incited to eager
desire for knowledge, while at the same time his emotions remained fresh
and sensitive to outward impressions. Entering on the study of natural
science when there was a pause in the march of discovery, but a pause
presageful of fresh advances, he found outward circumstances singularly
favourable to his success; seizing these favourable circumstances he made
rapid advances. Like Lavoisier, he began his work by proving that there is
no such thing in Nature as transmutation, in the alchemical meaning of the
term; as Lavoisier had proved that water is not changed into earth, so did
Davy prove that acid and alkali are not produced by the action of the
electric current on pure water. We have shortly traced the development of
the electro-chemical theory which Davy raised on the basis of experiment;
we have seen how facts obliged him to doubt the accepted view of the
composition of hydrochloric acid and chlorine, and how by the work he did
on these subjects chemists have been finally convinced that an element is
not a substance which _cannot be_, but a substance which _has not been_
decomposed, and how from this work has also arisen the modern theory of
acids, bases and salts.
We found that, by the labours of the great Swede J. J. Berzelius, the
Daltonian theory was confirmed by a vast series of accurate analyses, and,
in conjunction with a modification of the electro-chemical theory of Davy,
was made the basis of a system of classification which endeavoured to
include all chemical substances within its scope. The atom was the
starting-point of the Berzelian system, but that chemist viewed the atom as
a dual structure the parts of which held together by reason of their
opposite electrical polarities. Berzelius, we saw, greatly improved the
methods whereby atomic weights could be determined, and he recognized the
importance of physical generalizations as aids in finding the atomic
weights of chemical substances.
But Berzelius came to believe too implicitly in his own view of Nature's
working; his theory became too imperious. Chemists found it easier to
accept than to doubt an interpretation of facts which was in great part
undeniably true, and which formed a central luminous conception, shedding
light on the whole mass of details which, without it, seemed confused and
without meaning.
If the dualistic stronghold was to be carried, the attack should be
impetuous, and should be led by men, not only of valour, but also of
discretion. We found that two champions appeared, and that, aided by others
who were scarcely inferior soldiers to themselves, they made the attack,
and made it with success.
But when the heat of the battle was over and the bitterness of the strife
forgotten, it was found that, although many pinnacles of the dualistic
castle had been shattered, the foundation and great part of the walls
remained; and, strange to say, the men who led the attack were content that
these should remain.
The atom could no longer be regarded as always composed of two parts, but
must be looked on rather as one whole, the properties of which are defined
by the properties and arrangements of all its parts; but the conception of
the atom as a structure, and the assurance that something could be inferred
regarding that structure from a knowledge of the reactions and general
properties of the whole, remained when Dumas and Liebig had replaced the
dualism of Berzelius by the unitary theory of modern chemistry; and these
conceptions have remained to the present day, and are now ranked among the
leading principles of chemical science; only we now speak of the "molecule"
where Berzelius spoke of the "atom."
Along with these advances made by Dumas, Liebig and others in rendering
more accurate the general conception of atomic structure, we found that
the recognition of the existence of more than one order of small particles
was daily gaining ground in the minds of chemists.
The distinction between what we now call atoms and molecules had been
clearly stated by Avogadro in 1811; but the times were not ripe. The mental
surroundings of the chemists of that age did not allow them fully to
appreciate the work of Avogadro. The seed however was sown, and the
harvest, although late, was plentiful.
We saw that Dumas accepted, with some hesitation, the distinction drawn by
Avogadro, but that failing to carry it to its legitimate conclusion, he did
not reap the full benefit of his acceptance of the principle that the
smallest particle of a substance which takes part in a physical change
divides into smaller particles in those changes which we call chemical.
To Gerhardt and Laurent we owe the full recognition, and acceptance as the
foundation of chemical classification, of the atom as a particle of matter
distinct from the molecule; they first distinctly placed the law of
Avogadro--"Equal volumes of gases contain equal numbers of molecules"--in
its true position as a law, which, resting on physical evidence and
dynamical reasoning, is to be accepted by the chemist as the basis of his
atomic theory. To the same chemists we are indebted for the formal
introduction into chemical science of the conception of types, which, as we
found, was developed by Frankland, Kekule, and others, into the modern
doctrine of equivalency of groups of elementary atoms.
We saw that, in the use which he made of the laws of Mitscherlich, and of
Dulong and Petit, Berzelius recognized the importance of the aid given by
physical methods towards solving the atomic problems of chemistry; but
among those who have most thoroughly availed themselves of such aids Graham
must always hold a foremost place.
Graham devoted the energies of his life to tracking the movements of atoms
and molecules. He proved that gases pass through walls of solid materials,
as they pass through spaces already occupied by other gases; and by
measuring the rapidities of these movements he showed how it was possible
to determine the rate of motion of a particle of gas so minute that a group
of a hundred millions of them would be invisible to the unassisted vision.
Graham followed the molecules as in their journeyings they came into
contact with animal and vegetable membranes; he found that these membranes
presented an insuperable barrier to the passage of some molecules, while
others passed easily through. He thus arrived at a division of matter into
colloidal and crystalloidal. He showed what important applications of this
division might be made in practical chemistry, he discussed some of the
bearings of this division on the general theory of the molecular
constitution of matter, and thus he opened the way which leads into a new
territory rich in promise to him who is able to follow the footsteps of
its discoverer.
Other investigators have followed on the general lines laid down by Graham;
connections, more or less precise, have been established between chemical
and physical properties of various groups of compounds. It has been shown
that the boiling points, melting points, expansibilities by heat, amounts
of heat evolved during combustion, in some cases tinctorial powers of
dye-stuffs, and other physical constants of groups of compounds, vary with
variations in the nature, number and arrangements of the atoms in the
molecules of these compounds.
But although much good work has been done in this direction, our ignorance
far exceeds our knowledge regarding the phenomena which lie on the
borderlands between chemistry and physics. It is probably here that
chemists look most for fresh discoveries of importance.
As each branch of natural science becomes more subdivided, and as the
quantity of facts to be stored in the mind becomes daily more crushing, the
student finds an ever-increasing difficulty in passing beyond the range of
his own subject, and in gaining a broad view of the relative importance of
the facts and the theories which to him appear so essential.
In the days when the foundation of chemistry was laid by Black, Priestley,
Lavoisier and Dalton, and when the walls began to be raised by Berzelius
and Davy, it was possible for one man to hold in his mental grasp the whole
range of subjects which he studied. Even when Liebig and Dumas built the
fabric of organic chemistry the mass of facts to be considered was not so
overpowering as it is now. But we have in great measure ourselves to blame;
we have of late years too much fulfilled Liebig's words, when he said, that
for rearing the structure of organic chemistry masters were no longer
required--workmen would suffice.
And I think we have sometimes fallen into another error also. Most of the
builders of our science--notably Lavoisier and Davy, Liebig and Dumas--were
men of wide general culture. Chemistry was for them a branch of natural
science; of late years it has too much tended to degenerate into a
handicraft. These men had lofty aims; they recognized--Davy perhaps more
than any--the nobility of their calling. The laboratory was to them not
merely a place where curious mixtures were made and strange substances
obtained, or where elegant apparatus was exhibited and carefully prepared
specimens were treasured; it was rather the entrance into the temple of
Nature, the place where day by day they sought for truth, where, amid much
that was unpleasant and much that was necessary mechanical detail, glimpses
were sometimes given them of the order, harmony and law which reign
throughout the material universe. It was a place where, stopping in the
work which to the outsider appeared so dull and even so trivial, they
sometimes, listening with attentive ear, might catch the boom of the
"mighty waters rolling evermore," and so might return refreshed to work
again.
Chemistry was more poetical, more imaginative then than now; but without
imagination no great work has been accomplished in science.
When a student of science forgets that the particular branch of natural
knowledge which he cultivates is part of a living and growing organism, and
attempts to study it merely as a collection of facts, he has already
Esau-like sold his birthright for a mess of pottage; for is it not the
privilege of the scientific student of Nature always to work in the
presence of "something which he can never know to the full, but which he is
always going on to know"--to be ever encompassed about by the greatness of
the subject which he seeks to know? Does he not recognize that, although
some of the greatest minds have made this study the object of their lives,
the sum of what is known is yet but as a drop in the ocean? and has he not
also been taught that every honest effort made to extend the boundaries of
natural knowledge must advance that knowledge a little way?
It is not easy to remember the greatness of the issues which depend on
scientific work, when that work is carried on, as it too often is, solely
with the desire to gain a formal and definite answer to some question of
petty detail.
"That low man seeks a little thing to do,
Sees it and does it:
This high man, with a great thing to pursue,
Dies ere he knows it.
"That low man goes on adding one to one,
His hundred's soon hit:
This high man, aiming at a million,
Misses a unit."
INDEX.
A
Acids, connected by Lavoisier with oxygen, 91;
Boyle's and other early definitions, 171;
opposed in early medicine to alkalis, 172;
grouped, 173;
salts, 173;
"the primordial acid," 174;
oxygen not a necessary constituent, 184;
new division of acids by Davy, 205;
acids of different basicity, 237;
modern conception of acids, 301.
Affinity, chemical, apparently suspended by electricity, 191;
history of term "affinity," 206;
tables of, 207;
dependent on electric states, 210.
Air, composition of, determined by Cavendish, 79;
Dalton's investigations, 116.
Alchemy, 5;
alchemical symbols of metals, 11;
quotations from alchemists, 15, 17;
alchemical poetry, 18.
Alcoates, 235.
Alkalis, 171;
fixed and volatile, 173;
mild and caustic, examined by Black, 176;
connection with earths, 178;
name of "base" given by Rouelle, 179;
Gay-Lussac's alkalizing principle, 203.
Ammonia, discovered by Priestley, 66.
Atmolysis, 243.
Atomic theory, dawn of, 117;
early views of Greek philosophers, 123;
of Epicurus and Lucretius, 124;
of Newton and Bernoulli, 125;
Dalton's new views--combination in simple multiples, 127, _et seq._;
the theory made known by Dr. Thomson, 129;
it is opposed at first by Davy, 130;
Dalton's rules for arriving at atomic weights, 132;
more accurately applied by Berzelius, 133, 162;
diagrams of atoms, 118, 136;
the theory as carried out by Gay-Lussac and Avogadro, 138, _et seq._;
conception of the molecule, 140;
molecular and atomic weight, 145;
Graham's work on molecular reactions, 249;
Berzelius's dualistic views, 212;
they are attacked by Dumas, 260;
conception of the compound radicle, 267;
Laurent's unitary theory, 272;
modern conception of molecule, 275;
revision of atomic weights, 285;
equivalency of atoms, 295.
Avogadro, his elucidation of the atomic theory, 138, _et seq._;
introduces the idea of molecules, 140;
law known as Avogadro's law, 143.
B
Base (of salts), 179;
basic lines in spectrum, 311.
Becher, John J., born at Speyer, 26;
his three principles of metals, 26;
his principle of inflammability, 48;
his views on acids, 174.
Berthollet, analyzes ammonia, 66;
adheres to the Lavoisierian theory of combustion, 95;
questions doctrine of fixity of composition, 126;
and necessary presence of oxygen in acids, 184;
shows variable nature of affinities, 208.
Berzelius, Johann J., 106;
determines weights of elementary atoms, 133;
his birth and education, 157;
works at Stockholm, 159;
his slight appliances and large discoveries, 161;
he reviews Dalton's atomic theory, 162;
his views superseded by Avogadro's generalization, 165;
he accepts law of isomorphism, 166;
and Davy's discovery of chlorine, 204;
his views on affinity of atoms, 209;
his dual classification, 212;
works at organic chemistry, 220;
his dualism attacked by Dumas, 260.
Black, Joseph, born at Bordeaux, 30;
his education, 31;
his thesis on magnesia and discovery of "fixed air," 33, _et seq._;
inquiries into latent heat, 39;
professor at Edinburgh, 41;
his death and character, 41, _et seq._;
_resume_ of his work, 102;
his examination of alkalis, 176.
Boyle, Hon. Robert, 25;
his "Sceptical Chymist," 76;
law known as "Boyle's law," 77;
opposes doctrine of elementary principles, 93;
his definition of an acid, 171;
extends the knowledge of salts, 177.
Bromine, discovered by Balard, 291.
C
Carbonic acid gas, or "fixed air," studied by Black, 35;
by Priestley, 57, 69.
Cavendish, Hon. Henry, rediscovers hydrogen, 63, 78;
and composition of water and air, 78.
Chloral, } produced by Liebig, composition determined by Dumas, 273.
Chloroform,}
Chlorine, discovered by Davy, 202;
replaces hydrogen in organic compounds, 271.
Colloids, 247.
Combination in multiple proportions, 127.
Combustion, studied by early chemists, 24 (_vide_ "Phlogistic theory");
studied by Black, 47;
his views of Lavoisier's theory, 51;
Priestley's views of combustion, 62;
Lavoisier's experiments, 83, _et seq._;
Liebig's combustion-tube, 263.
Compound radicle, 267;
the idea of substitution, 270, 276.
Conservation of mass, doctrine of, 82.
Crystallization, water of, 237.
Crystalloids, 247.
D
Dalton, John, his birth and education, 107;
"answers to correspondents," 109;
his meteorological observations, 110;
teaches at Manchester, 110;
colour-blind, 111;
pressures of gaseous mixtures, 113;
strives after general laws, 115;
first view of atomic theory, 117;
visits Paris, 120;
honours conferred on him, 121, 122;
dies, 123;
consideration of atomic theory (which see), 123, _et seq._;
his "New System of Chemical Philosophy," 129;
fixes atomic weight of hydrogen, 130;
small use he makes of books, 148;
inaccurate as an experimenter, 149;
his method compared with Priestley's, 151.
Davy, Sir Humphry, 106;
opposes the atomic theory, 129;
accepts same, 130;
studies the chemical aspects of electricity, 185;
experiments on the acid and alkali said to be produced by
electrolyzing water, 186;
apparent suspension of chemical affinities by action of electricity, 191;
discovers potassium, 197;
and sodium, 198;
the metallic bases of earths, 200;
proves the elementary nature of chlorine, 202;
Davy's birth and youth, 215;
experiments on heat, 217;
his work at Bristol, 218;
inhales gases, 220;
lectures at the Royal Institution, 222;
discovers iodine and invents safety-lamp, 224;
dies, 226.
Dialysis, 247.
Diffusion-rates of gases, 241;
distinguished from transpiration-rates, 242;
diffusion-rates of liquids, 245.
Dulong, his law of atomic heat, 168.
Dumas, Jean B. A., birth and education, 257;
physiological studies, 258;
meets Von Humboldt, 259;
attacks the dualism of Berzelius, 260;
Dumas's vapour density process, 262;
ethers and alcohols, 265;
chlorine in connection with organic compounds, 271;
determines composition of chloral and chloroform, 273;
studies fermentation, 287;
member of the National Assembly, 288;
takes office, 289.
E
Earths, 177;
Stahl's views, 178;
the connection between earths and alkalis, 178;
their metallic bases, 182, 200.
Economy of waste materials, 300.
Electric affinity, 191, 210.
Electricity, Volta's battery, 185;
used to decompose water, 185;
new metals discovered by its help, 197.
Elements: old doctrine of elementary principles opposed by Boyle, 93;
modern definition of element, 95
(_vide_ "Spectroscopic analysis"--basic lines, 311).
Equivalency, conception of, 294.
F
Fermentation, studied by Dumas, 287.
Fourcroy, calls Lavoisier's views "La chimie Francaise,", 95
G
Gay-Lussac, 138, 143, 201, 203, 257.
Gerhardt, 272, 279.
Graham, Thomas, early life, 233;
made Master of the Mint, 234;
his death, 235;
studies alcoates, 235;
formulates conception of acids of different basicity, 237;
considers hydrogen a metal, 238;
investigates phenomena observed by Doebereiner, 240;
diffusion-rates of gases, 241;
of liquids, 245;
his atmolyzer, 243;
his dialyzer, 247;
studies movements and reactions of molecules, 249.
H
Hales's experiments on gases, 34.
Heat, Black's study of latent heat, 39;
specific heat, 98;
Dalton lectures on, 117;
law of capacity for heat, 168;
heat as produced by friction, 217.
Helmholtz, 143;
vortex atoms, 125.
Hooke, Robert, his "Micographia," 24;
studies combustion, 34.
Humboldt, Alexander von, assists Liebig, 256;
and Dumas, 259.
Hydrochloric acid discovered by Priestley, 66;
a stumbling-block to Lavoisierian chemists, 200;
studied by Davy, 201.
Hydrogen, rediscovered by Cavendish, 63;
experimented on by Priestley, 66;
its atomic weight decided by Dalton, 130;
Graham considers it a metal, 238.
I
Iodine, discovered by Davy, 224.
Isomerism, 297.
Isomorphism, law of, 167.
L
Laplace, assists Lavoisier, 90.
Latent heat, Black's theory of, 39.
Laurent, his unitary theory, 272, 278.
Lavoisier, Antoine L., born at Paris, 79;
confutes idea of transmutation, 81;
paper on calcination of tin, 84;
meets Priestley, 61, 85;
his theory of combustion, 51, 86;
his chemical nomenclature, 96;
he is guillotined, 99;
_resume_ of his work, 103;
his views on salts, 183, 184.
Liebig, Justus, birth, 256;
Humboldt and Gay-Lussac, 257;
his improved combustion-tube, 263;
studies the cyanates, 264;
distinction between organic and inorganic chemistry effaced, 265;
produces chloroform and chloral, 273;
benzoyl, 274;
he leaves Giessen for Munich, 280;
his practical and economic discoveries, 283;
death, 284;
his failure to discover bromine, 291.
Lockyer, his work with spectroscope, 310
(and _vide_ "Spectroscopic analysis").
M
Mayow, John, studies combustion, 24.
Metals, new, discovered by Berzelius, 101;
by Davy, 197;
hydrogen a metal, 238.
Meyer, his views on acids, 174.
Mitscherlich's law of isomorphism, 167.
Molecule, conception of, 140;
molecular weight, 145;
molecular mobility of gases, 242;
movements and reactions of molecules, 249;
modern conception of, 275.
Morveau, De, embraces Lavoisier's views, 96.
Muriatic acid (_vide_ "Hydrochloric acid,") 119.
N
Nitric acid, discovered by Priestley, 65;
produced by electrolysis, 188.
Nomenclature, Lavoisier's system of, 96.
O
Oil, principle of, 254.
Organic chemistry, worked at by Berzelius, 229;
attempts to define it, 253;
loose application of the term, 255;
Woehler's manufacture of urea abolishes distinction of organic
and inorganic chemistry, 265.
Oxygen discovered by Priestley, 59;
Lavoisier's experiments, 87;
it is viewed by him as an acidifier, 91, 175;
Berthollet shows it not a necessary constituent of acids, 184
(_vide_ "Acids").
P
Paracelsus, 13;
his pamphlet, "Tripus Aureus," etc., 19.
Petit, 168.
Phlogistic theory, 26;
enunciated by Stahl, 27;
abandoned by Black, 46;
phlogiston described as a kind of motion, 49;
discovery of dephlogisticated air, 59;
the theory overthrown by Lavoisier, 92.
Phosphoric acid, 86.
Pneumatic trough, invented by Priestley, 57.
Potassium, discovered by Davy, 197.
Prussic acid, discovered by Berthollet, 184.
Priestley, Joseph, born, 52;
bred for the ministry, 53;
writes on electricity, 55;
his pneumatic trough, 57;
discovers oxygen, 59;
meets Lavoisier, 61, 85;
goes to Birmingham, 65;
his experiments on hydrogen, 66;
his house burnt by rioters, 71;
emigrates to America, 72;
dies there, 73;
_resume_ of his work, 102;
his method compared with that of Dalton, 151.
Q
Quantitative analysis neglected by early chemists, 29;
first accurately employed by Black, 33;
used by Lavoisier, 87.
R
Respiration explained by Lavoisier, 91.
Revolution, French, its effect on Priestley, 70;
Lavoisier guillotined, 99.
Richter's equivalents of acids and bases, 162.
Ripley, Canon, an alchemist, his poems, 18.
Rouelle, invents term "base," 179;
his studies on salts, 181.
S
Salts, 173;
"principle of salt" opposed by Boyle, 177;
earth or alkali the _base_ of salts, 179;
Rouelle's inquiries, 181;
Lavoisier's definition, 184;
considered as metallic derivatives of acids, 205;
alcoholic salts, 235.
"Sceptical Chymist, The," by Hon. Robert Boyle, 76-93.
Shelburne, Earl of, patron of Priestley, 58;
to whom he grants an annuity, 65.
Spectroscopic analysis, 302;
lines in solar spectrum, 306;
the solar atmosphere, 308;
Lockyer's mapping of the lines, 310;
basic lines, 311;
objections to his hypothesis, 313.
Stahl, George Ernest, born at Anspach, 27;
enunciates the phlogistic theory, 27, 48;
his "primordial acid," 174;
his essential property of earths, 178.
Sulphur dioxide, discovered by Priestley, 66.
Sulphur salts, discovered by Berzelius, 161.
T
Transmutation, confuted by Lavoisier, 81.
Transpiration of gases, 242.
Types, 279.
V
Valentine, Basil, an alchemist, 15;
his views on alkalis, 174.
Van Helmont, 24.
Vitriols, 180.
Volta's electric pile, 184.
W
Water, its composition discovered by Cavendish, 68-78;
nearly discovered by Priestley, 68;
confirmed by Lavoisier, 90;
decomposed by electricity, 185.
Weight of ultimate particles, 117, 132;
molecular and atomic, 145;
revision of atomic weights, 285.
Woehler, his account of visit to Berzelius, 160, 204, 229;
studies cyanates with Liebig, 264;
results of his discovery as to urea, 265.
Wollaston, supports atomic theory, 130.
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