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EXCHANGE




With the Compliments of

YALE UNIVERSITY LIBRARY

NEW HAVEN, CONN.. U. S. A.



YALE UNIVERSITY
MRS. HEPSA ELY SILLIMAN MEMORIAL LECTURES



THEORIES OF SOLUTIONS



*

4 -



SILLIMAN MEMORIAL LECTURES
PUBLISHED BY YALS UNIVERSITY PRESS



ELECTRICITY AND MATTER. By JOSEPH* JOHN
THOMSON, D.Sc., LL.D., Ph.D., F.R.S., Fellow of Trinity
College, Cambridge^ Cavendish Professor of Ex>eri-
mental Physics, Cambridge. <J

Price, $1.25 net ; postage 10 cents extra.

THE INTEGRATIVE ACTION OF THE NERVOUS
SYSTEM. By CHARLES S. SHERRINGTON, D.Sc., M.D.,
Hon. LL.D. Tor., F.R.S., Holt Professor of Physiology
in the University of Liverpool.

Price, $3.50 net ; postage 25 cents extra.

RADIOACTIVE TRANSFORMATIONS. By ERNEST
RUTHERFORD, D.Sc., LL.D., P.R.S., Macdonald Profes-
sor of Physics, McGill University.

Price, $3.50 net ; postage 22 cents extra.

EXPERIMENTAL AND THEORETICAL APPLICA-
TIONS OF THERMODYNAMICS TO CHEMISTRY.
By Dr. WALTHER NERNST, Professor and Director of
the Institute of Physical Chemistry in the University of
Berlin.

Price, $1.25 net ; postage 10 cents extra.

THEORIES OF SOLUTIONS. By SVANTE AUGUST
ARRHENIUS, Ph.D., Sc.D., M.D., Director of the Phys-
ico-Chemical Department of the Nobel Institute, Stock-
holm, Sweden.

Price, $3.00 net ; postage 20 cents extra.

THE PROBLEMS OF GENETICS. By WILLIAM BATE-
SON, M.A., F.R.S., Director of the John Innes Horticul-
tural Institution, Merton Park, Surrey, England.

In preparation.



THEORIES OF SOLUTIONS



BY

SVANTE ARRHENIUS

DIRECTOR OP THE NOBEL INSTITUTE OF THE ROYAL SWEDISH ACADEMY
OF SCIENCES, STOCKHOLM



WITH DIAGRAMS




NEW HAVEN: YALE UNIVERSITY PRESS

LONDON: HENRY FROWDE

OXFORD UNIVERSITY PRESS

MCMXII



Copyright, 1912
BY YALE UNIVERSITY

Published May, 1912



TO

JACQUES LOEB

IN ADMIRATION OF HIS APPLICATION OF
PHYSICAL CHEMISTRY TO BIOLOGY



240954



THE SILLIMAN FOUNDATION

IN the year 1883 a legacy of eighty thousand dollars was
left to the President and Fellows of Yale College in the
city of New Haven, to be held in trust, as a gift from her
children, in memory of their beloved and honored mother
Mrs. Hepsa Ely Silliman.

On this foundation Yale College was requested and
directed to establish an annual course of lectures designed
to illustrate the presence and providence, the wisdom and
goodness of God, as manifested in the natural and moral
world. These were to be designated as the Mrs. Hepsa
Ely Silliman Memorial Lectures. It was the belief of the
testator that any orderly presentation of the facts of nature
or history contributed to the end of this foundation more
effectively than any attempt to emphasize the elements of
doctrine or of creed ; and he therefore provided that lec-
tures on dogmatic or polemical theology should be excluded
from the scope of this foundation, and that the subjects
should be selected rather from the domains of natural
science and history, giving special prominence to astron-
omy, chemistry, geology, and anatomy.

It was further directed that each annual course should be
made the basis of a volume to form part of a series consti-
tuting a memorial to Mrs. Silliman. The memorial fund
came into the possession of the Corporation of Yale Uni-
versity in the year 1902 ; and the present volume consti-
tutes the eighth of the series of memorial lectures.



CONTENTS.



PAGE'

CONTENTS xi

INTRODUCTION xvii

LECTURE I.
SHORT HISTORY OF THE THEORY OF SOLUTIONS.. 1

Cosmogonical ideas regarding solutions. Thales regarded water
as the primary substance. The four elements. Plato and Aristotle.
The doctrine of transmutation of metals. The mercury of the
philosophers. "Osiris." Views of Isaac Hollandus, van Helmont
and Boyle. "Corpora non agunt nisi soluta" The universal
solvent "alcahest." Democritus' atomistic ideas. Gassendi intro-
duces the notion of atoms and molecules. The corpuscular theory
of solution. Nature of acids and bases. Contraction on mixing.
Crystal water. Newton's opinions on the solution phenomenon
and the dissolved state of water. Buffon's improvement. " Similia
simihbus solvuntur " Lavoisier discriminates between solution and
dissolution. Liquefaction and solution. Richter on deliquescent
salts. Berthollet and Proust. Constant composition of salts
with crystal water. Solution, a physical or chemical process? Ex-
amples Solutions from the point of view of the theory of electro-
lytic dissociation. Gore's and Hittorfs experiments. Ionic
reactions. Generalization of the ionic theory. Goldschmidt's ex-
periments regarding esterification.

LECTURE II.
THE MODERN MOLECULAR THEORY 17

Application of quantitative measurements in chemistry. The
constancy of mass. The work of Richter and Proust. Dalton's
atomic theory. The law of multiple proportions. The analytic
work of Berzelius. Gay-Lussac's law of gas volumes and Avogadro's
law. The kinetic theory of gases. Wald's opposition. Ostwald's
" law of integral reactions." Isomerisms. The Brownian move-
ment. Investigation of Svedberg, Ehrenhaft and Perrin. The
number of molecules in one grammolecule is about N=69.10..

xi



XU THEORIES OF SOLUTIONS.

Electric determinations of N. Other physical methods of de-
termining N. Charge of single droplets. Planck's theory of
radiant energy. Movement of molecules or ions according to
Svedberg. Dalton's repudiation of the laws of Gay-Lussac and
Avogadro.

LECTURE III.
SUSPENSIONS 36

Methods of preparing suspensions. The size of the suspended
particles. Their rate of diffusion. Their electric charge. Pre-
cipitation of suspended particles. Their catalytic action. An-
organic enzymes. Color of suspensions. Heat of suspension.
Precipitation of Raffo's sulphur.

LECTURE IV.
THE PHENOMENA OF ADSORPTION 55

Historical notes. The so-called adsorption-formula. Influ-
ence of temperature. Schmidt's discovery of a saturation-point
for the adsorption of dissolved substances. The laws governing
adsorption-phenomena. The work of Titoff and Miss Ida Horn-
fray. Points of saturation for gases. Heat of adsorption, its
variation and consequences thereof. Role of the molecular attrac-
tion. Compressibility of liquids. Adsorption of albuminous sub-
stances.

LECTURE V.

THE ANALOGY BETWEEN THE GASEOUS AND THE
DISSOLVED STATE OF MATTER 72

The development in this fundamental chapter is quite natural
and continuous. Two parallel lines of progress, the chief one
based on the similarity of gases and dissolved substances, the
other on the application of thermodynamics to solution. Newton's
statement. Gay-Lussac's ideas regarding the analogy between
evaporation and solution. His notion of equipollency. Bizio's
and Rosenstiehl's ideas. Horstmann's work. Guldberg and
Waage's law and its development. Thomsen's opinion. Sublim-
ation and solution according to the kinetic theory of gases. Shen-
stone's opinion. Mendelejew's ideas regarding solutions. Kirch-
hoff's studies on vapor pressure of solutions. Guldberg's funda-
mental applications of the thermodynamical laws of solutions.
The general laws of solutions deduced by Gibbs. Helmholtz's



CONTENTS.

introduction of the notion "free energy." Le Chatelier's law.
van't Hoff's discovery. The osmotic pressure and the work of
Traube, Pfeffer and de Vries. Planck's theoretical deductions.

LECTURE VI.

DEVELOPMENT OF THE THEORY OF ELECTROLYTIC
DISSOCIATION 91

The empirical and theoretical ways leading to the hypothesis
of electrolytic dissociation. Valson's investigations of additive
properties. The independency of the "elements" of dissolved
substances. Investigations by Kohlrausch, Gladstone, G. Wiede-
mann, Oudemans, Landolt and Hess. Rontgen's and Schneider's
measurements. Raoult's work on freezing points. Opposition
of E. Wiedemann. Williamson's theory. Grotthuss' chains.
Clausius' deductions from the kinetic theory. Bartoli's ideas.
Active and inactive molecules. Parallelism between electric and
chemical activity. Reactions of ions. Ostwald's measurement
of the activity of acids. The law of change of conductivity with
dilution.

LECTURE VII.
VELOCITY OF REACTIONS 112

Inversion of cane sugar studied by Wilhelmy 1850. Law of
monomolecular reactions. Action of catalytic agents of inorganic
nature, of enzymes, of high temperature and of ultraviolet light.
Action of invertase. Hudson versus Henri. Action of zymase
and analogous processes. Digestion process. Action of chloro-
phyll. Accelerating substances. Growth of bacteria. Retarding
processes. Schuetz's rule. Formation of ether according to Kre-
mann. Radioactive processes. Dissolution in acids. Photochem-
ical reactions. Decomposition of HI. Spontaneous decomposition
of ferments. Concomitant processes. Influence of temperature.
Van't Hoff's rule.

LECTURE Vm.

CONDUCTIVITY OF SOLUTIONS OF STRONG ELECTRO-
LYTES 131

Kirchhoff's, Guldberg's and Horstmann's theoretical investiga-
tions. The work of Berthelot and P6an de St. Gilles. Equilibria.
Strong electrolytes. Van't Hoff's equation. Migration numbers
of Hittorf. Influence of temperature. Noyes' work. Alcoholic
solutions. Godlewski's determinations. Peculiarity of H- and



XIV THEORIES OF SOLUTIONS.

OH-ions. Influence of fluidity. Different influence on different
groups of salts. Organic solvents. Influence of temperature.
Fused salts. Abnormal behavior of electrolytes on dilution.
Foote's and Martin's, Walden's and Franklin's measurements.
Lorenz on fused salts. Carrara's opinion.

LECTURE IX.
EQUILIBRIA IN SOLUTIONS 153

Henry's law. Investigations of Berthelot and Jungfleisch and
by Nernst. Moore on equilibrium in ammoniacal solutions.
Red blood-corpuscles and bacteria. Amphoteric electrolytes,
investigations by Bredig and Winkelblech, Walker and Lunde*n.
The laws of diffusion. Nernst's theory. Salt action. Guldberg
and Waage's opinion. Weakening of acids by their salts. Avidity.
Hydrolysis. Pseudo-acids and pseudo-bases of Hantzsch. Wake-
man and Godlewski on solutions in mixed alcohol and water.
Work of Kahlenberg. Van't Hofif's opinion.

LECTURE X.
THE ABNORMALITY OF STRONG ELECTROLYTES 172

Different ways of explaining Jahn's opinion. The electro-
static influence. The hydration theory. Hydration of ions.
Saturation. Specific weight of salt solutions. Expansion on
neutralization. Electrostriction. Bousfield's and Riesenfeld's cal-
culations. Washburn's method. Correction of Hittorf's figures.
Explanation of the data. Mobility of organic ions according to
Bredig. Influence of variable hydration on molecular conductiv-
ity.

LECTURE XI.

THE DOCTRINE OF ENERGY IN REGARD TO SOLU-
TIONS 196

Free energy of dissolved substances and of gases. Heat evolved
at solution or electrolytic dissociation. Hypothesis regarding
the possibility of developing the expression for the free energy
in a series. Discussion of formulae. Study of the solution
phenomenon. Pairs of non-miscible liquids. Heats of solution.
Influence of dissociation. Change of energy at electrolytic dis-



CONTENTS. XV

sociation. Noye's determinations. Compression with evapora-
tion. Influence of change of units. General results from Lunde*n's
figures. The free energy is better adapted to chemical calculations
than the evolution of heat.

BIBLIOGRAPHICAL REFERENCES.. . 226

INDEX OF AUTHORS 239

INDEX OF SUBJECTS. . . 243



INTRODUCTION.

IT is an exquisite honor to speak from this platform
in this celebrated university where Willard Gibbs enun-
ciated his standard work on "the theory of heteroge-
neous equilibria. ' ' I also feel very much indebted for the
invitation to give a series of Silliman lectures, which
have been delivered by the most prominent men of
the scientific world. I therefore extend to you my
warmest thanks for having conferred this rare distinc-
tion upon me.

The object of my lectures will be some chapters of
modern physical chemistry. This branch of science
has been treated in a rather great number of good or
even excellent text-books, here as well as in Europe.
It is therefore a difficult task to give something new
and something which has not already before been
worked out in a masterly manner. But it seems to
me as imprudent as to carry owls to Athens to give
you a course of physical chemistry as it is presented in
the text-books. Therefore I have confined myself to
some problems which are now under debate and which
are still not finished but which promise the greatest
interest for further investigations. Also when I refer
to older investigations, I try to exhibit such facts as
have not in a higher degree attracted the attention of
the authors of text-books in this branch, and thereby
to give a broader and more complete view of the excep-
tionaly fertile field which we cultivate. I have often

xvii



XV111 THEORIES OF SOLUTIONS.

found it useful to drag old historical data into the
light especially in order to give an idea of the strict
harmonical development of this subject, a circumstance
which is often forgotten even to such a degree that
physical chemistry is generally represented as if it had
like Minerva sprung out quite fully developed from
Jupiter's head.

What I wish to express to you is therefore something
which according to my opinion supplements the excel-
lent text-books which you already have perused. It is
of course agreeable to me to lay before you my personal
individual ideas. On the other hand it is quite clear
that it would be a great mistake if my attempt were
understood to be designed to embrace all the branches
or even the most important branches of modern
physical chemistry. But I feel quite sure that such
an intelligent auditory as that to which I have the
honor of speaking here will not commit this mistake
and I trust the lacunae of my exposition will be easily
filled up by you who have been introduced so thoroughly
into the different chapters of physical chemistry by
your excellent scientific leaders and by the unrivalled
interest which the enlightened scientific opinion here
in America even more than in the old world attaches
to this wonderful branch which is called physical
chemistry and which is of the greatest use not only for
the most important doctrines of the natural sciences
and medicine but also for its far-reaching applications
to modern industry. There are very few doctrines in
exact science where so few lecture experiments are
shown as in physical chemistry. This depends upon
its theoretical character. The methods of working are



INTRODUCTION. XIX

taken from the science of physics. There is almost
only one chapter, which is so to say specially adapted
for lecture experiments in physical chemistry, namely,
that regarding catalytic action. For this chapter, a
number of demonstrative experiments are worked out
by Professor A. A. Noyes and G. V. Sammet in Boston.
Another number of good lecture experiments are de-
scribed in a little book by Professor Emil Baur in
Braunschweig. It may suffice to draw attention to
these expositions of the relatively small prominence of
the experimental part of our science. The great progress
in physical chemistry depends upon the quantitative
measurements on which the general laws are based.
In most cases it has been necessary to collect the
evidence from a very vast field and an extraordinarily
great number of experiments in order to get a view of
the real situation of the problems and of the possibility
of solving them. Chemistry works with an enormous
number of substances, but cares only for some few of
their properties; it is an extensive science. Physics on
the other hand works with rather few substances, such
as mercury, water, alcohol, glass, air, but analyses the
experimental results very thoroughly; it is an intensive
science. Physical chemistry is the child of these two
sciences; it has inherited the extensive character from
chemistry. Upon this depends its all-embracing fea-
ture, which has attracted so great admiration. But
on the other hand it has its profound quantitative char-
acter from the science of physics. From this circum-
stance the great solidity and strength of our science
is derived. The results of these quantitative measure-
ments regarding the properties of a very great number of



XX THEORIES OF SOLUTIONS.

substances is very difficult to present by lecture experi-
ments; they must be given in diagrams and tables.
I feel it necessary to explain from the very begin-
ning why I have preferred to give a series of theoretical
lectures rather than of experimental ones; the cause
lies in the very character of the modern development
of our science. Therefore modern physical chemistry
is often called general or theoretical chemistry as in
the two excellent German text-books of Ostwald and
Nernst.

The theoretical side of physical chemistry is and will
probably remain the dominant one; it is by this peculiar-
ity that it has exerted such a great influence upon the
neighboring sciences, pure and applied, and on this
ground physical chemistry may be regarded as an
excellent school of exact reasoning for all students of
natural sciences.



LECTURE I.

SHORT HISTORY OF THE THEORY OF SOLUTIONS.

IP we go very far back into antiquity we find how
our modern chemical ideas slowly crystallised out from
limited experiences and a naive attempt at generaliza-
tion. It is very interesting to find how solutions, which
are now the chief material agent of the chemist, even
at that time attracted the main attention. In a great
number of the cosmogonic myths the world is said to
have developed from a great water, which was the
prime matter. In many cases, as for instance in an
Indian myth, this prime matter is indicated as a solu-
tion, out of which the solid earth crystallized out.

Later on we find that Thales (624-523 B.C.) describes
water as the origin of everything. Probably Thales
had taken up this doctrine from ancient Egypt, which
is according to all probability the country where the
first very modest development of our science took place.
Certainly the idea of the four primary elements, which
is generally attributed to its prominent advocate the
Greek philosopher, Empedocles (500 B.C.), is also of
Egyptian origin. There are philosophers who regard
one of the elements as the chief one, for instance Thales
water, Anaximenes air, Heraclitus fire and Xenophanes
earth, but water is generally preferred. Empedocles
taught the doctrine of the transmutability of the four
elements, that they were in a certain sense equivalent.

The doctrine of Empedocles was taken up by the



2 THEORIES OF SOLUTIONS.

philosophers Plato and Aristotle whose ideas dominated
the methods of reasoning until two hundred years ago
and who still exert a great influence in the philosophical
sciences. In Plato's work Timaios we read: "We
believe from observation that water becomes stone and
earth by condensation, and wind and air by subdivision;
ignited air becomes fire, but this when condensed and
extinguished, again takes the form of air, and the latter
is then transformed to mist, which coalesces into water.
Lastly rocks and earth are produced from water."
Evidently the four elements of antiquity correspond
nearly with what we now call states of aggregation.
The ancients had observed the transformation of water
into steam and vice versa, this phenomenon as well as
the deposition of solid substances from solutions or
suspensions in water was the chief one upon which they
built their theory. Under all circumstances water was
the chief material from which they gained then- experi-
ence.

In antiquity the chief products of industrial chem-
istry were the metals. Plato and especially Aristotle
developed the idea of transmutation of the metals.
Even in this department the condition of fluidity seemed
to be most valuable for the reactions and therefore the
fluid metal, mercury, attracted the attention of the
chemists more than the other metals did. It tinged the
metals generally silver-white and was supposed to be
the prime matter of all metals. This prime matter was
called the " mercury of the philosophers" and regarded
as the " ghost" of the metals, which was the bearer of
the metallic properties. In Egypt lead seems to have
played a similar role and therefore received the name



HISTORY OF THE THEORY OF SOLUTIONS. 3

of " Osiris" from the principal deity of the old Egyp-
tians. A rather moderate heat is sufficient for convert-
ing lead into the liquid state, in which it acts as a
solvent on other metals. Olympiodoros says " Osiris is
the principle of everything liquid, it is Osiris, which
causes the condensation in the sphere of fire." Under
the name of lead or " Osiris" also tin "the white lead"
in contradistinction to the common or " black lead"
was included. In many minerals from which lead was
extracted a small quantity of silver is contained. This
could easily be separated from the lead and as the
silver was more valuable it was regarded as "the perfect
lead." These considerations are quite characteristic
of the reasoning of the alchemists. When mercury was
discovered, about the tune of the Peloponnesian war, it
was found much more satisfactory for dissolving and
tinging metals than lead and was therefore supposed to
be the "materia prima." The readiness with which it
could by evaporation be separated from other metals
made the experiments with mercury much easier than
those with lead.

The liquid state was already at that time found to be
the most suitable condition for chemical reactions.
The chemistry of the Middle Ages up to the seventeenth
century retained the same view. In the writings of
Isaac Hollandus (at the beginning of the 15th century)
we read that "the philosophers have followed the
direction given by Nature and at first transformed
everything to water" (i. e., dissolved it) "before they
used it in the art of chemistry." According to van
Helmont (1577-1644), the greatest chemist of his time,
and the discoverer of carbonic acid (gas sylvestre),



4 THEORIES OF SOLUTIONS.

"water is the primary element, into which all substances
may be reduced." Boyle, the father of modern
chemistry (1626-1691) opposed the ideas of Aristotle
and his alchemical successors regarding the four ele-
ments; he expressed the opinion that only such sub-
stances should be called elements, which are undecom-
posable constituents of matter, but in his " Sceptical
chymist" he still expresses the opinion that water may
be transmuted into all other elements."

The experience of the alchemists was summed up
under the formula "the Substances do not act upon
each other unless they are dissolved " (corpora non agunt
nisi soluta) or that the salts do not give any reaction,
if not dissolved, and then not too much diluted (Salia
non agunt nisi dissoluta, nee agunt si dissoluta nimis) .
This last part of the sentence evidently refers to the
circumstance that precipitations, which are often
observed after mixing solutions of two different salts,
do not occur, if the solutions are too dilute, so that
the liquid retains the newly formed salts in unsaturated
solution. Van't Hoff and Le Chatelier find also that
reactions proceed much more regularly, when the
reacting substances are dissolved, than if they are not.

As the solubility of a substance was regarded as
the necessary condition for its entering into chemical
reactions, the great problem of chemistry was to find
a solvent for all possible substances. This hypothetical
solvent was called "alcahest" by Paracelsus (1493-
1541). The alcahest was regarded as "the stone of
the wise" or as the "life-elixir" and very many receipts
for its preparation were given. Kunckel (1716) gives
a very satirical and severe criticism of these receipts,



HISTORY OF THE THEORY OF SOLUTIONS. 5

when he says that the great problem was to find a
vessel which would not be dissolved by the alcahestic
liquid, otherwise there would be no possibility of
using it.

The most celebrated natural philosopher of antiq-
uity was Democritus of Abdera (born 460 B.C.).
He had proposed an atomic theory, according to
which matter consists of discrete atoms with empty
interstices. Plato taught that the molecules of one
substance might enter into the interstices between the
atoms of another substance. Aristotle opposed the
atomic doctrine. Through his great authority the revivi-
fication of the atomic theory was hindered until Gas-
sendi (1592-1655) took up and elaborated the ideas of
Democritus. According to Gassendi a number of atoms
could unite to form molecules. Solution depends then
upon the particles of the substance, which goes into
solution, entering into the pores of the solvent. As the


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