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. ^xuQxss .ON . ^i^cTfac . mno^MQ^Q .
A Thesis submitted to the Graduate School of the
University of Wisconsin in partial fulfillment of the
requirements for the degree of Doctor of Philosophy
Date .dJAUuary.lO..., 192J..
This thesis having been approved in respect of
form and mechanical execution is referred to you for
judgment upon its substantial merit.
STUDISS 01 8LB0TBI0 SHSOSMOSB
▲LYU 8ISIQKUEB M 8
▲ THBSIS PBBSSITSD TO THB ftBADUATS SCHOOL
or THs tnriYBRsiTT or wiscoffsur is pabtial
fOLriLUfui roB the sbobbs or doctob or
General Ubrary System
tJn'vwBjty of Wisconsin - Madison
728 State Street
Madison, Wl 53706-1494
Iha author wishes to express his highest appreoia-
tion for the assistanoe of ]>r# J« E# Uathews imder whose dir-
ection these researohes were prosecuted. Credit is also due
Dr« F* E* Bartell of the University of Michigan^ who first
incited the author's interest in the general prohlem of elec-
TABLB Of OOITBITS
Hi8torlo«l and Thaoretioal
Sonroe of Yoltage
If foot of change of pormoa'bility of tho momlbrano
Preparation of matoriala
Bffoot of Tarying the applied potential
Bffeot of aoid and alkali
Bffeot of temperatnre
Bffeot of the addition of certain salts
Bffeot of Tarylng concentration of the salt
Bffeot of added nater
Bffeot of Tarying dieleotrio constant
Sheer etioal Bisonssion
Summary and Oonclnsions
Preparation of Haterials
Bffeot of change of permeahility
Bffeot of Tarying applied potential
Bffeot of acid and alkali
Bffeot of temperature
Bffeot of the addition of certain salta
Bffeot of Tarying concentration of the salt
Bffeot of added nater
Studies on the Hof tneister Series
DoTeloimient of an adsorption orientation theory
Scmie ICathematical Considerations
Summary and Conclusions
ELECTRIC EITDOSMOSE Fart 1
Its Ueaaxirement using some Typical Organic Solyents
Wheneyer we hare a membrane or Its equivalent » that is,
fine capillaries, or even a solid surface (or medium) in contact
witli a solrent (a liquid medium) there will be dereloped an elec-
tric double layer at the surface of contact. This will depend in
magnitude and, in most cases, in nature, upon the relative dielec -
trie constants of the solid and liquid media. If a difference of
potential is now established in the liquid medium, either the liq-
uid or solid will migrate, depending upon which is fixed, in the
direction which depends upon the sign of the charge established by
contact. This electric charge will be affected by the presence of
any substance which may be adsorbed, as a molecule or ion, thus
altering the nature of the surface. With the same potential grad-
ient this will increase or decrease the flow according as such pre-
ferentially adsorbed substance bears a poaitire or negative charge
or orients itself in such a way as to produce such charge. Adsorp-
tion of a neutral substance may also affect the flow by o]^nging
the dielectric constant ratio. Whether the adsorbed substance is
^•utral or charged depends upon the membrane, its nature and sur-
face, the substance Aissolred or suspended, and the liquid medium.
Such phenomena are classed as electro kinetics.
There are two types of electro kinetics:
Class A. 1. The membrane is fixed and the liquid medium free
to more. This is known as electric endosmose.
Rreundlioh-zaplllarohemie . ^^^^^ ^ GoOgk
2. The partloles of solid migrate in the liquid
medium* This is known as cataphoresis.
Class B« 1. The ahoya conditions may he reyersed. If wat-
er is forced through fine capillaries a differ-
ence of potential will he estahlished at the
ends of the capillaries. Such a phenomenonis
illustrated by Quincke's diaphragm currents.^
2. The falling of small particles thru a liquid
may establish a difference of potential as
illustrated by the dropping electrode of Ost-
This work has to do entirely with Class Al« Electric
endoamose is a necessary concomitant of all electrolysis in both
aqueous and non-aqueous solutions. It is affected by and affects
such electrolysis in a positire or negatire manner depending upon
all factors which affect the nature of the membrane or solid med-
ium and the solution or liquid medium. Such solid medium may be
oovrely the container in which the experiment is carried out, thou^H
a porous cup or membrane will make such effects much more apparent.
"The name endosmose is a misnomer''* because we have here
no difference in concentration of the two solutions separated by the
. ^Wied^Ann., 7, 351-1879.
3 Zeit. phys. Chemie., 1, 583 (1887).
4 Bigelow, Theoretical & Physical Chemistry.
membrane, only as they beoome ohanged during the progress of the ex-
periment* Snoh misnomers are quite frequent in ohemieal literature
but the names are retained for traditional reasons. Eowever; recent
work by Bartell,^ Bartell and Hooker,^ and Jacques Loeb shows that
many of the peculiarities of **free osmosis** can only be explained by
the theoretical consideration now applied to electric endosmose; and
the relationship may not be so farfetched after all#
Practically all the experiments of a quantitatiye nature
on this problem hare been carried out with water as the liquid medium.
Only in a few cases hare other substances been used: liquid ammonia,
methyl alcohol, and ethyl alcohol. It was because of this and of
the meager quant itat ire data in general that these researches were
undertaken. Work was carried out with a number of typical non-aqueous
Bolyents in an endearor to determine if the principles and rules, ap-
plied to water, held for such. Besides certain preliminary work with
water the following solrents were tested: acetone, amyl alcohol, ni-
trobenzene, pyridine, benzaldehyde and n-butyl alcohol. Using membran-
es of the same material and nature (filter paper) in each case the
effects studied were: change of roltage, varying permeability of the
5 J. Am. Chem. Soc, 36, 646 fl914).
6 J. Am. Ohem. Soc, 38, 1029 (191ft)
7 J^ Oen. PhyaU'^lt 717 (1919); 2, 387; 563 (1920).
8 Ascoli-Comptes.rendus, 13l, ^369 (1903).
9 Bandouin-Comptes. rendus, 138, 898, (1904).
10 Barrat fc Harris-Biochem. Jou. , 6, 315 (1912)
Remy-Zeit-Phys. Chemier89, 467; 529 (1915)
membrane « presenoe of aold and alkali, addition of various cations
and anions, of varying concentration of the added salt, of the change
of temperatiLre and of added water hoth to the pure solvent and to the
solvent containing a dissolved salt* ?rom this data some very inter-
esting conclusions have heen drawn.
HI8T0RI0AL ASP THEORETICAL IgTRODUCTIQg
Tile phenomenon of electxie endosmose was first ohserved
by Reuss in 1807, working with two glass tubes (each containing
an electrode) which were filled with water, and placed upright in
a lump of clay, fhe clay acted as a membrane but not heing very
firmly packed also tended to migrate in the opposite direction to
that of the water which rose in the cathode tube# So he secured
both phenomena of endosmose and cataphoresis.
Porrett^ rediscovered the phenomenon in 1816 and it
was hecaui9e he thought he detected an analogy with **free osmosis**
that the name In use was adopted. De la Rive,^^ Becquerel,
Darrlell,^^ and lapier^^ also studied the phenomenon in a similar
way hut added nothing to its explanation*
^ Memoites de la soc« imp* de naturalist as a Koseau,
2, 327 (1807) •
^^ Thomsen's Jour. July, 1816 •
^^ Traite* de 1» Eleotr., 2, 379, (1825)
Ann* de Chim»et de Phys., 28, 125*
^* Traits' de 1» Bleotr., », 102 (1826 )•
^^ Ann* d. Physik u* Chemie, 1, 569 (1826).
^^ Phil* nag* July, 1846.
In 186S-56 Wiedemann^^ took up the work and presented
aereral generalisations. He used a porous clay oup containing a
platinum electrode and placed this in a larger vessel of the solu-
tion to be studied containing the other electrode. A glass tube
connected to the cup and passing horizontally oyer to a weighing
bottle served to measure the amount of liquid passing into the cup#
He also connected a manometer to this tube in his later experiments.
But obviously a large error due to hydrostatic pressure must have
been introduced in either case.
His oonslusions were three:
1. She mass of liquid transported in unit time
throu^ a porous membrane is directly proportional to the strength
of the electric current » and for a given membrane material and giv-
en current strength^ it is independent of the length and sectional
area of the membrane.
S. Ihe difference in hydrostatic pressure maintain-
ed by electric endosmose between the two sides of a porous membrane
varies directly as the current strength » and for a given membrane
material and a given current* is proportional directly to the length
and inversely proportional to the sectional area of the membrane; it
is also proportional to the specific resistance of the liquid in the
case of an aqueous solution.
3. Por a given membrane material, the difference in
hydrostatic pressure maintained between the two sides of a porous
membrane is proportional to the applied potential and is independent
^''^ Pogg. Ann., 87, 321 (1852); Wied. Ann., 99, 177 (1856)
of the dimensions of the membrane. So if E is the equilihriitm
height » the ourrent^ B the speoifio resistanoe, T the thiokness
of the membrane and 8 the cross seotional area
H* constant x CRT
JLlso sinoe BI represents the resistance of the membrane, the ex«
pression C B^ becomes CBI* or it equals the potential fall between
the sides of the membrane, - £• So the formula becomes
H^ constant x E
He also concluded that the current caused the direct transport of
liquid (i«e« toward the cathode) by rirtue of an attraction which
It exerted upon each element of rolume of the liquid trans f erred «
Ihls conclusion was contested by Graham, V* Quintus Ici-
liuB,^* and Brede and Longemann^^ ^^o showed that no transport of
liquid could be demonstrated unless a membrane or its equirftlent
In 1853 Baoult^*^ assumed the formation of compoxinds by
the products of electrolysis and the solrent; with a consequent
change of Tolume but submitted no experimental eridence to prore
In 1856 Hittorf,^^ who was then carrying on some studies
on migration yelocities of ions, said electric endosmose had no con-
nection with the Telocity of the ions*
^®Bhil. Mag., 8, 151 (1854) •
19 Lehrbuch der Experimental Physik, S* 642 (18B5)
£0 Ann. d. Physik- u. Chemie., 100, 149 (1867)
21 Oomptes rendus., 36, 826 (1853)
22 Pogg. Ann., 98, 9 (1858) Digitized by GoOgk
Welske In 1656 sAtd, ''Tihere is an aeotumilatlon of eleo-
trioity at the surface of contact of electrolytes and electrodes.
She less the conductance, the more Important is this accumulation.
She oation is a 'better conductor than the anion; so when this good
oonducting cation goes to the cathode it takes a negatire charge
from that electrode which spreads orer the cations » leaving no charge
on the cathode. In the case of anions they take a pes it ire charge
at the surface of contact with the anode, hut this charge does not
spread oyer the poor conducting anion and so the solution is driren
to the negative electrode. Though this theory is not clear, it is
imoportant as a forerunner of the Quincke, Eelmholtz theory which will
he cited later*
In 1860 ICattenci^^ considered electric endosmose as a phe-
nomenon entirely separate from electrolysis.
Wiedemann and Quincke in 1861^^ and Quincke in 1679^^
studied the phenomenon in a capillary tuhe, considering a membrane
as merely a bundle of such tubes and advanced a theory which with
certain modifications is accepted today. It was during these re-
searches that Quincke forced liquid thru a porous membrane and found
that differences of potential were produced at opposite ends of the
membrane pores. These **diaphragm currents** gave rise to the law:
^ Pogg. inn., 103, 466 (1858)
^ Comptes rendua, 51, 914 (1860)
Pogg. Ann*, 113, 513 (1861) •
^^ Wied. Ann., 7, 351 (1879); Pogg. Ann., 107, 1(1869)
-HO, 38 (1860)
*nniaxi water is forced at a certain rate through a porous memhrane
the difference of potential produced la Independent of the dimen-
sions of the membrane hut Is proportional directly to the hydros-
tatic pressure #**
Quincke considered electric endosmose as an electro capi-
llary phenomenon depending upon the natural potential differences
at the surface of separation of two unlike substances: solid and
solution. In the case of clay and water the water la contact with
the capillary wall is positively electrcified and is therefore ^
attracted to the cathode. Be also said, the smaller the pore the
greater the endosmose. If the solid la not fixed it will migrate
to the electrode bearing a charge opposite to that established on
it by contact. This flow will be continuous in most cases because
there la a steady re-establishment of the double layer.
Che experiments of these two men were rery elaborate and
important and they gare Belmholtz material for his mathematical
theory of electric endosmose. They used distilled water and aolu-
tiona df salts and acids and found that the addition of such elec-
trolytes to pure water decreased the endosmose. Quincke foiznd that
the rate raried inrersely as the fourth power of the diameter o^he
capillary tube used. Coated with shellac » the glass tube gare a
greater flow but silrer tubes gare less flow. He also noted that
alcohol was slower than water and that turpentine in glass gare a
reverse flow but if lined with sulphur the flow was toward tha
cathode again. Both state that the encCosmose in equal periods of
time is directly proportional to the intensity of the electric
current and under like conditions Independent of the area or thick-
nets of tlia porous wall*
Bnglamami^^ in 1874 tried the effect of different meift-
l)rane8 with a rather imlque apparatus and was one of the first to
note that the presence of electrolytes changed the endosmose*
It was left to Helmholti^® to develop quant itatirely and
nathematlcally the qualitatlye results of Quincke. He put forth
very clearly the Idea of an electric double layer theory which had
been previously suggested. The distrihutlon of charges in this lay-
er is such that the solid surface is charged oppositely to the liq-
uid in contact with it and this orientation produces the electric
double layer* He demonstrated by fonmilae that endosmose varied
directly as the specific resistance of the solution^^which was later
disproved by Holmes^^ in the case of certain nitrates.
Lamb has shown that if the liquid is not a perfect insu-
lator the application of a potential gradient will result in a con-
tinuous flow of liquid along the surface of the solid.
?reund^^ in 1879 found that with Zn SO4 solutions endos-
mose varied inversely as the concentration*
Grornez in 1879, from his studies, concluded that the
addition to water or alcohol of any substance which changes the con-
^''^Aroh. Heerland, 9, 332, (1874).
^®Wied* Ann. 7, 337 (1879)
^^octors Dissertation - Johns Hopkins University (1907).
^^hil. Mag., 25, 52 (1888)*
Allied. Ann*, 7, 51 (1879).
OoBDptea rendus., 89, 303 (1879)*
duotivity would deoreasa the amonnt of liquid transf erred •
Gore In 1880 apeaks of negative endosmose with alcoho-
lic solutions of barium bromide. With sixty-seven substances he
found endosmose with all except ECH«
In 1890 Shaw^, after a careful study of the problem,
said that endosmose is a feature of the mschanism of electrolysis,
the motion being due to a drift of complex ions made up of an ion
of the salt attached to a large number of solvent molecules. Also
IhetKao?^ suggested that the inverse proportion of the concentra-
tion of the solution and electric endosmose shows that in dilute
solutions the complex ion must carry many thousand molecules but
it is not directly connected with electrolytic processes.
Coehn's work gives a coorprehensive expression to the
double layer theory of Quincke and Eelmholtz. As to why such an
electric double layer should exist he suggests that, as the endosmose
increases with the difference in dielectric constants of the membrane
and solution, whenever two non-miscible substances, one of which is
a pure liquid, are in contact, the substance with the higher dielec-
tric constant is positive to that with the lower* Although he worked
only with pure solvents, this rule has explained most subsequent phe-
nomena under similar conditions. It must be remembered in applying
this rule that the least trace of a charged adsorbable substance must
naturally affect the charge, as will be seen in later work.
33proc. Hoy. Soc, 31, 253 (1880).
^. A* Heport, 202 (1890).
^^Theory of Solutions., p. 292.
36wied. Ann., 64, 227 (1898).
In the year 1903 Smoluohowski^''^ developed the formula,
whloh now 'bears his name, for the volume of liquid transferred in
unit time through a slnigle capillary*
After a series of masterly researches hy Perrln in 1903-
6^® Preundlloh In 1909 gave the present accepted expression to
the formula for the volume of liquid transferred:
T* nr^ e ED *
where (n) Is the number of capillaries under consideration, (r) the
radius of the capillary, (e) the dielectric constant of the liquid,
(x() the vlsooslty coefficient of the liquid and (1) the length of
With a porous membrane, a bundle of capillaries, the equ-
Y» Q e ED
where q Is the cross sectional area of the membrane*
Since E» HI and R«l where V is the speeiflc conduct 1-
TT- elD = constant x I
showing that the endosmose for a given liquid and membrane la pro-
portional to the current strength, agreeing with Wiedemann fs first
^''^Bnll* d. I » Acad.d* Science de Cracovle. (1903)*
^®Jou^ Chem. u. Phys., 2, 601 (1904)-3, 50 (1905).
Comptes rendus*, 136, 1388-137, 513 (1903) •
S^Kaplllarchemle, £45 (1909); Zelt. Phys* Chem., 73,
385 (1906); Zelt. Phys. Chem., 79, 409 (1912).
Taylor-Chem. of Colloids, p. 66.
law# If, Instead of allowing the liquid to escape, the pressure
la allowed to rise
Pa 2e BD
following Poiseuille'a law for narrow capillaries.
In most instances, in the earlier work, the solution moved
toward the cathode and the rule had been accepted that water in con-
tact with any solid is positively charged. Perrin found many
apparent exceptions to this rule. He used an apparatus in which ttie
membrane eould he changed hy disconnecting and refilling with a pow-
dered substance. He meaaured the flow in a horizontal capillary tube
but made no provision for the escape of gases produced during eleot*-
rolysis. Using membranes oi ^cx^^^j t»i^phthalene,^«»?^wi>«*nicfct#r/f^^si|ir^T;^
^vyk«ie#V4H^^^^^^'^» sulphur, salol, carborundum, gtlatine, and cellu-
lose he studied the endosmose with water mainly t^ut also tested it
with other solvents. With chloroform, ether, petroleum, benzene and
carbon disulfide he obtained no endosmose but secured a flow with
methyl alcohol, ethyl alcohol, acetone, acetaldehyde and nitrobenzene.
He tried the effect of acids and bases and of neutral salts of vary-
ing concentrations, the salts being dissolved in solutions already
adidic or basic. He came to the following conclusion: ''Every mem-
brane tends to become positively charged against an acid solution and
negatively charged against a basic solution. Every ion of unlike
sign tends to neutralize this charge on the membrane and this tenden-
cy increases rapidly with the valence of the ion."
*^ Loc. Cit.
42 1,00, oit.
Fretindlioh,*^ following, suggested a theory of
••preferentiil adsorption'' of ions to explain eleotrio endos*
mose* If the cation is adsorbed most, the membrane becomes
positively charged and if the anion is adsorbed most, the
membrane is negative*
In 1900 Oleson encountered the phenomenon of
electric endosmose and in 1906 Hardy observed that parti-
cles of gloubin in solutions of varying concentrations moved
al; the same rate*
In ttte years 1900 to 1904 and later some irorlc iras
done nhich nas bound to have a direct bearing upon theories
pertaining to eleotrio endosmose • In 1900 5ernst showed