THE AI\IERICAN MINERALOGIST, VOL ,16, MARCH_APRIL, 1961

IMBIBOMETRY-A NEW METHOD FOR THEINVESTIGATION OF CLAYS

J. KoNra, Institute of Petrology, Charles Unioersity,Pr ague, C zechosloaakia.

Assrn.{cr

A method for rapid identification of clay minerals in natural clays or in artificial ag-gregates prepared by elutriation and sedimentation of clay particles is described. The be-

havior of a drop of water and a drop of ethylene glycol on the surface of a smoothed section

is observed. The section is easily prepared on glass- and emery-cloth. The following physical

properties are decisive: (1) total surface area of the particles, (2) marked swelling of mont-

morillonite and "open" illite and no swelling of kaolinite and "closed" illite, (3) small wet-

tability of aggregates of the kaolinite group minerals and greater wettability of illite and

montmorillonite aggregates. The speed of imbibition of the liquid by the clay aggregate is

regulated by the absorption equation. The method is explained on the basis of the experi-

mental data, obtained by the investigation of eleven clays from Central Europe.

OnrcrN AND DEVELopMENT ol rHE MBruoo

The method of observing the behavior of drops of water and ofethylene glycol on sections of unconsolidated clay rocks was worked outin our laboratory (Konta, 1956). Two polar l iquids, differing consider-ably in their viscosity, were used.

It was expected that water and ethylene glycol would be quickly im-bibed by the unconsolidated clay rocks, in which the particles of clayminerals are large and thick. The imbibition ought to be slower for ag-gregates in which the clay particles are rather small and thin. The lessviscous water should be imbibed more quickly and cause a greater inter-micellar swelling of montmorillonite clays than the more viscous ethyleneglycol. During the experimental work it was found that in addition tothe speed of imbibition and the extent of swell ing, a further highly im-portant diagnostic property of clay aggregates was noted, namely thewettabil ity.

Until now no special name has been given to the new method (Konta,

1959 a,b). In the present paper there is applied to this new method thename of imbibometry. The investigation of water and ethylene glycolimbibition on sections of unconsolidated clay aggregates can be quanti-

tatively measured and is reliable for the rapid identification of clay min-erals. Besides, this method has a wider use in the investigation of someclay-rock properties which are important in geology and technical prac-tice.

B,q.srs or rrrE METHoD

The method is based on certain physical properties of clay minerals andclay aggregates in the presence of polar liquids. They are:

289

290 J. K)NTA

(1) The total surface area of the particles.(2) Marked swell ing of montmoril lonite and "open" i l l i te and none

for kaolinite and normal illite.(3) Wettabil ity of the aggregates.

These physical properties become apparent simultaneously during theimbibition of a drop of water or a drop of ethylene glycol on sections ofclay aggregates and therefore it is necessary to observe and record simul-taneously the phenomena caused by all three properties.

The total surface area of the clay particles is fully characteristic foreach chief group of clay minerals and is the chief physical property af-fecting the speed of imbibition of a drop of water and of ethylene glycolby the surface of the clay sections. Crystals of the kaolinite group min-erals, which form the thickest plates of all the clay minerals, have thesmallest total surface area, usually in several m.,/g.up to several tensm.'/9.; their highest value reaches about 40-60 m.2f g. Minerals of theillite group have crystals essentially thinner and a total surface areaseveral times larger, usually in many tens m.2f g. most often from 70 toI50 m.2/g.; and "open" illite more than 200 or 300 m.2/g. Finally, min-erals of the montomorillonite group have the thinnest crystals and theirtotal surface area is usually in hundreds m.r/g., most often between 500m.2 and 800 m.z/g.

The swell'ing of montmorillonite and of "open" illite (van der Marel1960) makes possible a quick and easy determination of the presence ofthese minerals in a clay. ft is necessary, while applying the imbibomet-ric method, to note on the sections of the clay not only the swell ing itselfbut also the speed of imbibition (in seconds) and the wettability.

The wettability of unconsolidated but coherent aggregates of clay min-erals represents a very important property and makes it possible to dis-tinguish the kaolinite clays from illite and montmorillonite. Kaoliniteclays have the smallest wettability. On sections of kaolinite, a drop ofwater or ethylene glycol always takes up a relatively small circular area(Fig. 1 a,b). On il l i te (F'ig. I c,d) or on montmoril lonite (Fig. 2) a drop ofwater or ethylene glycol spreads over a considerably larger area. Whenethylene glycol is used, and in some cases even with water, characteristicsmall spurs are formed. The imbibition ratio is the area occupied by onedrop of ethylene glycol divided by the corresponding area for water. Thisratio is less than 1 for kaolinite, but always above 1 for illite, and espe-cially so for montmorillonite.

MarnpuatrcAr, ExPRESSToN

The rate of imbibition depends both on the physical properties of theclay aggregate and on the character of the liquid. The purity of the

IMBIBOMETRY

Ftc. 1. (a) Characteristic small circular areas taken by drops of water and of ethyleneglycol. Kaolin from Sedlec near Karlovy Vary, western Bohemia.

(b) Silty kaolinite clay from Jarov near Plzeil, western Bohemia.(c) Greater areas taken up by a drop of water and a drop of ethylene glycol, with char-

acteristic small spurs if ethylene glycol is used. Illite clay from Chlum near Beroun, central

Bohemia.(d) Greater areas taken up by a drop of water and a drop of ethylene glycol, with char-

acteristic small spurs. Illite ciay from Fiizerradvany, Hungary.

liquid, and the temperature can be controlled, and atmospheric pressureshould be normal.

The speed of imbibition of the liquid by the clay aggregate is regulatedby the absorption equation:

r: -- 'J- /-4-\ '.e s ' o ' h \ A /

where:

l,:the time of the complete imbibition of the l iquid in seconds,s:the effective surface area of mineral particles (in cm2/cm3 of

the substance),

r:the viscosity (in poises at 20" C.),€: the efiective porosity (in /s:l}O),

291

(d)(b)

292 I. KONTA

d:the surface tension of the l iquid (in dynes/cm2; in the value thegravity acceleration is, therefore, included),

h:the constant including the shape of the particles and the tor-tuosity of pores in the clay aggregate (in the majority of claysits value remains constantl it depends, however, on the direc-tion of imbibition, i.e. whether it is for instance parallel or per-pendicular to the lamination of the rock),

q/ A: the amount of the l iquid (q in cm3) sorbed on the area (A, in cm2)during a known time.

An analogous equation has been used to express the sorption propertyof hardened Portland cement paste (Powers and Brownyard, 1948).

Ftc. 2 (a) Swollen areas taken up by a drop of water (right) and ethylene gtycol (left).Montmorillonite clay from Istenmez6, Hungary. (Sample No. 10.)

(b) Swollen area after imbibition of a drop of water (left) and less evident swelling onbentonite section if ethylene glycol is used (right). Braiany near Most, northern Bohemia.(Sample No. 9.)

From this equation it follows that for the imbibition rate of a knownconstant amount of polar liquid on a known area and under a constanttemperature and constant conditions of purity of the liquid, as well asan unchanging direction of the imbibition, only two properties of clayare decisive, namely, the total surface area of the particles (s) and theeffective porosity (e). The time of imbibition of the liquid by a clay ag-gregate is in direct proportion to the efiective surface area of. the particlesand inversely proportional to the effective porosity of this aggregate.

The ef ective porosity of the clay aggregate is a further important phys-ical property which also has an influence on the imbibition speed of theliquids, as follows from the equation given above. In the majority of un-consolidated, yet coherent kaolinite and illite clays, the values of theeffective porosity varies between 25-50/e under laboratory conditionsof humidity and temperature. In montmorillonite rocks the effectiveporosity is still smaller, usually between I0-207a under Iaboratory hu-midity and temperature conditions. The experimental work has shownthat the imbibition speed on the sections of clays of difierent mineral

(b)(a.)

IMBIBOMETRY

composition is mainly influenced by the total surface area of the particles,which value varies with the chief groups of clay minerals, i.e. kaolinite,illite and montmorillonite. The differences in the speed of the imbibitionof liquids by clays of app.roximately identical mineral composition andof not considerably different values of the total surface area of theparticles, are mainly c&us€,d by differences in effective porosity.

This important finding is represented by several diagrams drawn upon the basis of data obtained from the study of eleven samples of un-consolidated clay rocks of different mineral composition. The approxi-mate quantitative mineral composition of these rocks had been givenin the author's articles (Konta, 1959 a,b). Since the values obtained arenecessary for the understanding of the following four figures, they willbe repeated here in the abbreviated form of a triangular diagram(Fig. 3) .

KAOLINITE100%

to r

rtdl'to* r rr" u r.ou, t t t

SILT

50YoIRON0xrDES

x l t

U N D E C O M P O S E D H I N E R A L Q- TIIAIHIv PLAGIOCLASE & PYROXENE)

1007oILLITE

ROCKS WITH PREDOMINATING O KAOLINITE. ILLITEr PPEN' ILLITEX IIONTI.IORILLONITE

Frc. 3. The approximate semiquantitative mineral composition of eleven clay rocksstudied. The data were obtained by evaluation of the results of these methods: investiga-tion under polarizing microscope, r-ray analysis, DTA, gravimetric thermal analysis andimbibometry. The numbers of the points in the triangular diagram correspond to the num-bers in all other diagrams and tables.

5 O

<J

(J

Yc J )

294 J. KONTA

In Table I, data are given concerning the efiective porosity, densityand the total surface area of the particles of eleven samples investigated.The last values have been found by the absorption method according toDyal and Hendricks (1950), namely in all cases with finely powderedsamples sieved through 200 mesh with aperture of 0.074 mm.

In Fig. 4 the values of effective porosity expressed in (7o:100)3 aregiven. On the horizontal axis, the times during which one drop of wateris imbibed by the sections are plotted. The times found are related to auniform basic area (cf . Konta, 1959 a,b). The method of calculating of theimbibition times are illustrated in Tables II and III. Figure 5 is similarto Fig. 4, but for ethylene glycol. Ilere too, the values of the imbibitiontimes have been related to a uniform basic area.

From Figs.4 and 5 this main conclusion follows: The effective po-rosity has little decisive influence upon the speed of imbibition of waterand ethylene glycol by the unconsolidated but coherent clay aggregates.Ifowever, in samples of nearly identical mineral composition, lvhich donot differ greatly in the values of the total surface area of the particles,the difierences in effective porosity have a marked influence upon thespeed of imbibition. This can be best seen in kaolinite clays.

In addition to the effective porosity and the total surface area of the

raslnr'""T$'J"".";i:xH'3#'l'^"Jxrorar'Sunr"c'cr

Sample

Effectiveporosity(approxi-

mate data)

Total Densities Totalsurface of samples surface

in dried at in cm.2/cm.3m. r /E . 110 " c . x101

Kaolinite clays

1. Von5ov-Novd Ves, w. Bohemia2. Star6 Sedlo near Loket, w. Bohemia3. Sediec near Karlovy Vary, w. Bohemia4. Jarov, near Plzei, w. Bohemia

Illite clays

5. Chlum, near Beroun, c. Bohemia6 Chlum, centr . Bohemia7. Fiizerradvany, Hungary

8. VonSov near Cheb, w. Boh.9. Braiany near Most, n. Bohemia

10. Istenmezd, Hungary11. Komloska, Hungary

Clays with predominating montmorillonite and "open" illite

4 3 . 8 4 t . r3 1 . 5 4 5 . 53 7 . 0 3 3 93 5 . 5 5 8 . 5

3 3 . 6 7 9 . 33 5 . 1 7 2 . 744.4 148.8

1 3 . 8 3 5 8 . 217 .7 348.719.6 730 0tt.4 667 .5

2 . 6 4 1 0 8 . 5 02 . 5 9 1 1 7 . 8 52 68 90 .852 68 156.78

2 . 7 5 2 1 8 . 0 82 .70 t96 .292.78 413.66

2.83 l0 r3 .7 l2 . 7 5 9 5 8 . 9 32. f f i 1898.002.80 1869.00

IMBIBOMETRY

particles, another important factor appears in montmorillonite clays orin clays containing the "open" illite, which considerably influences thespeed of imbibition of the polar l iquids into the sections. This importantfactor is the phenomenon of swell ing. Especially during imbibometrictests with water such a strong swell ing takes place, that immediatelyafter the contact of water and clay on the surface of a polished sectionthe original effective porosity grows several times. This is the cause of aconsiderably quicker imbibition of water than would correspond only tothe value of the effective porosity of the aggregate and the total surface

MBIBITION TIME OF 1 DROP OF WATERRELATED TO THE UNIFOR}I BASIC AREA

Frc' 4' Depend""'" o*l;:r"":::3::*""',".Tv and imbibition speed

area of the particles (cf. Fig. 4). An especially strong swell ing took placein both the montmoril lonite rocks from Hungarian localit ies.

The relation between the total surface area of the clay particles andthe speed of imbibition of water and ethylene glycol are shown in Figs.6 and 7. In Table I, in the fourth column are given the values of the totalsurface area of eleven clay rocks investigated, expressed in cm.2/cm.3 ofthe substance X104. From these figures this main conclusion follows:The speed of imbibition of a drop of water and ethylene glycol by sec-tions of unconsolidated clay rocks is chiefly determined by the value ofthe total surface area of the particles. The other physical properties ofclay particles and their aggregates are of smaller import. This is onlyvalid for the use of polar liquids with nonswelling or slightly swellingclays. In strongly swelling clays, instead of remaining constant, the ef-

296 J. KONTA

0.

1 17I

ROCKS WITHPREDOMINATIN6O IGOLINITE.ILLITET,OPEN* ILLITEX l,1ONTMORILLONITE2

II

\4

R25

1i!g c_ ,!0-

1 .Eminules

IMBIBITION TIME OF 1 DROP OF ETHYLENEGLYCOLRELATED TO THE UNIFORM BASIC AREA

Frc. 5. Dependence between effective porosity and imbibition speedof one drop of ethylene glycol.

Frc. 6. (left) Dependence between total surface area and imbibition speed of one dropo{ water.

Fro. 7. (right) Dependence between total surface area and imbibition speed of one dropof ethylene glycol.

Eez

FU>Go

U

FUrr4

6432

zF

=

F

z

-=F

-t, 6 16 32 64 128

secondsII1BIBITION TIT1E OF 1 DR(]P OF WATERRELATED M THE UNIFORI'1 BASIC AREA

m00

zF

--

E

E

z

ff

t

2 1 , 8 1 6 3 2 6 1mlnules

IITEIEITION TIIIE OF 1 DROP OF ETHYTENEGLYCOLRELATED TO THE UNIFORH BASIC AREA

IMBIBOMETRY

TlBr;e II. C,trcur,error.r ol tm, Rnsulr,lNr lMsrsrrroN Trur ol l Dnop ol'Warnn a,no .q, Dnop ol ErnylnxB Gr,vcor. oN TEE Por-rsuno SncrroN or

rne Nlruner, Klor,rx lnou Srnr,nc Nnln Kanr,ow V,qny, Bonnura

297

Real area Recordedoccupied by imbibitiona drop, in time, in

mm.2 seconds

Uniform basicatea

Resultant imbibitiontime, in seconds

Real area

Water:

(a)

(6)

(")

(d)

13

10

85

102

i I :o.ntt89

102_ : 1 . 1 4 689

n] : t .0 ,89

80

S9:0 .8SS

0.955X13:12 sec .

1 . 1 4 6 X 1 0 : 1 1 s e c .

1.022X12:13 sec.

0 .899X14:13 sec .

Average:12 sec.

9 l

80

t2

I4

Ethylene Glycol:

(a) 56

(6) se

\c) J)

(d) se

(e) 55

( J ) s3

k) ss

(h) s3

56- : 1 .01855

59- - 1 . 0 7 3J J

.).)_ 1

.).)59- : 1 .07355

_ - 1

55

- :0 .964J J

JJ- :o .964

55- :4 .964

443:8:55 mm.2, is the uniform basic area

1 . 0 1 8 X 1 2 1 : 1 2 3 s e c .

1 .073X134:144 sec .

: 119 sec .

1 .073X115 :123 sec .

:139 sec.

O.964X127:722 sec.

0 .964X135-130 sec .

0 .964X133:128 sec .

Average:129 sec.

t2l

134

119

1 1 5

139

r27

135

133

fective porosity onwith a polar liquid,fore it is necessary

the surface of the section is increased many timesand hence the liquid imbibes rather quickly. There-

for the determination of the effective surface area of

298 r, KONTA

Tnrln III. Cerrur,lrron or rrm Rnsur,reNr IunrnrrroN Trur ol e Dnop orW,lrpn .alro l Dnop or Burvr.rr.rn Gr.ycor, oN rnn Sarooranl Srcrrox ol'

Ke,or,rxrrn Cuv rnou J.mov Nean Pr-zrir, Bonnure

Real area Recordedoccupied by imbibitionby a drop, time, in

in mm.2 seconds

Uniform basicarea

Resuitant imbibitiontime, in seconds

Real area

Water:

\a)

(b)

\c)

(d)

96- : 1 . 0 7 989

95- : 1 . 0 6 789

89- : I89

99- : 1 . 1 1 289

t6

L I

l t

1 8

96

95

89

99

1.079X16:17 sec .

1 . 0 6 7 X 1 7 : 1 8 s c c .

1Xl7:17 sec.

1 . 1 1 2 X 1 8 : 2 0 s e c .

Average:18 sec.

\c)

(,1)

Ethylene Glycol:

(a) 68

(b) 7s

(g) 7l

0 7 2

(g) 77

(h) 88

(i.) 87

6R: : l . 2 3 6J J

/.')- : 1 . 3 6 4

78- : 1 .418

o.)-: l 1825.5

t l

- : l . 2 g l.).)

72- : 1 . 3 0 955

- : 1 . 4 C 0

8B: : 1 . 6 0 0.).)87- : 1 . 5 8 2.)5

151

It1

124

134

78

65

1 . 2 3 6 X 1 5 1 : 1 8 7 s e c .

1 . 3 6 4 X 1 1 1 : 1 5 1 s e c .

l .4l8Xl24:176 sec.

1 .182X134:158 sec .

1 . 2 9 1 X 1 3 1 : 1 6 9 s e c .

1 .309X120:157 sec .

1 .400X129:181 sec .

1 .600X131:210 sec .

1 . 5 8 2 X 1 2 1 : 1 9 1 s e c .

Average:176 sec.:2 min. 56 sec.

131

120

129

131

l2 l

IMBIBOMETRY 299

the particles or of the effective porosity to use nonpolar liquids. For the

purpose of identification of clay minerals, the procedure of the imbibo-

metric method here described, has proved to be a fully satisfactory one.

PnBp,qnarroN oF SECTToNS

The clay is roughly ground by circular movements on glass-paper no'

50, and then the surface of the section is smoothed on emery-clothno' 240

or finer. Thus the preparation of a section requires no more than 2-4

minutes. By using the same type of emery cloth sections of equal qual-

ity can be obtained.During the preparation of sections it is important to observe the fol-

Iowing rules:

(1) The grinding is always done in dry state.(2) Sections which should serve for the identification of clay minerals or for the deter-

mination of the relative age of ciay rocks are aiways made parallel to the stratification. In

clay aggregates without stratification a number of sections should be prepared, and in vari-

ous directions.(3) On the section or in the area where the liquid is imbibed, there should be no pores or

cracks visible by eye or by lens.(4) When the grinding is finished it is necessary to remove carefully the loosened cLay

powder on the surface of the polished section by means of a soft brush.

(5) The surface of the prepared section is always dull and it should not glisten in any

case (as required by metallographic microscopy).(6) The surface of the section must be free from grease.

For other purposes sections can be made perpendicular to the strati-

fication, or with varying orientations.Smooth seclions of sand,y or s'ilty-sand,y clays are for the most part

difficult to prepare. For imbibometric identification of clay minerals in

these rocks it is necessary to prepare artificial solid plates, by elutriation

and sedimentation of dispersed particles. The natural sample of the rock

is pulverized and elutriated in a tall beaker filled with water. After

thorough stirring and diqpersion of clay particles, adding a suitable dis-

persive solution, the suspension in the beaker is left to settle in a quiet

place. Care must be taken so that the orientation of clay particles is not

changed during the drying of the sediment. The dried sediment ready for

the preparation of the section has the form of a solid disc about f to 1 cm'

thick.

IrrlrsoMBrnrc TESTS

The working process during imbibometric tests is quite simple:

(1) The section is 6xed on plasticine in a horizontal position.

(2) On the surface of the polished section a drop of water is dropped from a vertically

held pipette (constant size) from a height of about 4 to 6 mm. Simultaneously, we obsetve

and ascertain:

300 J. KONTA

(o) The size and the shape of the area occupied by the drop.(D) The time during which the drop gets entirely imbibed.(c) The changes on the surface of the section during the imbibition and mainly after

the imbibition of the liquid.(3) This complex observation must always be carefully registered, and the area in which

the drop was imbibed, copied on a transparent paper.Then the same process is used in the case of a drop of ethylene glycol, which rs more

viscous and is imbibed by all aggregates more slowly than water. rt is recommended thatall the observations be entered in a card index

PREDt]14INATIN6IlIN ERALIN THE ROCK

KAOLINITE

ILLITE

MONTMORILTONITE& ,,opFN" tt l tTE

WATE R

n 5 t- - '

1 0 9 - 6x

6 16 3? 6r, 128seconos

FORI1 OF IHE SURFACE OFAREA TAKEN UP POTISHED SECTIONBY THE DROP AFTER ABSORPTION

SMOOTH

SMOOTH

SWOLLEN

SMOOTH

SMOOTH

SWOLLEN OR DULL

^

{ [

\J

( )

/-)\ )

PREDoMTNATTNG ETHyLENEGLyC0L iRlX,of,,"["' 33l,TfiEf!,r'o*IN THE ROCK BY TIIE DROP AFTER ABSORPTION

KAOLIN ITE

ILLITE

MONTMORILLONITE& ,r0pENx ILLITE

1 ? 4 6 1 6 3 2 6 4minu les

Fro. 8. Identification table serving for entering observations obtainedduring the imbibometric tests.

Tne UsB oF IMBTBoMETRy loR IooNrrrrc.c.troN oF Crey MruBner,s

The relation of the size of the area occupied by the drop on the sectionto the speed of imbibition is best evident from the mathematical equa-tion previously given. The Iarger the area occupied by the drop, theshorter is the time of imbibition. Every area on the section occupied bythe drop is carefully traced on a transparent millimeter-lined paper andthus its size is ascertained with relative precision. Even quicker is thedetermination of the size of the irregularly shaped area by a suitableplanimeter.

7 6 5O'

1 0 f l I I) 0 ( X I

IMBIBOMETRY

The actual measured time of a complete imbibition of a drop of waterand a drop of ethylene glycol has then to be transferred to a uniformbasic area and the resultant imbibition time is obtained. It is the timeduring which the drop should be imbibed if i t occupied on every sectionsuch an area as it occupies on the section of the natural pure kaolinfrom Sedlec near Karlovy Vary, Bohemia. A drop of water Iet down fromthe pipette from the height of 4-6 mm. on the natural pure kaolinfrom Sedlec near Karlovy Vary occupies a circular area of average size89 mm.2 (computed from four measurements). A drop of ethylene glycolunder the same conditions occupies an area of average size of 55 mm.2(computed from eight measurements). In Table II the manner of calcu-Iation of the resultant imbibition times for the pure kaolin sample fromSedlec is given. In both cases the measured values are related to a uni-form basic area for water and ethylene glycol. In Table III the calcula-tion for the section of silty kaolinite clay from Jarov near Plzen, Bohemia,is given.

The resultant values giving the imbibition times are entered in a table(Fig. S). In the upper part of the table the resultant imbibition times ofa drop of water related to a uniform basic area with regard to the wet-tabil ity and to the surface change of the section after imbibition are en-tered. In the lower part the corresponding times for ethylene glycol arelisted.

Anorr.q.rous SnonrBNrnc oR PRoLoNGATToNoF THE furrerrroN 'filrn

In some cases the imbibition speed of water and ethylene glycol maybe essentially shorter or longer than might be expected, considering theclay minerals present in the sample. The character of the predominat-ing clay mineral can be determined, however, on the basis of mere wetta-bil i ty, and swell ing or nonswelling of the sample. These properties canbe recognized on the smootheil section by the different size of the area occu-pied by a drop of water or a drop of ethylene glycol, further by a char-acteristic contour of the area, and finaliy by a change of the surface ofthe polished section upon imbibition.

The shortening of the imbibition time of the liquid which does not cor-respond to the size of the effective surface area of the clay particles canbe the result of 'different factors. Of these the most important are:

(o) Presence of a greater number of clastic grains.(b) Swelling of montmorillonite or of "open" illite.(c) Placing drop in the direction of the preferred orientation of the clay particles in

samples without evident stratification.(d) Presence of admixture of carbonate minerals.

301

302 L KONTA

(e) Presence of soluble salts, especially of halite.(/) Formation of cracks on the section during imbibition.

The prolongation oI the imbibition time of the liquid is most often in-f fuenced by:

(g) A greater consolidation of the clay rock and a total porosity under 25 per cent.(/z) Presence of finely dispersed organic substance (enlargement of theefiectivesurface

area).

It is therefore always important before and in the course of imbibomet-ric tests to determine for every rock studied if the imbibition will be in-fluenced by some of these factors. The majority of these unfavorable fac-tors can be eliminated in imbibometry by the making of artificial solidplates of the clay. Thus can be eliminated the factors given above undera, c, d, e, and g.

GrNBnar UsB or fMsrsorrprnv

First, it is possible to identify clay minerals on sections of unconsoli-dated but coherent clay aggregates by a drop of water and of ethyleneglycol. These aggregates can be either natural, or artificial if the naturalclay is not suitable for the making of the section required. It is furtherpossible to determine, imbibometrically, the value of efiective porosity,if the total surface area of the particles is determined beforehand (e.g.,bya simple method according to Dyal and Hendricks, 1950). By means ofimbibometry it is possible in clays to determine the direction of the maxi-mum imbibition by making sections of various orientations. Imbibometryalso quickly reveals the extent of swell ing in argil laceous rocks contain-ing montmorillonite or "open" illite. The results are of relative natureonly when using polar liquids. When using a polar and a nonpolar liquidon the same section the results begin to have a quantitative character.

The imbibometric method can also, in some cases, be applied to prob-Iems connected with the determination of the relative age of clay rocksin a definite uniform geologic area. In clay rocks of relatively earlier geo-logic age the suitable l iquid wil l imbibe more slowly than into later rockswhich in most cases are less consolidated, i.e. oI greater total porosity.At the same time, the mineral composition of clay rocks must be approxi-mately the same.

On the basis of recent experimental work we can say that in the futureother l iquids, polar and nonpolar, wil l be used in imbibometry.

AcrNowr,BtGMENTS

The author is indebted to Professor R. E. Grim for making changes in$entence construction in the preparation of this manuscript.

IMBIBOMETRY

RnlnnnNcns

Dvnr,, R. S., ,lwo Hnxomcr<s, S. B. (1950): Total surface of clays in polar liquids as a char-acteristic index. S oi,l. Sci., 69, 421432.

Kontl, J. (1956): Schnelle petrographische Identifikation der Tonminerale in den An-schlifien mittels Wasser und Ethylenglykoll. Chernie il.er Erd.e,18, 179-193.

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