Solubilization of Water-Insoluble Dye in Soap Solutions: Effects of

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Sept., 1946

EFFECTS OF ADDEDS A L T S O N [CONTRIBUTION FROM

SOLUBILIZATION OF W A T E R - I N S O L U B L E

DEPARTMEKT OF CHEMISTRY,

DYE

1731

STAWPORD UNIVERSITY ]

Solubilization of Water-Insoluble Dye in Soap Solutions: Effects of Added Salts BY JAMES W. MCBAINAND SISTER AGNESANN GREEN,I.H.X. Solubilization consists in the spontaneous passage of molecules of a substance insoluble in a given solvent into a dilute solution of a detergent in that solvent, to form a thermodynamically stable solutiort.1.2 This phenomenon is characteristic of solutions of colloidal electrolytes, and from a theoretical consideration of the probable mechanism any factor affecting the formation of colloidal particles would be expected to influence the solubilizing power.3 The addition of salt containing a common ion to solutions of anion active or catimon active detergents or colloidal electrolytes has been shown t o affect the amount of insoluble material solubilized in dilute solut i o n ~ . ~Hartley ~ ~ * ~ found that sodium chloride enhanced the solubilizing action of cetyl pyridinium chlorides; McBain and Johnson found a similar effect when potassium chloride was added to potassium laurate and myristate.6 Using potassium laurate as a representative detergent of the anion active type, a series cf measurements has been made on the solubiliziny ability of soap over a wide range of concentrations in the presence of a constant amount, 1.0 N , of different salts. Salts greatly increase the solubilizing power of potassium laurate for dye. This increase extends over the whole range of concentration of soap. It is most striking in dilute solutions where the soap would solubilize but little if at all; but up to the highest concentration of soap the solubilizing power per mole of soap is still increasing. The quantitative relation does not vary greatly with the potassium salt used. I n the concentration range between 0.25 and 1.OO N soap, vrpith 1 N salt present, the solubilization of dye per mole of soap continues to increase with increasing concentration of soap. In tf7e case of soap alone, where solubilization seemed to reach a nearly constant level in this range i t increased again in still higher concentrations of soap. The physical and colloidal properties of potassium laurate which have already been studied add to the significance of these data. According to o ~ n i o t i cand ~ ~ conductanceg ~ measurements, this soap reaches full colloidal form in about 0.2 LV aqueous solutions. The nearly constant amount of dye solubilized per mole of soap ( 1 ) AlcBain a r i d RicBain,

THIS J O U R X A L , 68, 2610 (1936). r I I m d Vinoirad, i b i d . , 63,670 (1941). 71 ibilization and Other Factors in Detergent .4ctim ” in “Advances iii Colloid Science,” Vol. I , Interscience Publishers C o , Inc.. Keiv York, 1942, pp. 99-142. ( 4 ) LIcBain a n d >[errill, I n d . E n g . Chem , 34, 915 (1942). (j)McRain and Johnson, THISJ O U R N A L , 6 6 , 9 (1944). (6) Hartley, J . Ch,%z. Sac., 1968 (1938). (7) h l c s a i n a n d B,>lduan,J . P h y s . Chem., 47, 94 (1943). (8) McBain a n d Brady, THISJOURNAL, 65, 2072 (1943). (9) McBain, Laing and Titley, Trans. Chem. Soc. (London), 116, 1282 (1919).

beyond this concentration indicates almost no increase in the proportion of colloidal particles in the pure soap solution throughout most of the more concentrated range until much higher concentration is reached. The effect of salt which magnifies the solubilization and still produces a marked increase in all concentrations of soap points to either a n increase in effectiveness or in amount of the effective colloidal micelles.

Experimental Materials.-Orange OT (F. D. and C Orange No. 2 ; 1-o-tolyl-azo-2-naphthol) which had been recrystallized from boiling alcohol and dried a t 80” was used. Treated thus, the dye was in crystalline form, bright orange-red in color, and insoluble in water and in inorganic salt solutions a t room temperature. Potassium laurate was prepared by Dr. M. E. L. McBain by neutralization of Kahlbaum “purest” lauric acid with carbonate-free potassium hydroxide. Stock solutions were prepared from this according t o two methods. (a) For a conveniently weighed-out stock solution, 0.10 mole of soap was added t o 100 g. of water, containing 0.004 equivalent of potassium hydroxide t o suppress hydrolysis. The volume normality of this solution was then calculated t o be 0.819 N by the formula

+

N , = 1 0 0 0 ~ 4 ~ 5 ~ ~ 1 0MN,) 00 by using the density reported by Bury and Parry,1awhere d is density and M is molecular weight. This method eliminated the tediousness of preparing a definite volume of such a substance with such foaming properties. (b) One-tenth mole of soap was placed in a 100-cc. volumetric flask and enough water added t o dissolve it with only gentle rotatory agitation in a thermostat for five t o six hours a t 25’. This treatment did not produce foam, so that the solution could then be made up to the volume mark. T h e potassium chloride, potassium hydroxide, and potassium thiocyanate were Baker c. P. products. T h e thiocyanate was fused a t 120’ for forty-eight hours, cooled, powdered and again dried a t 120” for forty-eight hours.” This treatment produced a dry form sufficiently sta le for w( ighing. The potassium sulfate was a Kahlbaum product. Acetone of technical grade was distilled to obtain an optically clear liquid for dilutions in making dye concentration measurements in the Lumetron (Photovolt’s photoelectric colorimeter Model 402E). Equal volume mixtures of acetone and water were used in making dilutions for colorimetric measurements t o prevent the precipitation of the dye, salt, and soap. Method.-Series of solutions of varying soap concentration but with constant salt were made up by diluting a definite volume of the stock solutions of potassium laurate, after weighing the desired amount of salt into the volumetric vessel. These solutions were placed in 50 cc. glass bottles, with sufficient dye added t o form a small amount of excess solid, sealed with plastic caps, lined with pure gold foil, and placed on an agitator in a 25” water thermostat. Solutions of concentrations below 0.2 12’ were found t o require only two or three days t o reach equilibrium value for maximum solubilization. The more concentrated solutions required from one t o two weeks, depending on the concentrations. All solutions, including the dilute ones, were remeasured until constant. (10) Bury and P a r r y , J . Chem. Sac., 625 (1935). (11) Kolthoff and Lingane, T H I S J O U R N A L , 67, 2129 (1935).

mzm < : : 1

i1.*~+ 2.0

3

s

-

1.6

r

-x

.='" 0.8 r r,

," $ 0.4

*

Kc14

-

KClL

'

.

/------'

KCe

0

I n order t o measure dye concentration, the bottles were first placed upright in a stationary position in the thermostat foi ten to twenty hours until the excess dye had settled, leaving clear, transparent colored solutions above. One-cc. portions were then removed by serological pipets, and diluted in volumetric flasks with 50% acetone in preparation for measurements of percentage transmission by the colorimeter. The R-4200 blue filter (with transmission in the range 4000-5300 A , , was used, for which a calibration curve had been obtained by dissolving known amounts of dye in acetone and benzene From the instrumental readings of percentage light transmitted, the dilution of the 1-cc. sample, and the concentration of the solution, the amount of dye solubilized by the soap was calculated. 'Three or four measurements made a t different dilutions of the same solution were found t o agret within 270 on the calculation of mg. of dye per 100 cc. of solution For the very dilute solutions, 110 dilutions were made, and their transmission was compared directly with that of the pure soap solution of the same conccntration

Experimental Data

.. '

KC10

I

observed in the experiments reported in this paper. Tables I1 to VI11 present the recalculated values for grams of dye per mole of soap, and Figs. 1 , 2 and 3 shgw the graphs of Tables I to VIII; these supersede Figs. 1, 2 , and 1 of blcBain and Johnson and the corresponding colllliltls of their Tables I1 to 1911. Since the molecular weight of the dye is 262.3 the molar ratio between dye and total soap is obtainable by dividing the numbers given by 262.3. The values are low but not by any means negligible on account of the high molecular weight of the dye.l? Tables IX, X, XI and XI1 present the

is seen that in i l l 'cases the eleitrolytes greatly increase the solubilization of dye by the soap. In the graphs molar ratio of dye to soap is based upon the total soap. Several authors have recently suggested that it might be better to base the ratio upon that fraction of the soap which is in colloidal form if this were accurately known. Since above the critical concentrations simple fatty ions rapidly disappear from solution, the diagrams become identical with those here given and it would be quite erroneous to subtract the critical concentration from the total con-

c3

The solubility of Orange OT in vari' ous concentrations of pure potassium r 2.0 laurate was measured in order to extend previous data to a wider range of concentration, and to establish a refer- h 1 . 5 ' ence for the interpretation of the effects m LLI of salts. The results given in Table I 9 1 . 0 ' were a t first sight higher than those obtained by McBain and J o h n ~ o n . ~ This was found to be due to a systematic error entering into their method of calculating the amount of dye solu0.5 01 bilized by one mole of soap in a molal solution for which the amount of dye 0 0.1 0.2 0.3 0.4 0.5 0.6 07 0.8 per 100 cc. solume had been correctlv Concentration INvl . . of soaD. measwed and published. The nee&- Fig. 2.--Solubilization of Orange OT in various concentrations of soaps sary recalculation was made after carepotassium myristate, KC14; potassium laurate, KC12 ful consideration of their methods of preparrng each solution, and the resulting values centration of the soap. for potassiutll laurate (Table Iv) agree with those (12) McBaln and Richards, I ; I ( ! ~~~g Chein 38,642 (1946).

; Q)

M

ti

t

I

Sept., l9Mi

EFFECTS OF ADDEDSALTS ON SOL UBILIZATION

OF

WATER-INSOLUBLE DYE

1733

TABLE I TABLE V SOLUBILIZAT~ON OF ORANGE OT IN AQUEOUSSOLUTIONS OF SOLUBIL~ZATION OF ORANGEOT IN VARIOUSCOSCESTRAPOTASSIUM LAURATE (Kci2) AT 25' TIONS OF AQUEOUSSOLUTIONS OF POTASSIUM MYRISTA I I.: S vol. concn. G. dye/mole KCiz ( K C i r ) AT 25'

n.nnoi

..

,001 .. . no5 0.02 .Ol 0.02 ,025 0.176 049 0.462 I098 0.833 .125 0,970 ,250 1.038 .500 1,041 .820 1.041 1.000 1,076 1,500 2.167" a From supers:tturation. The viscosity of this solution may have kept it supersaturated, or have kept finely divided dye suspended.

Vol. concn. of soap

0.020 .040 .079 .119 ,159 ,196 ,396 ,592 ,793 (1.00 m )

R A T E A N D POTASSIUM L t Y R I S T A T E , A T

From undersaturation g. dye/mole soap

TIOSS OF

g.m%;/

345

TABLE IV SOLUBILIZATION OF ORANGEO T IK VARIOUSCONCEXTRATIONS OF AQUEOUSSOLUT~ONS OF POTASSIUM LAURATE (KC12) AT 25' vol. concn. o f soap

From undersaturation g. dye/mole KCu

From oversaturation g . dye/mole KCn

0,041 .082 .123 .164 .205 ,410 ,615 .819 ( I . 00 m;l 1.403 (2.00 r n )

0.473 ,842 ,873 .954 1,018 0.964 ,969 1.015 1.101

0.476 ,906 ,989 1.024 1.026 1.043 1.058 1.043

Y.

...

1 29 1.30 1 43 1 44 1 45 I 13 1 41 1 42

TABLE VI1 SOLURIL~ZATION OF ORASCEOT IS VARIOUSCONCENTRAvol. concn.

*

23"

From oversaturation g. dye/mole soap

1.28 1.32 1.41 1.41 1.37 1.37 1.38 1.40

of soap soap TABLE I11 SOLUBILIZATION OF ORANGEO T IN VARIOUSCONCENTRA- I . Potassium Laurate TIOSS OF AQUEOUS SOLUTIONS OF POTASSIUM CAPRATE 0.041 1.29 ( K C i o ) AT 25' 1.44 From From ,082 3." undersaturation oversaturation ,205 1.62 vol. concn. of soap g . dye/mole KCio g. dye/mole KCID .410 1.63 0.084 0.216 0 177 ,819 1.62 .168 ,221 ... (1.00 m j ,335 .308 0.330

.348

1.81 1.92 1 91 1.91 1.93 1.92 1.93 1.02

TABLE VI SOLUBILIZATION OF ORASCE O T I N VARIOUS CONCEZITRATIOSS OF A N EQCIMOLAR MIXTURE01' POTASSIUM LAT-

Nv

.839 ( 1 . 0 m)

From oversaturation g. rlye/mole KCir

1.63 1.81 1.88 1. 8,5 1.84 1.85 1.85 1.83 1,86

Nu TABLE I1 vol. concn. of soap SOLUBILIZATIOS OF ORANGEO T IS VARIOUSCONCENTRA- 0.040 TIONS OF AQUEOUSSOLUTIONS OF POTASSIUM CAPRYLATE ,080 ( K C * ) AT 25" ,120 From From .160 M'" undersaturation oversaturationa ,201 vol. concn. of soap g. dye/mole KCs g. dye/mole KCs .401 0.426 0.064 0.075 ,602 ,562 ,087 ... ,802 (1.00 TBj 1.532 ( 2 . 0 m) . 150 0,174 a In general results from undersaturation are nearer the equilibrium value than those from oversaturation because of the long persistence of oversaturation; the true values should be bracketed between them.

From undersaturation

g. dye/mole KClr

SOAPS AT 50 '

A',, vol. concn. of soap

g. Dye/ mole

soap

11. Potassium Laurate and Potassium MYristate Mixed 50: 50 0.040 1.71 ,080 1.90 .120 2.07 .160 2.18 .201 2.19 ,401 2.18 .602 2.19 ,802 2.18 (1.00 m)

N,

vol. concn. of soap

g. Dye/ mole soap

111. Potassium Myristate 0.020 2.47 ,040 2 ,i 3 .Oi9 2.96 .119 2.90 ,159 2.92 .190 2.99 ,396 2.96 .592 2.92 ,793 2.94

TABLE VI11

SOLUBILIZATIOX OF ORANGEOT IN VARIOUSCONCENTRATIONS OF POTASSIUM LAURATE AND POTASSIUM MTRISTATE AT

25"

IN THE

PRESENCE OF 1 m POTASSIUM CHLORIDE

Ym

Laurate g. dye/mole soap

n.om

1.53" 1.08 1.16 1.09 1.19 suspension; see later section

vol. concn. of soap

n ,025

,049 ,191 ,450 a Includes munication.

Myristate g. dye/mole soap

3.90" 3.78" 2.73 2.84

..

of this com-

1734

JAMES

W. MCRAINAND SR.AGNESANN GREEN,1.H.M.

Vol. 68

TABLE IX TABLE X SOLUBILIZATION OF ORANGE SOLUBILIZATION OF ORANGE OT IN AQUEOUSSOLUTIONSOT IN AQUEOUSSOLUTIONS O F POTASSIUhi LAURATE IN O F POTASSIUM LAURATE IN THE PRESENCE IN 1 m THE PRESENCE CF 1 9 ~ 1 POTASSIUM CHLORIDEAT POTASSIUM HYDROXIDE AT 25 23 O

N.

vol. concn. of soap

mg. Dye/ 100 cc.

0.0493 ,0975

5.38 10.6 15.7 21.4 27.0 63.4 85.3 134.8

.145

/

'*',,

2

2

K L WITH

.191 .236 .450 ,643 .819

IKCL

KL ALONE

o

l

d

.

.

,

a Includes suspension; munication.

*

Ne vol. concn. of soap

mg. Dye/ 100 cc.

1.19"

0,0047 .009 4 .024

1 .10

2.60 6.95 ,094 11.4 ,142 20.4 ,189 2s.2 .%36 36.9 . 4 10 70.1 ,615 124.1 see later section of this com-

,047

-2

(1.1 0.2 0.3 0.4 0.5 0.6 Concentration IS,]of soap. Fig. 3.--Solubilization of Orange OT iii varims concentrations of potassium laurate and potassiuin inyristate a t 25" in the presence of 1 M potassium chloride: M, myristate; L,, laurate. 0

TABLE XI

TABLE XI1

SOLUBILIZATION O F O R A S G E

~OLUBIl.lZATION O F OR.4NGE

OT IN AQUEOUS SOLUTIONS

OT IN .kQUEOCS

POTASSIUM LAURATE IN THE PRESENCE OF 0.5 m POTASSIUM SULFATE AT 25 O x2

OF

OF

S O L U l IONS

POTASSIUM LAURATE IN THE PRESENCE OF 1 m POTASSIUM'I'HIOCYANATE 4 T 0.7

vu1 concn. m g . Dye/ Discussion r 7 of sonp 100 cc. vol. concn. m g . Dye/ Solubilization in Solutions of Soap and Deter0.0205 2.26 of soap 100 CC. gents without Salt.-The graphs show that in 0.0236 2.55 ,0410 4.70 sufficiently dilute solutions of detergents there 6.10 ,0472 ,082 10.4 is no solubilization, presumably because there 12.25 .123 16.0 .0944 are no colloid.al particles in which the solubilized .142 17.5 .164 22.1 material can be incorporated. Then as suitable .189 24.0 .205 27.7 micelles form in the solution upon increase of COII31.2 .410 57.2 ,236 centration, the amount of dye solubilized by each 62.2 .615 91.3 .410 mole of soap rises t o a constant value, which in,615 103.5 .819 136.2 creases again only in the highest concentrations. Comparing the constant values for the various TABLE'XIII soaps in the homologous series it is seen that the SOLUBILIZATION O F ORANGE OT I N DILUTE AQUEOUS amount of dye solubilized per equivalent of soap SOLUTIOTS OF POTASSIUM LAURATE IN THE PRESENCE OF rises very rapidly, being 162 rng. for KC8, 347 for POTASSIW S~1.1.sA T 23 KClo, 1050 for KC12 and 1880 for KC14. This inU'ith 0.5 m RrSOi With 0.5 rn RsSOt N,, n i f i clye/l(JiJ c c . v d concn. of s r m p nig. dye/100 cc crease is out of all proportion to the increase in 0.0250 3.29" 0.26 the amount 0.r length of the hydrocarbon chain in .OlOO 1.09" 0.05 the molecule of soap which is only in the ratio ,0082 0.85" ..* of 1:1.25: 1.50: 1.75, whereas the amounts solu.0050 .55" 0.025 bilized are as 1:2.14:6.48:11.61. Hence the solu,0025 .25" ... bilization is obviously not proportionate to the .0010 .02" 0 amount of hydrocarbon in the soap molecules. .0001 .. 0 Where .practically all the soap is in the form of micelles, as in the higher concentrations, it must With 1 m RSCN With 1 m KCI also be true that the solubilization is not propor0.0250 2.72" 0.25 tionate to the amount O€ hydrocarbon in those .OlOO 1.15' .10 micelles. Of course, some micelles may be in.005 0.60" .05 capable of solubilizing ; the lack of proportional,0025 .20" .. ity between amounts of organic liquids solubil.001 ,02" 0 ized and the increase in X-ray spacings clearly ,0001 .. 0 indicates that the different micelles differ in solua Includes suspension; see a later section of this combilizing power. munication. O

Sept., 1946

EFFECTS O F

ADDEDS A L T S ON

SOLUBILIXATION O F WATER-INSOLUBLE

10

s X 8

KL

KL U

+

KOH

+

KCNI

+

I(

-

-

CL

a k ~6~~~ %* .$a 42 b 0

r

KL

--

ALONC

1735

concentration, the amount of dye per mole of soap increases steadily with increasing concentration of soap over the whole range, showing that the kind of colloidal micelles formed in the more concentrated solutions of soap are far more effective as solubilizers than those in lower concentrations. This was already noted for the highest potassium concentrations The greatest hydroxide, ofeffect soapfollowed is alone. produced by that by

M

k

0

DYE

I

1

I

I

I

I

I

1

I

produced by potassium thiocyanate. Still somewhat less, but equal to each other, are potassium chloride and an

I

I

I

I

I

1

'

-

sheets, :is revealed by the expanding Bragg's spacings. P McBain and PalitlGhave shown that the same forces which are operative in g producing the lamellar micelles of the ; solubilizing detergents in aqueous sohtion result in enhancing the true soh- .$ bility of substances in high concentra- % tions of mixtures of co-solvents. This .s is in addition to any solubilization through formation of colloidal micelles e 2 in such solvents. Comparison of the Effects of Salt.2 d I In all concentrations. salts (which 0 by themselves are non-solubilizing) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Concentration of potassium laurate. greatly increase the amount of solubilization by a. given amount Of Soap. Fig. 5.-Effect of 1 2tl potassium hydroxide and sulfate on solubilization This is especially striking in the lower by potassium laurate solution, a t 25'. concentrations of soap where no solubilization is observed until the salt is added. EviSolubilization and Suspending Action in Very dently the salt promotes the formation of colloidal Dilute Solutions of Soap.-Tables VIII, X and soap except in excessively dilute soap solution. especially X I I I , include dilute soap solutions In the second place, keeping the salt in constant but in the presence of 1 rn salts. Here a maxi(13) W. I). Harkins. R. w. M a t t o o n , M . L. Corrin and R s. mum total effect per mole Soap Was observed a t Stearns, J . Chem. I'hys., 13, ,534 (1945); W. D. Harkins, R . W. approximate~y 0,005 N soap. The effect was Mittoon a n d hl. L. 'Corrin, J . Coll. Sci., 1, 105 (1946). even higher during the first twenty-four hours, (14) E. W. Hughes, W. M. Sawyer and J. R. Vinograd, J . Chem. Phys., 13, 131 (1945'1. but fell off gradually to the approximately con( 1 5 ) s. RUSS and 1 . w. McBain, THISJOURNAL, 68,296 (1946). stant values observed a t the end of a week and (16) S. R . Palit srnd J. W. McBain, I n d . E n g . Chem., 88, 741

3

(19461.

(17) J . W. hlcBain and

4.V. Pitter, J . Chem. Soc., 893 (1926).

1736

FREDERICK

c. FOSTER AND LOUISP. HAMMETT

given in the tables. This maximum thus varied in such a way as t o indicate that i t was not an equilibrium. Furthermore, i t occurred a t a dilution far too low for the soap to be in colloidal form. This sharp peak of effect occurred over a very narrow range and rapidly fell off to zero on still greater dilution. Since a very minute :tbsolute amount of suspension would be sufficient to cause a large effect relative to the soap in this dilution, the following experiments were devised to eliminate suspension of solid dye by avoiding the presence of any solid dye. A saturated solution of dye was prepared in hexadecane and then excess hexadecane was added to reduce the concentration to 90% of saturation. Hexadecane is a hydrocarbon which is not itself solubilized in dilute potassium cc. of this solution was placed on laurate. Tw:, top of 20 cc. of the dilute soap solution containing salt. These irere then placed on a rotating plate in a thertnoc.tat a t 25’ in such a manner that the interfacc between soap and hydrocarbon was not broken, but the liquids were kept very gently stirrec:,. After a week of such treatment the aqueous soap layer was removed, and the concentratioii of dye in i t was measured. The maxima had entirely disappeared, showing that those observctd with solid dye were due t o suspension of residual fine fragments from dye crystals. These would be too small to play any role in coi1iparisor.iwith tlie wry much largcr :irnotmts of soap i l l grcxtcr conwiitr-ctt‘ions. Solubilization of a Non-electrolytic Detergent with and without Added Salt. -It is 01‘ great interest to coinpare the behavior of a 11011electrolytic detergciit such as X with that of the colloidal electrolytes so far investigated. X is an alkylated ;tr?.1 1)oly et1ii.r alcohol derived l’roni polymerizeti otliylt‘iic ositlc ant1 i t catiiiot ioiiize in aqueous :;elution. FIence thcrc c:m be no cornnioii i o i i efffect. Sevcrthc,lcss atltlitioil oi

1701.

68

salt in general might be expected to promote association. Measurements of the solubilization of Orange O T in 2Yo solution of X alone at 25’ gave 9.25 mg./100 cc. Addition of 10% potassium chloride raised this to 11.1 5 nig./100 cc., a result 20% greater. This is almost half as great an effect in increasing solubilization as if the salt had been added to a colloictal electrolyte such as potassium laurate This may be taken as an indication that non-electrolytic detergents are associated in aqueous solution. Summary The solubilization of water-insoluble dyes has been measured in aqueous solutions of soaps a t 25’. Whereas the amount of hydrocarbon chain in the molecule of soap or in the soap micelle increases from the caprylate to the myristate only in the proportion 1 : 1.25: 1.50: 1.75, the solubilization increases disproportionately as 1:2.14 : 6.48311.61. In all concentrations of potassium laurate above N / l O O O the addition of potassium hydroxide or of potassium salts greatly increases the amount of solubilization. This solubilization occurs a t dilutions of soap far below those in which soap alone can be solubilized, owing to the absence of colloidal micelles, but it increases rapidly and steadily with increasing concentration of soap showing that the kinds of micelle? cxisting in higher concentrations are inore effective than those formed in lower concentrat’ions Rxtreniely dilute soap solutions, especially i n the pr(”;cncc of salt, exhibit a powerful suspenditig .iction lor aiiy initlute particles of dye, ;L pheiioiiiciio~iquite distinct from solubilization. Solut~ili7atiotiby a non-electrolytic detergent i\ .dso eiihancetl by the presence of potassium chloritic, iiitlic,~titiq iiicrc,iictl .issociation of the tlctcrgeiit. STANFOKI) ITNIV1:KSI I\‘, CALIF.

RECEIVED h l A R C I i 22, 1946

The Kinetics of the Reaction of Hydroxyl Ion with the Meso and Racemic Di-ptoluenesulfonates of Butylene Glyc01-2,3~ BY FREDERICK C. FOSTER** AND LOUIS 1’. HAMNETT ICIIj)2CII- (CII,{)