Tracer Electrophoresis. II. The Mobility of the Micelle of S

Jan., 1955

MOBILITY OF MICELLE OF SODIUM LAURYL SULFATE

45

empirical parameter) to the non-regular mixtures of a hydrocarbon and a non-hydrocarbon, some derived results of experimental determinations are given in Table VI.

In Table VI, column 5 represents an arbitrary and empirical solubility parameter for the hydrocarbon-ascribing all the effect of deviation to the alteration of the parameter of the hydrocarbon. It is considered significant that essentially the same TABLE VI numerical value of the parameter is obtained for each hydrocarbon, whether it is derived from calcuCOMPARISON OF VALUES OF (6, -&)' etc., FROM COMPONENTS lations based on the behavior of mixtures with subA N D SOLUTIONS PROPERTIES stances of higher, or of lower parameter. 1 2 3 4 5 (81 - 62) from GilpnarPnt, Acknowledgments.-The director of this work properties of Hydrocarbon, Temp., Pure cornSoluAEv/u)oJ (J. B. H.) gratefully acknowledges the assistance of System ponents tions"+ (14 - 31 a grant from the National Science Foundation, a 1.901 1.110 7.89 TiC14-C7Hls 323.2 part of the time made available by which was spent 1.798 1.098 7.54 333.2 on this work; the authors acknowledge the assistCClr-CsH18 323.2 1.271 1,000 8.24 ance of the Atomic Energy Commission (as repre1.000 8.11 333.2 1.218 sented by Carbide and Carbon Chemical's Co.), the 2.65 7.75 C~ F I~ C I H I 333.2~ 1.56 Minnesota Mining and Manufacturing Co., and C~FigCgH18 333.2 1.73 2.77 8.05 the National Lead Co. in making samples of matea Calculated by equation 3. rials available free or at special prices.OK.

TRACER ELECTROPHORESIS. 11. THE MOBILITY OF THE MICELLE OF SODIUM LAURYL SULFATE AND ITS INTERPRETATION IN TERMS OF ZETA POTENTIAL AND CHARGE1BY D. STIGTER~ AND K. J. MYSELSContribution from the Department of Chemistry, University of Southern CaliforniaReceived July 89, 1864

Measurements of electrophoretic mobility of micelles of sodium lauryl sulfate in water and salt solution a t finite concentration of micelles are extrapolated to infinite dilution of micelles. Corresponding zeta potentials and charges a t the shear surface of the micelle are calculated according to several theories including new modifications of Booth's approach. The great effect of the curvature of the double layer and of relaxation effects is thus established for these systems which are far from ideal even a t the ChlC. A comparison of the zeta potential with that calculated from the charge of the lauryl sulfate ions forming a smooth micelle with a diffuse double layer leads to a large discrepancy. A"roughness" of the surface of the micelle is therefore suggested. The calculations involved required the computation of charge-potential and of potentialdistance relations for double curved layers a t high potential. These general problems are dealt with in appendixes.

The size, charge and shape of a micelle, besides their intrinsic interest, provide experimental tests for any theory of association colloids, yet they are sti

ll a matter of uncertainty. In the present paper we shall present accurate measurements of the electrophoretic mobility of micelles of pure sodium lauryl sulfate (NaLS) obtained by the tagging technique suggested by H~ y e r . This~ mobility is obviously related to the charge, size and shape of the micelle and to the composition of the solution. These relations are not yet fully elucidated but it is shown that they lead already to a reasonably accurate estimate of the f potential and of the charge of the micelle. The f potential is quite high: 65-100 mv. and the charge corresponds to 25-30% ionization, which is not readily explainable by the conventional picture of a smooth micelle surface. Since the experimental accuracy greatly exceeds that of the interpretation, the present data should be capable of yielding more accurate estimates of charge as the theories are developed further.(1) Presented in part at the J. W. MoBain Memorial Symposium of the Division of Colloid Chemistry at the American Chemical Society meeting, Chicago, September, 1953. (2) Bristol Myers Company Fellow, 1952-1953. Present address, Shell Research Laboratories, Amsterdam, The Netherlands. 64,966 (1950). (3) H. W. Hoyer and K. J. Mysels, THISJOURNAL,

ExperimentalMethods and Materials.-The open tube method of measuring electrophoretic mobilities4 and the sodium lauryl sulfate6 and orange OT tracer6 used have all been described previously. Oil red N-1700 obtained from the American Cyanamid Co. was purified by solution in acetone and precipitation with water repeated twice and followed by double recrystallization from ethanol-benzene. Validity of the Method.-Three questions may be raised concerning the validity of our measurements. Is the mobility of the tracer accurate? Does introduction of the tracer dye modify the micelle? Does the mobility of the tracer equal that of the micelle? The first question has already been discussed in the first paper of this~ e r i e s .~ The second question, about the disturbing effect of the dye, has been partially answered reviouslya but we can add the following: ( a ) D r . H . W. koyer has found7 that two different dyes, Sudan IV and Nile black, give the same mobilities (3.52 and 3.51 X cm.2 v.-l aec.-l, respectively) for the micelle of 5y0 otassium laurate solutions and we have found that orange 8 T and oil red N-1700 in 3.5% solutions of sodium lauryl sulfate give the same mobilities (3.70, 3.75 and 3.74, 3.73 X cm.2 v.-1 sec.-I, respectively). It would be quite a coincidence if the disturbing effect of different dyes were significant and yet the same. (b) The fact that orange OT in saturated solution does not affect measurably the critical micelle concentration of sodium(4) H. W. Hoyer, K. J. Mysels and D. Stigter, ibid., 68, 385 (19541. (5) R . J. Williams, J. N. Phillips and K. J. Mysels, Trans. Faradny Soc., submitted. (6) K. J. Mysels and D. Stigter, THISJOURNAL, 67, 104 (1953 …… 此处隐藏：6112字，全部文档内容请下载后查看。喜欢就下载吧 ……