Additions and Corrections
J. Phys. Chem. B, Vol. 101, No. 19, 1997 3901
ADDITIONS AND CORRECTIONS 1994, Volume 98 Maria To1 rnblom,* Ulf Henriksson, and Molly Ginley: A Field Dependent 2H Nuclear Magnetic Relaxation Study of the Aggregation Behavior in Micellar Solutions of CTAB and SDS Pages 7048-7050. In the course of our further work we have discovered an error in the computer program for the evaluation of field-dependent relaxation measurements within the exponential size distribution model discussed on these pages. The error concerns the calculation of the geometrical parameters for the micelles in the distribution and will, under certain circumstances, lead to a gross overestimation of the average aggregation number. The radius of the infinitely long micelles is also affected by the error through the corrected values usually lie within error limits. With the fitting results from the corrected program Table 5 on page 7049 should read as follows: TABLE 5: Parameter Values from Fittings of the Exponential Distribution of Spherocylinders Described in the Text to Experimental Data for CTAB in Water or Aqueous NaBr and SDS in Water or Aqueous NaCla msalt surmsurf. factant (mol/kg) (mol/kg) CTAB CTAB CTAB CTAB CTAB CTAB CTAB CTAB CTAB CTAB SDS SDS SDS SDS SDS
0.12 0.18 0.24 0.28 0.30 0.37 0.48 0.18 0.18 0.18 0.48 0.30 0.48 0.69 0.86
0 0 0 0 0 0 0 0.017 0.030 0.045 0 0.220 0.220 0.220 0.220
〈na〉b
R∞b (Å)
Slocb
123+07 -06 142+09 -12 146+06 -05 171+09 -10 177+11 -10 220+15 -15 298+44 -35 169+09 -11 210+16 -13 248+24 -22 74+11 -04 111+11 -10 144+11 -16 180+07 -04 308+21 -20
+5.9 19.2-3.8 +0 25.7-4.1 +0 25.7-1.3 +1.1 22.1-1.1 +1.1 20.5-0.8 +0.7 18.3-0.8 +1.2 18.1-1.1 +1.2 22.8-1.6 +1.0 20.1-0.7 +1.0 17.9-1.0 +7.0 14.9-3.9 +0 21.9-0.6 +0.7 21.2-1.2 +0.3 21.1-0.2 +0.5 20.2-0.5
+0.002 0.178-0.002 +0.003 0.177-0.002 +0.001 0.182-0.001 +0.002 0.182-0.002 +0.002 0.183-0.002 +0.002 0.186-0.002 +0.004 0.186-0.004 +0.002 0.181-0.002 +0.002 0.183-0.002 +0.002 0.186-0.003 +0.003 0.158-0.005 +0.004 0.168-0.004 +0.004 0.169-0.003 +0.001 0.169-0.001 +0.003 0.169-0.003
rms τf b dev (ps) (%) 35+1 -1 36+2 -2 36+1 -1 37+2 -2 37+2 -1 38+1 -1 39+3 -3 38+1 -2 38+2 -1 39+2 -2 27+2 -1 26+2 -2 27+2 -2 27+1 -1 30+1 -2
1.2 1.9 1.0 1.5 1.5 1.3 2.7 1.5 1.6 1.8 1.3 2.3 1.3 0.4 1.0
a The lateral diffusion coefficients were held at 76 × 10-12 m2 s-1 for CTAB and 140 × 10-12 m2 s-1 for SDS. The radii of spherical aggregates where held constant at the lengths of the all-trans hydrocarbon chain plus headgroup, i.e., 25.7 Å for CTAB and 21.9 Å for SDS. b The error limits represent 90% confidence intervals and were determined with Monte Carlo calculations (100 repetitions).
The quality of the fittings is still as good as for those presented in Figure 5 on page 7049, but the fitting results given in the figure caption must be corrected. The correct results for 〈na〉 and R∞ are given in the corrected Table 5. Though these aggregation numbers differ considerably from those originally presented, most of the conclusions drawn in the paper are still relevant. In order to obtain good fittings, there is still a need for a decrease in radius for long micelles, and the results are still very insensitive to the functional form of this decrease. They are also very insensitive to to the exact form of the aggregation number distribution. The average aggregation numbers for the CTAB samples are, however, no longer much higher in the distribution model than in the monodisperse models. In most cases the differences are within
3902 J. Phys. Chem. B, Vol. 101, No. 19, 1997
Additions and Corrections
error limits. With the corrected program there is also a significant dependence of the resulting average aggregation number on the value the lateral diffusion coefficient is held at in the fittings. An increase in Dlat give an increase in the resulting 〈na〉 of the same relative magnitude. The fittings still begin to fail when Dlat is increased to 110 × 10-12 m s-1. In consequence of the errors in aggregation numbers Figures 6-9 are also erroneous. The corrected figures are included here.
Figure 6. Resulting unnormalized aggregation number distribution functions of the fittings presented in Figure 5: (s) 0.12 m CTAB, (- - -) 0.28 m CTAB, (- ‚ -) 0.37 m CTAB, and (‚‚‚) 0.48 m CTAB.
Figure 8. Growth in the average aggregation number, 〈na〉, with the addition of NaBr to a 0.18 m CTAB solution.
Figure 7. Average aggregation number, 〈na〉, as a function of the molality of the surfactant for the CTAB/H2O system.
Figure 9. Average aggregation number, 〈na〉, as a function of the molality of the surfactant for SDS in 0.22 m NaCl.
1996, Volume 100 N. R. Gleason and D. R. Strongin*: Water Adsorption and Thermal Decomposition on FeAl(110) Page 18837. Acknowledgments were inadvertently omitted. The acknowledgments should read as follows. D.R.S. gratefully acknowledges support of this research from the National Science Foundation (DMR-9258544). Research carried out in part at the National Synchroton Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences.
