Noms
574
(a) the four equations of the above form for aI and at in phase A and in phase B. (b) a l A = UIB, UZA = UZB, XZA = 1, 51B X?B = 1 (c) 516 VIA ‘PzA = 1, (PIB f ‘92B = 1
+ +
+
By combining these, one may obtain the equatioii (2)
Rotariull at the suggestion of the senior author, applying the same reasoning, but starting with ai1 equation different from eq. 1, derived a similar equation, but one in which composition is expressed in volume fractions only, now known to be inferior to eq. 1. Substituting into this equation the molal volumes VI = 108.5 cc., ~7~ = 359 cc., the mole fractions according to Table I, and the corresponding volume fractions, gives & - 6 2 = 3.08. The &values from energies of mporization give 61 8 2 = 8.2 - 5.9 = 2.3. This mixture adds another to the many examples2 of mixtures of an aliphatic hydrocarbon and a fluorocarbon that are mutually less soluble than their solubility parameters would indicate according to eq. 1. I n phase B, x1 is 0.997, and a1 = I in both phases, hence we can calculate 8 2 - 61 for phase A by means of ey. 1. The result is 3.02, practically identical with the figure aboye, calculated by eq. 2. This work has been supported by a grant from the National Science Fouiidation. (1) G. J. Rotanu, R . J. Hanrahan and R. E. Fruin, J . Am. Chem. Soc., 76, 3752 (1954). (2) (a) J. H. Hildebrand, J . Chem. Phpis., 18, 1337 (1950); (b) J. B. Hickman, J . Am. Chem. Soc., 77, 6154 (19.55).
ULTRACENTRIFUGAL DETERJIINATION OF T H E MICELLAR CHARACTER OF KOK-IONIC DETERGEST SOLUTIOKS. I11 BY C. IT. DWIGGIKS, JR.,AND R. J. AOLEN Baitlesvzlle Petroleum Research Center, Buleau o f Mznes U. S. Department of the Inteisor, Bartlesczlle, Oklahoma Recstved October 66,1961
Determiiiatioiis of micellar molecular weights of non-ionic detergents in aqueous solutions by ultraceiitrifuga1132and light-~cattering~-~ methods have shown t>hat micellar molecular weights are highly dependent upon the types of detergents studied. In addition, ultracentrifugal studies have shown that the micellar molecular weights are highly dependent on the temperature2of detergent solutions. Thus it is likely that micellar molecular weights are dependent on the ethylene oxide chain length of the detergent molecules. The usual polyoxyethylated alkylphenol detergents are available as high-purity surfactants, but such detergents usually have a rather wide (1) C. W. Dwiggins, Jr., R. J. Bolen and H. N. Dunning, J. Phye. Chem., 64, 1175 (1960). (2) C. W.D-tggins, Jr., and R. J. Bolen, sbzd., 66, 1787 (1961). (3) 4. 51. Mankowich, zbzd., 68, 1027 (1954). (4) P.Debye, zbad., 61, 18 (1947). ( 5 ) P. Debye, J . Appl. Phye., 16, 338 (1944). (6) M. J. Schick, F. R. Eirich and S.M. Atlas, ”hIlcellar Structure of Nonionio Detergents,” 139th Kational Meeting, Amerlcan Chemical Society, St. Louis, Missouri, March, 1961.
Vol. 66
distribution of numbers of ethylene oxide groups. Polyoxyethylated alkylphenol detergents having no chain length distribution are very difficult to obtain, but fractions having much narrower chain length distributions than the detergents available commercially may be obtained by molecular distillation.’ Several properties of molecular distillation fractions of a polyoxyethylated nonylphenol detergent were ~ t u d i e d ,and ~ physical properties were significantly different for each detergent fraction. After these fractioiis became available, it was decided to study the effect of ethylene oxide chain length distribution on micellar molecular weights of polyoxyethylated nonylphenol nonionic detergent. Experimental The transient-state methods-10 for molecular weight determination using the analytical ultracentrifuge aided by synthetic boundary experiments,lI and application of the theory to determination of niicellar molecular weights of non-ionic detergents in aqueous solutions were discussed in the first tx-o papers of this series and will not be repeated. One set of detergrnt fractions was obtained from a polyoxyethylated nonylphenol having an average ethylene oxide mole ratio of 9.5. These fractions were cycles 9, 10 and 11 as described by Mayhew and Hyatt7 and had average mole ratios of 8.9, 9.7 and 10.7, respectively. A second set of fractions was obtained from a polyoxyethglated nonylphenol having an average ethylene oxide mole ratio of 6.0. These fractions were cycles 12 and 13 as described in ref. 7 and had average mole ratios of 7 . 6 and 7.7, respectively. The detergent fractions have much narrower polyoxyethylene chain length distributions than the parent detergents, but it is not claimed that they have no chain length distribution. The ultracentrifuge experiments were performed in a 2.5’, 12-mm. double sector cell, and a matched capillary synthetic boundary cell as described.’,? Great care was taken to maintain constant temperature and precise alignment, to prevent convection, and to prevent biological contamination. Values of the corrected concentration gradients at the airliquid meniscus vere used to determine micellar molecular weights.1 Pycnometers were used to obtain partial specific volumes as described previously.112 The pycno:eter water-bath was maintained constant to within 0.005 . Least-squares calculations were used to evaluate partial specific volumes as described previously.1.2 The average deviation of individual specific volume data from the lines fitted by least squares ranged from 0.00001 to 0.00004.
Results and Conclusions Micellar molecular weights and partial specific volumes for the various fractions are listed in Table 1. Decreasing the number of ethylene oxide groups results in increased micellar molecular weights in aqueous solutions. It is of interest that, for the lower ethylene oxide mole ratios, very small changes in the ethylene oxide mole ratio can produce quite large changes in micellar molecular weights. Cloud-point temperatures are reduced greatly when ethylene oxide mole ratios are decrea~ed.~ It appears that cloud-points are dependent on the micellar character of the detergent solutions, but the correlation between cloud-point temperatures and micellar molecular weights may be the result of other, more basic factors. ti’) R. L. illaybew and R. C . Hyatt, J . Am. Od Chembsts Soc., 29, 357(1952). (8) T. J. Archibald, J . Phys. Chem , 61, 1204 (1947). (9) H. K. Schachman, “Ultracentrifugation in Biochemlstry,” Academio Press, New York, N. Y..1959, PP. 181-199. (10) J. 31. Peterson and R. M. hIazo, J . Phys. Chem., 66, 566 (1961). (11) S. 111. Klainer and G. Kegeles, %bid., 69, 952 (1955).
NOTES
March, 1962
575 TABLEI1
TABLE I
PROPERTIES OF DETERGENT MICELLESIN AQUEOUS SOLUP R O P E R T I E l j O F POLYOXYETHYLATED N O K Y L P H E N O L N O N O F hfOLECULa4R D I S T I L L A T I O N FRACTIOA’S IONIC DETERGEKT AS A FUXCTION OF MOLE RATIOOF ETH- T I O N S O F BLENDS OF POLYOXYETHYLATED NONYLPHESOL AT 25.00’ YLENE OXIDE AT 28.00° hv.mole ratio of ethylene oxide
I O . 7b
Canon., wt.
%
0.6255 ,6255 .6255 .9982 .9982 .9982 I ,3454 1.3454 1.3454
Time of run, min.
420 1080 1262 1110 1440 1930 1140 1830 2880
Partial speoifio volume, ml./g.
0.908
... ...
... ...
... ...
... ... Mean
9.7b
0.9939 .9939 1,3203 I.3203
1080 1320 570 1380
0.926
... .
I
.
... Mean
8.gb
0.9864 ,9864 .9864 ,9864
630 1320 1802 2880
0.9265
... ... ... Mean
7.7c
0.9623 .9623 1.0386
1440 1680 1440
0.932
...
... Mean
7.6”
1.0343 1.0343 1,0343
1440 2400 3300
0.932 I
.
.
...
W t . % of0
Micellar mol. w t . , n x 10-4
7.6 mole ratio In blend
Time of run, min.
See Table I
0
4.54 4.69 4.44 4.46 4.69 4.68 4.55 4.95 4.84
Kt. ofb blended detergent
0.9347 ,9347 .9347
25.4
1110 1920 2880
Partial specific volume, rnl./g.
Mean 0.919
... ...
0.9165 ,9165 ,9165
50.1 50.1 50.1
1110 1500 1890
0,919
1110 1920 2880
0.920
... ...
4.65
-
14.4 21.7 22.4 22.5 22.2 96.3 98.5 101.3
Mean 98.7 Weight-average, anhydrous micellar molecular weights. 6 Molecular distillation fractions from detergent having 9.5 Molecmole ratio (average) of ethylene oxide; see text. ular distillation fractions from detergent having 6.0 mole ratio (average) of ethylene oxide; see text.
6.43 6.40 6.40 6.41
12.6 12.3 12.2
Mean 12.4
7.12 7.12 6.98 6.68
14.3 14.7 14.2 14.6
4.65
__
Mean
__
6.97
Micellar mol. wt., x 10-4
1.0150 1.0150 1.0150
75.3 75.3 75.3
... ...
33.0 33.0 33.1
Mean 33.0 Mean 98.7 See Table I 100 A series of mixed detergents was prepared by blending two of the molecular distillation fractions of polyoxyethylated noriylphenol. The fractions had ethylene oxide mole ratios of 10.7 and 7.6. The fractions were obtained from parent detergents having average ethylene oxide mole ratios of 9.5 and 6.0, respectively. Weight percentages of the blended detergents, of composition given in the first column, present in the aqueous solutions. Q
tergents having propertirs most desirable for specific applications. Acknowledgment.-The authors wish to thank the General Aniline and Film Company and especially Drs. R. L. b4ayhem and R. C. Hyatt for making detergent fractions available for this investigation.
0
Micellar molecular weights arid partial specific volumes of aqueous solutions of mixtures of two of the molecular distillation fractions are listed in Table I[. These results indicate that the detergent molecules having higher ethylene oxide mole ratios iiifluence the resultant micellar inolecular weights of mixtures of detergent fractions more than detergent molecules having lower ethylene oxide moL1 ratios. The departure from linear dependency of micellar molecular weight on composition is large. Thrse studies suggest that changing the ethylene oxide chain length distribution of polyoxyethylated nonylphenol detergents may produce significant variations in the micellar character of the detergent solutions. It thus is possible that changes in manufacturing conditions that produce significant variations iii the shape of the chain length uersug concentration curve as well as changes that produce variations in the average molecular weight may be of importance for synthesis of de-
MASS SPECTROGRAPHIC DETECTIOS OF MOLECLLAR SPECIES IN GROUP 111-V COXPOUNDS BY
h.J. 11HEa4RN A h D
c. I). T H U R M O X D
Bell TPlephone Laboratoizes, Inc., J l u i r a y Hall, X e i u Jersey Rccezbed October 25, 1961
Mass spectroscopy is being employed with increasing frequency in the analysis of solids. For general analytical work, the vacuum spark between electrodes of the sample is proving to be a quite satisfactory positive ion source. This is a high voltage device (50-100 kv.) and produces not only multiply charged atomic ions but also ions of molecular species. For instance, singly charged clusters as large as nine silicon atoms corresponding to mass 252 have been recorded. The high sensitivity for the detection of trace components makes the vacuum spark mass spectrograph a useful instrument for the detection and identification of molecular species despite probable fragmentation of such species by the high voltage (1) R. Brown, R. D Cralg, J. A. James, and C. XI. Wilson, Conferenoe on the Ultrapurification of Semieonductor Materials, Boston Massachusetts, April, 1961.
