Nov., 1952
C R I T I C A L C O N C E N T R A T I O N OF P O T . 4 S S I l T M
~ - A I , I ~ A N ~ C : A R R O X T I , A T X ~ 958
Thus, the curves for pl plotted.against x for several values of 7 are shown in Fig. 1. and g2 can The corresponding curves for cp2, then be immediately plotted, and as an example, X I = I , pi = 3 (67) those for $1 and #2 are shown i n Figs. 2 and 3, reThen, Eq. (GG) is spec tively. ( w - 1)2(2w + 1 ) = These figures indicate that #1 always has it,s maxX (2-r) ' imum point at the entrance of the bed and decreases e x (e' - 1)2(2e5 + I ) (08) monotonously with increasing distance x, while for Since this is cubic with o,this could be solved with #2, though its maximum point also appears at the the aid of the so-called Cardan's formula, or New- entrance of the bed i n the early st,age of the process, ton's method for finding an approximat,e solution of the maximum moves gmclually do\vnstream with any given equation. In the course of this compii- time. In this wny, after some time has elapsed, t,hese two maximum points are clearly separated. tation we have frequently encountered t8hecase This is not unlike the so-called chromatographic ( w - 1)2(2w + 1 ) = e2rumin the presence of moderate 490 mp disappears, with increase in molarity of concentrations of simple salts, and it need not be soap, well below the value of the critical concentraused in neutral solution provided the dye ion retains tion established by the visual procedure developed a charge opposite in sign to that of the long-chain by Corrin, Klevens and HarkinsZ3and described i n ion. The dye met'hod thus is applicable to slightly this report. However, even in the absence of maxima, the optical density a t 490 mp falls rapidly (14) J. W. McBain and Sister -4.A . Green, J . A m . Chem. Soc., 68, in the same concentration range a t which the 1731 (1946). (15) J. W. MrBain, M. E. Laing and A. F. Titley, J . Chem. Soe., 115, values of log lo/lfor the band maxima at the two 1279 (1919). longer wave lengths show their rapid rise (Figs. (16) C. R. Bury and G. A. Parry, ibid., 026 (1935). 1-5). This molarity range is interpreted as repre(17) I
0.6-
c
U
0"
u)
c
"""-I
1.0-
5 -I W
ln
2
Potossium Octanoote in 5x Molar Pinacyonole
U
0.4-
0.0
I
I
a,
0
0 ,2 0.2-
0"
490 mp
0.6 0.8 1.0 I.: Molarity of Soap. Fig. Z.-Intensities of absorption by 10-6 molar pinacyanole a t average positions of band maxima as functions of concentration of potassium heptanoate. 0.0
0.2
0.4
filtered reaction solution was concentrated and cooled. The precipitated soap was collected and recrystallized from three to five times in absolute ethanol, until the critical concen-
Fig. 4.-Intensities of absorption by 5 X 10-5 molar pinacyanole s t average positions of hand maxinia as functions of eoncentration of potassium octanontc (hy permission of AI. L. Corrin, Uriiv. of Chicago). tration reached a constant value. Drying was effected by continuous evacuation at room temperature. 11. Preparation of Solutions .--All solutions were prepared by weighing the solute in a volumetric flask and bringing the solution to volume at 25'. A stock solution of pinacyanole chloride of ten times the molarity used in the subsequent measurements was made. I t was found convenient to stir the dye briefly in water at 40 to 45" to effect rapid and complete solution. Before the soap solutions were brought to volume, one-tenth volume of stock
Potassium Nnnanoate
concentration of dye occurred above which valucs for the critical concentration remained constant. The concentration of 5 X 1 0 - 6 molar was above tbis minimum for all soaps studied except the hexanoate, and ttic pinacyanole was used at this molarity in all dcterminat,ions from the heptanoate to the tetradecanoatc. The critical concentration of the hexanoate was measured in 10-4 molar pinacyanole. Spectrophotometric measurements were made a t the same conceiitrations of dye, and additional st,udies were conrluct,ed a t lower molarities t,o t,eveal the effetat of dye concentration also in this procedure.
in
6- 5 xlO-' Molar Pinacyanole
; 4-
.-
X
s
-0
Vol. 58
SIMONH. HERZFELID
956
1.2-
I
c
z
% 1.0-
Results The valucs for the critical coiwentrations of tthe nine potassium n-alkanecarboxylat,es from the hexanoate to the tetradecanoate as determined by visual means with pinacyanole are shown in column 3 of Table I. l'hey were computletlby means of the eqnnt,ion
Lo
f
c 0
'j 0.8-
I
al
1
0
5 0.6-
C'p
0
v)
where C, is the britical concentrat,ion in moles per liter, V , and M A are the initial volume and molarity of the soap solution, respectively, and VT is the sum of, the volumes of all solutions present at the end-point. The last signifiennt di@s in column 3 are somewhat unc,ert#ain.
0 ' 0
QJ ..-+
E 0.4-
2 0
.c" 0.2-
0"
0.01 0.0
0.1
= VAA~A/VT
TABLE I
d
0
0.2 0.3 Molarity of Soap.
Fig. 5.4ntensities of absorption by 5 x 10-6 molar pinacyanole a t average positions of band maxima a8 functionR of concentration of potassium nonanoate. pinacyanole was added. In the visual method with the short-chain soaps, the solutions were allowed to age briefly in order to let the color attain its maximum blue value. The initial molarity of soap in the visual studies was made about 1.5 times the anticipated critical value. 111. Analytical Procedures. (A) Visual Method.-A measured volume of soap-dye solution, usually 5.00 ml., was introduced into a 50-ml. volumetric flask. To this the dye solution in 1 : 10 dilution was added from a buret until the initial blue color had changed to the first definite bluepurple. This color was chosen so as to give the same critical concentration for potassium dodecanoate as that which had been obtained spectrophotometrically by Corrin, Klevens and Harkins.12 The same end-point was used in all subsequent titrations. I t was observed with light from a white fluorescent lamp through the neck of the stoppered, Thc inverted flask held perpendicular to the line of visio;. Detemperature of the room was maintained at 25 f 1 terminations were made a t least in triplicate. (B) Spectrophotometric Method.-From the absorption spectrograms of potassium nonanoate a t ten different niolarities (from 0.0539 t,o 0.2982) as det,ermined with a Beckman spect,rophotomet,er, the average positions of t)he band mnxinitt were established a t 490 f 2 mp, 561 f 1 mp, and 604 f 2 mp. The deviations from t.hese positions for t,he heptanoate and hexanoate usually were less t'han 5 mp. From the spectrograms for pot,assiuni octanoat'e as determined by C o r r i t ~ the , ~ ~average positions appear a t 489, 563 and 607 mp. Because of the rapidity with which tho transmission charmteristics of pinacyanole in a freshly prepared soap solution change, it was considered desirable to measure the opt.ical densit.ies quickly a t the average positions of t'he three bands. All measurements thus were made a t 490, 561' and 604 mp and were completed except in one series (Fig. 5, 490 mp) within three minutes after t.he soap, pinacyanole and water were brought together. The value of log I o / I as a funct.ion of soap concentrat,ion was then plotted for each band. No temperature control was made in these spect,rophotometric studies. IV. Choice of Pinacyanole Concentration.-In the visual met,hod, it was found wit,h all soaps that a minimum
.
(27) M , I.. Corrin. unpublished data. Department of Chemistry. University of Cllirago (1947).
CRITICAL CONCENTRATIONS 0~ POTASSIUM n-ALKANECARBOXYLATES A S DETERMINED BY M E A N S O F PINACYANOLE Molarity
of
pinacyanole
Seal,
Hexanoate ITeptanoate Octanoate Nonanoate Decanoate Undecanoate Dodecanoate Tridecanoate Tetradecanoate 4 From unpublished Chicago, 1947.
Critical molarity Spectrophotometric
Viuiial nietliod
method
1 x IO-' 1.49 I .o 5 x 10-5 0.780 0.55 ,401 ,27" 5 x 10-5 5 x 10-6 .20L .21 5 x 10-6 .on% .. 5 x 10-5 ,0492 .. 5 X ,0234 .. 5 10-6 ,0126 , . 5 X IOv6 ,0089 .. dat,lt by M. L. Corrin, Universit,y of
x
The influence of change in pinacyanole molarity on the indicated critical concentration is illustrated in Table 11. In the visual procedure, determinations of the critical concentrations of soaps of longer chain length than the octanoate were found to be independent of pinacyanole concentrat,ion within TABLE I1 CONCENTRATION O N T H E I N D I C A T E D CRITICAL CONCENTRATION
EFFECT OF PINACYANO1.E
Molarity
of
Soap
pinacyanole
potassium hesanoate Potawium hexanoate ' Potassium hexanoate Potassium heptanoate Potassium heptanoate PotaRsium heptanoate Potassium heptanoate Potassium octanoate Potassium octanoate Potassium octanoate Potassium octanoate
5 X 1 X 10-4 2 X IO-' 1X 2,5 X 5X 1 X lo-' 1 X 2 . 5 X 10-6 5 X 1 X 10-4
Critical molarity Speotrophotometric niethod
Visiial method
1.22 1.40 1.48
...
0.670 .780 ,780 ,340 .388 ,401 ,402
.. ..
..
0.45
..
0.55
.. * ,
.. .. ..
.
CRITICAL CONCENTRATION OF POTASSIUM n-ALKANECARBOXYLATES
Nov., 1952
957
the range employed. Corrin, Klevens and HarTABLE V kinsZ3 report a slight influence of pinacyaiiolc ABSORPTIONBY POTASSIUM IIEPTANOATE I N 5 x 10-61r coilcentration in their spectrophotometric deter- 1'INACYANOLE CHLORIDE AT AVERAGE \VAVE L ~ ~ N G TOHB S minations of the critical concentrations of potasBANDMAXIMA sium dodecanoate and sodium hexadecyl sulfate. log Io/I at log Io/I at log l o / I a t RIolatity 400 inH 561 Inp 604 nip The optical densities for pitlacyanole chloride ill 0.123 (M) 0.104 0.100 (M)" 0.300 the presence of potassium hexanoate, heptanoate .098(M) .145(M) .401 .09G and iioiianoate a t varying concentrations of soap, .500 .ooo .210(M) .320(M) both above and below the critical levels as deter.GO1 .055 .347(n1) .~~o(RI) mined visually, are given in Tables 111, IV, V and ,701 .026 .372(M) ' .738(M) VI. The underlined molarity in each table is the .7GO .025 .373(M) .779(M) maximum concentration at which a red compoiieiit .781 .024 .370 ( M ) .78G ( M ) in the color of the solution was observed visually ,801 .021 .3G4 ( 11) .78G (M) in white fluorescent light. The data are shown __ graphically in.Figs. 1, 2 , 3 and 5. Figure 4 is ,899 .021 .3G1 (&I) .802(M) taken from unpublished work of M. L. C o r r i 1 ~ ~ 7 a ( M ) denotes occurrcncc of a inasiniuni a t or near tlic These curves for the shorter-chain soaps fail to indicatcd wavc length. exhibit the rapid change in slope at the critical TABLE VI concentration that has been observed by Corrin, ABSORPTION BY POTASSIUM r\TONANUATE I N 5 x 10Iclevens and HarkinsZ3for the dodecanoate and CHLORIDE AT AVERAGEWAVELENGTHS OF tetradecanoate. Furthermore, the mid-point of PINACYANOLE BAND RfAXIMA the rapid drop or rise (Figs. 1-5) does not occur a t log l o / l a t log 10/l at log l o / [ at the same concentration as the critical value estab604 nip 490 nip 561 ~ i i p RIolarity lished by visual means. This discrepancy has not 0.0539 0.309(Rf)" 0.238 0.240 ( M ) been encountered with soaps of longer. chain leiigth. .0764 .338(M) ,210 .220 (RI) TABLE I11 ABSORPTION BY POTASSIUM HEXANOATE I N 1 X 10-4 M PINACYANOLE CHLORIDE AT AVERAGE W A V E LEKGTHS OF B A N D h/IAXIMA at log Io/I at 490 iiip 561 mp
og Io/I
Molarity
log I Q / I at 604 nip
0.285 (hI1.1) 0.153 (M)" 0.212 ( M ) 0.600 .448(M) .IG7(M) .315(M) 0.800 ,913 ( M ) .155 .G43(M) 1 .ooo ,721 ( M ) 1.252 ( M ) 1.200 ,062 1.347(M) .051 .717(M) 1.300 1.400 ,047 ,7 15 (hf ) 1. 415 ( R 4 ) ,044 .713(M) 1.448(M) 1.450 ,042 .706 ( M ) 1 . 6 5 1 (.M) 1.400 .- ._ ,040 , G98 ( A T ) 1 ,512 ( 51) 1.751 1.979 ,037 .G92 ( M ) 1.535 ( M ) a (RI) sigtiifics occurrence of a iiiasiiiiuni at ur near (Iic iiiclicalcd mavc length.
TABLE IV 1'UTASSIUM HEPTANOATE IN PIKACYANVLti CHLORIDE AT AVERAGE W A V E
ABSORPTIUNBY
1
x
10-'nr
LENGTHS OY
BANDMAXIMA hlolarit,y
0.200 ,300
I
og I d 1 a t
490
rnp
0 , 2 7 3(RZ)" ,278 ,250
log I Q / I at 561 m p
lor [ / l o at 604
nip
0.420 (nil ..I60 ( R Z ) ,478 (R4) .ti78 ( R L ) .7oti ( M ) . io3 (R2) .ti83 ( M ) .682(,12) .G78 ( M ) .663 ( M )
0 ,ti08 ( A I ) .ti76 (11) .'loo ,825 (11) ,501 . Oti8 1.258 (31) ,601 ,057 1,452( b l ) __ ,055 1.525 ( Y I ) ,700 1.527 ( M ) .760 ,054 ,780 ,053 1.532(R4) .801 1.541 (MI .052 ,899 .051 1.520 ( M ) 1.001 ,048 .598(M) 1.308(M) a ( M ) denotes exisGence of a maximum a t or near the indicated wave length.
The interpretation of ,these graphs becomes iticreasingly more difficult with dccreaxc in the oliaiii leiiglli of the soap. If the iiiolarity of soap
.lo4 .490(M) .113 .430 ( RI ) .I42 ,308 ( M ) ,169 .3Gl(M) .200 .351(R1) __ ,215 .204 , .230 .072 .298 ,031 ( M ) denotes occurreiicc or a indicatcd wave length.
.215 .215(M) .220 .227(M) .234 .255(M) .219(M) .25F(M) .303(M) .417(M) .537(M) .995(M) .G15 ( M ) 1,204 ( M ) .G58(M) 1.482(M) iiiaximuni at or near tlie
at which the most rapid change in light absorption occurs is taken as the critical concentration, the ivalues recorded in Tables I and I1 may be selected. Soaps of shorter chain length than the hexanoate were not iiicluded in this study. Micellisation of sodium pentanoate has been reported by Hess, Philippoff and Kiessig,zl on the basis of X-ray evidence, to occur a t 2.24 to 2.35 molar. Bunbury and Martin12sfrom observation of washing power, density, and conductivity, concluded that micellization was not exhibited by the alkanecarboxylates below the hexanoate. Davies and Burys came to the same conclusion from density measurements. The visual method with pinacyanole ceases to be applicable with the pentanoate. Discussion From Figs. .1-5 it is seen that the intensity of absorption a t or near 604 mp continues to increase with increasing molarity of soap after the optical densities a t the shorter wave lengths have come to essentially constant values. I t may be inferred from this that the human eye is sufficiently sensitive to light in the region of 604 mp to see a red component in the dye-soap solution until the absorption of this wave length has reached nearly its maximum intensity. Until such time as the theory of micellisation has been more completely and unequivocally (28) 11. (1914).
AI.
Dunbury and 11. E. Martin, J . C h c m Soc., 105, 417
SIMONH. HERZFELD
958
Vol. 56
worked out, i t will be difficult to reconcile the by Debye to be the energy change per CH2 group spectrophotometric and visual findings for the divided by 2.303(3kT), IC being the Boltzmaiin constant and T the absolute temperature. Comshorter-chaiii soaps. It has been found that the critical concentrations bination of this relationship with equation (3) of the homologous alkanecarboxylates, as obtained gives the energy equivalent of a single methylene by the visual method with pinacyanole (Table I), group as equal to (2.303 X 0.301 X 3 k T ) , or 2.08 k T . On a gram mole basis at 25", this becomes fit the empirical equation 1230 cal./mole. This value is 4.2% higher than log C, = a + bN (2) the increase of 1180 cal./mole for each additional in which N is the number of carbon atoms in the CH, group in the experimental heats of vaporizaalkyl. This Yelationship is shown in Fig. 6. The tion of normal alkanes.31 The difference may be laid to the decrease in the quasi-interfacial energy +0.3 1 _I I I I I I I I 1 that accompanies micellization, provided that vaporization and the separation of long chains in solutions are associated with identical energy changes. C ~ r r i i iarrives ~~ a t equation (2) from -0. I 0 SPECTROPHOTOMETRIC concepts based entirely on the law of mass action and attempts to evaluate the 'constants from con2 -0.3 siderations of the free energy changes that accomv , -I W pany micellization. 8 -0.5In Fig. 6, all critical molarities by the visual " method fall closely on the straight line defined by G -0.7 equation ( 3 ) . Corresponding values by the specIa trophotometric procedure for the six, seven and CY eight carbon homologs clearly fall below this 2 -0.9 w straight line. Deviations from the linear relationV z ship between log C, and the number of carbon -1.1 atoms have been found for the short-chain members -I of homologous groups by several earlier investigaa -1.30 tors. Scot't and Tartar,24for example, by means of t cx measuremeiits of equivalent conductivity and u -1.5density, found the linear relatioiiship to hold from decyl- to hexadecyltrimethylammonium bromide. 5 -1.7 The value of log C, for the octyl homolog, however, was observed to fall below the extrapolated line. - 1.9 For the alkanesulfonic acids, the same authors report a linear relatioilship from eleven to fourteen -2.1 carbon atoms but find that the value for the nine carbon homolog falls below the extrapolated -2.3 5 6 7 8 9 IO I I 12 13 line. NUMBER OFCARBON ATOMS I N ALKYL RADICAL. A partial explanation of the adherence of the Fig. 6.-Variation of the critical concentration of the n- soaps of shorter chain length to the linear relationalkane-carboxylates with chain length. ship between log C, and N fouird i n the presently described visual investigation may be drawn from linearity of log C, with N had been noted previously the spectrophotometric findings as represented in for several homologous series of electrolytes by Figs. 1 to 5. The curves show that for alkaneStauff ,2g by H a r t l e ~ , ~ Oby Hess, Philippoff carboxylates of fewer than nine carbon atoms, not and Kiessig,21 and by Scott and Tartar.24 Com- only do the changes in the optical densities in the putation by the method of 'least squares of the regions of the three band maxima occur over wide parameters in equation (2) from the visually deter- ranges of concentration, but the intensity of abmined critical molarities gives the following specific sorption a t 604 m,u continues to rise with increase equation for the potassium n-alkanecarboxylates in molarity of soap even beyond the critical concenlog C , = 1.70 - 0.301N tration as established by visual means. In the (3) In a homologous group of long-chain electrolytes, light of these observations, the critical conceatraprovided the chain lengths are sufficiently great, tions for the six, seven and eight carbon soaps the work done against the coulomb forces can be obtained by the visual method and shown in Table taken as independent of ,chain length. The work I appear to represent upper limits. Changes with time were noted in the color of performed by a number of chains in the transition from a free to an associated state, however, clearly freshly prepared solutions of the short-chain soaps increases linearly with the number of methylene and pinacyanole, both visually and spectrophotogroups in each chain. Debye8 has shown that this metrically. The rate of change decreased with work is a logarithmic function of C,, and it follows shortening of the carbon chain. When a 2.25 that N should he n logarit81imicfunction of C,. molar solut,ioii of potassium hexanoate with pinaThe coefficient of N in equation (2) has been shown ( 3 1 ) U. 8. Bureau of Standards. A4nierican Petroleuiii Institute Re-
,
L
(29) J . StauH, is. physik. C'hern., A183, 5 5 (1938). (30) U. S. Hsrtley. Kol(oid Z . , 88, 22 (1939).
searcli Project No. 44. (32) M . L. Corrin, J . Colloid Sei, 3, 333 (1948).
XOV.,
1952 EFFECT O F SALT ON CRITICAL CONCENTRBTIONS OF
cyanole was first prepared, it was distinctly reddishviolet. On standing, the color became blue, and the change appeared complete in about 20 minutes. With a solution of the heptanoate of above the critical concentration, the change to blue seemed complete in about 10 minutes. Spectrophotometrically, it is found that at 490 mp the iiitensity of absorption decreases with time, whereas at 561 and 604 mp the optical densities increase with time. This time effect is veiy pronounced with the six and seven carbon soaps. The wide scattering of points a t 490 mp in Fig. 5 below the indicated C, which were determined a t from three to 15 minutes after the solutions were made, illustrates
POTASSIUM
~-ALKAKECARBOXYLATES 959
the importance of the time effect. The rate of change in optical density with time varies with soap conceiitration but i n general is significant only for ' / z hour. The readings a t 490 mp may decrease by nearly 50% during that period, and at 561 and 604 mp they may increase by as much as 10%. Ultimately, due to the instability of the dye, all three bands will fade. These observations are not in disagreement with the view that micelles continue to farm for a coiisiderable time after the longchain electrolyte has been dissolved. The discrepancies between the visual and spectrophotometric results reported herein may in part be egplained by this phenomenon.
EFFECT OF SALT ON T H E CKITICAL CONCENTRATIONS OF POTASSIU3.I r i - ~ ~ L I ~ d N E C A ~ ~ B O S ~AS L ADETEKPVIINED TES BY THE CH-INGE I N COLOR OF PINACYANOLE' BY SIMOK H. HERZFELD Depcwlrnent of Chemistry, Unicersilij of Chicago, Chicago 37, tllinois Receired September. 86, 1051
It has been shown that for the potassium Ii-alkaiiecalbosylates, the critical concentration and also the rate of change of the critical concentration cvith increase in t,he concentration of added potassium chloride, are decreasiiiy I'unctions of the concentration of the salt,. The data are found to fit equation ( 1 ) in which Cp is the critical molarity atid Ci the total volunie nornialit8y of count,erion. The slope of this line is found to be essentially indepentient of chain length. Hohbs2 interprets a as a function of the thermal energy and the work of inicellc formation. Corrin3 ~ ~ U R O I that I S b is the ratio of the number of couiiterions t o that of long-chain ions in the micelle at the critical concentration, and argues that the ratio is independent of the concentration of added salt. Both Mobbs and Corrin :irrive at equations of the same forin as the empirical equatiou shown above.
Introduction Numerous workers4-14 have reported that the presence of salt increases the tendency of lougchain electrolytes to micellize. The first systematic investigation of salt effect \vas carried out by Corrin and Harkiii~,~5 who studied the effects of various inorganic salts over wide ranges of c,oncentration on both anionic and cationic long-chain electrolytes. Corrin and Harkins, within the limits of their experiments, found that these effects were independent of the valence and composition of the ion possessing a charge of the same sign as that of the aggregating ion. Ions of opposite sign were
restricted to sodium, potassium, chloride and bromide. The rate of decrease of the critical molarity, C,, with iiicreasiiig iioimality of added salt was found to diminish rapidly with rise in salt concentration. In the cases studied, the data fitted the equation
J . A m . Chem. S o r . , 61, 644 (1939). (9) H. V. Tartar and R. D. Cadle, T H IJOURVAL. ~ 4 3 , 1173 (1939) ( I O ) H. F. Walton, J . Am. Chem. Soc., 68, 1180 (1946). (11) R. S. Steams. H. Oppenheiiner. E. Simon and W. D. Harkins. J . Chem. Phys.. 15, 406 (1947). ( 1 2 ) P. Debye. .4nn. iV. Y . .4cnd. S c i . , 51, 575 (1949). (13) P.Debye and E. W. Anacker, T H I SJ C I U R S A L55, , G4.L (1951). ( I 4 1 H. A. Scheraga and J. IC. Backus. J . A m . Chem. SOC..7 3 , 5133 (1951). ( 1 . 5 ) k1. 1., Cnrrin and M '. D. Harkiiis. ib;,/,, 69, 683 (lU47).
The soap and pinacyanole were of the same lots used in the work described in the preceding report. The salt, pot,assium chloride of reagent grade, was dried at. 110". Measured volumes of soap and salt solutions of known normalit,ies, prepared a t 2 5 " , were mixed in varying rat,ios. Each mixture was brought by dilution at constant concentration of dye to t,he critical molarity in the manner employcd in the earlier work. The end-point,s usually became
log Cp = u
+ b log Ci
(1)
in which Ci is the total concentration in gram equivalents per liter of ions opposite in sign to the long-chain ion. The slope of this line was observed to vary moderately with the constitution of the micellixing ion and to remain less than one i n all cases. Merrill and GettyL6confirmed the findings (11 This investigation was carried out under the sponsorship of the of Corriii and Harkins for the case of sodium dodecReconstructioii Finanre Corporation, ORce of Rubber Reserve. i n anoate. coiiiiection with the Cover'ninent's synthetic rubber prograiii. S. H. The present investigation \vas undertaken to Herzfeid, Cheiniqtry Division, Office of Scientific Research, Air Research slid Develol~liientCoiiitiiaiid, Baltiiiiure 3, RId. study the salt effect i n a homologous series of long( 2 ) h.1. E. Hobbs, T H I SJ O U R X A L . ~675 ~ , (IUBI). chain electrolytes. The findings a t lower coiiFen( 3 ) A I . L. Corrin, J . Cu//osrl Sci., 3, 333 (lU.18). t,rations of salt have been demotiatrated to fit equa( 4 ) G . S. Hartley, Tmiix. F n r o d n y Jor., 30, 444 ( 1 0 3 4 ) . tion (l),and the slope has been shown to remain (j) R. C. Murray, i/Jid., 31, 1U9 (1935). ( G ) 0. S. Hartley and D. T;. Runiiirles, P m c . R O U .S q r . ( L O I ( C / ? I ~ )constant within the limits of accuracy of the A168, 420 (1938). method. . (7) G . S.Hartley. J . C/iem. Soc., 19G8 (1938). Experimental Methods ( 8 ) K. A. Wright. .A. D. Abbott, V. Siverts and H. 1'. Tartar,
-~
(115)
R. C. RIerrill and R. Getty, TIUSJOURNAL, 52, 774 (lY48).
