Thermodynamic Behavior of Electrolytes in Mixed Solvents

8 Effects of Salts Having Large Organic Ions on Vapor-Liquid Equilibrium JOHN A. BURNS and WILLIAM F. FURTER

1

Downloaded by UNIV OF ARIZONA on March 11, 2017 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0155.ch008

Department of Chemical Engineering, Royal Military College of Canada, Kingston, Ontario, Canada, K7L 2W3

The salt effects of potassium bromide and a series of five sym metrical tetraalkylammonium bromides on vapor-liquid equi librium at constant pressure in various ethanol-water mixtures were determined. For these systems, the composition of the binary solvent was held constant while the dependence of the equilibrium vapor composition on salt concentration was in vestigated; these studies were done at various fixed composi tions of the mixed solvent. Good agreement with the equation of Furter and Johnson was observed for the salts exhibiting ei ther mainly electrostrictive or mainly hydrophobic behavior; however, the correlation was unsatisfactory in the case of the one salt (tetraethylammonium bromide) where these two types of solute-solvent interactions were in close competition. The transition from salting out of the ethanol to salting in, ob served as the tetraalkylammonium salt series is ascended, was interpreted in terms of the solute-solvent interactions as relat ed to physical properties of the system components, particular ly solubilities and surface tensions.

nphe

a d d i t i o n of salts to a l i q u i d m i x t u r e to a i d i n the

separation

A of the components of that m i x t u r e by fractional distillation has important implications i n terms of theoretical studies a n d practical applications. T h e complexity of the salt effect i n v a p o r - l i q u i d e q u i l i b r i a and the sparse conclusive work i n this field are largely responsible for the limited applications it has received industrially, despite a potential for d r a m a t i c a l l y i m p r o v e d separation performance i n certain systems. N o t only is the effect of the salt on a system complex, but variations occur f r o m system to system; that is, each system is unique. In addition, the nature of the effects, as w e l l as their magnitudes, tends to be c o m 1

To whom correspondence should be addressed.

99

Furter; Thermodynamic Behavior of Electrolytes in Mixed Solvents Advances in Chemistry; American Chemical Society: Washington, DC, 1976.

100

THERMODYNAMIC BEHAVIOR OF ELECTROLYTES


position dependent, even w i t h i n a given system. Consequently, the scope of the salt effect even o n binary, let alone m u l t i c o m p o n e n t , systems becomes astronomical. Despite the many proposals submitted, no one theory has yet been able to predict satisfactorily the effects of salts o n v a p o r - l i q u i d e q u i l i b r i a f r o m pure-component properties alone. If a treatment applies for a certain type of salt, e.g., inorganic, then it fails i n the case of others, e.g., the tetraalkylammonium ( T A A ) salts of the present investigation. Regardless, compensating factors a i d i n producing convenient behavioral trends for w h i c h plausible explanations can be tendered a n d e m p i r i c a l generalizations noted. In this w a y it is possible to s i m p l i f y an otherwise unmanageable situation. Applications of salt effects to both v a p o r - l i q u i d a n d l i q u i d - l i q u i d phase equilibria were reviewed i n 1958 b y Prausnitz and Targovnik (1). M o r e recently several authors (2, 3, 4) have offered comprehensive treatises of salt effects o n nonelectrolytes i n mixed-solvent solution; however, most studies have been c o n f i n e d to effects of salts o n activity coefficients a n d solubilities of the nonelectrolyte in aqueous solution. In some cases, a detailed mathematical treatment has been a p p l i e d to those salt effects (4,5, 6). A n extensive review of the literature of salt effect i n v a p o r - l i q u i d e q u i l i b r i u m a n d distillation processes prior to 1966 has been c o m p i l e d b y F u r t e r a n d C o o k (8) w h o list over two h u n d r e d references. Previously, studies have concentrated on saturated solutions of mainly inorganic salts i n b i n a r y solvent mixtures (9-15). S i m i l a r experiments using a fixed salt concentration below saturation have been reported (16,17). L o n g and M c D e v i t (7), and more recently Gubbins and T i e p e l (5), reviewed the salt effects of aqueous solutions of tetraalkylammonium ( T A A ) halides. These authors report that the T A A cations salt i n most nonelectrolytes, and this effect becomes more pronounced as the size of the T A A cation increases, as opposed to salting-out of these solutes b y most other electrolytes. T h i s observed behavior has been accounted for by either an influence on water structure (18) or association between the ion a n d the nonelectrolyte (18, 19, 20). T h i s latter tendency of nonpolar groups to adhere to one another i n a n aqueous environment has become k n o w n as h y d r o p h o b i c b o n d i n g (21). F r o m t h e r m o d y n a m i c considerations a n d after a sequence of s i m p l i f y i n g assumptions has been a p p l i e d , i n c l u d i n g those of constant temperature a n d pressure, an equation for the salt effect i n v a p o r - l i q u i d equilibria under conditions of constant mixed-solvent composition has been derived (22,23). T h e equation, i n its simplest f o r m , reduces to \n^ = kz. a

(1).

This equation relates a so-called "improvement factor/' the logarithm of the ratio of relative volatility w i t h and without salt present, to the salt concentration i n the l i q u i d phase under the c o n d i t i o n of f i x e d mixed-solvent composition, b y a salt effect parameter k. Usually, the a d d e d salt lowers the volatility of both components i n the l i q u i d phase. If the extent of this l o w e r i n g is different for


8.

BURNS A N D FURTER

Salts Having Large Organic Ions

101


the two volatile components, as is usually the case, there w i l l be an enhancement of one component and depletion of the other i n the equilibrium vapor phase, that is, an alteration in vapor composition caused by the addition of the salt. Equation 1 also appears to a p p l y (8, 12, 24) to some ternary systems even if the l i q u i d composition is varied. ( H o w e v e r , under such conditions E q u a t i o n 1 w o u l d become p r i m a r i l y e m p i r i c a l a n d lose m u c h of its theoretical significance.) Also, k has been f o u n d to vary w i t h the system a n d the temperature (23,25). O f the many systems investigated, few studies involved the simpler conditions of constant l i q u i d composition w h i l e v a r y i n g the salt concentration. These are precisely the conditions to w h i c h E q u a t i o n 1 should be applied, but there are other factors involved (for example, temperature, pressure, solute-solute interactions). Nevertheless, it is possible to explain certain salt effect trends i n general terms by the physical nature of the components involved i n the m i x t u r e , although i n consistencies with such generalities exist (15). Other relations have been devised to correlate more adequately the salt effects on v a p o r - l i q u i d e q u i l i b r i a under conditions of v a r y i n g l i q u i d composition (26, 27), but either the c o m p l e x i t y or the e m p i r i c a l nature of the resulting equations limits their usefulness. Recently Jaques a n d F u r t e r (28) reported results under suitable conditions to w h i c h E q u a t i o n 1 should a p p l y rigorously, a n d they observed that the equation was indeed satisfactory for additions of s o d i u m b r o m i d e , a m m o n i u m chloride, a n d sodium chloride to ethanol-water mixtures, a n d for the c a l c i u m c h l o r i d e methanol-water system. H o w e v e r , for these systems the solubilities and boiling point elevations at the l i q u i d composition values used were not large. Burns and F u r t e r (29) f o u n d similar results for the potassium b r o m i d e - , a m m o n i u m brom i d e - , a n d potassium i o d i d e - ethanol-water systems, but the correlation was unsatisfactory for potassium a n d s o d i u m acetates i n ethanol-water mixtures. Alcohols exhibit a bif unctional nature i n aqueous solution. O n the one hand, there exists a h y d r o p h o b i c h y d r o c a r b o n group w h i c h resists aqueous solvation; on the other, there is the hydrophilic h y d r o x y l group w h i c h interacts intimately w i t h the water molecules. F r a n k s a n d Ives (30, 31) have r e v i e w e d e x p e r i m e n tation a n d theoretical treatises o n the structure of water, the structure of l i q u i d alcohols, and the thermodynamic, spectroscopic, dielectric, and solvent properties and P - V - T relationships of a l c o h o l - w a t e r mixtures. Sada et al. (27) r e v i e w e d , in particular, the salt effects of electrolytes i n alcohol-water systems and discussed the various correlations of the salt effect applied to these systems. Inorganic salts were used almost universally i n these salt effect studies. T h e present study investigates the effects of a series of salts while maintaining certain f i x e d factors. T h e contribution of the cation to the salt effect b y tetraa l k y l a m m o n i u m bromides (R4NBr) on the ethanol-water system w i t h the l i q u i d composition held constant is studied. These T A A cations exhibit an ambivalent nature i n aqueous solution; the smaller cations display p r e d o m i n a n t l y electrostrictive interactions (32), i.e., hydrophilic b o n d i n g or net breaking of hydrogen bonds i n water, w h i l e the larger ones display h y d r o p h o b i c b o n d i n g (33), or the net m a k i n g of hydrogen bonds i n water w h e n the salt is added. T h e salts of the


102


present investigation were chosen to complement and extend studies b y Jaques and Furter (28) and further work done by the present authors (29). They include potassium, a m m o n i u m , t e t r a m e t h y l a m m o n i u m , t e t r a e t h y l a m m o n i u m , tetran - p r o p y l a m m o n i u m , and t e t r a - n - b u t y l a m m o n i u m bromides i n ethanol-water mixtures at fixed l i q u i d composition.


Experimental T h e data were obtained by means of an i m p r o v e d O t h m e r recirculation still (34), as modified for salt effect studies by Johnson and Furter (22,35). T h e r m a l energy was a p p l i e d to the still b y means of a heating mantle controlled b y a rheostat i n order that the b o i l i n g rate could be adjusted effectively. Suppression of b u m p i n g of the solution a n d both thermal a n d physical homogeneity were m a i n t a i n e d b y means of a magnetic stirring mechanism. Analyses of salt-free aqueous ethanol mixtures were obtained using 10-ml W e l d - t y p e pycnometers. These calibrated specific gravity bottles were i m mersed i n a 20-1. water bath thermostatted to 2 5 . 0 0 ° C , for two hr before being weighed. T h e mass of the bottles was obtained using a Becker C h a i n o m a t i c Balance accurate to four decimal places. Corrections for buoyancy were applied to the weights, and a tare was utilized. Alcohol concentrations were then obtained f r o m the experimental specific gravities b y interpolation of literature data (36) w i t h the use of a five-coefficient nonlinear least squares p r o g r a m adapted to an X D S Sigma 3 computer. Salt concentrations were obtained by the addition of k n o w n weights of dried salt to the solvent mixture. The compositions of the condensed e q u i l i b r i u m vapor samples a n d the previously prepared ethanol-water charges to the still were determined as previously outlined. T h e mole fractions of the salt, ethanol, a n d water charged to the O t h m e r still were thus accurately d e t e r m i n e d b y mass balance calculations. A n h y d r o u s ethanol (99.9+ % purity), c o n f o r m i n g to the specifications of the British Pharmacopoeia, was obtained f r o m G o o d e r h a m a n d W o r t s L t d . , Toronto, Ontario. T h e potassium and a m m o n i u m bromides were British D r u g Houses A n a l a r analytical reagent grade. T h e t e t r a m e t h y l a m m o n i u m a n d tetr a e t h y l a m m o n i u m bromides were reagent grade f r o m J. T . Baker C h e m i c a l C o . , Phillipsburg, N . J. T h e t e t r a - n - p r o p y l a m m o n i u m and t e t r a - n - b u t y l a m m o n i u m bromides were purchased f r o m Eastman K o d a k C o m p a n y , Rochester, N . Y. A l l salts were d r i e d for at least 72 h r i m m e d i a t e l y prior to use i n a v a c u u m d r y i n g oven; the temperature during d r y i n g depended on the thermal stability and fusion point of the salt. T h e d r y i n g temperature was adjusted to 120° C for the a m m o n i u m a n d potassium bromides, 1 0 0 ° C for t e t r a m e t h y l a m m o n i u m b r o m i d e , 9 0 ° C f o r t e t r a e t h y l a m m o n i u m b r o m i d e , 7 5 ° C for t e t r a - n - p r o p y l a m m o n i u m bromide and 6 5 ° C for t e t r a - n - b u t y l a m m o n i u m bromide. T h e d r i e d salts were stored under vacuum over P2O5. Laboratory distilled water was further purified


8.

BURNS A N D FURTER

103


by distillation over basic permanganate followed by an ion exchange treatment through a 38-cm C o r n i n g c o l u m n . T h e surface tension measurements were obtained w i t h a Precision C e n c o d u - N o u y Tensiometer, N o . 70540.

T h e solvents and saturated solutions were

prethermostatted to 2 5 . 0 ° C prior to each measurement.

T h e temperature of

the solutions was determined subsequent to the measurements, and adjustments were made to coincide w i t h a temperature deviation f r o m 2 5 . 0 ° C . producible values were retained.

O n l y re-

R/r and L for the p l a t i n u m r i n g used for the

surface tension measurements were 53.6 and 5.997 c m , respectively.

T h e factor


F , w h i c h corrects for l i q u i d elevated above the free surface of the l i q u i d by the ring i n the relationship y = M g / 2 L X F , was determined (37) for each particular solvent. T h e solubility studies were conducted g r a v i m e t r i c a l l y after the solutions were frequently shaken vigorously and m a i n t a i n e d at 2 5 ° C for 24 hr.

Results T h e data i n Tables I - X V I (see A p p e n d i x for all tables) show the isobaric v a p o r - l i q u i d e q u i l i b r i u m results at the boiling point for potassium, a m m o n i u m , tetramethylammonium, tetraethylammonium, tetra-n-propylammonium, and t e t r a - n - b u t y l a m m o n i u m bromides i n various ethanol-water mixtures at f i x e d l i q u i d composition ratios. T h e temperature, t, is the b o i l i n g temperature for all solutions i n these tables. In all cases, the ethanol-water composition was held constant between 0.20 and 0.35 mole fraction ethanol since it is i n this range that the most dramatic salt effects o n v a p o r - l i q u i d e q u i l i b r i u m i n this particular system should be observed. That is, previous data (12-15,38) have demonstrated that a m a x i m u m displacement of the v a p o r - l i q u i d e q u i l i b r i u m curve b y salts frequently occurs i n this region. In the results presented here, it should be noted that E q u a t i o n 1 has been m o d i f i e d to \og * w

CX

= k'z

(2)

where k' = it/2.303. Tables I V - X V I show that the tetraalkylammonium salts have a large effect on both solvents i n the binary solvent mixture, especially the larger tetraalkyla m m o n i u m bromides, i.e., ( n - C s H ^ N B r a n d (n-C4H9)4NBr. T h i s can be seen f r o m consideration of the b o i l i n g temperature alone. T h i s observation is also borne out by the surface tensions and solubilities at 25 ° C of the i n d i v i d u a l salts studied, the results of w h i c h are tabulated i n T a b l e X V I I i n water, i n ethanol, and i n an ethanol-water mixture at x = 0.206. F o r the higher homologs of the R 4 N B r series, these salts exert a large effect on the surface tensions of the solvent systems studied and show a m a r k e d increase i n their solubility i n ethanol.



104

THERMODYNAMIC

BEHAVIOR

OF

ELECTROLYTES

B y a n a l y z i n g the results shown i n T a b l e X V I I I and perusing Figures 1-12, the validity of a p p l y i n g E q u a t i o n 2 to the p r e d i c t i o n of the salt effects of the R 4 N B r salts at various fixed values of x for the ethanol-water system can be assessed. Figures 1-12 indicate the smoothed curves through the experimental points for the salt effects. F r o m these graphs a value for the salt effect parameter, k\ c o u l d be obtained; however, i n some instances it is d i f f i c u l t to justify a linear plot of logio OLJOL VS. Z (Figures 7, 8, 9). T h e values of k' i n T a b l e X V I I I were determined by means of a linear least squares calculation a n d i n some cases, as noted i n Figures 2, 5 - 8 , 1 1 , the intercept does not pass through the origin. Also i n Figures 1-5, 9 the salt additions were m a d e to saturation a n d the results are denoted by the sharp fall off of the graphical plot, or depicted by the dotted line in some instances. T h e relative average absolute deviation listed i n Table X V I I I is a numerical assessment of the feasibility of a p p l y i n g E q u a t i o n 2 to the systems studied. As previously mentioned, the values of k for the ternary systems were calculated w i t h a linear least squares plot of the experimental data. T h e average absolute deviation of log aja was then calculated by averaging the absolute deviations of the smoothed curve passing through the experimental points f r o m the linear least squares calculation, at f i x e d intervals of z. T a k i n g this average absolute deviation of log N a > N H + (CH ) N+ > ( C H ) N > ( n - C H ) N + > ( n - C H ) N + . F o r the anions, the order is C l " > B r ~ > I~ > ~ O A c . These sequences show that the salting out decreases w i t h ion size (compare Table X X ) and increasing ability of the ion to alter the degree of structure i n water (hydrophobic bonding). T h e ionic radius for - O A c w h i c h appears i n T a b l e X X was calculated b y means of the m e t h o d of C o n w a y et al. (57), accounting for the dead air space, a n d a partial m o l a l v o l u m e at i n f i n i t e dilution of 46.46 c m m o l e (53). The two inconsistent results i n the above series for cations are: (a) that k + > fc + w h i c h m a y be due to the ability of the water molecules to f o r m solvent co-spheres about the K ion more easily than the N a ion; and (b) that &NH + — ^ ( C H ) N w h i c h m a y be a result of the dissipation of charge on the nitrogen because of electron donation b y the hydrogens on the NH ion or the ability of water molecules to f o r m clathrate structures around the ( C H ) N i o n ; nevertheless, the inconsistency is slight, a n d possibly the explanation lies i n subtle ion-solvent interactions. 4

4

+

+


2

5

+

4

3

7

4

4

3

9

4

3

4

4

- 1

Na

K

+

4

3

4

+

+

+

4

3

4

+

Another noteworthy observation to be gleaned f r o m the results i n Table X I X is the consistency of kc for ( C 2 H 5 ) N at the three values of x for the e t h a n o l water mixtures, whereas those for ( C H ) N a n d ( n - C H ) N increase as x i n creases. This c o u l d be interpreted f r o m the point of v i e w that for ( C 2 H 5 ) N there is a balance between the electrostrictive nitrogen charge center a n d the hydrophobic a l k y l groups, but there is not the same balance existing for the other two cations (54, 58, 59). T h e r e m a i n i n g ions i n the table do not pose the same p r o b l e m because they are p r i m a r i l y electrostrictive i n nature. 4

+

3

4

+

3

7

+

4

4

+

Conclusion In this study it was f o u n d that K B r , N H B r , a n d ( C H ) N B r were effective in salting out ethanol f r o m an aqueous ethanol solution a n d hence increasing its concentration i n the e q u i l i b r i u m vapor, and that E q u a t i o n 1 c o u l d be a p p l i e d in order to predict the salt effects of these systems. ( n - C H ) N B r a n d (nC H ) N B r were effective i n salting i n ethanol, i.e., decreasing its concentration in the e q u i l i b r i u m vapor i n ethanol-water mixtures, and again E q u a t i o n 1 was f o u n d to hold. H o w e v e r , for the systems consisting of ( C 2 H s ) N B r - e t h a n o l water, E q u a t i o n 1 was unsatisfactory, a n d the salt was a borderline case w i t h respect to its salt effects i n ethanol-water mixtures. 4

3

4

3

4

9

7

4

4

4

F r o m the results, it can be c o n c l u d e d that large perturbations of phase e q u i l i b r i a m a y be obtained w i t h relatively small salt concentrations i n certain systems, and that the salt effect is specific. Salt effects can become important


8.

BURNS

A N D FURTER

115


in a variety of separation processes and biological processes. further applications w i l l be f o u n d .

H e n c e , no doubt,

Nomenclature k k' t


X

= salt effect parameter w h e n natural logarithms are used, d e t e r m i n e d f r o m v a p o r - l i q u i d e q u i l i b r i u m studies = salt effect parameter w h e n logio is used, = fc/2.303 = temperature, ° C = mole fraction of ethanol i n the l i q u i d phase, calculated on a salt-free basis = mole fraction of ethanol i n the vapor phase

y z a

= mole fraction of salt i n the l i q u i d phase = relative volatility i n the absence of salt = relative volatility i n the presence of salt, calculated using l i q u i d

So S

compositions on a salt-free basis = solubility of a substance i n water = solubility of the same substance i n an aqueous electrolyte solution

C R

= salt effect of an electrolyte d e t e r m i n e d f r o m solubility studies = salt effect of the anion = salt effect of the cation = the concentration of the electrolyte i n the aqueous solution = mean radius of the tensiometer ring used i n the surface tension studies,

r L

cm = radius of p l a t i n u m w i r e i n the r i n g , c m = mean circumference of the p l a t i n u m tensiometer r i n g , c m

y M

= surface tension, P a m , = 1 0 = mass, g

g F

= gravitational force = correction factor for liquid elevated above the free surface of the liquid b y the r i n g = 133.3 N m " = 133.3 P a

k k

s

A

kc s

lTorr TAA P2O5

+ 3

dyne c m

-

1

2

= tetraalkylammonium = phosphoric pentoxide


116


Appendix Table I.

Isobaric V a p o r — L i q u i d E q u i l i b r i u m Data for the

Potassium Bromide—Ethanol—Water System at


x = 0.206 ± 0.001 (760 ± 5 Torr) *

y

0 0 0.0085 0.0086 0.0252 0.0500 0.0505 0.0732 0.0885 0.0915 0.0915

0.5346 0.5352 0.5484 0.5492 0.5774 0.6166 0.6180 0.6519 0.6625 0.6614 0.6640

t

83.0 83.1 83.4 83.4 83.6 83.4 83.5 83.3 83.2 83.1 83.1

iog

1 0

—

a 0.0000 0.0002 0.0241 0.0286 0.0753 0.1429 0.1486 0.2123 0.2321 0.2305 0.2355

Table II. Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a for the Potassium Bromide—Ethanol—Water System at x = 0.309 (758 ± 3 Torr) *

y

0 0 0.0100 0.0113 0.0218 0.0275 0.0344 0.0438 0.0488 0.0608 0.0687 0.0768 0.0823 0.0881 0.0992 0.1033 0.1187 (sat'd.)

0.5837 0.5844 0.5983 0.6044 0.6158 0.6233 0.6316 0.6437 0.6508 0.6634 0.6732 0.6839 0.6882 0.6943 0.7013 0.7112 0.7213

t

82.0 82.0 82.1 82.2 82.2 82.2 82.3 82.6 82.7 82.9 82.9 83.0 83.2 83.5 83.6 83.8 84.0

logmen

0.0000 0.0005 0.0263 0.0373 0.0581 0.0719 0.0873 0.1100 0.1235 0.1479 0.1670 0.1885 0.1971 0.2094 0.2238 0.2446 0.2662


BURNS A N D F U R T E R T a b l e III.


Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a f o r the

P o t a s s i u m B r o m i d e — E t h a n o l — W a t e r S y s t e m at


x = 0.311

(758

± 3 Torr) log

— a

z

y

t

0 0.0045 0.0128 0.0199 0.0230 0.0339 0.0436 0.0484 0.0577 0.0710 (sat'd.) 0.0804 (sat'd.) 0.1375 (sat'd.)

0.5839 0.5913 0.6084 0.6204 0.6228 0.6405 0.6571 0.6618 0.6755 0.6761

82.0 82.0 81.9 81.9 82.0 81.8 81.6 81.7 81.5 81.5

0.0000 0.0134 0.0442 0.0662 0.0707 0.1038 0.1354 0.1445 0.1713 0.1724

0.6792

81.6

0.1784

0.6782

81.4

0.1768

1 0

Table I V . Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a f o r the A m m o n i u m B r o m i d e — E t h a n o l — W a t e r S y s t e m at x = 0.206 (755 ± 4 T o r r ) z

y

t

0 0 0.0083 0.0110 0.0222 0.0312 0.0472 0.0600 0.0765 0.0892 0.1065 0.1144 0.1363 0.1403 0.1581 0.1588 0.1761

0.5351 0.5353 0.5439 0.5458 0.5605 0.5707 0.5877 0.6003 0.6102 0.6293 0.6394 0.6477 0.6674 0.6684 0.6770 0.6766 0.6773

83.6 83.7 83.8 83.9 84.0 84.0 84.0 84.1 84.3 84.4 84.5 84.6 84.9 85.0 85.2 85.2 85.1

iog

— a 0.0000 0.0000 0.0153 0.0188 0.0445 0.0625 0.0929 0.1155 0.1336 0.1688 0.1877 0.2044 0.2414 0.2434 0.2604 0.2595 0.2610 1 0


THERMODYNAMIC BEHAVIOR O F E L E C T R O L Y T E S


Table V . Isobaric V a p o r — L i q u i d E q u i l i b r i u m Data f o r the A m m o n i u m Bromide—Ethanol—Water System at x = 0.305 (765 ± 4 Torr) z

y

t

0 0.0129 0.0179 0.0421 0.0464 0.0691 0.0746 0.0947 0.0999 0.1189 0.1243 0.1428 (sat'd.) 0.1478 (sat'd.)

0.5791 0.5961 0.6107 0.6304 0.6339 0.6537 0.6584 0.6775 0.6832 0.6943 0.6990 0.7023

83.0 83.1 83.2 83.5 83.9 84.0 84.2 83.9 84.3 84.5 84.9 85.2

a 0.0000 0.0303 0.0568 0.0932 0.0998 0.1372 0.1463 0.1838 0.1950 0.2177 0.2273 0.2361

0.7025

85.5

0.2361

Table V I . Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a f o r the A m m o n i u m Bromide—Ethanol—Water System at x = 0.309 (758 ± 3 Torr) log

a

z

y

t

0 0.0125 0.0231 0.0252 0.0413 0.0503 0.0588 0.0778 0.0865 0.1034 0.1162 0.1305 (sat'd.) 0.1407 (sat'd.)

0.5819 0.5962 0.6117 0.6147 0.6322 0.6400 0.6477 0.6654 0.6725 0.6883 0.6970 0.7011

82.5 82.7 82.7 82.9 82.9 82.9 83.1 83.4 83.6 83.9 84.1 84.4

0.0000 0.0256 0.0537 0.0594 0.0917 0.1062 0.1210 0.1549 0.1690 0.2005 0.2183 0.2268

0.7013

84.5

0.2273

l 0


BURNS A N D F U R T E R Table V I I .


Isobaric V a p o r — L i q u i d E q u i l i b r i u m Data f o r the

Tetramethylammonium Bromide—Ethanol—Water System at


x = 0.206 (757 ± 3 T o r r ) *

y

t

0 0 0.0069 0.0086 0.0201 0.0203 0.0365 0.0389 0.0517 0.0566 0.0666 0.0742 0.0797 0.0912 0.0973 0.1108 0.1109 0.1109 0.1249 0.1384 0.1515 (sat'd.)

0.5346 0.5347 0.5416 0.5426 0.5529 0.5551 0.5683 0.5699 0.5824 0.5838 0.5882 0.5978 0.6000 0.6112 0.6128 0.6250 0.6256 0.6251 0.6346 0.6422 0.6416

83.8 83.9 83.8 83.8 84.0 84.0 84.1 84.1 84.1 84.2 84.2 84.3 84.3 84.5 84.5 84.7 84.8 84.8 85.2 85.2 85.0

Table VIII.

iog -a 0.0000 0.0000 0.0122 0.0139 0.0321 0.0359 0.0592 0.0621 0.0842 0.0867 0.0947 0.1119 0.1159 0.1363 0.1391 0.1616 0.1628 0.1619 0.1795 0.1938 0.1926 l 0

Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a for the

Tetramethylammonium Bromide—Ethanol—Water System at x = 0.305 (758 ± 3 T o r r ) z

y

0 0.0078 0.0079 0.0232 0.0277 0.0428 0.0461 0.0652 0.0710 0.0836 0.0934 0.1037 0.1117 0.1190 (sat'd.)

0.5791 0.5928 0.5926 0.6123 0.6169 0.6321 0.6348 0.6538 0.6635 0.6727 0.6819 0.6900 0.6995 0.7012

t 83.0 83.5 83.6 83.5 83.7 83.8 83.9 83.7 83.9 83.7 83.8 83.9 84.0 84.2

iog

— a 0.0000 0.0244 0.0240 0.0599 0.0683 0.0964 0.1014 0.1375 0.1562 0.1742 0.1926 0.2088 0.2283 0.2318 1 0


THERMODYNAMIC

Table I X .

BEHAVIOR

O F ELECTROLYTES


T e t r a m e t h y l a m m o n i u m Bromide—Ethanol—Water System at x = 0.309 (760 ± 4 T o r r )


t 0 0 0.0079 0.0160 0.0300 0.0341 0.0607 0.0614 0.0868 0.0924 0.1112 0.1123 0.1253 (sat'd.) 0.1257 (sat'd.)

Table X .

log

0.5819 0.5820 0.5947 0.6055 0.6217 0.6268 0.6547 0.6542 0.6790 0.6858 0.6994 0.6999 0.7089

82.0 82.0 82.2 82.3 82.3 82.3 82.6 82.7 82.8 83.3 83.5 83.5 83.6

a 0.0000 0.0004 0.0229 0.0426 0.0723 0.0817 0.1342 0.1334 0.1817 0.1955 0.2231 0.2242 0.2430

0.7056

83.8

0.2361

1 0


T e t r a e t h y l a m m o n i u m Bromide—Ethanol—Water System at x = 0.206 (758 ± 3 T o r r ) *

y

t

0 0 0.0049 0.0050 0.0126 0.0147 0.0240 0.0293 0.0377 0.0441 0.0511 0.0590 0.0642 0.0735 0.0788 0.0869 0.0933 0.1029 0.1071 0.1089

0.5346 0.5345 0.5378 0.5387 0.5406 0.5436 0.5457 0.5475 0.5495 0.5497 0.5532 0.5549 0.5563 0.5573 0.5580 0.5586 0.5592 0.5596 0.5601 0.5599

84.0 84.0 84.1 84.2 84.5 84.6 84.9 85.1 85.5 85.8 86.2 86.2 86.3 86.8 87.2 88.0 88.2 89.0 89.2 89.3

iog

a 0.0000 0.0000 0.0055 0.0071 0.0105 0.0158 0.0194 0.0225 0.0261 0.0264 0.0325 0.0355 0.0380 0.0397 0.0410 0.0421 0.0431 0.0438 0.0447 0.0444


1 0

BURNS A N D FURTER Table X I .



T e t r a e t h y l a m m o n i u m Bromide—Ethanol—Water System at


x = 0.245 (758 ± 3 T o r r ) z

y

0 0.0066 0.0159 0.0270 0.0296 0.0513 0.0523 0.0764 0.0986 0.1409 0.1796 0.2148 0.2273

0.5797 0.5810 0.5873 0.5923 0.5934 0.6013 0.6045 0.6140 0.6211 0.6293 0.6389 0.6438 0.6480

Table X I I .

t 83.0 83.0 83.3 83.6 83.8 84.0 84.3 85.6 86.8 89.8 93.5 96.3 97.7

iog

— a 0.0000 0.0023 0.0136 0.0225 0.0246 0.0388 0.0446 0.0620 0.0750 0.0903 0.1082 0.1173 0.1254 1 0


Tetraethylammonium Bromide—Ethanol—Water System at x=

0.305 (755 ± 4 T o r r )

z

y

t

0 0.0072 0.0074 0.0212 0.0217 0.0348 0.0354 0.0481 0.0485 0.0613 0.0618 0.0738 0.0745 0.0859 0.0922 0.0979 0.1090 0.1097 0.1213

0.5791 0.5878 0.5855 0.5972 0.5962 0.6059 0.6048 0.6116 0.6128 0.6195 0.6194 0.6267 0.6256 0.6322 0.6355 0.6376 0.6409 0.6424 0.6455

82.5 82.6 82.7 83.0 83.0 83.2 83.5 83.9 84.0 84.1 84.3 84.7 84.8 85.2 85.7 86.1 86.7 86.8 87.0

iog

a 0.0000 0.0156 0.0114 0.0323 0.0305 0.0481 0.0462 0.0586 0.0607 0.0731 0.0728 0.0864 0.0844 0.0966 0.1067 0.1067 0.1130 0.1157 0.1216


1 0

122

THERMODYNAMIC

Table XIII.

BEHAVIOR

OF

ELECTROLYTES


T e t r a e t h y l a m m o n i u m B r o m i d e — E t h a n o l — W a t e r S y s t e m at


x = 0.316 (758 ± 3 Torr) z

y

t

0 0.0094 0.0294 0.0460 0.0581 0.0676 0.0762 0.0834 0.1075 0.1073 0.1159 0.1636 0.2062 0.2313 0.2588 0.2804

0.5987 0.6007 0.6112 0.6246 0.6287 0.6293 0.6383 0.6383 0.6473 0.6509 0.6532 0.6671 0.6777 0.6797 0.6842 0.6892

82.0 82.3 83.0 83.7 83.9 84.0 84.2 84.5 85.8 86.1 87.5 90.0 94.8 98.5 101.0 103.4

iog -a 0.0000 0.0036 0.0227 0.0474 0.0550 0.0562 0.0729 0.0729 0.0900 0.0968 0.1013 0.1281 0.1491 0.1530 0.1620 0.1722 1 0

Table X I V . Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a f o r the T e t r a - n - p r o p y l a m m o n i u m B r o m i d e — E t h a n o l — W a t e r S y s t e m at x = 0.206 (758 ± 3 Torr) z

y

t

0 0 0.0034 0.0040 0.0092 0.0115 0.0164 0.0227 0.0229 0.0301 0.0338 0.0381 0.0443 0.0450 0.0485 0.0485 0.0550 0.0658 0.0754

0.5346 0.5347 0.5310 0.5317 0.5293 0.5251 0.5252 0.5187 0.5182 0.5173 0.5088 0.5060 0.5012 0.5001 0.4995 0.4961 0.4922 0.4865 0.4752

83.7 83.8 84.0 84.0 84.7 84.9 85.3 85.9 86.0 86.6 86.8 87.4 88.0 88.1 88.5 88.6 89.1 89.9 90.9

a, a 0 0 -0.0062 -0.0050 -0.0063 -0.0166 -0.0153 -0.0254 -0.0285 -0.0277 -0.0449 -0.0498 -0.0582 -0.0600 -0.0610 -0.0670 -0.0738 -0.0837 -0.1034


BURNS A N D FURTER


Table X V . Isobaric V a p o r — L i q u i d E q u i l i b r i u m D a t a f o r the T e t r a - n - p r o p y l a m m o n i u m K r o m i d e — E t h a n o l — W a t e r S y s t e m at


x = 0.305 (758 ± 3 Torr) z

y

t

0 0.0046 0.0050 0.0057 0.0112 0.0139 0.0143 0.0222 0.0228 0.0252 0.0335 0.0335 0.0357 0.0427 0.0441 0.0459 0.0532 0.0545 0.0556 0.0636 0.0666 0.0669 0.0815 0.0815

0.5791 0.5809 0.5792 0.5791 0.5793 0.5800 0.5793 0.5768 0.5760 0.5750 0.5742 0.5753 0.5728 0.5721 0.5677 0.5682 0.5648 0.5665 0.5651 0.5632 0.5619 0.5616 0.5567 0.5578

82.8 83.0 83.1 83.3 83.5 83.6 83.6 83.9 83.9 84.0 84.2 84.2 84.3 84.8 84.9 85.1 85.4 85.4 85.7 85.9 86.0 86.3 87.0 87.0

Table X V I .

iog

a 0.0000 0.0032 0.0001 -0.0001 0.0003 0.0017 0.0003 -0.0042 -0.0055 -0.0072 -0.0086 -0.0069 -0.0111 -0.0125 -0.0203 -0.0193 -0.0255 -0.0224 -0.0248 -0.0282 -0.0304 -0.0310 -0.0397 -0.0377 1 0


T e t r a - n - b u t y l a m m o n i u m B r o m i d e — E t h a n o l — W a t e r S y s t e m at x = 0.200 (762 ± 2 Torr) z

y

t

0 0.0017 0.0048 0.0116 0.0197 0.0283 0.0344 0.0453 0.0522 0.0522

0.5253 0.5263 0.5170 0.5040 0.4937 0.4752 0.4547 0.4403 0.4281 0.4291

83.9 84.0 84.2 84.8 85.3 86.5 87.7 88.3 89.1 89.0

a 0.0000 0.0018 -0.0145 -0.0370 -0.0549 -0.0872 -0.1229 -0.1482 -0.1697 -0.1679


124

THERMODYNAMIC

BEHAVIOR

OF

ELECTROLYTES

Table X V I I . Physical Properties o f Saturated Solutions of Potassium Bromide and Various Tetraalkylammonium Bromides in Water, E t h a n o l , a n d 0 . 2 0 6 M o l e F r a c t i o n E t h a n o l - W a t e r at 2 5 ° C .

Solvent

Surface Tension Pa m x i O (±0.2)

Salt

H 0

72.0 73.4 60.7 56.0 54.6 51.2 42.2 22.3 22.3 22.4 22.3 25.6 27.2 29.2 30.5 29.5 31.3 30.3 36.7 36.6 41.0

2

KBr NH Br (CH ) NBr (C H ) NBr (n-C H ) NBr (rc-C H ) NBr 4

3

4


2

5

4

3

7

4

C,rLOH

4

9

4

KBr NH Br (CH ) NBr (C H ) NBr (n-C H ) NBr (n-C H ) NBr 4

3

4

2

0.206 m . f .

5

4

3

7

4

4

9

4

a

KBr NH Br (CH ) NBr (C H ) NBr (n-C H ) NBr (n-C H ) NBr 4

3

4

2

s

4

3

7

4

4

9

4

Solubility m

3

(mol

kg' ) 1

z

5.6 ± 0.1 8.0 ± 0.2 6.3 ± 0.2 15.0 ± 0.2 10.4 ± 0.2 >15

0.092 0.126 0.102 0.213 0.158 0.213

0.01 0.33 ± 0.02 0.02 ± 0.01 2.8 ± 0.1 5.0 ± 0.1 10.5 ± 0.3

0.0004 0.015 0.0009 0.114 0.187 0.326

1.9 3.5 2.3 10.3 8.3 13.5

0.043 0.076 0.052 0.196 0.164 0.242

± ± ± ± ± ±

0.1 0.2 0.2 0.2 0.2 0.3

0.206 mole fraction C H 0 H - H 0 is 44.8% C H 0 H by volume.

a

2

s

2

2

5

Table X V I I I . Salt E f f e c t Parameters a n d Reliability o f E q u a t i o n 1 to Predict the Salt E f f e c t f o r Potassium B r o m i d e a n d Tetraalkylammonium Bromides i n Ethanol—Water Mixtures at V a r i o u s V a l u e s o f x R.A.A.D* k' X Salt (%) 1.3 KBr 2.89 ± 0.04 0.206 2.5 3.02 ± 0.09 0.311 3.9 NH Br 1.61 ± 0.07 0.206 3.0 1.67 ± 0.06 0.246 5.8 1.83 ± 0.10 0.305 4.5 1.94 ± 0.11 0.309 1.3 1.44 ± 0.03 (CH ) NBr 0.206 2.4 1.97 ± 0.06 0.305 5.9 1.98 ± 0.10 0.309 4

3

4


8.

BURNS A N D F U R T E R

Salts Having Large Organic

Table X V I I I . Salt 2

s

(rc-C H ) NBr 7

4

(n-C H ) NBr 4

9

4

R.A.A.D." (%) 10.6 11.1 11.5* 11.5 1.3 9.3 1.6

k'

0.206 0.245 0.305 0.316 0.206 0.305 0.200

4

3

(Continued)

X

(C H ) NBr

125

Ions

0.41 0.58 0.75 0.65 -1.34 -0.53 -3.33

± ± ± ± ± ± ±

0.07 0.07 0.10* 0.08 0.03 0.03 0.10

R . A . A . D . is the relative average absolute deviation (see Results). * These values are approximated for purposes of comparison since this system was investigated only to z = 0.12 as compared with 0.27 for the other ( C H ) N B r - E t h a n o l Water systems (see Results).


0

2

5

4

Table X I X . C o n t r i b u t i o n s o f V a r i o u s Ions to the Salt E f f e c t Parameter Ion Contributions

0

Salt

k'

KBr NH C1 NH Br (CH ) NBr (C H ) NBr (n-C H ) NBr (>i-C H ) NBr NaCl NaBr KBr KOAc NH C1 NH Br (CH ) NBr (C H ) NBr KBr KI NaOAc KOAc NH C1 NH Br (CH ) NBr (C H ) NBr (n-C H ) NBr

2.89 2.30* 1.61 1.44 0.41 -1.34 -3.33 3.54^ 2.90^ 2.95^ 2.11 2.30* 1.67 1.70 0.58 3.02 2.33 2.05 2.25 2.20 1.90 1.98 0.65 -0.53

4

4

3

2

4

5

4

3

7

4

4

9

4

4

4

3

2

4

5

4

4

4

3

4

2

s

3

4

7

4

kc 1.50 0.21 0.21 0.05 -0.98 -2.73 -4.72 1.45 1.45 1.50 1.50 0.21 0.22 0.25 -0.97 1.50 1.50 1.30 1.50 0.20 0.20 0.46 -0.97 -2.05

Based on the convention that &c = k/Jor KBr; that is ky+ = 1.50. * Interpolated from work presented in Reference 28. Averaged from work presented in Reference 28. ^Interpolated from present work.

a

c


k 1.39 2.17 1.39 1.39 1.39 1.39 1.39 2.09 1.45 1.45 0.61 2.09 1.45 1.45 1.45 1.52 0.83 0.75 0.75 2.00 1.52 1.52 1.52 1.52 A

126

THERMODYNAMIC

Table X X . Ion Na K NH + (CH ) N+ (C H ) N (n-C H ) N (n-C H ) N+ cr Br r OAc +

+

4

3

4

2

5

3


4

+

4

7

9

4

4

+

BEHAVIOR

OF

ELECTROLYTES

F o r m a l R a d i i o f V a r i o u s Ions at 25°C i n A Radii 0.96 1.33 1.45 2.85 3.48 3.98 4.37 1.79 1.96 2.20 2.25

Reference 55,56 55,56 55,56 57 57 57 57 55,57 55,57 55,57 (see Discussic

Literature Cited 1. 2. 3. 4.

Prausnitz, J. M., Targovnik, J. H., Ind. Eng. Chem. Data Ser. (1958) 3, 234. Battino, R., Clever, H. L., Chem. Rev. (1966) 66, 395. Sergeeva, V. F., Russ. Chem. Rev. (1965) 34, 309. Conway, B. E., Desnoyers, J. E., Smith, A. C., Philos. Trans. R. Soc. London (1964)

5. 6. 7. 8. 9.

Gubbins, K. E., Tiepel, E. W., Ind. Eng. Chem. Fundam. (1973) 12, 18. Tiepel, E. W., Ph.D. Thesis, University of Florida, 1971. Long, F. A., McDevit, W. F., Chem. Rev. (1952) 51, 119. Furter, W. F., Cook, R. A., Int. J. Heat Mass Transfer (1967) 10, 23. Costa Novella, E., Moragues Tarraso, J., An. R. Soc. Esp. Fis. Quim Madrid (1952) 48B, 441. Ramalho, R. S., Edgett, N. S., J. Chem. Eng. Data (1964) 9, 324. Yoshida, F., Yasunishi, A., Hamada, Y., Chem. Eng. Tokyo (1964) 28, 133. Meranda, D., Furter, W. F., Can. J. Chem. Eng. (1966) 44, 298. Meranda, D., Furter, W. F., AIChE. J. (1971) 17, 38. Meranda, D., Furter, W. F., AIChE. J. (1972) 18, 111. Meranda, D., Furter, W. F., AIChE. J. (1974) 20, 103. Dobroserdov, L. L., Il'yina, V. P., Tr. Leningr. Tekhnol. Inst. Pishch. Prom. (1958) 14, 139. Klar, R., Sliwka, A., A. Phys. Chem. Frankfurt (1958) 28, 133. Wen, W-Y, Hung, J. H., J. Phys. Chem. (1970) 74, 170. Desnoyers, J. E., Pelletier, G. E., Jolicoeur, C., Can. J. Chem. (1965) 43, 3232. Saito, S., Lee, M., Wen, W. Y., J. Amer. Chem. Soc. (1966) 88, 5107. Kozak, J. J., Knight, W. S., Kauzmann, W., J. Chem. Phys. (1968) 48, 675. Furter, W. F., Ph.D., Thesis, University of Toronto, Toronto, Ontario, 1958. Johnson, A. I., Furter, W. F., Can. J. Chem. Eng. (1960) 38, 78. Johnson, A. I., Furter, W. F., Can. J. Chem. Eng. (1965) 43, 356. Ciparis, J. N., "Data of Salt Effect in Vapor-Liquid Equilibrium," Ed. Lithuanian Agr. Acad. Kaunas, USSR, 1966. Jaques, D., Furter, W. F., Can. J. Chem. Eng. (1972) 50, 502. Sada, E., Kito, S., Morisue, T., Kagaku Kogaku (1973) 37, 983. Jaques, D., Furter, W. F., Ind. Eng. Chem. Fund. (1974) 13, 238. Burns, J. A., Furter, W. F., data not yet published. Franks, F., Ives, D. J. G., Quart. Rev. Chem. Soc. London (1966) 20, 1. Franks, F., "Physico-Chemical Processes in Mixed AqueousSolvents,"Heinemann Educational Books Ltd., London, 1967.

A256, 389.

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.



8.

BURNS A N D FURTER


127

32. Conway, B. E., Verrall, R. E., Desnoyers, J. E., Z. Physik Chem. Liepzig, Falkenhagen Anniversary Papers (1965) 230, 157. 33. Lindenbaum, S., Boyd, G. E., J. Phys. Chem. (1964) 68, 911. 34. Othmer, D. F., Anal. Chem. (1948) 20, 763. 35. Johnson, A. I., Furter, W. F., Can. J. Technol. (1957) 34, 413. 36. "International Critical Tables," Vol. III, National Research Council, McGraw-Hill, New York, 1928,p116. 37. Bulletin 101, Central Scientific Company, Chicago, Ill., p 6. 38. Cook, R. A., Furter, W. F., Can. J. Chem. Eng. (1968) 46, 119. 39. Richards, F. W., Combs, L. B., J. Am. Chem. Soc. (1915) 37, 1656. 40. Harkins, W. D., Brown, F. E., J. Am. Chem. Soc. (1919) 41, 499. 41. "Handbook of Chemistry and Physics," 51st Ed., R. C. Weast, 1970-71, p. F-30. 42. Linke, W. F., "Seidell's Solubilities: Inorganic and Metal Organic Compounds," Vol. II, 4th Ed., Am. Chem. Soc., Wash., D. C., 1965. 43. Frank, H. S., Z. Phys. Chem. Liepzig (1965) 228, 364. 44. Lindenbaum, S., J. Phys. Chem. (1966) 70, 814. 45. Narten, A. H., Lindenbaum, S., J. Chem. Phys. (1969) 51, 1108. 46. Desnoyers, J. E., Arel, M., Perron, G., Jolicoeur, C., J. Phys. Chem. (1969) 73, 3346. 47. Desnoyers, J. E., Ichhaporia, F. M., Can. J. Chem. (1969) 47, 4639. 48. Desnoyers, J. E., Arel, M., Can. J. Chem. (1967) 45, 359. 49. Aveyard, R., Heselden, R., J. Chem. Soc., Faraday Trans. 1 (1974) 70, 1953. 50. Bockris, J. O'M., Bowler-Reed, J., Kitchener, J. A., Trans. Far. Soc. (1951) 47, 184. 51. Gross, P., Chem. Rev. (1933) 13, 91. 52. Larsson, E., Z. Phys. Chem. (1930) 148, 148; (1927) 124, 233; (1931) 153, 299; (1930) 148, 304. 53. Millero, F. J., Chem. Rev. (1971) 71, 147. 54. Krishnan, C. V., Friedman, H. L., J. Phys. Chem. (1970) 74, 2356; (1969) 73, 3934. 55. "Handbook of Chemistry and Physics," 51st Ed., R. C. Weast, 1970-71, p. F-152. 56. Glasstone, S., "Elements of Physical Chemistry," D. Van Nostrand, New York, 1946. 57. Conway, B. E., Verrall, R. E., Desnoyers, J. E., Trans. Far. Soc. (1966) 62, 2738. 58. Kay, R. L., Vituccio, T., Zawoyski, C., Evans, D. F., J. Phys. Chem. (1966) 70, 2336 59. Kay, R. L., Evans, D. F.,J.Phys. Chem. (1966) 70, 2325. RECEIVED July 14, 1975. Research financially supported through Grant No. 9530-142 from the Defence Research Board of Canada.


Thermodynamic Behavior of Electrolytes in Mixed Solvents

Recommend Documents