Hydrotropic Solubilities: Solubilities in Aqueous Sodium Arylsulfonate


Solubilities in Aqueous Sodium Arylsulfonate Solutions. HAROLD SIMMONS BOOTH AND HOWARD E. EVERSON1. Western Reserve University, Cleveland 6, ...
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HYDROTROPIC SOLUBILITIES Solubilities in Aqueous Sodium Arylsulfonate Solutions HAROLD SIL\IIMONS BOOTH AND HOWARD E. EVERSON' Western Reserve University, Cleveland 6 , Ohio study was made of the solubility of t e n selecte3 solutes in several concentrations of aqueous sodium benzenesul-

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fonate, sodium p-cymenesulfonate, sodium toluenesulfonate, and sodium xylenesulfonate solutions at 25.0" and 60.0" C., with the object of determining the relative effectiveness of these salt solutions as hydrotropic solvents. The results indicate that, in general, the aqueous sodium xylenesulfonate solutions are most effective as solvents for the solutes studied.

I

N 4 previous article ( I ) the authors reviewed earlier investigations of others and discussed their own work on hydrotropic solubilities in 40% sodium xylenesulfonate. Initially their studies on hydrotropic solubilities were focused on the solubilizing effect of commercial aqueous sodium xylenesulfonate solutions on many slightly water-soluble or -insoluble materials ( I ) . The object of the present part of the investigation was t o determine the relative effectiveness of other salts similar to sodium xylenesulfonate in hydrotropic action. Therefore sodium xylenesulfonate was compared with sodium benxenesulfonate, sodium p-cymenesulfonate, and sodium toluenesulfonate a t several concentrations in aqueous solutions a t 25.0"and 60.0" C. Ten solutes were selected for this study which exhibited solubilities in the-initial study ( I ) from very soluble to insoluble. These solutes were: acetophenone, aniline, benzaldehyde, benzene, carbon tetrachloride, cottonseed oil, o-cresol, cyclohexanol, ethyl acetate, and n-hexane. All the solutes used were either C.P. or highest grade commercial samples purchased expressly for this study. The hydrotropic salts were furnished by The Wyandotte Chemicals Corporation of Wyandotte, Mich., in the form of aqueous solutions and are listed in Table I together with their properties. The different concentrations of solutions used for these determinations were made from the stock solutions by dilution with distilled water or by evaporation where necessary. EXPERIMENTAL PROCEDURE

of o-cresol were measured a t 31.0 * 0.5" C., as the freezing point of this material is but slightly below this value. The constant temperatures were maintained by the use of mercury bulb-type thermoregulators immersed in constant temperature water baths. Mercury bulb thermometers calibrated against a U. S. Bureau of Standards thermometer were used to check the temperatures throughout the solubility determinations. As w~tspointed out in the initial study, the solubiliiy of a liquid solute can be determined well within 0.1 ml. of solute for a given volume of solvent. Howww, with o-cresol and cyclohexanol in some of the intermediate concentrations of hydrotropic salts, this degree of accuracy is not attained as it is difficult to observe the appearance of a second phase when solute is added t o solvent. In some cases, such as o-cresol in aqueous 10.0% sodium p cymenesulfonate, it is not possible to make a satisfactory solubility determination by the method used. One factor involved is the similarity in density of the two phases which makes separation next t o impossible. Another factor is the ease with which these materials form colloidaI solutions. RESULTS

The results of the solubility determinations are shown in Tables 11, 111, IV, and V. These results are expressed in milliliters of solute dissolved in 100 ml. of solvent. No attempt was made to determine the solubility when it was greater than 400 ml. of solute per 100 ml. of solvent. The maximum concentration of hydrotropic salt used for the determinations in the

AND CHARACTERISTICS O F STOCK SOLUTIONS TABLE I. ANALYSES

OF

HYDROTROPIC SOLVENTS

Total solids % SO^-- a s % COa as NaaCOa, p H a t 25.0' C. (glass electrode) Density,at 25.0' C., g./ml. Alcohol-insoluble, %

NLSO~ %

Sodium Sodium Sodium Benzene- p-Cymene- Toluenesulfonate sulfonate sulfonate 32.00 35.10 38.20 0.02 0.49 0.62 0.005 0.02 0.17

Sodium Xylenesulfonate 41.70 0.37 0.12

7.54 7.00 8.05 8.05 The methods used for the solubility determinations were those 1.149 1.120 1.164 1.165 employed in the previous study ( 1 ) . ... ... 0.80 0.45 However. in the -present stud; the solute-solvent mixtures wvere not centriTABLE11. SOLUBILITIES IN AQUEOUSSODIUMBENZENESULFONATE SOLUTIONS fuged to cause separation of excess Soly M1. Solute/Ml. Solvent solute. Temp., Sodiim beneenesuifonate, % ' Separation was accomplished by gentle Solute O C. 0.0 5.0 10.0 1 5 . 0 20.0 22.0 25.0 32.0 rotation of the solubility tubes while Acetophenone 25 0.54 0.60 0.80 .. 1.30 .. . . . 2 . 6 5 0.97 .. 1.62 .. .... .. 3.56 60 0.80 0.83 they were immersed in the constant~ ~ i l i ~ ~ 25 3.80 3.88 4.29 .. 6.92 .. 34.0 60 4.90 5.00 5.30 . . 8.82 .. ,.. 29.6 temperature bath. This procedure is 25 0.40 0.60 0.70 .. 1.05 .. .. .. ,. 2.53 much slower than the use of a oentri60 0.96 1.10 1.16 .. 1.89 .. 3.81 <0.05 . . .. . <0.05 25 0 . 1 1 < 0 . 0 5 ~ 0 . 0 5 .. fuge but makes i t easy to maintain the Benzene 60 0.19 0.10 0.10 .. 0.11 .. ... 0.15 25 0.10 0.06 0.06 .. 0.08 .. , , . 0.10 Carbon tetraohloride samples at constant temperature, par60 0.10 0.08 0.10 .. 0.10 .. ... 0.20 ticularly for the solubility determinaCottonseed oil 25 <0.05 <0.05 <0.05 . . <0.05 . , . . . <0.05 60 <0.05 <0.05 1 0 . 0 5 < O . 05 .. 0.05 tions made at 60.0" C. o-Cresol 25 2.20 2.74 3 . 6 6 2210 >400 . . .. ,. .. <>400 6 0 3 . 0 8 3 . 4 6 4 . 2 5 1 1 . 3 >400 >400 All solvent and solute volume meas. . 11 34 .. 18 22 78 .:0s >400 >4bO >400 25 3.40 4.08 4.43 Cy~lohexanol urements except that of o-cresol were 60 3.38 3.71 4.05 .. >400 Ethyl acetate 25 8.80 8.74 8.86 .. 10.5 .. ... made a t 25.0 * 0.1" C. The volumes 60 7.40 7.86 8.14 .. 9.56 . . . 11 33 ..61 -

I

-

Present address, Department of Chemistry, University of Cincinnati, Cincinnati 21, Ohio.

n-Hexane

25

60

1

2627

<0.05 <0.05

<0.05 <0.05

<0.05 <0.05

.. ..

10.05 <0.05

....

..

__.

.. .

10.05 <0.05

INDUSTRIAL AND ENGINEERING CHEMISTRY

2628

IK AQVEOCS ~ O D I T X CY CYMENE SULFONATE SOLUTIONS TABLE 111. SOLUBILITIES Sols., 311. Solute/hIl. Solvent Sodium p-cymenesulfonate, Yo 5.0 8.0 10.0 15.0 20.0 0.90 . . 2.37 . . 7.33 1.42 , . 2.64 , . 9.53 5.50 11.9 42.0 6.71 , . 13.4 ,. 4s.0 1.06 . . 2.20 , . ,.io 1.10 , . 2.69 .. 8.62 0.12 . . 0.12 0.21 0.34 . . 0.56 . 0.89 0.10 . . 0.12 , . 0.14 0.10 . . 0.18 . . 0.20 10.05 . . 40.06 . . 10.05 <0.05 10.0: <0.05 13.0 33:G . . 66:3 82.7 11.3 27.2 . , a z4.3 92.0 13.6 30.1 04.2 76.7 11.0 25.9 43:2 61.6 70.6 9.89 , , 14.6 .. 26.6 8.39 .. ,, 13.1 ., ,. 26.4
Temp.,

c.

Solute .ice t ophenone

0.0

0.54 0.80 3.80 4.90 0.40 0.96 0.11 0.19 0.10 0.10 10.05 10.05 2.20 3.08 3.40 3.38 8.80 7.40 10.05 <0.05 <0.05

25 60 25 60 25 60 25 60 25

lniline Benzaldehyde Benzene Carbon tetrachloride

GO

Cottonseed oil

25 60 25 60 25 60 25 60 25 60

o-Cresol Cyclohexanol Ethyl acemte n-IIexane

..

..

...

..

<0.05

a K O accurate figure can be obtained a t this concentration of hydrotropic salt obtain a satisfactory phase seyaration of these materials.

TilBLE

.

.

a3

<0.05

34.6 35.7 35.7 208.8 267.9 28.9 34.5 0.43 1.88 0.71 0.88 <0.05

10.05

188.3 198.4 145 119.4 64.8 67.4 <0.05 <0.05

i t is not possible t o

SOLUTIONS Iv. SOLUBILITIES Ih' AQUEOUS SODIUM TOLUENESELFONATE Soly., MI. Solute/LII. Solvent Sodium toluenesulfonate, 70

,--

Temp., Solute

c.

Acetophenone

25 60

Aniline

25 60 25

Benzaldehyde Benzene

5.0

0.54 0.80 3.80 4.90 0.40 0.96

0.63 0.99

60

Carbon terraohloride

25 60 25

Cottonseed oil

60 25

o-Cresol

0.0

60

0.11

0.19 0.10 0.10

<0.05 <0.05

4.05 5.40 0.90

1.05 0.10

0.11 0.12 0.14

10.0 15.0 0.91 1.37 . . 5.25 , . 6.28 . . 1.09 . . 1.44 . . 0.10 . . 0.13 0.24 , ..

..

0.44 <0.08

.. ..

20.0 25.0 2.77 3.40 . , 23.2 ., .. 22.9 2.56 . . 3.22 , . 0.13 . . 0.32 0.36 .. .. 0.64 . .

<0.05 <0.05 <0.05 < O , 05 3.36 32.5 272 >400 3.64 18.4 283 >400 4.42 8.68 61.8 54.1 365 >400 4.13 8.62

10.05

30.0

40.0

. ..

1 5.4 16.0

..

.. .. .. .. .. .. .. .. ..

iib:s 400~ 116,9400 ,..

.. . ... .. .. .. ,., .. , .. .

.. .. .. . ...

11.6 15.7 0.22 00.48 .44

1.00

<0.05
25 2.20 >400 60 3.08 >400 Cyclohexanol 25 3.40 .. 60 3.38 . . . >400 >400 E t h y l acetate 25 8.80 9.21 10.2 14.3 7.40 7.88 8.88 . . 13.3 . . . 28.3 27.9 n-Hexane 25 10.05 <0.05 <0.05 . . <0.05 . .. <0.05 60 <0.05 < 0 . 0 6 <0.05 .. 10.05 . . . <0.05 a Separation of solid phase takes place a t a concentration of 2.5 m1./100 ml. a n d completely redisnolrres a t 50 m1./100 nil.

..

..

TABLE v. SOLUBILITIESI N

~ L Q U E O U SS O D I U M XYLENESULFONATE

,--

Solute Acetophenone ilniline Benzaldehyde Benzene Carbon tetrachloride Cottonseed oil o-Cresol Cyclohexanoi Ethyl acetate n-Hexane

Temp., O C. 25 60 25 60 25 60 25 60 25 60 25

60 25

GO 25 60 25 60 25 60

00 0.54

0.80 3.80 4.90 0.40 0.96 0.11 0.19 0.10

5 0 0.74 1,07 4.30 5,86

1.00 1.08 0.11 0.21 0.10 0.10

SOLUTIONS

Soly., Mi. Solute/lIl. Solvent Sodium xylenesulfonate, Yo 10.0 15 0 20 0 25 0 4.86 1.40 .., 5.46 1.65 ... 28.3 7.10 , . . 31.2 5 S . Q 8.84 , . . 4.60 . * 1.50 . . . 1.81 . . . 5.12 . . 0.11 . . 0.11 , . , 0.21 . . . 0.27 0.10 . . 0.10 . . . 0.10 . . 0.10 ...
30 0

... ...

>400 >400

...

...

..

0.10 < O , 05 < 0 . 0 5 < 0 , 0 5 <0.05 2.20 7.8 6.4 ,.,.a 3.08 17.3 3.40 4.0 5,03 20.2 3.38 11.3 8.80 10.0 8.03 10.1 7.40
,...

23G:4

275 131 127

...

...

...

...

>400 >400 >400 >400

17.7 16.6 <0.05

<0.05

.. .. I

.

.. .. ..

..

40.0

29.6 31.2 >400 >400

24.2 28.9 0.37 1.01 1.10 0.20

<0.05

1 0 .05

...

...

42.6 43.6

.

.

I

...

2400

<0.05 <0.05

a No accurate figure can be obtained a t this Concentration of hydrotropic salt as it is not possible t o obtain a satisfactory separation of these materials.

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cases of sodium benzenesulfonate and sodium p-cymenesulfonate represents a concentration of a nearly saturated aqueous solution of those salts at 25.0" C. I n those particular cases, therefore, no higher concentration of salt was used. For the remaining two salts the maximum concentration was 40.0%. Benzene, carbon tetrachloride, cottonseed oil, and n-hexane exhibit no appreciable increased solubility in aqueous SolutionS of the sodium arylsulfonate salts used in this study. The appar-

cnt anomaly of carbon t,et,rachloride was of interest and the experiment was repeated several times with the same results. The results were also plot,ted in curves, but the solubilities varied wid el^ and made comparison impractical. A q u e o u s s o d i u m berixeneeulfonatc solutions are in general the least effect'ivc of the hydrotropic solvents invcstigat,ed; however, these solutions are excellent solvents for o-cresol and cyclohexanol. Aniline, o-cresol, and cyclohexanol are shown to be quite soluble in aqueous sodium p-cymenesulfonate s o l u t i o n s . Acetophenone, benzaldehyde, and ethyl acetate exhibit moderate in these solutions. The higher concentrat,ions of aqueous sodium toluenesulfonate dissolve aniline, o-cresol, and cyclohexanol to a value greater than 400 ml. of solute per 100 ml. of solvent. Bcet,ophenone, benzaldehyde, and ethyl acetate are moderately soluble in this solvent. Aqueous solutions of sodium xylenesulfonate] made from the mixed xylenes, are the best, solvents for the solutes investigated. Aniline, o-cresol, and cyclohexanol exhibit a solubility greater than 400 ml. of solute per 100 ml. of solvent in the higher concentrations of this hydrotropic salt. Scetophenone, benzaldehyde, and ethyl acetate show moderate solubility in aqueous sodium XyhEsulfonate SOhltionS. The results of the solubility determinations are in accord with t,he hypothesis that polarity of the solute favors solubility in aqueous sodium arylsulfonate solntions, as it likewise does in water. This statement can be made only in a qualitative sense as there are many variables q-hich may affect the solubility, and a t the present time these variables cannot be evaluated to provide a quantitative relation of the solubility to the properties of the solute arid solvent. '

>400

...

>400 >400

, . .

Vol. 41, No. 11

ACKNOWLEDGMENT

The authors are indebted to Thomas

H. Vaughn, vice president in charge of research and development, Wyandotte Chemicals Corporation, and t o H. Earl Tremain of the same organization for suggestions and encouragement during the course of these investigations.

LITERATURE ClTED

(1) Booth, H. S., and Everson, H. E., IND.ENG.CHEM.,40, 1491 (1948). February , 1949, In\,estigation Chemicais Corporation, Wyandotte, Mich.

R E C E I T ED

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