INDUSTRIAL AND ENGINEERING CHEMISTRY
reactor with a large vapor space at moderate velocities. There should be sufficiently high light intensity to activate the reaction, and~recyclingof unreacted gases should be possible. Similar predictions for the conditions favoring maximum production of trichlorides and of tetrachlorides may also be derived from the data. ACKNOWLEDGMENT
The authors wish to express their thanks to A. L. Henne for his helpful criticisms and suggestions. LITERATURE CITED
Brown, H. C., Kharasch, J. S., and Chao, T. H., J . Am. Chem’ Soc., 62, 3435 (1940).
Groll, H. P. A., Hearne, G., Rust, F. F., and Vaughan, W. E., IND. ENQ.CHEM., 31,1239-44 (1939). Halogen Chemicals, 616 King Street, Columbia, S. C. Hass, H. B., McBee, E. E., and Weber, Paul, IND. ENG.CHEM., 27, 1190 (1935).
Hass, H. B., McBee, E. E., and Weber, Paul, Ibid., 28, 333 (1936).
Hass, H. B., and Weber, Paul, Ber., 67,9745 (1934). Henne, A. L., private communication, Ohio State Univ., Columbus. Hersh, J. M., and Nelson, R. E., J . Am. Chem. SOC.,58, 1631
Jacob, R . , Bull. soc. chim., 7, 581-6 (1940). Kleinfeller, H., Bor., 62B, 1582-90 (1929). Mouneyrat, Ann. chim. ( 7 ) ,20, 534 (1900). Newman, M. S., IND. ENG.CHEM.,ANAL.ED.,1 2 , 2 7 4 (1940). Norris, J. F., and Olmsted, A . W., “Organic Syntheses,” Collective Vol. I, p. 138, New York, John Wiley & Sons (1932). (14) Oeconomides,Bull. Soc. Chem., 35,498 (1881). (15) Perkin, W. H . , J . prakt. Chem. ( 2 ) , 3 1 , 4 9 3 (1885). (16) Porgorshelski, Z., J . Phys. C h m . (U.S.S.R.), 36, 1129-84
(9) (10) (11) (12) (13)
(1904); Chem.Zentr., 75 ( l ) , 668 (1905). (17) Rogers, A . D., and Nelson, R . E., J . Am. Chem. Soc., 58, 1027 (1936). (18) Taft, R. W., Jr., M. A. thesis, p. 33, Univ. of Kansas, 1946. (19) Ibid., pp. 15-21. (20) Taft, R. W., Jr., and Stratton, G. W., Trans. Kansas Acad. Sci., 48, 319 (1945). (21) Ibid.,50, 225 (1947). (22) Taft, R. W., Jr., and VanderWerf, C. A., J . Chem. Education, 23, 8 2 (1946). (23) Timmermans, J., and Martin, J.Chim. Phys., 23,778 (1926). (24) Tishchenko, D. V., J.Gen. Chem. (U.S.S.R.), 8 , 1232-45 (1938). 125) Underwood, W., and Gale, J. C., J . Am. Chem. Soc., 56, 2119 (1934). (26) Vaughan, W. E., andRust, F. F.,Org. Chem., 5,449-71 (1940). (27) Whaley, B. R., private comniunication, Halogen Chemicals.
RBCEIVED March 6, 1947.
HYDROTROPIC SOLUBILITIES Solubilities i n 4 0 Per Cent Sodium Xylenes ulfo na te HAROLD SIMMONS BOOTH AND HOWARD E. EVERSON Western Reserve University, Cleveland 6 , Ohio
A study was made of the solubility of a variety of materials in aqueous 40% sodium xylenesulfonate solutions at 25.0” C. At the same time, and under as nearly like conditions as possible, the solubility of these materials was determined i n distilled water. This afforded a means of indicating the solvent power of the aqueous 40% sodium xylenesulfonate solutions. When solubility of the solute in water is measurable, its solubility in aqueous 40% sodium xylenesulfonate is generally considerably greater than in water.
N A limited sense, hydrotropic solvents are aqueous solutions of salts that cause greater solubility of insoluble or slightly water-soluble substances than does pure water a t the same temperature. Neuberg ( I S ) reported this phenomenon in 1916 and made a rather extensive study of a number of these materials. Because these salts increase the solubility of many slightly water-soluble or insoluble materials, many industrial applications are possible. These can be divided roughly ifito four classes: 1. Crystallization media, as in the use of aqueous calcium cymene sulfonate solution for the purification of benzoic acid, sulfanilic acid, and salicylic acid (5). 2. Selective solvents in extraction of one material from another, as in separating lignin from cellulose in the McKee pulp process ( 3 , 6 , 7 ) . In a similar process, Lau (4)made a study of the extraction of lignin from bamboo pulp and gave the advantages of this method as: production of a higher yield of bamboo pulp compared with that from other processes; repeated use of the solution, with simple and complete recovery of the chemicals employed; no evil smelling gas and no difficulty in disposing of waste liquor; and no chemical other than the hydrotropic solution needed. A selective solvent would be advantageous in the separation of materials with similar boiling points, such as aniline and dimethyl-
aniline ( 3 ) . After extraction of one material from another, the solute generally can be removed, to a considerable degree, from the hydrotropic solution by dilution with water, giving solvent and solute layers that can be separated easily. After this second separation, the aqueous hydrotropic solution can be reconcentrated and recycled through the separation process. 3. Reaction media for certain processes that might otherwise require volatile and flammable solvents. This is advantageous from the standpoint of elimination of explosion hazards, toxic vapors, and loss of solvent by evaporation. A very good example of this is a process for the synthesis of etlylenediamine (8). 4. Finallv, solvents in the field of electrochemistry. Certain water-insoluble materials can be dissolved and electrolyzed with comparative ease. Here again, solvent hazards are eliminated. I n addition, lower voltages can be employed as many of the solutions of hydrotropic solvents are good conductors. This has been shown by the process of electroreduction of aromatic nitro compounds in an aqueous solution of hydrotropic salt (9, IO). Electro-oxidation can be carried out, as shown by the work of McKee and Heard ( I I ) , in the electrolytic oxidation of benzaldehyde t o benzoic acid in hydrotropic solution. Further applications of hydrotropic solutions in industry are discussed in an excellent review by McKee (6). The phenomenon of hydrotrophyis onewhichmany investigators have tried to explain. Makara ( l a ) presents a summary of the various theories. Of these, perhaps t h a t of Bancroft (1) gives the best explanation on the basis of a mixed solvent theory according to which the hydrotropic salt dissolves in a solvent, such as water, and in solution the salt itself then acts as a solvent. These theories can be summarized in the statement that “like dissolves like.” The object of this investigation was to study the hydrotropic solvent action of aqueous sodium xylenesulfonate solutions. Of the various known hydrotropic solvents, sodium xylenesulfonate was selected for this study because of its cheapness, availability, and stability of its aqueous solutions; and because of the
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
latter characteristic, it is possible t>o ustf thesc solutions over and over again in cyclic procesar~s. No attempt has been inade here to present a coinplete phase st,udy of any of the qolute-solvent systenls, because a favorable iudicatioii of solubility in hydrotropic solutions coniparcd wit'h solubility in wat,er a t a given temperat,urt: was sufficient, for the present project.
Vol. 40, No. 8
In 100 ml. of
100 of distilled wntw, id. Ill
40% sodlurri xylenePulfonatr \elution,
29.6 >400 ,400 >400
kXPEKIh1 & Y rA1, PKOCh1)lJK h
As it 15 ab desired to nieasure the solubilitie~ a large number of materials in aqueous sodium xylenesulfonatc~solutions, rapid methods of determination neie deshable. For this leason, ordinary quantitative aiialytical nwthod, were not used. Thr methods finally employed were:
< 0 . 0 2 grnru >400
38.0 4.0 24.2 0.37 0.06 graiir ?. F, gramis .>. 3 granii
0.44 1 0 .02
I . The residw-volume method of Vaughlt and Sutting ( 1 4 ) for solids. 2. A modification of thrb nic4hod d by Hanslick ( 3 ) for liquidi.
The fhbt of these methoda, 111 principle, involves the fact that when t h r solvent becoineh satui ated with solute, fuither additions of solute yield a proportional amount of undissolved residue, which can be measured voluinetrivally for a number of additions of solute The data obtained from this can be plotted as grams of solute added against volumc oi" undissolved residue. A straight line is obtained, which, when extrapolated to zero volume, of undissolved residue, gives the number of grams of dissolved solute in t h r given quantiix of solve11t.
Iii this pal ticulai investigatiori, htoppeied GoetA tubes n ith capillaries graduated froni 0 t o 1 ml. in fitepa of 0.05 inl. were used. i known volume of solvent (generally 50 nil.) was added to the tuhe in a ronstani temperature water bath and weighed quantities of solid solute were added to this solution. The mixture was then shaken for 5 minutes, returned to the bath for a minimum oi 10 minutes, aud then centrifuged for 5 minutes. After thib treatment, the volume oi residue % a s deteimined directly. The procedure of shaking and centrifuging Fas repeated to make sure that equilibrium between solvent aiid solute had been reached hefOW thr final volumr deteriiiination mas made. The second method caii be divided into two submethods: (1) for liquid solutes that have a specific gravity greater than that of the solvent, aiid (2) for liquid fiol~~% with a sperifir gravity less than that of the solvent.
0.50 0 . 2 0 graill 0.48 gram
1.10 ?.60 0.0 3.0 grama 0.09 1.2 gram
C'iil orof orni
Cottonaeed oil Cresol, o .
>400 >400 >400
DT ( l , l , l - t r i ~ l i i [ ) r o " ~ , ~ - i , i ~ - , , . ohlorophenyl ethane) Ilecahydronapht halene Diamino diphenyl (benzidinej Dianiyl ether, is0 (is0 ainsl e t h e r ) Dichlorobenzene, o Dichlorobenzene p Diethylene oxide'(dioxaua-I,&) Diethyl ketone irihenyl ether (phenyl etlwi.! ther (dirthvl ethrri thy1 aoetatb thy1 benzoate Ethplena dihrouiiiic, t'urfural Heptane, 11 Hexane, 7c Heptyl a l a o h ~ ~,I l , Iodoforni Keryl henayl chioridc. P-l\Iercaptobenzotliina~rli~ Methyl benzoate Methylene bromide JIethylanr chloride LIixed amyl chloridw Naphthenic acid
pht,hol, a rihthol, ,4 robenzene roethane romethani. rotoluene, o rotoluene, 711 Nitrotoluene, 71 Pentaerythritol Phenetole Phenyl ethyl a l c o l d , P Propionitrile Propyl alcohol, n Propyl. aicohol, irio
0.32 10 02 gra rr,