506
INDUSTRIAL AND ENGINEERING CHEMISTRY
vulcanization by polynitro compounds remains unchanged: Bruni and Geiger showed that the addition of nitrosobenzene to rubber involves no het consumption of carbon to carbon unsaturation. If the same type of condensat,ion occurs with the polynitroso compound, which we have considered to be formed from the polynitro compound, no chnngc in unsaturation should be expected2. The foregoing hypothesis resembles only superficially one proposed by Ostromislensky (25), who at.t,empted to prove that polynitrobenzene vulcanization entails transfer of oxygen to thi, rubber: .-irSOp +ArSO 0
+
His observation, ho-rever, that neither nitrosobenzene nor isonitrosocamphor is an effective vulcanizing agent is irrelevant, since both of these substances are monofunctional and arc therefore incapable of directly joining tn-o rubber chains. ACKNOWLEDGMENT
The authors are grateful to S. B. Lippincott for synthesizing some of the reagents used in this study, to John il. Thomas for assisting in the experimental work, and to their colleagues who carried out the compounding and evaluation work, and with whom they had the opportunity of discussing some phases of the problem. They are also indebted to Harry L. Fisher for helpful criticism of the manuscript. LITERATURE CITED
(1) Alessandri, L., Atti. accad. Lincei, [ 51 24, 62 (1915) (2) Aiessandri, L., Gazz. chim. {tal., 51, 125 (1921). (3) Ibid., 54,426 (1924). 3 These views appear t o he inconsistent with the results of Blake and Bruoe [IND.ENG.CHEM.,29,866 (1937)],who concluded t h a t double bonds
in natural rubber are consumed during vulcanization b y polynitro compounds. However, these authors based their conclusions in p a r t on t h e ohNervation t h a t t h e polynitro compounds they employed were inert toward Wijs reagent. They were presumably unaware of the fact (26)t h a t aromatic nitroso groups, t h e formation of which we propose i n our hypothesis, react readily with Wijs reagent. Also, one of us ($6‘) observed t h a t , in the reaction of a n olefin such as 2-niethyl-2-butene with Wijs reagent, t h e total uptake of halogen under certain conditions is markedly reduced when a few per cent of a compound such as p-nitrosodimethylaniline is added t o t h e olefin. These results suggest t h a t t h e apparent consumption of rubber double bonds obeerved b y Blake and Bruce may not b e real. I n t h e event t h a t their conclusions prove correct, our hypothesi8 for vulcanization b y polynitro compounds would require revision.
Vol. 38, No. 5
Angeli, A., Alessandii, L., and Pegna, R., Atti. accatl. Lancei, [ 5 ] 19,650 (1910). Biill, R., and Halle, F., Taturwissenschaften, 26, 12 (1938). Bruni, G., and Geiger, E., Atti. accad. Lincei, 161 5, 823 (1927); Rubber Chem. Tech., 1, 177 (1928). Burkhardt, G. N., Lapworth, .I.,and Walkdcn, J., J . Chem. Soc.. 127. 1742. 2458 119253. I’armer, E. H., T r a n s . Faradag Soc., 38, 340 (1942); R u h b ~ i Chem. Tech., 15, 765 (1942); 16, 769 (1943). I’isher, H. L., ISD. ESG. CHEY.,31, 1381 (1939); U. S.Patents 1,918,328 (1933) and 2,170,191 (1939) ; Rubber Chem. Tech., 13, 50 (1940), Fisher. 13. L., and Gray, -1.E.,IKD. ENG.CHEM.,20, 294 (1928); Rubber Chem. Tech., 1, 101 (1928). Forster, RI. O.,and Barker, 11. F., J . Chem. Soc., 103, 1918 (1913). Forster, M.O., and Fiwz, €1. E., Ibitl., 91, 1942 (19073. Fuller, C. S., Frosch, C. J . , arid Pape, N. R., J . Am. Chem. Soc.. 62, 1905 (1940); Rulrhw Chem. Tech., 14, 338 (1941). Hammick, D. L., J . Chem. SOC., 1931, 3105. Hammick, D. L., lI., and Sparks, IT. ,J., Australian Patent 112,875 (1941). Thomas, R. M., Sparks, IT, ,J., Frolich, P. K., Otto, M., and Mueller-Cunradi, >I,, J . Am. C‘hem. Soc., 62, 276 (1940). Wright, J. >I., and Davies, €3. L., T r a n s . Inst. Rubber Intl., 13, 251 (1937); Rubber Chem. Tech., 11, 319 (1938). Zerewitinoff, T., and Ostromislensky, I. I., B e l . , 44, 2402 (1911). THEwork reported here was carried out in 1942. Earlier publication
was
withheld in accordance with secrecy orders b y t h e U.S. P a t e n t Office.
Solubility of Oxygen and Nitrogen in Organic Solvents from -25” to 50” C. C. B. KRETSCHMER, JANINA NOWAKOWSICI,
ASD
RICHARD WIEBE
U.S . D e p a r t m e n t of A g r i c u l t u r e , N o r t h e r n R e g i o n a l Research Laborutory, Peoria, I l l .
I
N COSNECTIOK with a general study of the physical properties of various organic compounds, the solubility of oxygen and nitrogen in methanol, ethanol, 95% ethanol, isopropanol, nbutanol, acetone, iso-octane, as well as in two mixtures of ethanol with acetone and iso-octane, was determined at temperatures between -25’ and 50’ C. From these data the solubility of air was calculated. All substances were carefully purified. Table I lists the densities, boiling points, and treatment of the solvents. Commercial nitrogen w&s freed from oxygen by passage through alkaline pyrogallol. Analysis of the oxygen indicated the presence of 0.4% of nitrogen for which a small correction was applied in the final data. Both gases were thoroughly dried by passage through Drierite.
The apparatus (Figure I) was similar t o that of Horiuti ( 4 ) and the method was described by him in great detail. For convenience the procedure will be, outlined briefly: The 40-ml. gas buret, B, was calibrated by mercury displacement with a standard meter bar and cathetomet,cr. The probable error of the calibration did not exceed 0.05 mm., equivalent with the buret used t o 0.005 ml. The volume between m and stopcock 2 was dctermined separately and wa,s added to the buret volume. Pressures were measured on manometer C in conjunction with a barometer, since stopcock 8 was then opened to the atmosphere. All thermometers were checked against a certified platinum resistance thermometer.
May, 1946
I N D U S T RY A L A N D E N G I N E E R I N G C H E M I S T R Y To Oat Purifying Train
501 4
7
Figure 1. Diagram of Solubility Apparatus
In the case of solubility apparatus A consisting of a pipet with magnetic stirrer indicated in Figure 1, it was necessary to know only the total volume (50 ml.) from K to stopcock 2, since the gas phwe was determined in each case by displacement with mercury as will be shown later. After being boiled under reflux to eliminate most of the dissolved air, approximately 40 ml. of purified solvent were introduced through stopcock 3 into the evacuated solubility apparatus A . Air had previously been displaced from capillary 8 by mercury. To eliminate any possible remaining air, A was opened intermittently during the course of one hour to the vacuum through stopcocks 2 and 4, while the solvent was kept under its own vapor pressure with the magnetic stirrer in operation. The loss of solvent was kept small, particularly in case of mixed solvents. Stopcock 2 was then closed and enough mercury introduced through 3 to fill A completely with solvent and mercury. A measured amount of gas from B was admitted through 2 until the mercury level was lowered to point K. The amount of mercury displaced by the gas was weighedand its volume was equal to the volume of the gas phase. Subtracting this value from the total volume of solubility apparatus A gave the amount of solvent used. The magnetically operated stirrer shown in A was now operated; fresh gas from B was introduced intermittently, which quickly closed stop6ock .2 when pressure equilibrium was established between A and B, in order to prevent any diffusion of
solvent vapors to the gas buret. Final equilibrium was cstahlished after 1-3 hours of stirring. Determinations were made on fresh portions of the solvent at all temperatures except a t 0" C., in which case the solution saturated at 25' was cooled to 0" and equilibrium established at that temperature. T H E results were expressed in terms of the Ostwald coefficient defined as "the ratio of the concentration of the gas in the liquid to its concentration in the gas phase", or expressed in terms of experimental values:
where V A = volume of solubility pipet V B = volume of gas transferred from gas buret V , = volume of gas phase in solubility pipet A P = pressureinA P, = vapor pressure of solvent' TA,T B = temperatures of A and B , respectively
*
The Bunsen absorption coefficient may be derived by multiplying the Ostwald coefficient by 273.16/T, where T i s the absolute temperature of the experiment. I t was found necessary to correct for the small increase of volume of the solvent with gas absorption and average values of the Angstrijm coefficients of 0.002 and 0.0022 for oxygen and nitrogen, respectively, taken TABLE I. PURIFICATION AND PROPERTIES OF SOLVENTS from Horiuti's work (4) were Density, d:' B.P. at 760 Mm., C. assumed for all solvents. The Purification Obsvd. Reptd. Obsvd. Reptd. k g s t r o m coefficient' is deEthanol Fractionated dried with M (8) 0.78508 0.78508 (9) ................. 95% ethanol (by vol.) Redistd., mahe up with H96 0.80724 . . . . . . . . ................. fined as O
Methanol
Iso-propanol n-Butanol Acetone Iso-octane (2,2,4-trimethylpentane) d:'
Fractionated, dried with metallic A1 (10) Same Same Treated with ApO (8) dried with Cas04 (Drier+), frActionated Certified material dried with CaSOr. fractionated
(all values for iso-octane except d:'
0.78690 0.78651 (8)
0 78081 0.7808 1 ) 0180573 0.8066{B)' 0.78490 0.7844 (6)
0.68774 0.69191"
........
64.50
82.24 117.67 56.10-0.14 99.24
were determined by Natl. Bur. of Standards).
64.51 ( 1 2 )
82.26 ( 1 ) 117.73 ( I f ) 56.10 (6)
........
6 = AV/V 1 6 multiplied by the mold volume of the gas at normal temperature and preesur'e ie equal to the partial molal volume of the gas in solution.
Vol. 38, No. 5
INDUSTRIAL AND ENGINEERING CHEMISTRY
508
TABLE11. OSTWALDABSORPTIONCOEFFICIESTS T Solvent Aba. ethanol
95% ethanol (by vol.)
water Methanol
Isopropanol n-Butanol
+
Vapor ~ ~ pressure, ~ , , C. Jim. -25 1.63O 12.2" 0 25 59.On 222.2a 50 -25 1.63= 0 12.2a 25 57 6 221.3 50 -25 5,4Q 0 30.1 127.5 25 50 417.2 0 7.6 42.6 25 177.1 50 0 O.Sa 25 6.4& 50 33.7"
Ostwald Coefficients 02 Air 0,1280 0.2387 0.1523 0.1391 0.2409 0.1615 0.1489 0 2417 0 1692 0.1606 0.2481 0.1798 0 0944 0 1825 0 1137 0.1053 0.1868 0.1232 0.1160 0.1917 0 1326 0 1290 0.2019 0.1450 0.1435 0 2427 0 1652 0.1532 0 2446 0,1733 0.1645 0.2476 0.1827 0.1765 0.2650 0.1937 0 1353 0 2443 0 1592 0 146: 0 2463 0 1684 0 1617 0 2532 0 1822 0.1075 0.2085 0.1296 0.1225 0.2100 0.1417 0.13.58 0.2171 0.1536
T Solvent
Pi2
where AT/ = increase in volume of solution V = volume of gas dissolved taken at N.T.P. Since the correction involved amounts to only about 0.2'3'0, even a 10% error in 6 is well within the limits of accuracy. A short section of the capillary below stopcock 2 was at room
Acetone
- 25
0 25 - 25
Iso-octane
Acetone in ethanol (50% by vol.) Iso-octane in ethanol (50% by vol.)
a From
~
C.
0 25 50 0 25 50 0 25 50
Vapor ~pressure, ~ . , Mm. 16.0 69.3 229.9 2.5 12.8 49.0 146.7 48.9 167.6 472.5 22.2 95.3 316.6
Ostwald Coefficients 0% Air 0.2390 0.1570 0.2570 0.1777 0.2794 0.2031 0.3874 0 2367 0.3701 0.2442 0.3725 0.2580 0.3864 0.2762 0.2409 0.1643 0.2352 0.1816 0.2733 0.2028 0.3119 0.2077 0.3163 0.2208 0.3225 0.2347
K2 0.1340 0.1554 0.1816 0.1943 0.2088 0.2258 0.2452 0.1427 0.1609 0,1829 0.1785 0.1939 0.2100
International Critical Tables.
temperature, and the gas volume was corrected t o the temperature of thc bath. h-0 corrections werc applicd for deviations from perfect gas laws or for the loiwring of the solvent vapor pressure by the solute since calculations showed these t o be much less than the experimental error. The average deviation of the
-2 I
-2.9
I
I
-3.0
-2.7
z
W
9
xo
k -2.8-
I
I
I
I
I
i
i 1
r I U
0
-3.4 -
1
i
I -31
DO30
Figure 2.
.0035 . W O RECIPROCAL OF THE ABSOLUTE TEMPERATURE, 'K.
Solubility of Nitrogen at Gas Pressure of One Atmosphere
.0030
Figure 3.
.0035 .0040 RECIPROCAL OF THE ABSOLUTE TEMPERATURE, *K.
Solubility of Oxygen at Gas Pressure of One Atmosphere
IN D U S T R I A L A N D . E N G IN E E R IN G C H E M 1 S T R Y
May, 1946
oxygen in 50-50 acetone-ethanol solutions are from 2 to 470 lower than the ones calculated from the data for the individual components; the reverse is true for the 50-50 solution of iso-octane and ethanol. For many practical purposes such a n error may not be significant, and the solubility of air in these solutions may therefore be calculated from the data given. Figures 2 and 3 are plots of the logarithm (base 10) of the mole fractions of nitrogen and oxygen against 1f T when the partial pressure of the gas is one atmosphere. From the slopes of these curves the heats of solution may be calculated from the equation:
TABLE 111. HEATSOF SOLUTION AT 25 C. Nitrogen, cal./mole
Solvent Methanol Isopropanol n-Butanol Acetone Iso-octane Acetone ethanol Iso-octane ethanol
++
TABLEIV.
Solvent Methanol Ethanol Acetone
Oxygen, cal./mole
- 290 - 140 - 240
110 310 120 220 390 560 190 510 190
Abs. ethanol
95% ethanol
-250 - 290 120 -230 80 -270
COMPARISONOF OSTWALDCOEFFICIENTSWITH THOSE OF OTHERINVESTIGATORS Gas N2
N2 N2 N2
N2
0 2
Temp.,
C. 25 25
-25 0
25 -25
01
0
02
25
-0stwald Present investigation
0.1645 0.1489 0.1340 0.1554 0.1816 0.2390 0.2570 0.2794
*
Coefficient Just
-
Horiuti
0.1415 0.1432
.... ...
....
0,1336 0.1553 0.1795 0.2357 0.2550 0.2791
....
0.1460
,...
.... ....
so9
I
d In N / d T = AH/RT2
The values for A H , the heat of solution per mole a t 25 a C. (Table 111),range from +560 calories for nitrogen in acetone to -290 for oxygen in ethanol, an indication that heat may either be absorbed or evolved in this process. Except for isolated values only a few data are available with which the present values may be compared. The comparison in Table IV shows good agreement with those of Horiuti (4) while those of Just (6) are too low. Presence of water might have been responsible for his low results. ACKNOWLEDGMENT
individual measurements from the mean was 0.3%; maximum deviation amounted to 0.9%. This agrees well with the a priori estimate of the probable error of 0.5%. Table I1 shows the experimentally determined data as well as the calculated values for the solubility of air. I n this case the aolubility of argon was assumed to be equal to that of oxygen since the work of Lannung (7) showed that such an assumption will introduce only a slight error. The solubility of air in all the alcohols as well as in acetone is considerably less than in iso-octane. The decided reduction of &hesolubility of air in 95% ethanol compared with pure ethanol checks Just’s measurements (8) of the solubility of nitrogen in methanol-water solutions. He found that practically all the drop occurred between 0 and 50% water. The experimentally determined values of 7 for nitrogen and
?he authors wish to thank Lyle C. Woods for assistance in making these measurements. LITERATURE CITED
Brunel, Crenshaw, and Tobin, J.Am. Chem. SOC.,43, 561 (1921). Clarke, Robinson, and Smith, J . Chem. SOC.,1 9 2 7 , 2 6 4 7 . 13) Fieser, “Experiments in Organic Chemistry”, p. 363, New York, D. C. Heath and Co., 1941. (4) Horiuti, Juro, Sci. Papers Inst. Phys. Chem. Research (Tokyo), 17, No. 341,125-256 (1931). (5) International Critical Tables, Vol. 111,pp. 33, 218 (1928). (6) Just, Gerhard, 2.physik. Chem., 37,’342 (1901). 52, 68 (1930). (7) Lannung, Axel, J . Am. Chern. SOC., (8) Lund and Bjerrum, Ber., 6 4 , 2 1 0 (1931). (9) Osborne, Natl. Bur. Standards, Bull. 9, 327 (1913). (10) Walden, Ulich, and Laufl, 2.physik. Chem., 114, 275 (1925). (11) Wojciechowski, J . Research Natl. Bur. Standards, 17, 721 (1936), [ f
1) 2)
Purification of Commercial Benzene bv AzeotroDic Distillation I J JOHN GRISWOLD AND R. H. BOWDEN’ The University of Texas, Austin, Texas Nonaromatic hydrocarbon impurities were separated from an “industrial pure” coke-oven benzene by azeotropic distillation with acetone. From a fractionation analysis, the impurities were found to consist chiefly of cyclohexane, C, paraffins, and naphtherres, in which n-heptane and dimethylcyclopentanes predominate. The approximate purity of the original benzene was 98.5%; it is shown that benzene of approximately 99.7% or higher purity may be readily prepared by azeotropic distillation of the commercial material with acetone.
A
SUPPLY of benzene was recently needed which would be
pure enough for experimental work on fractional distillation. Commercial preparation of the specification grades of benzene from by-product coke-oven light oil includes acid treat1
Present address, Magnolis Petroleum Company, Beaumont, Texas.
ment and fractionation, which remove most of the nonaromatic impurities from the oil. However, near-boiling nonaromatic hydrocarbons form nonideal solutions and, in some cases, azeotropes with benzene (6); this behavior prevents complete elimination of such compounds by regular distillation. Nonideal hydrocarbon mixtures (including azeotropes) may be separated by various other methods, including distillation in the presence of a selective extraneous component. Azeotropic distillation is one of the easiest to carry out, and ita principles have been discussed (9). Its mathematical aspects have also been presented (2, 3 ) . The process is applicable to the separation of cyclohexane and impurities from benzene (4), and it is the basis of two methods using methanol and methyl ethyl ketone, respectively, for the purification of toluene from petroleum fractions ( 2 , S , 8). The work reported here is an introductory study of the =eotropic purification of a commercial coke-oven benzene with ace-
