588
Vol, 36, No, 6
INDUSTRIAL AND ENGINEERING CHEMISTRY LITERATURE CITED
In general, the research showed that bitiiminous materials could be made to coat water-wet aggregate t o produce a highly water-resistant mix a t a reasonable cost by :t modified i\/IcI,eod type of treatment. As developed, the treatment may have possibilities for application in road construction where unifolmly thin mattes can be laid and adequnte drninage assured. In special applications where a water-resistant mixture of bitumencoated aggregate is desired and where the plastic propertie? of t h e mass is not a problem, the treatment should be useful. Further research may point the way toward more general application.
Uijkstra, F. (to Shell Development Co.), Cntiadiau Patent 406,399 (1942). Dohxe, H., and Spoun, F. (to I. G. FaIbeniiidustrie), U.8. Patent 2,191,293 (1940). Il’in,B., 2. physiie. Chem., A155,403 (1931). Johnson, J. M . , U. S. Patent 2,177,568 (1939). McCoy, P. E. (to Am. Bitumuls Co.), Ibid., 2,313,759 (1943). Mack, Charles, J . Soc. Chom. Ziad., 60, 111 (1941). McLeod, N. W., ilssoc. Asphalt. Paving Tech., PTOC. Tech. Sffiysions, 9, 1 (1937). N. V. de Bataafsche Petroleum Ma.atsoliappij, Dutch Patent 51,212 and Brit. Patent 533,170 (1941). Pfeiffer, J. P. (to Shell Development Co.), U. 8. Patent 2,225,570 (1940). Roediger, J: C . (to Standard Oil Development Co.), Canadian Patent 405,350 (1942). Standard Oil Development Co., Rxit. Patent 533,927 (1941). Ibzd., 545,287 (1942). Whitacre, C. H. (to Standard Oil Co. of Ohio). U. S. Patent 2,286,244 (1942).
ACKNOWI.EDG.\lFLYT
This work was done under the joint qmiisor4iip of the tVi+ consin State Highway Commission, thc Wisconsin Alumni Research Foundation, and the Cniversity of Wisconsin. Man!, persons gave valuable aid and advice during the course of the work. J, W. Williams, 0. A. Hougen, and Joseph Zapatn ,deserve particular mention. More complete details are t o be found in the Ph.D. dissertation of the author, submit,tod to t h r facult>pof the University of Wisconsin in ,lune, 1940.
Winterkorn, H. F., IND.Ena. CHEM.,26,815 (1934). Ibid., 30, 1362 (1938). Winterkorn, H. F., Assoc. Asphalt Paving 7%&., P ~ o c .T e d Sessions, 9 03 (1937).
f L
NITROBENZ
H. Milton Woodburn, Keith Smith, and Hyman Tetewsky T H E UNIVERSITY OF BUFFALO, BUFFALO, N. Y .
I\’ RECENT years much progress has been made in establish-
I
ing relations between structure and physical properties, or among various physical PI operties---for example, two papers by Francis (4, 6). To fortify and test such correlations it is important that as many properties as possible be included. Critical solution temperatures are not often considered except in the one case of “aniline points” for hydrocarbons. Therefore, a btudy was undertaken of other critical solution temperatures. The results are here reported for the critical solution temperature of ten paraffins with nitrobenzene and of six paraffins with ,S,,S’-dichloroethyl ether (Chlorex). No record of the critical solution temperatilies of paraffins with &@’-dichloroethyl ether has been found, although this solvent has been used for the extraction of certaiii petroleum fractions (9). The critical solution temperature%of paraffins with nitrobenzene have been determined for a relatively small number of hydrocarbons (1, 3, 6, 8,10, 11, 1 2 ) . I n cases where more than one figure has been published, it is apparent that some of them are 01 doubtful value. Table I lists these recorded values. For comparison the data obtained in thib work are given, as well as values for the critical solution temperatiires of the parafhns with aniline. WETHOD
These critical solution temperatures weie tlr~eiImried in sealed glass capsules made from 9-mm. Pyrex tubing, 8-10 mi. long. Reasons for using this technique were ( a ) to allow the use of small samples of pure hydrocarbons difficult to obtain, ( b ) to prevent evaporation and loss of volatile hydrocarbons during the determination, and ( c ) to allow repetition of the measurement as often
as desired without, t,he possibility of contanfiiation by water absorption. Agitation duririg t,he determination was accomplished by magnetic stirring. A headless nail, about 3 cm. long and sealed i n glass, was placed in the capsule before introduction o f the liquids and sealing. The sealed capsule was fastened by a short length of rubber tubing to a glass holder arid inserted into the hollow tube of an electromagnet (Figure 1). The latter was made by niriding KO.24 13. & S. gage, cotton-sheathed copper wire around a t,hin-walled, l/,-inch iron pipe for a length of 4 cm. and a depth of 1.5 cm. Variable resistances were placed in series in the circuit t,o control the strength of the electronlagnets, and a circuit breaker (Diamond flash button, made by Eagle Electric Manufacturing Company, Inc.) was included t o tnrn the current 011 and off ttutomatically. Placement of the capsule relative to the electromagnet was such that the covered nail was pulled up through the interface and allowed to drop by gravity while the current was ofl. Very efficient stirring resulted. A by-pass in the circuit allowed the flasher to be cut out., leaving t,he magnet energized and holding the bob up, so that an unobstructed view ~
~~~~
~
~
~
~~
T h e critical solution temperatures of ten paraffin hydrocarbons w i t h nitrobenzene and six w i t h 6’,8’-dichloroethyl ether have been carefully determined. Several values recorded in t h e literature are shown t o be i n error. Among t h e normal paraffins, as t h e number of carbon atoms increases, t h e numerical difference between t h e critical solution temperature and t h e aniline point shows a steadily increasing value for nitrobenzene solutions and a steadily decreasing value for p,B’-dichloroethyl ether solutions.
June, 1944
INDUSTRIAL AND ENGINEERING CHEMISTRY
589
of the liquid could be obtained. The iron pipe TEMPERATURES OF PARAFFINS TABLE 1. CRITICALSOLUTION above the electromagnet was perforated by sevCritical Soln. Temp., C., in: eral holes to allow circulation of the bath liquid ____ Nitrobenzene Chlorex around all paIts of the capsule. Both pipe and Detd. detdLo' Aniline, No. c magnet were coated with spar varnish to prevent Atoms Hydiorarbon Pub. value (+O.O5O) ( * O . O a ) pub. value rusting and electrical leak. 4 n-Butane 4 Isobutane Three of these magnets were fastened in a 5 n-Pentane row in a wooden support placed on the top of 5 Isopentane .. 7 8 . 4 (4) a constant-temperature bath. The latter was constructed of glass, insulated, and covered with n-Hexane 19"c$, 14.8 12.70 6 20.60 aluminum foil. Windows through the insula(S),21 (6) 2 1 . 3 (81, tion allowed observation of Ihe tubes. Tem1 9 . 2 (11). 21.02 (IO) perature was controlled by a mercury-filled 6 2-Methylpentane 25.61 ... 24.05 (3). glass thermoregulator with an adjustable contact 25.7 (8) 3-Methylpentane B 21.4 (8) ... needle having 44 threads per cm. and a thread 2,2-Dimethylbutane 6 27.9 (8) 33:bO ... 2,3-Dimethylbutane 6 24 1 8 ) length of 7 cm. One complete turn of the 7 n-Heptane l 1 : 5 IS) 19:48 16:60 needle represented a temperature change of 7 18.05 (3) 2-Methvlhexane ... 7 .. ,.. . . 23: 08 2,2,3-T~imethylbutsne ... about 0.17" C. The thermometer used for re(triptane) 8 n-Octane 20.68 20.67 cording temperatures was certified by the 2,5-Dimethylhexane 28.3 (iij 8 ... National Bureau of Standards, graduated in 0.1' 2,2,4-Trimethylpentxne 8 . . . ,. 30:38 9 2 i :00 n-Nonane . . . . . . . 21.78 divisions, and easily readable with a hand lens n-Hexadecane (cetane) 38.52 16 ....... 47.93 to 0.02". Capsules were prepared by constricting and storing in a sulfuric acid desiccator. When removed from the desiccator, they were capped a t all times by a tube The use of a bath controlled by a thermoregulator made it carrying a drying tube filled with anhydrous calcium chloride and possible to increase or decrease the temperature as gradually as phosphorus pentoxide. Liquids were weighed in and delivered from desired or to hold it at any point indefinitely. Thus, solution weight burets having long, slender, delivery tubes. It was contemperatures could be approached from below or above the exart point with no difficulty. venient to know the weight of a drop of liquid delivered by such burets so that the desired weight could be easily approximated Before using the apparatus for nitrobenzene points, the by counting the number of drops introduced into the capsule. method was checked by determining the critical solution temThe stopcocks of the burets were lubricated with a tiny amount perature of 2,2,Ptrimethylpentane with aniline. The value obof pure phosphoric acid rather than commercial stopcock grease. tained (80.1"C.) checked with that recorded by Francis ( 4 ) . When the buret containiog the nitrobenzene had been weighed, I n determining a critical solution temperature, it is often noted a capsule was removed from the desiccator and the tip of the that the temperature-composiLion curve bas a rather flat region buret was introduced well past the constriction. The calculated near the critical point. This region may extend over several number of drops was allowed to run in, and the capsule was weight per cent changes in concentration and, consequently, capped and placed in a mixture of Dry Ice and chloroform while offers a check on the value chosen. This is illustrated by the the buret was weighed again. The same procedure was used for data for points close to the critical solution temperature of nintroducing the hydrocarbon except that the capsule was not pentane with nitrobenzene: removed from the cooling bath during the addition. Finally Soln. Critical S o h . Weight % Soln. Weight % n-Pentane Temp., C. n-Pentane Temp., C. Temp., C. the constricted portion of the capsule was quickly fused together
.
37.52 50.60 50.76
24.50 25.15 25.15
I
52.14 54.90 55.86
25.15 25.13 25.10
... 25: i5
T o save space other similar data are omitted. PURITY OF MATERIALS
The nitrobenzene used was purified (7) by distillation under reduced pressure, neutralization and drying with anhydrous sodium carbonate, and final fractionation through an insulated column of the total condensing type packed with glass helices. The length of the packed section of the column was 40 cm. Aniline was purified in the same way. Refractive indices checked with those recorded in International Critical Tables. The @,@'-dichloroethyl ether (Chlorex) was a commercial sample purified by fractional distillation. The refractive index checked with the recorded value. The refractive indices of the hydrocarbons follow, together with those recorded by Francis ( 4 ) .
.-----ny
Figure 1.
Assembly of Magnets and Capsules
Hydrocarbon n-Pentane n-Hexane n-Heptane n-Octane n-Nonane 2 2-Dimethylbutane 2:Methylpentane 2,2,4-Trimethylpentane 2,2,3-Trimetbylbutane triptane) n-&exadecane
-
Detd.
Published
1.4350
1.4344 (2)
INDUSTRIAL AND ENGINEERING CHEMISTRY
890
DISCUSSION
R’hile the data given are insufficient to lead to definite conclusions, certain comparisons may be brought out with the better known aniline points. When aniline is used with paraffins the densisies involved are such that critical solution temperatures closely approach the solution temperatures of equivolume mixtures. Therefore, it is common practice to make quick deterruinations o€ aniline point by measuring volumes of the liquid. rather than by weighing them. With nitrobenzene the ciitical solution tenipwatures are more nearly in the region of 50% by veight, and this may mean 60-6,5% by volnme, depending on t h e hydrocarbon.
Vol. 36, No. 6
95
85
15
J $65 U J
e P
€55
c C
+P
45
v)
m ,-
.-+ 35 6 56
54
25
15
I 0
Jt 3:
52
6
4
0 Aniline (2,4).
0
Figure 3. 50
8 90 12 Number of Carbon Atoms C HiQrobenzene. 0 Chlorex
46
44
Figure 2. Difference between Aniline Points end Critical Solution Temperatures w i t h Other Solvents for Normal Paraffins
Examination of the numerical differences between the critical d u t i o n temperatures as determined with aniline and those deteimined with nitrobenzene and with Chlorex shows an interesting relation (Figure 2). I t appears that among the normal paraffins there is a steadily increasing difference between aniline and nitrobenzene points as the number of carbon atoms increases, whereas there is a steadily decreasing difference between aniline and Chlorex points. It seems logical that these curves should be useful in predicting the nitrobenzene and Chlorex points of the normal hydrocarbons between nonane and hexadecane. This theory has not been experimentally confirmed because of the lack of pure samples of the hydrocarbons in question. However, the predicted values for the missing hydrocarbons are marked by crosses on Figure 3 and bear out this assumption. Also, investigation of a more complete series of hydrocarbons may show that these differences can be helpful in identifying an wnknown sample, a t least as to its carbon content. Thus for the isomeric groups above, the aniline-nitrobenzene differences, with one exception group themselves into narrow ranges:
+-
16
Estd. Points.
Critical Solution Temperatures of Normal Paraffins
S o . of C Atoms
48
14
Aniline-Nitrohenzsne Diffrrmw 46.36 47.60,45.50,48.HR 48.22,50.52 49.72,31.:32 52.52
. I plot of the number of carbon atoms in the normal paraffins against their critical solution temperatures (Figure 3) 5 h o w 3 that a niininium occurs with aniline points at hexane and with nitrobenzene points a t heptane, and that the Chlorex points lie on practically a straight line. KO explanation is offered for this observation. ACKNQWLEDGM E N T
Grateful acknon-ledgment is made t o A. W. Francis, BoconyVacuum Oil Company, Inc., who suggested this problem; to n‘lerrill R. Fenske, Pennsylvania State College, who supplied eight of the hydrocarbons; and to Gould H. Cloud, Esso Ltihoratnries, who furnished cetane and triptane. LITERATW RE C I T E D
Dessart, A., Bull. soc. ehim. Belg., 35, 9 (1926); 1,andoltBornstein, Tabellen, Erg. IIa, p. 476 (1931). Doss, M. P., “Physical Constants of Principal Hydrocarbons”. New York, Texas Co., 1942. Erskine, A. M., IND.ENQ.C H m f . , 18, 695 (1926). Francis, A . W., Ibid.,33, 554 (1941). Ibid., 35, 442 (1943). Francis, A. W., IND. ENG.CHEM.,ANAL.ED.,15, 447 (19.23,. Hilke, O., 2. Physik, 103, 350 (1936). Maman, A., Compt. rend., 198, 1324 (1934). Page, J. M., Buchler, C. C., and Diggs, S.H., IND.EM:. CHEM.. 25, 418 (1933). Timmermans, J., thesis, Brussels, 1911; Landolt-Rornst~,iri. Tabellen, HwI, p. 760 (1923). Timmermans, J., Z.p h y s i k . Chem., 58, 129 (1907). Timmermans, J., and Hennaut-Roland, J . chim. phys., 29, 5259 (1932) ; Landolt-Bornstein, Tabellen, Erg. 1118,. p. 678 (1935).
