INDUSTRIAL AND EKGINEERING CHEMISTRY
1136
diffusion constant, sq. cm./sec. m = term number of series in Equations 2 and 3 n = term number of series in Equation 2 R = half slab thickness, cm. v = moisture concentration, grams/cc. x = distance from one face of the slab, in a direction normal to the surface, cm. f(x') initial moisture distribution, as a function of distance x' from one face a = rate of drying, grams/sec./sq. cm. K
=
0 ?r
1
= = =
Vol. 25, No. 10
time, sec. 3.142 KB/Rz LITERATURE CITED
(1) Newman, Trans. Am. Inst. Chem. Eng., 27, 203 (1931). (2) Sherwood, T.K., IND.ENG.CHEW,21, 12 (1929). (3) Ibid., 21, 976 (1929). (4) Ibid., 24, 307 (1932).
RECEIVED M a y 4, 1933.
Vapor-Liquid Equilibria of Hydrocarbon Mixtures E. C. BROMILEY AND D. QUIGGLE,Pennsylvania State College, State College, Pa.
F
EW vapor-liquid equilibrium data are available for hydrocarbon mixtures, so this work was undertaken to
find binary mixtures more suitable than benzene-toluene or benzene-carbon tetrachloride for testing the efficiency of fractionating columns. Four binary and two ternary mixtures were investigated, as follows: Binary: N-HeDtane-toluene Tolugne-N-octane 2,2,4Trimethylpentane (iso&tane)-N-octane Normal heptane-methylcyclohexane Ternary: N-Heptane-methylcyclohexane-toluene N-Heptane-methylcyclohexane-acetone
I n the ternary mixtures the concentrations of toluene and acetone were kept reasonably constant. PROPERTIES OF hI.4TERIALS USED The S-heptane was that approved by the Bureau of Standards for knock rating purposes. It was obtained from the California Chemical Company and had the following properties : Boiling point a t 760 mm., Freezing point, C . Densitv. - . d?O Refractive index, n y
C.
98.4 -90.8 0,6839 1,3878
The 2,2,4-trimethylpentane was also the st'andard fuel approved by the Bureau of Standards for knock ratings. It was obtained from the Rohm and Haas Company of Philadelphia. Its properties were: Boiling point a t 760 mm., Freezing point, O C. Density, d i 0 Refractive index, n y
C.
99.2 -107.5 0.6919 1.3916
The N-octane was prepared in the course of some research in this laboratory, and had the following physical propert'ies : Boiling point a t 760 mm., Density, dzo Refractive index,
C.
n2
125.4 0.7026 1.3970
The toluene was a fractionated sample of Baker's analyzed material with the following properties : Boiling point a t 760 mm., Density, d i 0 Refractive index, ny
C.
C. P.
110.4 0.8659 1.4966
The methylcyclohexane was Eastman's technical grade which was fractionated and then washed with concentrated sulfuric acid, neutralized with sodium carbonate, washed with water, and dried. Its properties were:
Boiling point a t 760 mm., Density, d i 0 Refractive index, ng
C.
100.8 0.7693 1.4232
APPARATUS The vapor-liquid equilibrium was obtained in a simple and compact equilibrium still reported by Othmer (3, 4). I n addition to the electric heating of the still a winding of asbestoscovered chrome1 wire was placed around the still within about 0.5 inch (1.27 cm.) of the surface of the liquid. By adjusting the heat in this winding, condensation of vapors was avoided until they reached the condenser. Condensation of vapors before the condenser would have given erroneous results while a slight superheating of the vapors would not. Since the entire apparatus was of glass, condensation of vapors in the still could be readily seen and the necessary heat applied to avoid it. This method of obtaining vapor-liquid equilibria is very satisfactory and is better than the methods used by Evans ( I ) , Zawidski ( 7 ) , or Rosanoff, Lamb, and Breithut (Or). It is simple in operation, is subjected t o few errors if condensation in the still is avoided, and gives reproducible results. The still was designed to operate with about 200 cc. of material, but variations in quantities from 75 t o 250 cc. gave equally satisfactory results. AXALYTICAL PROCEDURE To make the analyses of the equilibrium mixtures as simple as possible, density and refractive index were used whenever there was sufficient difference in these properties. Mixtures of known composition were prepared and measurements made of the refractive index with an Abb6 refractometer, of density with a Nicol pycnometer, and of boiling point with a specially constructed Cottrell apparatus capable of being operated a t any desired pressure. From these data suitable curves were drawn and used as a basis for analysis. These data are given in Tables I-IV under Known Mixtures. Figure 1 shows a convenient method of plotting density or refractive index against composition. I n the cases of the X-heptane-toluene and N-octanetoluene mixtures both density and refractive index were used for analysis, for with an accuracy of 2 in the fourth decimal place for either density or refractive index, these analyses are correct within 0.1 to 0.2 per cent. For the 2,2,4-trimethylpentane (isooctane)-N-octane mixtures, boiling points a t 760 mm. were used for analysis. Boiling points could be read to 0.1' C. and this permitted greater accuracy than when using density or refractive index for analysis. The boiling point was found to vary linearly
I X D U S T R I A L A K D E N G I N E E R I N G CHE3ZIISTRY
October. 1933
1137
-
TABLEI. DATAo s ~--HEPTAXE A N D TOLI-ESE ~IIXTLREJ--.-
--I(uonx Mole fraction .V-heptane
0.0000 0.0593 0.1209 0.1949 0.2689 0.3412 0.4153 0.5044 0.5916 0.2929 0. ,870 0,8823 1.0000
~~‘D”
dio 0.8659 0.8510 0,8368 0.8197 0,8039 0.7894 0,7753 0.7582 0,7434 0.7267 0.7130 0.6990 0.6839
1.4966 1.4871 1.4783 1.4682 1,4588 1.4500 1.4417 1,4318 1.4226 1.4130 1.4045 1.3964 1.3878
TABLE11.
B.
€1.
110.40 109.15 107.90 106.40
....
104.00 102. x5 101. so 100,80 100.05 99.30 98 90 98.40
heat supplied, and the time for each determination were-the EXPTLVALUES EXPTLV ~ L U E S same in every instance. The experimental error is within F R O M D E N S I T Y F R O V REFRLCTIVE M E ASUREIIENTS, I N D E X MEASURE- 0.2 t o 0.4 per cent. MOLE MENTS. MOLE For the A’-heptane-methylcyclohexane mixtures, density FRACTION FR.ACTION N-HEPTANE .\‘-HEPTANE alone was used for analysis, the error being not greater than Liquid Vapor Liquid Vapor 0.3 per cent. The ternary mixtures of X-heptane-methylcyclohexane0.0105 0.0220 0.0795 0.1335 0.0615 0.1095 0.0940 0.1520 toluene were analyzed by pipetting 10 cc. of sample into a n 0.0900 0.1480 0.1985 0 . 2 8 7 0 0.1370 0.2125 0.2900 0 . 3 8 4 0 18-gram, 50 per cent cream bottle and centrifuging with 25 cc. 0.1420 0.2210 0.3510 0.4390 of concentrated sulfuric acid which removed the toluene. 0 . 1 7 0 0 0.2590 0.4090 0.4930 0 , 2 2 8 0 0.3225 0.5005 0.5785 The S-heptane-methylcyclohexane layer was then floated 0 , 2 6 3 5 0.3600 0,5720 0.6380 0.4025 0.4900 0,6780 0.7245 into the stem of the cream bottle by adding more concentrated 0.4580 0 . 5 4 0 0 0.8580 0.8735 sulfuric acid, and the volume measured. The difference 0.5220 0.5985 0.9300 0.9370 0.5650 0.6050 0,6540 0.6836 0.7615 0.7885 0.8370 0.8810
TOLUESE AND
DATA O S
FROM
Moie fraction toluene 0.0000 0.1487 0.2577 0.3696 0.4665 0.5606 0.6537 0.7250 0.8076 0.8740 0.9406 1.0000
N
di0 0.7026 0.7192 0.7319 0.7469 0.7607 0.7755 0.7918 0.8050 0.8214 0.8369 0.8514 0.8659
MIXTCRES----Mo!e fraction n’D” toluene B p
c.
1.3970 0.0000 1.4073 0.1150 1.4150 0.2170 1.4229 0 , 3 0 5 0 1.4311 0 . 3 9 5 0 1.4403 0.5095 1.4499 0.6190 1.4582 0.7080 1.4684 0 , E030 1.4774 0.9020 1 , 4 8 7 1 1.0000 1.4966
TABLE 111.
125.40 122.80 120.50 119.00 117.45 115.55 113.90 112.75 111.90 110.95 110.40
DENSITY
FRON
0
0.0000 0.0432 0.0913 0.1399 0.1778 0.2269 0.2740 0.3574
TIVE
INDEX
0.1640 n. 2970 0.4100 0.4605 0.5265 0.5855 0.6235 0.6620 0.6975 0.7300 0.7785 0.8030 0.8325 0.8555 0.8825 0.9225 0,9550
0.055 0.112 0.164 0.227 0.282 0.322 0 382 0.444 0.490 0.542 0.578 0.651 0.685 0.726 0.803 0.838 0.916
0.094 0.183 0.252 0.328 0.409 0.440 0.500 0.558 0.596 0.638 0.670 0.723 0.750 0.781 0.841 0.870 0,929
c.
c. 0.4549 0.5411 0.6390 0.7218 0.8201 0,8983 1.0000
113.70 111.30 108,70 106.60 103.95 101.80 99.20
0.051 0.107 0.160 0.208 0.248 0.281 0.321 0.360 0.392 0.424 0.464
TABLEIv. DATAO X HEPTANE 7 K ~ o ~ ~MIXTURESMole fraction .V-heptane d:’ ~L’D” 0.0000 0.0787 0.1638 0.2486 0.3372 0.4126 0.5186 0.6056 0.6993 0.7942 0.9338 1.0000
0.7693 0.7613 0,7535 0,7454 0.7377 0.7312 0.7218 0.7145 0.7069 0.6992 0.6884 0.6839
1.4232 1.4200 1.4165 1.4135 1.4100 1.4075 1.4036 1.4004 1.3970 1,3942 1.3899 1.3878
-
B.p. 100.80 100.55 100.35 100.15
....
99.70 99.20 99.00 98.85 98.60 98.50 98.40
AND
01
0.105 0.197 0.290 0.356 0.409 0.450 0.500 0,535 0.575 0.610 0.650
0.488 0,560 0.588 0.658 0.698 0.739 0.788 0.835 0.892 0.933
0.675 0.735 0.755 0.810 0.835 0.854 0 . 890 0.915 0.945 0.969
03
$0-6
03 05
8 0’4
05
072
07
08 MCL FRACTION n M?JAhrf
FIGURE 1. DER’SITIES OF N-HEPTA\EMIXTURES TOLUENE
between this volume and the original 10 cc. gave the volume of toluene. A portion of the top layer of S-heptane and methylcyclohexane was pipetted off and analyzed by density as in the binary mixture. In testing the accuracy of the above method of analysis, a definite volume of a known mixture of S-heptane and methylcyclohexane was placed in the bottle and a known volume of toluene added (totaling 10 cc.), the mixture being treated exactly as above. It was found that the toluene was quantitatively removed and the remaining volume of S-heptane-rnethylcyclohexane could be read accurately within 0.5 per cent. Analysis of this layer showed it to be of exactly the same composition as when placed in the bottle. TABLE
v.
DATAON N-HEPTANE,METHYLCYCLOHEXASE, -4XD TOLUEXE
(Experimental values from extraction a n d density measurements)
MOLEFRACTIONS O F LIQUID
METHYLCYCLOHEXANE
0.0350 0.0620 0,1030 0.1430 0.1920 0,2290 0.2890 0 3330 0.3810 0 4200 0 4750 0.5210
e-2-e
$
NEXPTL. VALCES F R O M DENSITY EXPT.heptane 11EASUREMENTS, > I O L E FRACTION 1 0.0460 N-HEPTANE 2 0.1026 Liquid Vapor Liquid Vapor 3 0.1590
0.0310 0,0580 0.0950 0,1330 0.1800 0.2160 0.2715 0.3170 0 3630 0.4010 0.4560 0.5010
OB2
-e
MEABOREIIENTS, MOLEFRACTIONMOLEFRACTION TOL uE N E TOL u E N E Liquid Vapor Liquid Vapor
-
125.40 124.15 123.15 121.70 120.85 119.15 118.50 116.05
00
02
REFRAC-
>IEASCREMENTS,
0.0970 0.2030 0.3000 0.3460 0.4075 0.4800 0.5270 0.5710 0.6145 0.6630 0.7215 0.7570 0.7945 0.8235 0.8580 0.9075 0,9450
2 64
EXPTLV A L ~ E S
DATA O S 2,2,4-TRIMETHYLPESTANE AND x-0CTAh.E K h - o n . ~MIXTCRES-Mole Mo!e EXPTL.V.4LUES fraction fraction F R O M BOILING POINTS, 2,2,4-tri2,2,4-tri1 f O L E F R A C T I O N 2,2,4methyl methylTRIMETHYLPENTAXE pentane B. p. pentane B. p. Liquid Vapor Liquid Vapor 7 -
086
.Y-OCTAKE
EXPTL. VALCES -KNOT!
0.6340 0.6705 0.7080 0.7320 0.7940 0.8200 0.8600 0.8980
0.5590 0,5990 0.6470 0.7090 0.7560 0.7960 0.8430 0.8790 0.9060 0.9310 0.9540 0.9800
0.5780 0.6180 0.6660 0.7280 0.7710 0.8100 0.8535 0.8900 0.9130 0.9400 0.9625 0.9860
v-ith mole fraction. Owing to the tendency of the more volatile 2,2,4-trimethylpentane to boil off the solution when boiling points were being taken in the Cottrell apparatus, the same conditions of operation were employed for each sample; that is, the quantity of sample taken, the amount of
4 5 6 7 8 9 10 11 12 13 14 15 16 17
0.2040 0.2540 0.2890 0,3240 0.3575 0.4070 0.4475 0.4790 0.5170 0.5500 0.6030 0.6235 0.6605 0.6885
Methylcyclohexane Toluene 0.7385 0.2155 0.6805 0.2170 0.5930 0.2480 0.5355 0.2605 0.5005 0.2455 0.4705 0.2405 0.4395 0.2365 0.4000 0.2425 0.3485 0.2445 0.3005 0.2620 0.2565 0.2645 0.2225 0.2605 0.1730 0.2770 0.1360 0.2610 0.1000 0.2765 0.0795 0.2600 0.0445 0.2670
MOLEFRACTIONS O F VAPOR NEXPT.heptane 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
0.0550 0.1120 0.1765 0,2230 0.2810 0.3185 0,3550 0.3885 0,4425 0,4835 0.5180 0.5600 0.5790 0.6470 0.6720 0,7065 0,7390
Methylcyclohexane 0.7635 0.7045 0.6046 0.5500 0.5075 0.4750 0.4395 0.4005 0.3446 0.2985 0.2570 0.2200 0.1826 0.1340 0.0975 0.0750 0.0395
Toluene 0.1815 0.1835 0.2190 0.2270 0.2115 0.2065 0.2055 0.2110 0.2130 0.2180 0.2250 0,2200 0.2385 0.2190 0.2305 0,2185 0.2215
The same accuracy was found to prevail in the analysis of the ternary mixture of iV-heptane-methylcyclohexaneacetone upon extracting the latter (in the same manner as above) with water. Tests also showed that all of the acetone was removed in one extraction.
As \(!(il, irusr1 'Vahlcs \ e1rd \ I , t k tc,1oeiie Rliil acetime were present in t i l e ririgirial >uistiiri?.i ill sticlr aniounts that t,heir rnole fraetioiis in the liquid mid vapor pii fairly eosistant. T . \ ~ i , eVI. D . \ n os S 9 i (I;rperime,,tas
YLi!UBB
i,,m extraCli0,L sild tieri$ity eieun"re,iloiii"a)
Sl&l; F*l.+riiona0,' vaiun ilotlwiN'.yfio-
Mom Fimcrroua oc i i i c u x ~
Methyleyeiof i x m haptone hexane 0 . 0 W 0.8385 1 2 0.0605 0.8070 0.1200 0.7465 3 0.1730 0.70!J0 4 5 0.2336 o.64io 0.8595 0.5350 0.4350 0.4585 0.4710 o.:ms (I 0.6350 n . m 5 SO 0.5850 0.2635 IS 0.6340 0.2325 12 0.6440 0.1865 ? ..I
e
b
13
0.1S35
14 1.5
0.7915
16
0.7540 0.8085
0.1240
0.09S0 0.0620 0.0445
..il.riona E x i ihwtane ~ 0,0000 0,1615 1 2 0 U2$15 0.1:325 0 0585 0.!1:45 3 0.088,5 0.1180 4 o.ii$15 %, 0.1166 0,lOii 6 I). 0.1065 7 0.
u.1405 0.1415 0.1515 0.14:15
0.1696 0.11125 0.1550 0.1465 0.1470
x o
IO 11 12 S3 14
0. 0. 0.2206 0 0.
IICXI(IIIIA c c t w c 0.:4:450 0 . 6 6 5 0
0.3655 0.3395 0.:?21,5
0.0050 0.0020 0.5c100 0 ~ 2 8 7 5 0.5870
0.1046
0.6750
O.El8.5 O.Bl(I0
I5
0. 0. 0.8535
0.0280
16
0.3610
0.0200
The two systems N-lieptanc~~tolucne arid tu1ueneN-octane are well siiited t.o tile drterniiiiatiini of efficiencies of fraetiiisi..
~
A Spanish Pharmacy by
JOSE J I M E N Y~ A n ~ s u a (1837-I!XKA)
The original painting (22'/3 by 3?/, iiichcs irr sisi:) is reprcsmtative of the modem Spanish School. It ahows the pliarmecist with his apprentice deciphering a pn:saript,ion, while Dr. Sungssdo and liiv friends nro discussing politics. This painting was formerly owned by Mr.George: I,. S m e y OS Rrcmklyri and was purchased a t the E'ischhof sale in N e w York by MF.Charles K a y s w Sbr $1400. This is No. 34 in the saries. I.
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