ANALYTICAL EDITION
February, 1946 ~~
~
Table
VI.
Accuracy and Precision of Proposed M e t h o d
Petroleum Cresylic Acids
Cresylic dcids Founda Mg./lOO ml. technical octane MU. 0.0 0.0 10.6 10.5 10.4 10.6 10.3 10.6 10.6 10.3 10.6 10.6 10.5 10.6 Systematic error Standard deviation
(B.R. 220-225' C.) Added
92.2 92.2 92.2 92.2 92.2 92 2
92.4 92.2 90.9 91.5 90.8 91.3 Systematic error Standard deviation
Recovery
7c ...
98.8 97.9 97.2 97.2 98.8 98.8 -1.9 10.7 100.2 100.0 98.6 99.2 98.5 99.0 -0
.
109
mixture only-that is, the amount of color produced by the various phenols varies markedly. Accuracy of the method will depend upon the proper choice of a standard. The experimental work reported in this paper demonstrates the \vide scope and versatility of the method. I t has found extensive use in research, control, and specification analytical work involving various types of materials and phenolic compounds. ACKNOWLEDGMENT
The authors wish to thauk F. D. Tuemmler for his interest and encouragement and K. R. Fitzsimmons for assisting in part of the analytical work. Especially, they wish to thank D. R. McCormick, who materially assisted in writing the manuscript. LITERATURE CITED
7
*O 6
Folin, O., and Denis, W., J . Biol. Chem., 22, 305 (1915). Gibbs, H. D., Chem. Rev.,3, 291-319 (1926). Gibbs, H. D., J . Biol. Chem., 72, 649 (1937). Houghton, G. U.,and Pelly, R. G., AnaZyst, 62, 117-20 (1937). Stoughton, R. W., J. Biol. Chem., 115, 293-9 (1936). Wetlaufer, L. A., Van Natta, F. J., and Quattlebaum, H. B., I N D . ENG. C H E M . , ANAL. ED.,11,438-9 (1939).
a Spekker photoelectric absorptiometer.
of the phenols presents only a minor problem. In any application it must always be realized that the colorimeter response per milligram of phenol is a specific property of that phenol or phenol
Analysis of Ternary Mixtures of MethylcyclohexaneTo1uene- Ani1ine C. S. CARLSON', A. E. SCHUBERT',
AND
M. R. FENSKE
Petroleum Refining Laboratory, School of Chemistry and Physics, The Pennsylvania State College, State College, Pa.
A method of analyzing the ternary mixture methylcyclohexanetoluene-aniline has been developed. The refractive index of the ternary mixture and of the residual binary hydrocarbon after removing the aniline b y acid extraction completely defines the ternary system. With the aid of an experimentally established curve, the ternary analysis can b e found.
T
HE analysis of a binary liquid mixture can often be made by measuring one physical property such as refractive index or density, when a second variable such as temperature is fixed. The introduction of a third component complicates the problem and necessitates fixing another variable to permit analysis by the measurement of one physical property. Unfortunately, fixing another variable is not easy, since both temperature and pressure (1 atmosphere) have already been fixed for the t n o-component bystem. Varteressian and Fenske (,8) analyzed mixtures of n-heptanemethylcyclohexane-aniline by means of refractive index measurements for the special case of liquid-liquid extraction where the solution was saturated and in equilibrium with a second immiscible solution a t a given temperature and pressure, and also applied this method to the system benzene-ethyl alcohol-water ( I ) under the same conditions. The method of analysis described in this paper is concerned with the case where the solution is not saturated under specified conditions, but exists as a completely miscible solution. PROPERTIES OF M A T E R I A L S USED
The methylcyclohexane was the best commercial grade furnished by the Rohm and Haas Company of Philadelphia. I t was extracted n-ith concentrated sulfuric acid, washed, dried, and then fractionated in a laboratory column of approximately 35 theoretical plates. The best cuts from the fractionation were combined 1 2
Present address, Standard Oil Development Company, Linden, K.J Present address, General Electric Company. Schenectady, N. Y .
and used in this work. properties :
The purified material had the following
50% boiling point a t 760 mm., C. 0 t o 50% boiling point spread, O C. Density, dzo Refractive index, ng
100.90 0.0
0.7695 1.42310
The t,oluene was also purified before use. The best commercial grade of nitration toluene furnished by the Barrett Company, Frankford, Pa., was fractionated in a large column of approximat'ely 75 theoretical plates. The best cuts from the fractionation were sulfonated with concentrated sulfuric acid and separated from impurities by steam-distillation, after which the toluene was regenerated by hydrolysis. The regenerated toluene was then first fractionated to remove any by-product of hydrolysis. The purified material had the following properties: 50% boiling point at 760 mm.,
C. 0 t o 50% boiling point spread, O C. Freezing point, O C. Density, dzo
110.65 0.0
-95.2 0.8672 1.49685
Refractive index, n%'
The aniline was the n,ater-n.hite commercial product of the Dow Chemical Company. Before use, it was dried over Baker's sodium hydroxide pellets and then subjected to three successive simple distillations, discarding a generous portion of the fore-
Table I.
Analysis of Mixtures of Methylcyclohexane-Toluene-. Aniline
(Using refractive index of binary hydrocarbon mixture and of t e r n a r y mixture) Composition of Test XIixtures, Weight Per Cent Gravimetric Composition By Analysis P e r Cent Error Ma T A 11 T A M T A 1 8.24 36.80 54.95 8 . 3 2 2 0 . 9 0 23.52 5 5 . 6 0 2 0 . 8 3 33.80 9 . 6 0 56.70 33.4 13.20 14.85 71.90 1 3 . 1 o 36.70 40.70 22.60 3 6 . 8 a 11 = methylcyclohexane, T =
4
37.1 54.6 23.4 55.8 9 . 3 57.3 14.6 72.3 40.4 22.8 toluene, A =
+0.73 -0.48 -1.18 -0.76 +0.27 aniline.
+0,81 - 0 . 6 4 -0.51 -3.13 -1.68 -0.74
+0.36
+1.06 +0.56 +0.88
INDUSTRIAL AND ENGINEERING CHEMISTRY
I10
Vol. 18, No. 2
ANALYTICAL PROCEDURE Table
II. Composition of Hydrocarbon Portion of Ternary Mixtures, M o t hylcyclohrxane-Toluene-Aniline
(Expressed a8 mole per cent methyloyclohexane on a binary hydrocarbon basis) Cornnosition bv Refraot i v i Index, Analysis Gravimetric after Removal of Aniline Composition b y Dilute H C P Per Cent Error 17.4 17.5 0.57 45.5 45.4 -0.22 76.75 77.1 0.46 45.2 45.5 0.66 45.9 46.05 0.33 r a One volume of concentrated hydrochloric acid diluted to 5 volumes with diatilled water.
runnings and the residue. properties:
The purified aniline had the following
Density, d:O Refractive index, n y
1.0219
1.5863
Since the system being analyzed consists of one phase and threi. components, the phase rule, P V = C 2, indicates that there are four variables. Two variables, tcmpcrature and pressure, can be easily fixed. When a third variable is fixed, measuremcnt of a fourth variable will define the syst,em. The third variable fixed is the ratio of niethylcyclohexane to toluene or the composition of the hydrocarbon portion of the inixiiirc on a solvent-free basis.
+
+
Table I l l . Refractive Index vs. Composition of MethylcyclohexaneToluene-Aniline Mixtures with M o l e Per Cent Methylcyclohexane in Toluene as Parametern wt,. ,% Aniline
ny
Ternary Mixture
0.0 hlole Sa 1.4969 1.5048 1.5132 1.5226 1.5306 1.5394 1.5486 1.5581 1.5669 20.2 Mole %
40.0 hlole % 0.00 1.4621 10.23 1.4730 19.98 1.4831 29.95 1.4944 40.50 1.5070 50.60 1.5188 59.80 1.5300 70.00 1.5440 80.30 1.5586 59.4 hlole 0.00 9.90 19.70 30.25 40.40 50.10 60.20 70.20 80.60
4
%
Wt. % iniline
I
Ternary ~ Mixture L
9.9 Mole % 1.4874 1.4957 1.5048 1.5136 1.5241 1.5334 1.5439 1.5535 1,5664
The refractive index, n y ,of the ternary mixture is read. The aniline is then removed from the mixture by extraction with dilute hydrochloric acid (1 volume of concentrated acid diluted to 5 volumes with distilled water). The refractive index, n:O, of the hydrocarbon after this extraction is also read. From the latter datum, the composition of the hydrocarbon mixture can bc obtained by means of a refractive index-composition chart. Thi$ comp,osition and the refractive index of the ternary mixture are m obtain the used in conjunction with the curves in Figure 1 i weight per cent of aniline in the ternary mixture. From this value and the composition of the hydrocarbon portion of the mixture, the over-all composition is calculated. To chcck the accuracy of this method of analysis, five mixtures of methylcyclohcxanc-toluene-anilinc wcre made up gravimetrically and analyzcd. The gravimetric analyses and the experimental analyses of the mixtures are listed in Table 1. The pcrccntagc error is bascd upon the gravimetric analysis as corrcct. Examination of thc analyses shows good agrcement. in most cases, while no value is greatly in error. Two sources of error exist in these analyses: the accuracy with which the refractive index of the ternary mixture can be read, and the accuracy of the hydrocarbon analysis after the aniline has been removed by dilute hydrochloric acid extraction. A study of the data in Tablc I1 will show that in almost every case the accuracy of the hydrocarbon analysis is within the accuracy of the refractive indcx measurements. Hcre again the percentage error is based upon the gravimetric composition. The technique cmploycd in obtaining thc rurves in Figure 1 was as follows:
A binary hydrocarbon mixture of methylcyclohexane-toluene of known composition was weighed out and combined with weighed amounts of aniline. The refractive indexes of these mixtures were read and a curve of refractive index versus weight per cent aniline was plotted with mole per cent methylcyclohexane in the binary hydrocarbon mixture as parametcr. Ten points were obtained to establish each curve, and ninc such curves were deter-
30.3 hlole % 1.4700 1.4809 1.4897 1.5002 1.5115 1.5235 1.5343 1.5470 1.5591 49.05 Mole 0.00 10.50 20.15 29.90 40.45 50.65 61.50 70.70 79.80
% 1.4852 1.4660 1.4769 1.4888 1.5020 1.5140 1.5289 1.5418 1.5550
70.1 hlole % 0.00 1.4408 10.20 1.4520 29.80 1.4762 1.4722 26.45 1.4905 40.70 50.60 1.5046 60.40 1.5191 69.20 1.5335 80.20 1.5515
78.4 hlole % 90.0 Mole % 0.00 1.4355 0.00 1.4285 10.90 1.4472 10.50 1.4400 19.50 1.4580 20.40 1.4505 30.30 1.4720 40.50 1.4865 Phase separation occurred 49.80 1.5000 here 69.90 1.5325 79.90 1.5494 Mole % methylcyclohexane in toluene on binary basis.
I
I
I
40 60 80 100 MOL PER CENT METHYLCYCLOHEXhNE IN TOLUENE ON SOLVENT-FREE BASIS
20
Figure 1.
Analysis of Ternary Mixtures
1.42
A N A L Y T I C A L EDITION
February, 1946
111 ACKNOWLEDGMENI
Table
IV.
Refractive Index, M o l e Per Cent Hydrocarbon Composition Data for Figure 1 for System M o t h ylcyclohexane-Toluene-Aniline
Mole 7 MethylcscloRexane0 w,t. 70aniline i n ternary 0
5 . 10 15
20 25 30 35 40 45 50 55 GO
65
io 75 80 82
I1
