Analysis Data for the Ternary System Acetone-BenzeneWater EDITH HONOLD AND HELMUT WAKEHAM, Southern A rapid and accurate method of analyzing mixtures containing acetone, benzene, and water has been developed, using density and tafractive index data at 25' C.
T""
need for a rapid and accurate method of analysis for mixtures containing acetone, benzene, and water arose in connection with solvent-recovery problems in pilot-plant-scale operations on the extraction of rubber from goldenrod leaves. The method described below has proved very practical and satisfactory. The fundamental data as well as the method should find applications in other investigations of solvent extraction or ternary liquid behavior involving this system. The components of the system acetone-benzene-water are coinpietely miscible a t 25" C. for concentrations of acetone greater than 65 weight %; for lower proportions of acetone two pl:a.,c: may be formed when both benzene and water are present 7.7 : ~ ext,ent. y Density and refractive index data for the acetone-benzene and acetone-water binary systems which are each mutually soluble have been determined by others over limited temperature ranges and are summarized in the International Critical Tables ( 7 ) . More recently Ernst et al. (6) and Young (11) have reported additional density data on the acetone-water system a t 25" and 20" C., respectively. Solubility curves and tie line data for the ternary system a t 15", 30",and 45" C. were obtained by Briggs and Comings (4) by means of refractive index measurements. In the present investigation density and refractive index data at 25' C. for this system in the region of complete miscibility were obtained t o permit analysis of mixtures in the homogeneous portion of the ternary diagram.
I
I
Regional Research Laboratory, N e w Orleans, La. EXPERIMENTAL
MATERIALS. Reagent rades of acetone and benzene were used without further puriication. Densities and refractive indices of the original starting liquids a t 25" C. were found to be as follows: acetone, d. 0.7857, nn 1.3562; benzene, d. 0.8731, n~ 1.4972. These values agree sufficiently well with the better literature values summarized in the Annual Tables of Physical Constants ( 1 ) to permit analyses with an accuracy of 0.5% by the method herein described. Distilled water was used throughout. Refractive indcx was determined with a dipping refractometer of precision *O.ooOo5 on the solutions held in a metal cup which was surrounded by water circulated from a constant-temperature bath. Dcnsity was measured by National Bureau of Standards calibrated hydrometers havin a precision of *0.0002. For this determination approximatJy 250 cc. of the solutions were used in large stoppered test tubes immersed in the bath and were allowed to come to temperature equilibrium for a t least 30 minutes before reading. The bath, set for 25" C., maintained the temperature constant to within +0.05' C. Solutions were prepared by weighing out the components to 0.01 gram on a 2-kg. capacity analytical balance. Mixtures amounting to 300 cc. were prepared to give ample material for density me urement and to decrease inaccuracies due to e v a p oration of tp;Se more volatile components. TERNARY SYSTEM
The method of analyzing three component systems by rneasuring two independent properties has been described by Berl and Ranis (3) and others (2, 6, 8, 9, 10). In the present method reTable
I
Weight % Benaene
94.96 86.28 77.44 69.72 62.03 54,04 49.07 44.50 90.03 82.07 73.75 66.21 80.13 71.42 64.98 69.57 66.89 64.84 54.16 49.41 40.61 19.76
5.04 4.58 4.11 3.70 3.29 2.86 2.60 2.36 9.97 9.09 8.17 7.33 19.87 17.71 16.11 30.43 29.26 28.36 45.84 50.59 59.39 80.24 100
.....
I370
I390 INDEX OF REFRACTION
Figure 1.
1419
95.44 79.82 74.91 69.25 61.56 53.81 47.16 43,95 90,47 81.53 73,60 80.14 76.50 68.39 69.75 67.92 65,75 60.98 57.80 49.10 48.10 39,85 39.77 29.85 21.47 20.02
I430
.....
Refractive Indices for Mixtures of Acetone, Benzene, and Water
499
I. Experimental Data
Weight % Acetone 100
......
....
16.36 21.50 27.43 35.49 43.61 50,523 53.94 ,...
9.88 18.65 ,... 4.54 14.66 ...,
2.63 5.74 .... 5.21 ....
....
.... ... .... .... .... I
....
Weight % Water
...... ...
9.14 18.45 26.58 34.68 43.10 48.33 53.14
....
8.84 18.08 26.46
....
IO.87 18.91
....
3.85 6.80
....
.... .... .... ....
4.56 3.82 3.69 3.32 2.95 2.58 2.26 2.11 9.53 8.59 7.75 19.86 18.96 16.95 30.25 29.45 28.51 39.02 36.99 50.90 51.90 60.15 60.28 70.15 78.53 79.98 100
Db
nD
1 ,3562
1.3625 1,3654 1.3671 1 ,3675 1.3666 1.3650 1.3634 1.3617 1 ,3688 1.3710 1.3718 1.3714 1.3812 1 ,3823 1.3814 1.3950 1.3952 1.3952 1.4166 1.4229 1.4350 1.4666 1.4972 1.3581 1.3784 1.3850 1.3927 1.4029 1.4145 1.4233 1.4288 1.3600 1.3719 1.3828 1.3626 1 ,3678 1.3795 1 ,3634 1.36M 1 ,3699 1 ,3629 1.3686 1.3606 1.3600 1.3572 1.3573 1.3524 1.3477 1.3467 * 1.3325
Densityat 25' C.
so0
INDUSTRIAL AND ENGINEERING CHEMISTRY Table II.
Refractive Index
1.335 1.340 1.345 1.350 1.355 1.160
1.365
1.370
Weight
Derived Data for Ternary Diagram at 95' Weight
%
Weight
%
Renzene
3.2 9.9 17.5 25.6 35.0 97.0 93.7 90.4 47.9 43.40
96.8 91.1 82.5 74.4 65.0 3.0 1.3 0.0 2.1
5.0 9.6 52.1 54.5
93.0 89.6 88.7 86.0 82.2 77.9 73.4 68.5 50.W
7.0 5.4 5.0 4.0 2.8 2.1 1.6 1.5 3.8
0.0 5.0 6.3 10.0 15.0 20.0 25.0 30.0 45.4
89.0 87.0 85.5 81.9 78.0 73.6 68.9 63.8 56.7"
11.0 10.0 9.5 8.1 7.0 6.4 6.1 6.2 6.8
0.0
3.0 5.0 10.0 15.0 20.0 25.0 30.0 36.5
85.1 81.6 77.8 73.8 69.3 64.5 60. ga
14.9 13.4 12.2 11.2 10.7 10.5 11.0
0.0 5.0 10.0 15.0 20.0 25.0 28.1
81.1 77.6 73.9 69.8 65.1 63.7'
18.9 17.4 16.1 15 2 14.9 15.2
5.0 10.0 15.0 20.0 21.1
77.1 73.8 71.1 70.1 65.8 65.Oa
22.9 21.2 20.0 19.9 19.2 19.2
Acetone
0.0
%
Water 0.0 0.0 0.0
0.0 0.0 0.0
Refractive Index
1.380
1.385
Den-
0.0
0.800
0.810
0.820
0.830
0.840
%
Weigh1
Benzene
73.3 70.1 69.9 66.3 64,So ,391, 69.5 68.6 66.2 63.5"
26.7 24.9 25.0 23.7 19.2 30.5 30.0 28.8 27.5
,400
65.8 62.6 61.4O
34.2 32.4 31.5
0.0 5.0 7.1
,405
62.1 59.0 58.6a
37.9 36.0 35.8
0.0 5.0
,410
58.5 55.6O
41.5 40.0
0.0
1.415
55.0 52.5"
45.0 43.8
3.7
51.4 49.3"
48.6 47.7
0.0
47.7 46.2O
52.3 51.2
0.0
44.2 43.1"
55.8 54.9
0.0
59.3 62.7
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
1.390
1.420
%
Water 0.0
5.0 5.1 10.0 16.0
0.0 14 5.0 9.0
5.6 4.4 0.0
1.435 1.440 1.445 1.450 1.455 1.460 1.465 1.470 1.475 1.480 1.485 1.490 1 495
40.7 37.3 33.9 30.6 27.3 24.1 20.7 17.4 14.0 10.7 7.4 4.1 0.8
66.1
E 4 75.9
79.3 82.6 86.0 89.3 92.6 95.9 99.2
2.6 2.0
5.0 8.9 10.0 15.0 15.8 Denaity
98.4 94.6
0.0 5.4
95.2 91.6 88.0 84.3 82.6
0.0 5.0 10.0
91.8 88.3 84.6 83.4 80.9 77.3 73.7 70.7 88.4 84.4 84.8 81.2 77.5 73.8 71.0 70.2 66.7 63.1 59.6 58.6 84.9 81.2 77.6 73.9 71.1 70.3 66.8 63.3 59.5 58.5 56.1 52.6 47.3 81.3 77.6 74.0 70.8 66.5. 65.1 35.7
3:: 0.0
5.0 10.0 11.6 15.0 20.0 25.0 29.3 0.0 5.6
5.0 10.0 15.0 20.0 24.0 25.0 30.0 35.0 40.0 41.4 0.0
5.0 10.0 15.0 lk.9 20.0 25.0 30.0 35.0 36.5 40.0 45.0 52.7 0.0
5.0
10.0 14.2 20.0 22.3 64.3 Cloud point data.
1.6
0.850
77.7 74.0 70.5 70.2 66.3 64.7" 24.5
22.3 5.0 9.5 10.0 15.0 17.7 75.5
0.0 21.0 20.0 19.8 18.7 17.6
0.860
73.9 70.0 66.1 62.ga 13.5
0.0
5.0 10.0 14.4 86.5
26.1 25.0 23.9 22.7
0.870
69.8 66.1 62.0 61 .05 2.9
0.0 5.0 10.0 11.5 97.1
30.2 28.9 28.0 27.5 0.0
0,880
65.6 62.0 58.7a
0.0 5.0 8.9
34.4 33.0 32.4
0,890
61.7 56.1"
0.0 6.9
38.3 37.0
0.900
57.4 53.4"
0.0 5.3
42.6 41.3
0.910
j2.8 50.3"
0.0 3.8
47.2 45.9
0.0
4.8 3.4 2.0 0.7 0.0 8.2 6.7 5.4 5.0 4.1 2.7 1.3 0.0 11.6 10.0 10.2 8.8 7.5 6.2 J
..e
4.8 3.3 1.9 0.4
0.0
0.0
0.0
l5,l 13.8 12.4
0.920
48.2
0.0.
4 6 . 6a
2.8
51.8 50.6
0.930
43.3 42.2"
0.0 1.9
56.7 55.9
0.940
38.0 37.30
0.0 1.1
62.0 61.6
0.950 0.960 0.970 0.980 0.990
32.3 26.1 19.5 12.3 5.0
0.0 0.0 0.0 0.0 0.0
67.7 73.9 80.5 87.7 95 0
11.1
10.0 9.7 8.2 6.7 5.5 5.0 3.9 2.4 0.0
18.7 17.4 16.0 15.0 13.5 12.6 0.0
so
3.0 WEIGHT
1 428
0.0
aity
0.790
yo
L.
Acetone
1.430 1.375
Weight
Weight
Vol. 16, No. 8
PERCENT
WATEP
Figure P. A n a l sir Diagram for Acetone-Benzene-Water Mixtures Antaining M o r e Than 50% Acetone
fractive indices and densities were determined for a number of solutions of known composition, so that lines of equal density and of equal refractive index could be constructed. These lines were plotted on a triangular chart in such a way that the romposition of an unknown could be found by interpolation of its measured density and refractive index values. Two series of mixtures were prepared, one starting with acetone and water in different proportions, the other with acetone and benzene; the third component was added stepwise until the cloud point was reached, measurements of refractive index and density being made after each addition. The data of the one series thus overlapped and served to check the data of the other over most of the region of homogeneous mixture. Table I includes experimental data for the ternary system a t 25" C. From graphical interpolation of these data it was possible to construct plots of the refractive index us. acetone composition for various mixtures of constant water or constant benzene contents as shown in Figure 1. Using values obtained from this figure lines of common refractive index were constructed on the triangular chart for the ternary diagram. The density lines were determined in a similar manner. Figure 2 shows both sek of lines for ternary mixtures containing more than 50% acetone. Data used to construct the curves in Figure 2 and additional data covering the system for mixtures with less than 50 weight % acetone are given in Table 11. If the density and refractive index of a homogeneous unknown of acetone, benzene, and water are determined a t 25" C., the composition in weight per cent of the sample may be found to the nearest 0.5% by interpolation of data in Figure 2 and Table 11. Cloud-point compositions a t 25" C. were compared to data obtained by intGrpolation of values reported by Briggs and Comings (4) at l 5 O and 30" C. Good agreement between these two sets of data was observed over the entire solubility curve. ACKNOWLEDGMENT
The help and suggestions of Evald L. Skau of this laboratory :ire gratefully acknowledged. LITERATURE CITED
(1) Annual Tahles of Physical Constants, N. Thon, ed., Sections 301
and 921. Frick Chemical Laboratory, Princeton, N , and 1942. (2) Barbaudy. M . J . , Bid!. w e . chim., (4) 39, 371 (1926). (3) Berl, E . , and Ranis, L . , R e r . , 60 (11), 2225 (1927).
J., 1941
August, 1944 (4)
ANALYTICAL EDITION
Briggs, S. W., and Comings, E. W., IND.ENG.CHEM.,35, 411 (1943).
(5) Coull, J., and Hope, H., J . Phys. Chem., 39,967 (1935). 16) Emst, R. C., Litkenhous, E. E., and Spanyer, J. W., Ibid., 36,
842 (1932). ( 7 ) International Critical Tables, Vol. 111, pp. 112, 163; Vol. VII, pp. 68, 82,New York, McGraw-Hill Book Co., 1928.
Analysis
OF
501
(8) Othmer, D. F., White, R. E., and Trueger, E., IND.ENG. CHEM.,33, 1240 (1941). (9) Schneider, C. H., and Lynch, C. C., J . Am. Chem. SOC.,65, 1063 (1943). (10) York, R.,and Holmes, R. C., IND.ENG. CHEX., 34, 345 (1942). (11) Young, W.,J . SOC.Chem. Ind.. 52, 449T (1933).
Cellulose Derivatives
Total Acyl in Cellulose Organic Esters by Saponification in Solution CARL J. MALM, LEO E. GENUNG, ROBERT F. WILLIAMS, JR.~,AND M A R Y ALICE PILE Eastman Kodak Company, Rochester, N. Y. Mast Mpanification methods for the determination of total acyl in ceiluiore organic acid esters involve heterogeneous conditions. A ~ r \ e t h dhrr been developed in which the sample i s saponified i n *ol,tion. A* a result, homogeneous saponification conditions exist which eliminate errors due t o the condition of the sample, improve thc arcdraey, shorten the time of saponification, and give a better end point. The effects of time, temperature, and alkalinity were studied and the optimum conditions for each were established. The rang? d applicability of this method i s discussed i n d compared with the Coerstadt and alcoholic alkali methods. Thz basic principle followed rnvolves solution of the sample i n a suitable solvent, followed by siepwireirdditionr of alkali and water under conditions such that the ester remains i n solution until saponification i s practically complete. The regenerated or only slightly esterified cellulose
finally precipitates i n a soft finely divided form which does not interfere with completion of the reaction or the back-titration. The precision obtainable by this method has been evaluated and limits of uncertainty (maximum range within which nearly all carefully run values should fall) are * O . l t o 0.9% acetyl, depending on the type of ester being analyzed. A mersure of the accuracy of the method was obtained by analyzing samples for free hydroxyl and for acetyl or apparent acetyl (saponification value calculated as acetyl) and complete acyl in the case of cellulose mixed esters. The observed acetyl or rpparent acetyl values were compared with those calculated by difference from observed free hydroxyl contents and molar ratios of the acyl groups i n the case of cellulose mixed esters, assuming exactly 3 hydroxyls per glucose unit of cellulose. The agreement was well within experimental error.
HE determination of total acyl in cellulose organic esters by baponifidhn in solution overcomes some of the difficulties e n c o u n t e d in the heterogeneous saponification methods such as t,ha E b e r s h i t (or Knoevenagelj and th- alcoholic alkali methods dessribed in thc first paper of this series (6). A solution method iias been developed which eliminates the effect of the physical form of the sample, permits the use of a lower alkalinity and a diopter time of saponification, and gives a more satisfactory end point. an4 E slight improvement in accuracy. However, the solvei,k XIUS;; be varied to suit the composition and solubility of each t>-pciof ester, and the manipulation is somewhat involved au.i rnu.t, be varied for each different t.ype of ester. It is thus lwtter atlapkd tlo routine analyses of familiar samples than to iwlntec! analysrs of unknown samples. neiple followed involves solution of the sample in a t, followed by stepwise additions of alkali and ndi tions such that the ester remains in solution ! >apoftAriLtioni s practically complete. Khen the regenerc t c d C J oniy ~ x!ightly esterified cellulose finally comes out of solution it ;s 111 a oft finely divided form which does not interfere with tile cornpieticin of the reaction or the back-titration. Conditions of tcn,perature and alkali concentration are chosen to ensure a complcte rea( tion and to avoid the formation of acids by the decomposition of cel11~11~s~~. A t leuhi thrce saponification methods are now available for the anal:+& of kite organic esters of cellulose. The Eberstadt method i-. simple and best adapted t.o the acetone-soluble cellulose acetates and to hydrolyzed ceLiulvse acetate propionates and acetate 1.utyra tes having low propionyl and butyryl cont.ents, if these samples are in good physical form. I t is also recommended for cellulose acetates having less than 15%, acetyl. The alcoholic alkali method is simple and is widely applicable to cellulose esters, hut usually is less accurate than the Eberstadt method. Both mtthods are inaccurate when the liquid medium used
swells and softens the ester excessively but does not dissolve it. The saponification in solution method described in this paper may be used on solvent-soluble cellulose acetates, propionates, butyrates, acetate propionates, and acetate butyrates. It is particularly useful for esters not readily analyzable by the Eberstadt method'and where good accuracy is desired. There are several references in the literature to methods in which the cellulose ester is dissolved in-a solvent, such as acetone or pyridine, and the alkali added dropwise. Partial sapodfieation is thus carried out in solution, but no precautions are given for maintaining a solvent system and for holding the saponifying ester in solution as long as possible.
1
Now in service of U.S. Coast Guard.
Barnott (1) described a procedure, applied only to acetonesoluble cellulose acetates, by which a 0.3-gram sample was dissolved in 30 ml. of acetone and was saponified with 50 ml. of 0.1 N sodium hydroxide for 24 hours a t room *temperature. After diluting with water, the excess alkali was back-titrated with 0.1 N acid using phenolphthalein indicator. It was necessary to run a blank on the reagents and on cellulose and a considerable correction was applied. Battegay and Penche (t)analyzed cellulose acetate by dissolving a 0.3 to 0.5-gram sample in 30 ml. of pyridine a t 40' C. The solution was cooled to 25' C., and 50 ml. of 0.5 N alkali were added. .ifter shaking for 0.5 hour the excess alkali was back-titrated. Murray, Staud, and Gray (9) developed a rapid acetyl method in which a 0.5-gram sample was dissolved in 20 ml. of pyridine and was saponified for 0.5 hour a t about 50" C. with 20 ml. of 0.5 N alkali. This method is rapid and applicable to a certain range of cellulose acetates, but the temperature used is too high. Charriou and Valette (3) determined the acetyl in cellulose acetates by dissolving a 1.5-gram sample in 100 ml. of acetone and adding 50 ml. of 0.5 'V sodium hydroxide dropwise with agitation. The flask was stoppered and agitated vigorously for 0.5 hour and the excess sodium hydroxide titrated with 0.5 N sulfuric acid using phenolphthalein indicator. A Du Pont specification ( 4 ) gives a method in which a 1.5-gram sample is dissolved in 100 ml. of acetone, 50 ml. of 0.5 N sodium hydroxide are added dropwise, and after 3 hours of agitation the excess is titrated with 0.5 N hydrochloric acid using phenolphthalein indicator.
