LITERATURE CITED
Table 111.
Summary of Crystallization Procedure and Results
Starting Material Portion Freezingfrom Volume, point, Compound Fig. 15 ml. C. n-Octadecane -4 112 26 0 n-Nonadecane B 157 30 9 n-Eicosane C 155 34.6 n-Heneicosane D 157 38.2 n-Docosane E 151 41.2 n-Tricosane F 141 43.9 n-Tetracosane G 92 46.9 Table IV.
(1) American Petroleum Institute Re-
Crystallization Procedure Final Sample No. of Vol. of Vol- Freezine crystal- Temp., solvent, ume, point, lizations O C. ml. ml. “C. 6 10 125 50 27.15 7 15 100 44 31.89 7 15 125 44 36.15 6 28 100 40 40.33 7 28 125 46 43.92 c 28 125 47 47.42 28 150 45 50.93
-
i
Freezing Points of
C18
to
C24
n-Paraffins
Freezing Point in Air a t 1 Atni., O C. Hydrocarbon n-Octadecane n-Sonadecane n-Eicosane n-Heneicosane n-Docosane n-Tricosane n-Tetracosane
This investigation 27.15 31.89 36.15 40.33 13.92 47.42 50.93
,4solution of the ?I--paraffinin methyl ethyl ketone was cooled to the desired temperature. The crystals were separated from the mother liquor by centrifuging (in an International Centrifuge Co. centrifuge, S o . 418, %inch basket. 3600 r.p.m.), and were melted and washed n i t h hot water. This procedure was repeated. ilfter each crystallization the freezing point was determined for processing purposes with a mercury-in-glass thermometer to the nearest 0.1’ C. 1J7hen there was no perceptible change in freezing point for three successive crystallizations, the n-
(1)
(10)
(0
28.184
28.10 31.75 36.35
28.2 32.0 36.6 40.2
31
no
3G.44 40.5 44.4 4i.G 50.9
44.0
47.5 50.6
paraffin material was passed through silica gel in order to remove water and any possible trace of methyl ethyl ketone. An accurate freezing point was determined (under the supervision of ii. J. Streiff) on each purified sample, using the standard procpdure of the .%PIResearch Project 6 ( 3 ) . The results of the purification of the individual n-paraffins are summarized in Table 111. The freezing points of the n-paraffins obtained in this investigation are compared with values from the literature in Table IV.
search Project 44, “Selected Values of Properties of Hydrocarbons,” Carnegie Institute of Technology, Pittsburgh, Pa. (2) Charlet, E. RI., Lanneau, K. P., Johnson. F. B., ANAL.CHEM.26, 861 (1954). ’ (3) Glasgow, A. R., Jr., StreifF, A. J., Rossini, F. D., J. Research iVatl. Bur. Standards 35,219 (1945). (4) Mair, B. J.,Pignocco, A. J., Rossini, F. D.. ASAL. CHEV. 27, 190 (1955).’ ( 5 ) Montjar, Ill. J., “Fractionation of Hydrocarbons by Adsorption,” thesis, Carnegie Institute of Technology, Pittsburgh, Pa., October 1954. (6) Rossini, F. D., Mair, B. J., Streiff, il. J., “Hydrocarbons in Petroleum,” Reinhold, New York, 1953. (7)Schaerer, A. A,, Busso, C. J., Smith, A. E., Skinner, L. B., J . Am. Chem. SOC.77, 2017 (1955). (8) Schiessler, R. W., Flitter, D. J., Ibid., 74, 1720 (1952). (9) Schlenk, W.,Jr., Ann. 565, 204 (1949). (10) Tilicheev, M. D., Peshkov, V. P., Yuganova, S. A., J . Gen. Chem. ( U . 8. S. R.) 21, 1229 (1951). RECEIVEDfor review April 19, 1956. Accepted October 22,1956. Investigation performed under the American Petroleum Institute Research Project 6 in the Petroleum Research Laboratory, Carnegie Institute of Technology. The material in this report is taken from a dissertation submitted to the Carnegie Institute of Technology in partial fulfillment of the requirements for the degree of doctor of philosophy by W. J. Marculaitis, holder of a fellowship of the American Petroleum Research Institute Research Project 6, 1953-55, and of E. I. du Pont de Kemours I%Co., Inc., 1955-56.
Qua nti tut ive Se pa rati o n a nd Determina ti o n
of Glycol Mixtures by Azeotropic Distillation HELEN M. ROSENBERGER and CLARENCE J. SHOEMAKER Chemical Research and Engineering Department, A. 6. Dick Co., 5700 W. Touhy Ave., Chicago 31, 111.
A method for separating and quantitatively determining the per cent by volume of the constituents in an aqueous polyhydric alcohol mixture is based on the well-established principle of azeotropic distillation of the components from an immiscible solvent. Benzene, tetrachloroethylene, and d-limonene were selected as entrainers. This investigation was undertaken primarily as a mode of analysis for mixtures containing water-soluble tinctorial agents and water-soluble resins.
F
of aqueous polyhydric alcohol mixtures, containing water-soluble tinctorial agents and REQUEXT ANALYSIS
100
@
ANALYTICAL CHEMISTRY
water-soluble resins, has led to the utilization of azeotrope formation for separation and subsequent identification of the constituents. The widely used analytical methods have had certain undesirable characteristics. Standard oxidation methods involving periodic acid (1) or potassium dichromate are critically dependent upon sample size and are limited by specificity. The presence of tinctorial agents seriously impairs the colorimetric procedures, such as formation of the sodium cupriglycerol complex (12, 13) with glycerol or colored complexes of the hydroxyl compound with ammonium hexanitrato cerate ( 3 ) . The
use of ethyl alcohol as a diluent in the former test causes precipitation of the water-soluble resins present in the sample. Previous publications have cited the separation of water from glycols (7) and the determination of certain polyhydroxy compounds b y selective entrainment with cyclohexane, turpentine, toluene, xylene, chloroform, methylcyclohexane, Decalin, and benzene. Ethylene glycol, propylene glycol, and trimethylene glycol were entrained in cyclohexane, and water and glycerol were entrained in Decalin (8-11). Experimental results in this laboratory have shonwi that ethylene glycol-
Tetrachloroethylene, boiling point, 119121" C. (stabilized with ethyl alcohol). Round-bottomed boiling flask, $ joint. Glas-Col heating mantle and rheostat, or suitable controlled heat source. Bllihn condenser, drip tip, $ joint. Distilling receiver, Stark and Dean (Barrett type), 7 ,graduated in 0.1 or 0.02 ml . Distilling receiver, oil diluting, modified with funnel, $, as illustrated in Figure 1, graduated in 0.1 or 0.02 ml. PROCEDURE
Figure 1.
Moisture trap for solvents heavier than water Density, 1.6
yclohexaiie and glycerol-Decalin do not form azeotropes. The former is borne out in the compilation of data by Horsley (5,e),listing typical compounds n hich n ere investigated for possible 'izeotrope formation with ethylene glycol. I n this study three-component mixtures of water, ethylene glycol, and glycerol were successfully separated quantitatively b y employing benzene, tetrachloroethylene, and d-limonene as selective entrainers. Benzene entrains only water and none of the polyhydroxy alcohols. Therefore, the Ivater recovered from a n azeotropic distillation using benzene as the entrainer represents a direct measure of the water concentration of the sample. Tetrachloroethylene forms azeotropes with both water and ethylene glycol b u t not glycerol. Water, ethylene glycol, and glycerol are all carried over with d-limonene. This allows a separation to be performed with comparative ease or each component t o be quantitatively determined by subtractive analysis. I n practice, when separation is not desired, three separate distillations for such a triconiponent mixture are usually employed. This sidesteps the necessity of solvent iemoval and is much less time-consuming. I n this v o r k water and ethylene glycol were estimated simultaneously by use of tetrachloroethylene, and the percentage of each 11-as (
determined b y refractive index (4) of the distillate. Sample size is not necessarily limited, although i t is expedient to maintain it wifhin the volume of the collection trap and yet give suficient volume of distillate for accurate reading. Hoviever, if the distillate exceeds the volume of the trap, i t may be quantitatively transferred to another graduated vessel and the reaction continued. Tetrachloroethylene will entrain other polyhydroxy alcohols, such as 2,3butylene glycol (8.25'%), diethylene glycol (12.2oJ,), and 1,3-butylene glycol (20.8%) after 15 to 20 hours of continuous refluxing.
The moisture content of both the ethylene glycol and glyceiol was determined and a correction was made in preparation of the synthetic mixtures. I n the examples cited, 10 nil. of sample \vas carefully introduced into a 250-nil. round-bottomed flask by means of a 10ml. buret graduated in 0.02 ml. Several glass boiling beads and 100 to 150 ml. of the entrainer were added. The receiver and condenser were assembled and the mixture was refluxed steadily using a rheostat-controlled heating mantle. Each sample was refluxed until the collected volume of the entrained liquid remained constant. The condenser was rinsed with small portions of the solvent to wash any adhering droplets into the receiver and the volume of distillate read directly. The time required for various samples, from initial reflux to completion of distillation, is given in Table I . . -4Stark and Dean (Barrett type) ieceiver (2) was employed with benzene and d-limonene; a modified oil-diluting receiver (Figure 1) was used when tetrachloroethylene was the entrainer. Receivers of both the Barrett type and oil-diluting type have been fabricated in various capacities to accomniodate the specific requirements for this pioblem. Capacities range from a total volume of 2.5 nil. graduated in 0.02-nil. divisions to 25 nil. graduated in 0.2ml. divisions. The proceduie as outlined requires little or no attmtion evcept for determining when the entrained volume is constant.
REAGENTS A N D APPARATUS
Ethylene glycol and glj-cerol, c.P., analyzed for moisture. Benzene, thiophene free. d-Limonene, boiling point 1T5-17i0 C.
Table I.
ANALYTICAL RESULTS
Typical results obtained from analysis of aliquots of s p t h e t i c mixtures con-
Representative Hours Required for Complete Distillation
Composition of Synthetic Mixture, % Ethylene Water glycol Glycerol 80 33 9 96 9 71 21 07 49 80 29 13 0 99 76 03 22 98 12 32 9 96 77 72
5
Tetrnchloroethylene 2
3
4 5
6
2 5
Benzene
d-
Limonene
VOL. 2 9 , NO. 1 , JANUARY 1957
5 5 6 5
101
~
Table II.
Sample I I1 I11 IV
I'
VI 1'11
-
wntcl.,
Present
50 83 21 07 80 33 0 99 12 32 46 52 4 63
Per Cent Volume Analysis of Synthetic Mixtures
-
Found 50 80 21 20
Error -0 06 + O 62
-0 78
i 9 70 1 00
+1 01 -1 E2 -0 04 -0 43
12 10
46 50
4 61
taining known percentages of water, ethylene glycol, and glycerol are shown in Table 11. Considering the 10-ml. sample used, these values may appear more mathematical than real. Horn-ever, all receivers used were either graduated in 0.02-ml. divisions or the distillate was quantitatively transferred to a receiver graduated to this precision. ACKNOWLEDGMENT
The authors are grateful t o Keith S. Hoover for his encouragement of this
Ethylene Glycol, % ' -Present Found Error 24 90 24 80 -0 40 1 9 80 49 60 -0 40 9 96 10 30 l 3 41 76 03 i i 20 -1 54 9 96 9 90 -0 61 53 48 53 10 -0 i l c)5 37 94 i 0 -0 70
project and to the A. B. Dick Co. for making this publication possible.
Present 24 2'7 29 13 9 i1
22 98 77 i 2
Glycerol, % Found 23 90 28 70 9 80 22 80 7 ; 00
Error
-1 52 -1 48 $0 93 -0 i8 -0 94
H
J( Libmann.
LITERATURE CITED
(1) Allen, N., Charbonnier, H. Y. Coleman, R. AI., IND. EXG. HEM,, ANAL.ED. 12, 384-7 (1940). (2) Dean, E. W., Stark, D. D., J. I n d . Eng. Chem. 12, 486-90 (1920). (3) Duke, F. R., Smith, G. F., IND. EKG. CHEM.,ANAL.,ED. 12,201-3 (1940). (4) Fogg, E. T., Hixson, A. N., Thompson, A. R., .4NAL. CHEM.27, 160911 (1955). ( 5 ) Horsley, L. H., I b i d . , 19, 508-600 (1947).
Metayer, G., Compt. rend. 224, 16435 (1947). Spagnolo, F., ANAL.CHEW25, G668 (1953). Whyte, 1,. K., Oil & Soap 23, 323-6 (1946). RECEIVEDfor review August 16, 1956. Accepted October 2, 1956.
Alpha-Methoxyphenylacetic Acid as Reagent for Detection of Sodium Ion WlLKlNS REEVE and IVAN CHRISTOFFEL' Chemistry Department, University of Maryland, College Park, Md.
b a-Methoxyphenylacetic acid forms a difficultly soluble sodium acid salt. A reagent consisting of a partially neutralized aqueous-alcoholic solution o f this acid i s described for qualitatively testing for sodium. The test can b e carried out in the presence of large amounts of ammonium, lithium, potassium, and magnesium salts, and in the presence of anions such as chloride, nitrate, phosphate, and sulfate.
A
LPHA-METHOXYPHEXYLACETIC
ACID
forms a sodium acid salt [C6H5CH(OCH3)COOH. CGH&H(OCHa)COONa] which is unusual in that i t is difficultly soluble in water. I n the course of some synthetic work (8), a-methoxyphenylacetic acid was purified b y meany of this salt, and the latter was studied because of its unusual solubility characteristics. Present addrese, Xitrogen Division, Allied Chemical 6: Dye Corp., Hopewell, Va.
102 *
ANALYTICAL CHEMISTRY
a-Methoxyphenylacetic acid is more selective for sodium than the zinc, magnesium, and nickel uranyl acetate reagents. As much as 30 mg. per ml. of lithium ion as chloride or nitrate does not interfere, whereas 1 and 2 mg. interferes with the uranyl acetate reagents (3, 6, 6). The reagent is two t o three times as sensitive t o sodium ion as the copper uranyl acetate reagent proposed b y Caley (3) for those situations where lithium may be present. The test can be carried out in the presence of large amounts of potassium, rubid. ium, ammonium, and magnesium salts, and also in the presence of such anions as chloride, nitrate, phosphate, and sulfate. A big advantage is that a confirmatory test is possible which apparently eliminates all other elements except large amounts of cesium. The reagent differs from the uranyl acetate-type reagents in that the formation of the precipitate is slow, requiring 1hour or more a t 0' C. when the amount of sodium ion is below 1 mg. per ml.
of test solution. Furthermore, about 0.3 mg. of sodium ion per ml. is the lower limit that can be detected on a test tube scale, giving a dilution limit (4) of 1 t o 3300. The zinc uranyl acetate reagent, which is the most sensitive of the uranyl acetate group of reagents. is variously assigned corresponding dilution limits of 1 to 2,000,000 ( 7 ) , 1 to 50,000 (6),and 1 to 4000 (4). Kolthoff's zinc uranyl acetate reagent can detect about 0.02 mg. of sodium ion per ml. after standing 1 hour, but the concentration of other ions, such apotassium and particularly lithium. must be low or they also precipitate during this time (8). Under optimum conditions, when the concentration of lithium ion is below 1 mg. per ml. ant1 t h a t of potassium is 5 or 50 mg. per ml., depending on the procedure employed, Kolthoff has shown that 0.02 to 0.05 mg. of sodium can be detected, thuq giving a lithium-sodium ratio of about 20 t o 1 and a potassium-sodium ratio of about 250 to 1. The latter is re-
