Sublimation of Tribromophenol in a Gradient Temperature Tube Furnace Yasumasa Shigetomi Okayama College of Science, Shuku Okayama-shi, Japan A FEW REPORTS are available on the separation of various substances by sublimation in a gradient temperature tube furnace. This technique is known as sublimatography ( I , 2). The authors have separated quinones (3),chlorophenols (4), and other aromatic compounds (5, 6) from analogous compounds. In this experiment, tribromophenol was sublimed in the gradient temperature tube furnace and was separated from pentabromophenol, chlorophenol, and other aanlogous aromatic compounds. The results are given in this report.
Asbestinc cloths
Copper spiral pipe
Sub1 h a t e tube
China tube
EXPERIMENTAL
The gradient temperature tube furnace used in the experiment is shown in Figure 1. It is a China tube with an inside diameter of 5 cm and a length of 100 cm, wound with I-KW nichrome wire. The windings were closer together on the upper part than on the lower part of the tube. A slidac type simple transformer was attached to the nichrome wire for the purpose of heating with electricity at an appropriate voltage. A copper spiral tube with an inside diameter of 0.5 cm was placed inside the tube, and for cooling, air is sent into this tube at a uniform velocity with an aspirator. In this experiment, the combined cooling and heating processes brought the temperature inside the China tube to the desired level. To sample temperature inside the tube, holes for a thermometer were drilled at intervals of 15 cm. Through the simple transformer, current at 45 V was applied to raise the temperature inside the tube. The hourly change of temperature was observed and is shown in Figure 2. As the figure shows, the temperature ceased changing inside the tube four hours after the application of the electric current. The thermometer indicated the temperature as 160, 139, 96, and 60 “C from the top downward. The change of temperature in the tube at various voltages was examined and the relations between the voltage and the temperature gradient were determined in advance so that a suitable temperature gradient might be chosen for the separation. The sample tube for sublimation was an ordinary glass tube with an inside diameter of -8-9 mm. The sample was wrapped in aluminum leaves and placed in the upper part of the sublimation tube. The pressure within the tube was reduced to the desired point. The sample tube was then put into the gradient temperature tube furnace.
RESULTS AND DISCUSSION Sublimation of Tribromophenol in an Ordinary Vacuum Sublimation Apparatus. The ordinary reduced pressure sublimation apparatus (7) was used. Fifty milligrams of 2,4,6(1) E. Shibata and S. Saito, J . Chem. Sac. Jap., 80, 604 (1959). (2) K. Yoshimura, Jap. Anal., 11, 397 (1962). (3) Y . Shigetorni and K. Yoshizumi, J. Chem. Sac. Jap., 89, 530 (1968). (4) K . Emi and Y. Shigetorni, Jap. Anal., 19, 1069 (1970), (5) Y.Shigetomi and S. Yamamoto, ibid., 17, 1477 (1968), (6) Y . Shigetorni and K. Kawada, J . Chem. Sac. Jap., 92, 876 (1971). (7) E. W. Berg, “Physical and Chemical Methods of Separation,” McGraw-Hill Book Company, Inc., New York, N.Y., 1963, p 44.
Heat proof cement
Ther m ometer
Figure 1. Gradient temperature tube furnace tribromophenol was put in the apparatus and the pressure within the apparatus was reduced to 10-1 mm Hg with a vacuum pump. The apparatus was immersed in an oil bath. The temperature of the bath was raised at the rate of 2 “C per minute. The relations between the temperature and the reduction in quantity of tribromophenol by sublimation were examined. The results are shown in Figure 3. As the figure shows, tribromophenol sublimates at -6580 “C. This temperature range may be considered to be identical with that of the sublimation zone in the gradient temperature tube furnace. Effect of Pressure on Sublimation in the Tube Furnace. A study was made to see if there were any relations between the pressure within the sublimation tube and the temperature range of the sublimation zone when tribromophenol was sublimated in the gradient temperature-tube furnace. The results are shown in Figure 4. The figure shows that the temperature range, -65-80 O C , at the pressure of 10-1 mm Hg is the temperature range of sublimation zone in a tube when 50 mg of the sample was put in the sublimation tube, the pressure within the tube was reduced to 10-1 mm Hg, and the sublimation tube was put in the gradient temperature tube furnace and sublimated for l hour. Almost the same experiment was carried out at other pressures. As the figure indicates, the temperature range of the sublimation zone tends to rise slightly with elevation of the pressure within the tube. Separation of Tribromophenol from Mixtures with Other Compounds. From the previous experiment, we learned that
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5
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Figure 2. Relation between time and temperature in gradient temperature tube furnace with 45-V current 1. Thermometer at lowest position 2. Thermometer at lower secondary 3. Thermometer at middle 4. Thermometer at upper secondary 5. Thermometer at upper
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Figure 5. Effects of the amount of added reagent on recovery
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Phenol
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Figure 3. Weight loss curves for 50 mg of tribromophenol by sublimation in 10-l mm Hg
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P- benzoquinone &A
Figure 6. Sublimed zone of various compounds the temperature range of the sublimation zone of tribromophenol changes with the change in the pressure within the sublimation tube, and that 1-hour sublimation leaves unsublimed tribromophenol in the aluminum leaves as the pressure increases. Furthermore, too much tribromophenol remains unsublimed in 1-hour sublimation at lo-' mm Hg. Therefore a study was made to see how much sample should be sealed in the 8-mm glass tube. Sublimation tubes containing different amounts of tribromophenol, but at the same pressure (10-l mm Hg), were put in the gradient temperature tube furnace for sublimation. After 1-hour sublimation, by weighing the contents of the sublimation zone in tubes, the relations between the sealed amount of sample and the recovered sample were determined. The results are shown in Figure 5 . According to the figure, after 1-hour sublimation, 100% of the tribromophenol was recovered when the amount of the sample was below 70 mg. When the amount exceeded 70 mg, part remained unsublimed. From these facts, the proper amount of the sample is probably about 50 mg for a sublimation tube 8 mm in diameter.
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Figure 4. Effects of air pressure for sublimed zone at the state of equilibrium 412
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Table I. Separation of Tribromophenol from Its Mixtures with Other Analogous Compounds" Recovery Melting of Quantity point of tribromoof recovered phenol, adduct, tribromophenol, "C Adduct mg P-Benzoquinone 10 99 95 96 Naphthalene 10 99 95 96 Phenol 10 100 95 96 Pentabromophenol 10 100 95 96 Pentachlorophenol 10 95 96 99 a Tribromophenol(50 mg) was mixed.
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Table 11. Melting Point of Tribromophenol Substance Melting point, "C Ordinary tribromophenol 90 91 Tribromophenol sublimated in tube furnace 95 96 Tribromophenol sublimated by ordinary method 93 94
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To examine if it is possible to separate tribromophenol from other analogous compounds such as pentabromophenol, etc., 50 mg of each of these compounds was put in the sublimation tube, the pressure reduced to 10-1 mm Hg, and sublimed for 1 hour in the gradient temperature tube furnace. The resulting position of the sublimation zone of these compounds is shown in Figure 6. As the figure shows, the positions of the sublimation zone of these compounds are different from that of tribromophenol. It was, therefore, concluded that it might be possible to separate tribromophenol from these compounds. Accordingly mixtures of tribromophenol and other compounds were sublimed. By weighing the contents of sublimation zone corresponding to tribromophenol, the recovered quantity of tribromophenol was determined. The results are shown in Table I. Of course, sublimation zones
corresponding to the other compounds, which were added as impurities, appeared in the tubes. Table I shows that tribromophenol can be separated quantitatively from other compounds. Purification of Tribromophenol. Ordinary tribromophenol was purified by sublimation. The results are shown in Table 11. The tribromophenol which was purified in the gradient temperature tube furnace is higher in melting point and purer than when purified by the ordinary sublimation method. In the process of sublimating tribromophenol in the gradient temperature tube furnace, there was formed a secondary sublimation zone. The melting point at the secondary sublimation zone was 88 "C. Though we could not determine the quality and quantity of the substance forming the secondary sublimation zone at once, this method was recognized to be more convenient than the normal vacuum sublimation method for the purification of reagents and the concentration of impurities. RECEIVED for review October 15, 1971. Accepted August 179 1972.
Stability of Metal Dithiocarbamate Complexes R. R . Scharfe, V. S. Sastri, and C. L. Chakrabartil Department of Chemistry, Carleton University, Ottawa, Ontario K l S 5B6, Canada
SEVERAL INVESTIGATIONS were carried out earlier in this laboratory to clarify important aspects of the chemistry of dithiocarbamic acids, such as the decomposition mechanism (1-3) and the basicity of dithiocarbamic acids (4). Complexation reactions of dithiocarbamic acids were reviewed by Hulanicki (5). A careful study of the literature (9,however, shows a lack of definitive information on the stability constants of metal dithiocarbamate complexes. Recently, stability constants of metal complexes with morpholine dithiocarbamic acid were determined by the solvent extraction method (6). The objectives of the present study were as follows: i) to 1
All correspondence to be addressed to this author.
(1) K. I. Aspila, V. S. Sastri, and C. L. Chakrabarti, Talanta, 16, 1099 (1969). ( 2 ) S. J. Joris, K. I. Aspila, and C. L. Chakrabarti, ANAL.CHEM.,
647 (1970). (3) K. I. Aspila, S. J. Joris, and C. L. Chakrabarti, ibid, 43, 1529 (1971). (4) S. J. Joris, K. I. Aspila, and C. L. Chakrabarti, ibid., 41, 1441 (1969). (5) A. Hulanicki, Talanta, 14, 1371 (1967). (6) V. S. Sastri, K. I. Aspila, and C L. Chakrabarti, Can.J . Chem., 47,2320 (1969). 42,
determine the stability constants of complexes of some divalent metal ions with a variety of N-substituted dithiocarbamic acids, and ii) to determine the effect of various substituents at the nitrogen atom in disubstituted dithiocarbamic acids on the magnitude of stability constants. Solvent Extraction. Solvent extraction of a metal ion into a chloroform solution of a dithiocarbamic acid (HDTC) may be represented as follows (6, 7).
and the equilibrium constant for the above extraction reaction is called the extraction constant, K , and is given by
K = IM(DTC>nIorgIH+l" [M"+I[(HDTc)or~I'
(2)
In the presence of a masking agent, X, which forms a nonextractable metal complex, MXy, where X stands for the anion of the masking agent,
(3) (7) J. Stary and K. Kratzer, Anal. Chim. Acta, 40, 93 (1968).
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