R. B. Hasbrouck for submitting some of the compounds reported. LITERATURE CITED
(1) Brooks, R. T., Sternglana, P. D., ANAL.CHEM.31,561-5 (1959). (2) Coats, N. A., Katritaky, A. R., J . Org. Chem. 24, 1836-7 (1959).
(3) Glynn, E., Analyst 72, 248-50 (1947). (4) Hjorth-Hansen, S., Anal. Chim. Acta 6,438 (1952). (5) Katritaky, A. R., Quart. Revs. 10, 403 (1956). ( 6 j Kennedy, J., Lane, E. S., Willans, J. L., J. Chem. SOC.1956,4670. (7) Polonovski, M., Bull. SOC. Chim. Belg. 39, 24 (1930). (8) Streuli, C. A., ANAL.CHEM.30, 9971000 (1958). (9) Varyukhina, L. V., Pushkareva, Z. V.,
J . Gen. Chem. (U.S.8.R.) 26, 1953-8
(1956). (10) Wimer, D. C., ANAL. CHEM.30, 7780 (1958). (11) Win&, D. C., Ibid., 30, 2060-1 (1958). DAVIDC. WIMER
Analytical Research Department Abbott Laboratories North Chicago, Ill.
An Improved Exhaust System for the Perkin-Elmer Vapor Fractometer R. J. DiCenzo, Ferris Institute, Big Rapids, Mich. SIMPLE MODIFICATIONof
the Perkin-
A Elmer Model 154-C Vapor Fractometer is herein reported which gives superior results and eliminates contamination of fractions. During numerous attempts to use this instrument on a preparative scale, it was noticed that the effluent vapors had been assuming a gradually increasing odor indicative of decomposition within the exhaust network. It seemed plausible that such decomposition, if it existed, would account for the contamination of the fractions being collected. The entire flow system was removed, and the contamination was traced to the three-way solenoid valve, which upon disassembly revealed accumulations of tars throughout. The design of the exhaust system is such that the path traveled by the effluent vapors is lengthy and winding. Further, most of the exhaust system is located outside of the oven and is thus a t a considerably lower temperature than the incoming vapors. Therefore, the system tends to condense the hot vapors before they emerge from the instrument. This is especially true of the solenoid valve, which confronts the vapors with a large, cool mass. Finally, those vapors which do condense within the system are prevented from flowing out of the instrument by three sections of vertical tubing incorporated into the network. These problems and the contamination of the fractions were eliminated by the following simple modification. The complete exhaust network, including
Figure 1. A. 6. C. D.
E.
F.
874
the solenoid valve, was disconnected from the detector cell and removed. A hole approximately 35 mm. in diameter was drilled through the left outer wall of the cabinet and was extended through the wall of the heating chamber itself. The hole was located 55 mm. from the bottom of the cabinet and 135 mm. from its forward edge. A piece of stainless steel tubing, 3.2 X 255 mm., was used as the exhaust pipe and was bent in two places. The first bend was made a t an 80" angle and was located 25 mm. from one end. A suitable Swegelok connector was then attached to this end. The other bend was made at a n angle of 45" and was located 25 mm. from the other end. T o this end was attached a threeway, stainless steel, medical stopcock consisting of one female Luer, one male Luer, and one male Luer-Lok fitting. The stopcock was attached by soldering the end of the tube into the mouth of the female Luer fitting. The tube was then tightly wrapped between bends with heavy asbestos cord and then wound with several turns of suitable resistance wire, with the free ends of the wire located near the stopcock to s n e as power leads. The wire was itself nrnpped with asbestos cord for insulation. A thermometer was positioned along the axis of the tube, and the entire unit was encased in several layers of asbestos tape impregnated with plaster
Improved exhaust system
Thermometer Three-woy medical stopcock Stainless steel tubing Power leads for autotransformer Asbestos insulation Swegelok connector
ANALYTICAL CHEMISTRY
of Paris, and allowed to harden. Care was taken to ensure that the temperature range of the heating chamber was visible on the thermometer when the unit was attached to the detector cell. The complete unit is shown in Figure 1. The new exhaust system was then installed in the heating chamber by connecting it to the detector cell T-tube outlet, and the hole in the cabinet wall was firmly packed with glass wool to minimize heat loss. Finally, the wire leads were connected to a variable autotransformer having a n output of 0 to 120 volts. The two free male Luer fittings allow a variety of collection systems to be adapted according to need. The LuerLok fitting is especially suitable for attachment of long, large bore hypodermic needles which can be lead into small, easily changeable test tubes immersed in refrigerant baths or ,containing solvents or adsorbent traps. The stopcock allows rapid and convenient diversion of the effluent to either of the outlets so that fraction cuts can be made quite readily. Finally, this unit offers a short, direct exhaust path to the vapors and can be heated to any desired temperature along its entire length. The common problems of condensation and contamination of frxtions are thereby minimized or eliminated.
