W. T. Rainey, Jr. and L. B. Yeatts, Jr. Oak Ridge National Laboratory' Oak Ridge, Tennessee
Purification and Quantitative Recovery of Materials by a Vacuum Technique
There are times when one may wish to do experimental work such as pyrolyses, radiolyses, etc., with pure liquid or solid chemicals in the absence of air. I n many of these instances, the pure compound is available only in small quantities making purification losses undesirable. IMoreover, if one desires to seal srtmples in glass or quartz ampoules for the experiment, which is often the case, it is simpler to weigh the sample before rather than after final purification. This, too, requires a quantitative recovery. Such recovery is difficult using common vacuum line techniques if vaporization of the starting material is desirable. The apparatus shown in the figure permits a quantitative recovery of the pure material which is volatile under vacuum. Air, and sometimes water vapor, is removed from the sample by pumping on the system during the course of completely vaporizing and recondensing the sample. Chromatographically pure biphenyl was freed of air and water vapor in this laboratory and is used as a case in point. A weighed sample of biphenyl in an an~poule was attached to the lower condenser, 5-10°C water was circulated through the condenser coils, and a mixtureof ice and water was poured into the cold finger. The system was evacuated and the sample heated to vaporize it while continuing to pump on the system. After complete vaporization of the sample from the an~poule, the system was shut off from the vacuum line by closing the stopcock in the figure. The biphenyl sample, which was now condensed on the coils and walls of both coildensers, was transfel~edback into the ampoule. This
'Operated for the U.S. Atomic Energy Commission by Union Carbide Corporation.
was accomplished by replacing the ice water in the cold finger with boiling water, circulating hot water through the condenser coils, TO turning on the heating tapes wrapped around the mndeusers, and immersing the ampoule in liquid nitrogen. The 2.mm procedure can he STOPCOCK iepeated as often as necessary. The stopcock was opened to the vacuum system while sealing the ampoule with the aid of a blowpipe. I n this manner, 99+% recoveries of the biphenyl samples were made. It is conceivable that many compounds could be purified and quantitatively recovered from minor volatile impurities by a judicious choice of the condensation temperatures. Equipment for pvriflsotion ond quontitotive recovery of volatile moterialr.
TO SAMPLE AMPOULE
Volume
41, Number 8, August 1964
/
451
