Feb., 1952
PREPARATION AND PURIFIC-4TION AND VAPOR PRESSURE OF
OF2
233
THE PREPARATION AND PURIFICATION OF OF, AND DETER3lIShTION OF ITS VAPOR PRESSURE B Y J. G. SCHNfZLEIN, J. L. SHEARD, R. C. TOOLE AND T. D. O'BRIEN School of C h i d r y , University of Minnesota, Minneapolis, Minnesota Rscsiaad January 19, 1961
OF%was prepared and purified. Iodometric and infrared analyses showed substantially 100% purity. The vapor pressure of OF2 was meaaured from - 195 t o - 145O and its boiling point shown to be - 145.3'
The preparation and purification of oxygen fluoride was undertaken to obtain the pure compound whose physical properties could be determined. The method of purification used by early workers1t2was repeated as a preliminary step, but further purification followed. Experimental Fluorine was generated in a Harshaw 1ow.temperature cella at a rate of 2-6 liters of gas per hour. This gas was passed through a 3% solution of NaOH which had been previously cooled in an ice-bath. The basic solution was continuously changed in the reaction vessel at the rate of 1-2 liters/hour (Fig. 1). The gaseous products were assed through a series of bubblers and traps and the partiai enriched OF2 was finally collected in a transfer ampoule K [ in Fig. 2). These ampoules were then inserted into the vacuuni line a t C (Fig. 3) for transfer to the storage bulbs 1-6.
APPARATUS
OIL PUMP
Fig. 3.
ft. glass column tightly packed with 1/8-in. single turn glass helices, and surrounded by a strip silvered evacuated jacket. The temperature of the distillation vessel was controlled by surrounding it with an asbestos jacket containing a nichrome heating element of 10 ohms resistance. This system was then surrounded by a large glass test-tube and the whole assembly then immersed in liquid nitrogcn in a dewar flask. The top of the column was surrounded by a hollow copper head which was automatically cooled by liquid nitrogen. I n practice the still was allowed to come to cquilibrium and the OF2 was distilled until the temperature b.ccanie constant at -144". Approximately l/d of the remaining liquid was distilled at -144' and discarded. About of the remaining liquid was distilled and collcctcd. Finally, most of the remaining liquid was distilled at 144' and collected, and the residue discarded. Two iodometric analysis of the "middle cut" showed 99.60% and 100.02oJ, purity, respectively. The infrared spectrum (Fig. 4) of this sample showed less than 0.1% SiF, (probably from the reaction of OF* with glass) and 0.002% CFI as thc only impurities.
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~
Fig. 1.
2
Fig. 2.-A, Sodium hydroxide solution bubbler (see Fig. 1); 1, fluorine inlet (copper tube); 2, sodium hydroxide solution inlet; 3, sodium hydroxide solution outlet; 4, siphon interrupter; 5 analysis outlet; B, water wash bubbler; C, carbon dioxide-acetone trap (-78"); 6, analysis outlet; D, column tra (approx. -130"), 7, analysis outlet; E, column trap ?a prox. -1600); 8, outlet for collection in ampoule I
