RESULTS A N D DISCUSSION
The results of a series of determinations of unsaturated olefins are shown in Table I. The conventional analytical procedure requires an ozone stream of constant concentration and an exact knowledge of the ozone concentration. In contrast, in our procedure, changes in the ozone concentration during the determination do not affect the results and it is not necessary to know the exact ozone concentration, Other advantages are that no warming-up time is required for the ozonator and that detection of the end point is not critical. An olefin can be ozonized a t temperatures ranging from room temperature to the temperature of an acetone-dry ice mixture. With the conventional method, most investigators (1, 3, 4)use temperatures below -20' C. At room temperature the solubility of ozone in
chloroform should be negligible. However, because of the risk of degradative reactions of certain olefins and of the solvent, we chose a temperature of -30" C. This temperature was maintained within +2' C. A solubility factor of 0.25 mg. of ozone was established and was used in all the calculations. This value for solubility of ozone in chloroform is about of that given by Boer and Sixma ( 2 ) a t -30' C. for a saturated solution of ozone in chloroform under equilibrium conditions. It can be expected that a much lower solubility figure would be obtained under the flow conditions prevailing in our experiments. Of the three solvents tested, chloroform gave the best results. The use of carbon tetrachloride poses some limitations because of its comparatively high melting point, -23' C. Ethyl acetate gave the least satisfactory results and gave low ozone values on the average.
ACKNOWLEDGMENT
The authors thank the Gulf Oil Corp. for olefin samples. LITERATURE CITED
(1) Boer, H., Kooyman, E. C., Anal. Chzm. Acta 5 , 550 (1951). (, 2.) Boer, H., Sixma, F. L. J., Rec. Trav. Chim. 70, 997 (1951). (3) Kharasch, M. S., Sosnovsky, G., Yang, N. C., J . Am. Chem. SOC. 81, ,5819 il959'i. __ -. ( 4 ) Maggiolo, A., Tumolo, A. L., J . Am. 0 2 1 Chemist's SOC. 38, 279 (1961). KLAUSF. GUENTHER GEORGE SOSKOVSKY ROBERT BRUNIER' IIT Research Institute Chicago, Ill. and Department of Chemistry Illinois Institute of Technology Chicago, Ill. 1 Present address, World Health Organization, Palais des Nations, Geneva, Switzerland. \ - - - - I
Determination of Potassium Ozonide SIR: There is considerable interest in the unfamiliar oxidation state compounds of the alkali metal ozonide type for air revitalization materials-e.g., potassium ozonide, K+03- ( 5 , 7 ) . The synthesis of potassium ozonide is relatively straight-forward. The passage of a dilute ozone-oxygen gas stream through a bed of dry, powdered potassium superoxide or hydroxide will yield potassium ozonide. The ozonide can be separated from the unreacted superoxide or hydroxide by extraction from the reaction mixture with liquid ammonia (1, 2 , 6, 9). To analyze the recovered product, it is important that the analytical method chosen be able to distinguish between the ozonide and possible superoxide impurity. Such a distinction is necessary regardless of the starting material used in the synthesis reaction since potassium ozonide is unstable with respect to potassium superoxide. In addition, because of the similarity in the chemistry of alkali metal ozonides and superoxides, analytical procedures based on the determination of the total amount of oxygen evolved upon reaction of the ozonide with water, dilute acids, or permanganate solutions, can lead to erroneous results as to the actual amount of ozonide in the sample. A distinction cannot be made, using such reagents, between the potassium superoxide and the potassium ozonide content. Although the chemistry of potassium superoxide and potassium ozonide is
Train and N p ,Gas Cylinder
Figure 1. Apparatus for thermogravimetric analysis of alkali metal ozonides
Tube
similar, there is considerable difference in the thermal stability characteristics of these compounds. Potassium superoxide is quite thermally stable. A dissociation pressure of only 0.1 mm. of Hg at 300" C. is observed for the decomposition of potassium superoxide to the peroxide and oxygen ( S , 4 ) : On the other hand, potassium ozonide decomposes at applicable rates at room temperature and above. The decomposition proceeds in the following manner:
+
KOz(s) '/zOz(g) (2) At 50 to 60" C., the decomposition reaction is complete within 30 minutes KO3(s)
(8, 6). Hence, a t slightly elevated temperatures, Reaction 2 proceeds a t a
sufficiently rapid rate to form the basis of a convenient analytical method for the determination of ozonide content in these samples. In these studies, the potassium ozonide samples were kept in tightly capped glass vials, placed in polyethylene bags charged with ,iscarite, and stored in a refrigerator at -30" C. All transferals were carried out in a dry box. Determination of the ozonide content in the samples studied was made by measuring the change in weight resulting from the thermal decomposition of the ozonide sample to potassium superoxide. EXPERIMENTAL
The apparatus designed for the thermogravimetric analysis of alkali metal ozonides is shown in Figure 1. A tared vial is charged with the ozonide sample VOL. 36, NO. 13, DECEMBER 1964
e
2509
Table I.
Sample weight, grams 0.2479 0.1692 0.3130 0.3200 0.1910 0.3798 0.2652 0,2544 0.1768
Quantitative Data for the Thermogravimetric Analysis of Potassium Ozonide Samples
Weight, grams 0.2061 0.14017 0.2634 0.2690 0.1583 0.3144 0.2203 0.2114 0,1469
Decomposition product Potassium superoxide analysis Total, From KOa, Initial, % grams grams grams 92.3 0.1902 0.1860 0.0042 92.4 0.1300 0.1265 0.0035 85.6 0.2255 0.2205 0.0050 85.0 0.2287 0.2265 0.0022 94.0 0.1488 0.1453 0.0035 91.9 0.2889 0.2904
