NOTES
March, 1963
713
change its labile hydrogens. These results are quite similar to the behavior of lysozyme6 as found in this Laboratory. OZONE FORMATION AT -196’l BY J. A. WOJTOWICZ, H. B. URBACH,AND J. A. ZASLOWKBY Olmn Mathieson Chemical Corporation, Organics Division, New Haven, Conneciicut Received September IO, 1966 2
4 sorbed &O
Fig. 3.-Differential
6
1
8
7
1
10
I2
(mrnoles/qrarnl,
heats of water vapor adsorption on poly-Lglutamic acid.
that permit exchange than would be the case if they were only able to exchange on the equivalent number of monosites holding water molecules. Differential heats of adsorption for HzO on this polyglutamic acid were calculated by the ClausiusClapeyron equation and the results are sown in Fig. 3. The values for the temperature intervals 17-27’ and 27-37’ are in relatively good agreement except in the range of the lowest amounts adsorbed. I n this range the precision of the isotherm data is not good enough to be certain of the calculated heat values. The values obtained for the temperature interval 37-57’ are much higher. The amounts adsorbed a t 57’ have become so small that the character of the adsorption might well have changed in this temperature interval, leading to these higher values. Finally, as a result of a study (to be published later) of the adsorption of NH3 on a sample of this same polymer one or two interesting observations may be made. Ammonia gas wa6 found to be very weakly adsorbed and it could be readily desorbed by evacuation. However, if H20 vapor is adsorbed up to about 10% gain in weight, then NHO gas is spontaneously adsorbed up to a certain amount. The HzO and NH, molecules, or their combination NHIOH, were desorbed *ata pressure of mm. for a long time. The polymer showed a weight gain equivalent to the binding of one NHI+ group per unit of the polymer. This suggests the exchange of an NH4+ for the H+ of the carboxyl group on the side chain. If an isotherm for the adsorption of HzO vapor at 17’ on this new polymer containing the NH4f groups is determined, then the HtO is adsorbed to a far greater degree than on the PGAc. This is shown as dotted curve A in Fig. 1. Here extrapolation of the straight line portion of this isotherm until it crosses the ordinate for the vapor pressure of HzO a t this temperature gives a value of adsorption of about two 13~0molecules per unit of this ammoniated polymer. Thus the presence of the NH4+on the carboxyl group makes the polymer about as hydrophilic as does the sodium ion.
Conclusion This investigation has shown that this polyglutamic acid material is able to exchange only a little more than SO% of its so-called labile hydrogens. Isotherms for the adsorption of HzO a t 17 and 27’ also show a moiiosite occupation of less than this fraction of the total number of hydrophilic sites. Thus both the structure of the polymer plus the nature of the side chains determine its capacity for adsorbing HzO as well as its ability to ex-
The low temperature reaction of oxygen atoms with molecular oxygen to form ozone has long been known. Although Harteck and Kopsch2indicated that the reaction proceeds to a large extent a t -190°, they did not indicate that the reaction was qtrantitative. Broida and co-workers, Ruhrwein and H a ~ h m a n ,and ~ Harvey and Bass5 have studied the reaction at liquid helium temperature. The quantitative formation of ozone a t these low tempera,tures was not indicated. The above studies were concerned with the trapping of oxygen radicals in frozen matrices. It was of interest in connection with studies on the thermal decomposition of ozone and the reaction of ozone with oxygen atoms to determine what percentage of the oxygen atoms which are present in a dissociated oxygen stream a t 1 mm. pressure are converted to ozone a t - 196’. Since this work was performed prior to the development of the so-called “absolute” nitrogen dioxide titration method,6 a calorimetric method for oxygen atom assay based upon total conversion of oxygen atoms to molecular oxygen was developed. An ice-calorimetric technique was chosen for the thermal measurements. The absence of significant quantities of ozone in a stream of oxygen atoms at ambient temperature and about 1 mm. pressure has been e~tablished.~~’ Experimental Electrolytic oxygen (less than 20 p.p.m. total impuritiesB) was used in all experiments. The apparatus consisted of a Wood discharge tube connected to a vacuum syst6m consisting of a 20 cm. length of 12 mm. i d . tubing and a detachable U-tube. The detachable U-tube could be replaced by ru‘Bunsen ice-calorimeter of conventional design (Fig. 1) which contained a U-tube of the same dimensions as the detachable U-tube. The oxygen flow rate of 2 mmoles/min. at I mm. was controlled by capillary tubing. A Welch Duo-Seal pump was used for evacuating the system. The discharge tube was activated by two neon sign transformers rated a t 15 kv. and 30 ma. which were connected in parallel. With the U-trap in place ozone could be condensed from the oxygen atom stream by cooling the tr&p with liquid nitrogen. After several minutes the discharge was turned off and the dewar removed. The product ozone was swept with gaseous nitr+ gen into a potassium iodide scrubber as the condensate was allowed to warm. The ozone productiofi rate wm determined by titration of the scrubber solution with sodium thiosulfate. The experiment was repeated with the same oxygen pressure setting until a statistically significant mean rate of ozone productivity (1) This work was performed under Contract No. AF 24 (645)-72; presented a t the 136th National Meeting of the American Chemical Society. Atlantic City, N. J., September, 1959. Inquiries should be direated t o J. A. Zaalowsky. (2) P. Harteck and U. Kopsch, Z . physik. Chem., 12, 327 (1931). (3) H. P. Broida and J. R. Pellam, J . Chem. Phys., 23, 409 (1955): H. P. Broida and 0. S. Lutes, {bid., 24, 484 (1958): H. P. Broida, Ann. N. Y . Acad. Sci., 67, 530 (1957). (4) R. A. Ruhrwein and J. S. Hashman, f. Chem. Phys., 30, 823 (1959). ( 5 ) X. B. Harvey and A.. M. Baas, J . JkoL Spectry., 2 , 405 (1958). (6) “Progress in Reaction Kinetios,” G. Porter, Ed., Pergamon Press. 1961, Chapter 1 by F. Kaufman. (7) J. T. Herron and H. I. Schiff, Can. J . Chem., 36, 1159 (1958). (8) H. B. Urbach, E. Fisher, and J. A. Zaslowsky, unpublished data.
Vol. 67
XOTES
densation (- 198') of B stream of oxygen atoms (about 5%) in oxygcn a quantitative yield of ozone is obtained. It is not known a t what conceiitration of oxygen atoms this conclusion would have to be modified due to possiblc competing reactions, such as 0 0 M + O2
i..-
Mercury
+ +
11.
4
\\
P 4
Elias, Ogryzlo, and Schiffg have shown that calorimetric met'hods such as the use of a silver probe in the gas phase give an assay value which is 25% higher than that, given by the nitrogen dioxide tit,ration method. This was attributed to the presence of metastable oxygen molecules (lAg, $22.5 kcal.). Harteck and Kopsch,* on the other hand, have indicated that only ground state oxygen is present several centimeters from the discharge tubc. The possibility of having a small percentage of metastable oxygen molecules in the prescnt oxygcn at,om-oxygen molecule stream cannot be discounted but it is likely that most of t,he metastable molecules have degraded prior to entry into the calorimeter. The low tempcratme rcactioii
P
Fig. 1.-Ice
+
ice-water ice mantle
Flask
- 196'
0
calorimeter.
was atttiined. Thc, ozone productivity indicated a minimum oxygen atom concentration of about 5%. The U-trap was replaced by the ice-calorimrter, which contained about 1 g. of palladium black. The calorimeter required several hours to attain thermill equilibrium. The heat leak wm determined to be insignificant over the period of each experiment. The discharge was started with the same oxygen flow rate which was used previously. It was shown that all the atoms recombined in the calorimeter since cooling the exit stream with liquid nitrogen did not produce any detectttble quantities of ozone. The beaker of mercury was weighed prior to and after each experinient of 5 min. duration. It required about 30 min. to reattain thermal equilibrium. The oxygen atom flow was determined by means of the equation
+ + ( A I ) -+ 0 2
Oa
+ (M)
discussed in this paper undoubtedly involves a heterogencous wall reaction, where 34 is t.he cold wall. The rate constant ( I O l 4 cc.2/mole2 sec.) for the homogcnel 1 would not permit the rapid rcaction ous noted in thc present research if the reaction were a homogeneous three-body rcaction. The ozone condenses in a narrow ring (about 1 cm. wide) in the liquid nitrogen t,rap. (0) L. Elias. E. A. Ogryzlo, and 11. I. SchiN, Can. J . CRem., S I , 1090 (19.79). (10) 11. B. Urbach, R. Wnuk, J. A. Wojtowicz. and J. A. Zaslowsky, Abstracts of Papers, 137th Meeting of the American Chemical Society .&tlantic City. 1989, p. 47-3. (11) S. W. Bonson and A. Axworthy, J . Chsm. Phys., 26, 1718 (1957). I
mmolcs O:/min. = (64.6) (Tlir~,)/58.91 where 64.6 is the absolute calibration factor in cal./g. of mercury drawn into the system, 58.9 cal./mmole is the heat of recombination of oxygen atoms, and WE, is the weight of mercury drawn into the system in time t (minutes) due to the melting of the icemantle. The oxygen atom flow (mmoles/min.) was
0.094
f
0.008 (9076 confidence level)
by the ozone condcnsation method (0
0.092
+
0 2 +0 3 )
(a)
BY
F.
?tl.4RTISEZ,
J. A. WOJTOWICZ, A S D J. A. Z.4SLOWSKY
Olin Mnthieaon Chemical Corporation, Oronnics Diuision, New Hairen, Connecticut
Receiked September 10, 19Gd
and
* 0.010 (!+0Oj,confidence level)
S-ILAY STT:T)IES ON THE PRODUCT OF THE KEACTTOS OF A ~ T O M I CHYDROGES AND LIQVID OZONE'
(11)
by the calorimetric proredure.
Discussion Since the precision of the iodimetric mcthod for ozone assay is considerably greater than that indicated in (a), thc variation noted within each series of experiments is attributed to the variation of oxygen atom output by t,hc discharge apparatus. It was noted that when the discharge was operatcd continuously (longer than 30 min.), the variation in ozone output by the condensation method mas f.1.77&. Unfortunately it was not possible with the present calorimetcr to achievc this steady-state condition with the calorimeter in plaw due to the large quantity of ice that would melt during the ttpprbach to thc steady-state condition. The conchsion is watranted, within thc precision of these maasuremcnta, tliai in the low-temperature con*
Tlie reaction of hydrogen atoms with liquid ozone at
- 19G' reportedly leads to the formation of a hydrogen supcroxide.2 The product decomposes above - 120' to give equimolar quantities of oxygen and hydrogen Tlie existence of this superoxide has been questioned by Gigucre3 on the basis of infrared studies. Hydrogen peroxidc deposited from the vapor a t - 196 and -269' has been examined by X-ray t m h n i q ~ e s . ~ The substancc is amorphous and does not exhibit the sharp lines characteristic of t,hc crystalline material. Crystallization occurs spontaneously a t - 183'. Thc ( 1 ) This work w a a supported by the Directorate of Research Analysis, Air Force Ofico of Scicntific Resenrch, fIolloman Air Force Base. under Contract AE' 49(038)-1137. (2) N. I. Kobozev, I. I. Skornkhodov, L. I. Sekrasov, and E. I. blaknrova, 7 h . F i z . Khim.. 31, 1843 (1957). (:I) 1'. Gigiicre and D. Chin, J . Chem. Phys.. 31, 1085 (1959). (4) L. 11. Bok. 17. A. Maner. and 11. S. Poiser, unpublished data; C ~ A, M. Bass and 13. P. Broida, "Formation and Trapping of Frcc Radicals, Aoadatkiic Proas Inc., New York, X. f., 1900,p. 322,
Z
