BERNARD E. SALTZMAN Public Health Service, Bureau of State Services, Occupational Health Program, U. S. Department of Health, Education, and Welfare, 1014 Broadway, Cincinnati 2, Ohio NATHAN GILBERT University of Cincinnati, Cincinnati 2 1 , Ohio
Ozone Reaction with 1-Hexene Clue t o S m o g Formation Application of newly developed chemical analytical methods shows yield of synthetic smog oxidants and their tendency toward surface a b sorption, and confirms kinetic r a t e constant for ozone reaction with 1hexene
By the nitrogen dioxide equivalent method, the consumption of ozone by reaction with 1 -hexene was shown to be first order with respect to ozone and hexene concentrations through most of the reaction, with a rate constant of 0.0135 patm.-l min.-’ at 22” to 28’ C., in good agreement with previously reported values of 0.013 to 0.015. The more complex picture obtained for later stages of the reaction by previous workers was shown to be due to nonspecificity of the iodide reagents. Simultaneous use of the neutral iodide and nitrogen dioxide equivalent methods permilted distinction of “synthetic smog oxidants” and unconsumed ozone. The reaction yield of synthetic smog oxidants was 17 to 25a/,. These oxidants liberated most of the iodine color slowly, rather than instantaneously and did not give the nitrogen dioxide equivalent test. An appreciable fraction was readily adsorbed on the glass surface of the reactor in spite of a small surface-volume ratio. It could be recovered from the surface over several days by flushing the reactor with pure air, half the adsorbed oxidants being liberated every 3 hours. Such effects could be important on the surfaces of the oil droplets in natural smogs.
A N Angeles
FEATURE of the os smog is that the obnoxious materials, rather than being the original pollutants, are derived from them by photochemical and chemical processes in the atmosphere. Ozone-olefin reactions play a n important role in this complex chain (7), and their products are closely related to the resulting eye irritation and plant damage (2, 3 ) . These reactions have been studied mass spectrometrically ( 7 ) , chemically ( 7 ) , and by infrared spectroscopy (4, 5, 7 7 ) . This report deals with the application of newly developed chemical analytical methods to study the kinetics of the gas phase reaction of ozone and 1-hexene, which produces a synthetic smog containing oxidants believed to resemble the natural ones. T h e analytical portion of this study (7-70) was conducted to develop means for distinguishing between the oxidants present in natural smog a t their extremely low concentrations, and to make possible kinetic studies of artificial mixtures a t similar concentrations. An accurate iodide reagent was selected for determining total oxidant, and its stoichiometry determined for ozone. Other oxidants liberating iodine were differentiated graphically by a kinetic colorimetry technique ( 9 ) . A radically different approach was used to develop a method (70) specific for ozone even in the presence of common oxidizing and reducing pollutants. By metering a controlled excess of nitric oxide into the sample air stream and allowing a minimal flow reaction time, ozone was quantitatively converted to (and subsequently determined as) nitrogen dioxide. Simultaneous application of these new methods to the present study permitted differentiation of organic oxidants from unconsumed ozone in the partially reacted mixtures with 1-hexene. SucUKcSUAL
cessful interpretation of the data also demonstrated the validity of the analytical methods.
Experimental Metered. constant flows of reactants and air were mixed and passed through a 10-liter reactor in a n all-glass system with ground-glass joints, except for a few butt-to-butt glass sections joined with Tygon tubing. Fluorocarbon grease was used sparingly as a lubricant. This dynamic flow system permitted withdrawal of the large samples needed. A completely turbulent reactor was used to avoid diffusion errors a t low space velocities, and to simplify the mathematical treatment of the data, permitting rates to be determined directly rather than as the slope of a curve. Experiments were conducted a t ambient temperature ( 2 2 O to 28’ C.) and humidities (0.9 to 3.0 mole %), as closer control appeared unnecessary. Purified air was metered a t 0.35 liter per minute into the ozone generator. 6, and a portion of the ozone output was metered into the reaction stream in mixer 11. The lamps were operated for several hundred hours to reach a stabilized condition. Tests showed that the output did not vary more than 1 to 2%; during a run. or more than 107, ovcr a period of days. Known mixtures of 1-hexene and air were prepared by pipetting liquid quantities of the highest purity grade 1-hexene [99%, boiling point 63-4’ C. (Matheson Coleman, and Bell 7772)] into a 47-liter carboy, 13. in a closed all-glass system. Many 50-ml. portions of the mixture could be withdrawn into a motor-driven glass hypodermic syringe and metered (generally a t 1 ml. per minute) into the reaction air stream through capillary glass lines. before VOL. 51, NO. 11
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NOVEMBER 1959
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8
AI
c
1. Compressed air inlet. 2. Needle valve. 3. Dichromate-concentrated sulfuric acid in fritted glass bubbler. 4. Ascarite. 5. Flowmeter. 6. Ozonizer using three Westinghouse 7 9 4 H ultraviolet bulbs. 7. Bottle containing Hopcalite for decomposing excess ozone. 8 . Waste ozone outlet. 9. Air inlet. 10. Universal gos mask canister. 1 1 . Mixing device. 12. M a nometer. 13. 47-liter carboy containing l-hex14. Motor-driven 50-ml. glass ene-air mixture. syringe. 15. Reactor (IO-liter glass bottle). 16. Dry- and wet-bulb thermometers. 17. Ballast midget impinger. 18. Trap. 19. Connec. tion to aspirator in hood. 20, 2 1 . Midget impingers for chemical sampling. 22. Tank of 1% nitric oxide in nitrogen. 23. Safety pressure vent. A, B. Three-way stopcocks for hexene-air mixture. C, D. Three-way stopcocks far chemical sampling. E, F. Stopcocks for nitric oxide-nitrogen mixture.
I
t 12
5
The ozone-1 -hexene reaction was studied at low concentrations in an all-glass system
replacement was needed because of depletion. A 1% nitric oxide-nitrogen mixture (tank 22) was metered when required, through capillary glass lines into the flow system by a motor-driven 50-ml. glass hypodermic syringe. T h e gas could be introduced into the air stream either upstream or downstream from the reactor. T h e capillary mixing tips. shown in enlarged detail in the diagram. were loosely packed with glass wool to avoid air oxidation of the nitric oxide. which was relatively rapid before its dilution to low concentrations. T h e stream was sampled (for nitrogen dioxide) downstream from the point where nitric oxide was introduced a t a location allowing about 4 seconds for the gaseous reaction with ozone. At the beginning of each day, both the hexene and nitric oxide syringes were flushed 10 times with 10-ml. portions of their respective gas mixtures. Stopcock C was kept in the sampling position. so that the waste gas bypassed the reactor. A short length of glass tubing was used in place of sampling bubbler 20 a t this time. T h e nitric oxide syringe was then kept closed a t a slight positive pressure, and was filled just before use. T h e hexene syringe was filled and started discharging a t the appropriate rate (usually about 1 ml. per minute). Stopcock C was then turned to direct the mixture to the reactor. Either one or three ozonizer lamps were lit, and all flows were adjusted as desired. T i m e was allowed for a t least six air changes in the reactor, to reach a steady state. This calculated value was checked by experimental measurements and found to suffice. Reactor outlet sampling was then conducted by diverting the entire
14 16
flow (using stopcock D ) through the sampling devices. A ballast bubbler, 17, which was bypassed during sampling, was used in the flow system to equalize pressure drops and avoid flow changes and disturbance of upstream conditions. The neutral iodide reagent (9) was used first in a midget impinger, following which the nitric oxide gas stream was started and run for several minutes to flush out the lines before sampling for nitrogen dioxide with Griess-Saltzman reagent (6) in a midget fritted bubbler. Calculations showed (8, 70) that a 10 p.p.m. excess of nitric oxide would give 95y0conversion of ozone to nitrogen dioxide under these conditions. Reactor inlet samples then were collected similarly, using stopcock C.
Series
I11
IV V VI VI-A VI1 VI11
IX X X-A a
Run Nos. 86-101 102-108 109-121 122-129 130-135 137-143 144-150 151-159 160-1 70 179-185
Results I n each series, both a constant flow rate through the reactor and a constant hexene feed concentration were maintained, while a different metered ozone inlet concentration was used for each run. T h e ranges of experimental variables for the study were as follows:
Space Inlet V e l ~ c i t y , ~ Hexene, Min.-* P.P.M. 0.0490 0.0294 0.0490 0.0490 0.0490 0.1763 0.1763 0.1763 0.0490 0.0490
7.07 11.8 1.41 35.9 35.9 10.0 2.02 37.2 35.9 35.9
Inlet ozone, p.p.m. 1.0-15.7 1 .8-18.8 0.3-14.2 0.5-15.1 8.2-79.2 2.1-19.4 1.9-20.0 0.7-20.1 2.8-66.9 0.04-0.66
Ranges Temp., O
c.
22-26 25-26 23-26 24-28 24-26 25-26 2 4-2 5 23-26 23-27 22-27
Water vapor, mole yo 1.1-1.9 1.4-1.6 1.2-1.4 1.2-3.0 1.1-2.6 0.9-1.0 0.9-1.0 0.9-1.2 1.1-1.4 1.2-1.8
Defined as flow rate divided by volume of reactor ( F / V ) .
To ensure accuracy, sampling periods shorter than a minute were not used. Dark colors resulting from very high oxidant levels in some runs were diluted with unexposed reagent into the proper absorbance range. After a series of samples had been collected, the next run was started by adjusting the various flows to new settings.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Reagent blanks were run almost daily. Nitrogen dioxide blanks were run on the last portion of each syringeful of nitric oxide a t the conclusion of every run by shutting off the ozone flow and collecting an extra sample a t the reactor inlet. All calculations included appropriate blank corrections.
Reactor inlet oxidant analyses by the two analytical methods were in good agreement (8-70), demonstrating lack of appreciable reaction within the 4-second age of the mixtures (Figure 1). The results by the two methods diverged for the same ozone-hexene mixtures after aging (reactor outlet analyses). The iodine results were
O Z O N E R E A C T I O N W I T H 1-HEXENE I
Figure 1. Reactor inlet oxidant analyses by two methods agreed
0.3
I
I
I
I
I
I
0.6
I
3
6
IO
30
NITROGEN DIOXIDE EQUIVALENT,
higher by a n amount increasing n i t h the degree of completion of the reaction. The results for these series are plotted in Figures 2 and 3. Nitrogen dioxide sampling could not be carried out a t the highest of the three space velocities used because of the flow limitations of the available fritted bubblers. Only a sinsle series was carried out a t the lowest space velocity because of the very long time required to reach a steady state. Series X-A \vas conducted a t loiv ozone concentrations in order to clarify the puzzling curvature a t the low ozone ends of the data plots given in Figures 2 and 3> A and B. I n this region the large excess of hexene ensured its presence a t substantially constant concentration in the reactor. If the reaction xvere first order with respect to ozone. a constant fractional consumption of ozone would be expected, yielding a straightline plot a t the low ends with a 45' slope. However, the data did not follow this pattern. I n the initial low concentration study, hopelessly wide variations were obtained, all indicating gains of oxidant in the reactor. However, after many hours of flushing the apparatus, stabilized conditions Were reached. For this series, the canister inlet, 9, was connected to the decomposed \vaste ozone outlet, 8. to draw air which was more purified than room air. Oxidant blank determinations were negligible. T h e ozonizer flow rate was increased to 5 liters per minute to lower the output concentration. I t was then determined that the curvature in Figure 2 a t low ozone concen-
P.P.M.
trations was due to blank errors in the nitrogen dioxide determinations. The blanks, varying from 0.1 to 0.3 p.p.m., resulted mainly from air oxidation of the nitric oxide a t high concentrations during dilution a t the mixing tips. An improved apparatus with very lo\v blanks has been described (70). T h e iodine equivalent data obtained for Series X-A are given in Figure 3, C. which shows a first-order reaction with respect to ozone with a constant ratio of ouilet to inlet oxidant concentration of 447,. T h e curvatures a t the low concentration ends of the iodide data plots in Figure 3, A and B, could not be explained on the basis of blank errors (iodine blanks were less than 0.01 p.p.m.). and therefore suggested a surface adsorption effect. Such a surface adsorption of organic oxidants is clearly demonstrated by the iodide reagent data plotted in Figure 4, -4. I n run 189, 67 p.p.m. of pure ozone was passed through the apparatus for 3 hours, and then displaced with pure air. Oxidant concentrations in the exit gas were close to the straight line showing the theoretical displacement relationships for a turbulent reactor. I n run 190, the experiment \vas repeated with a gas mixture containing 36 p.p.m. of 1-hexene in addition to ' 6 p.p.m. of ozone. T h e organic mixture showed significantly large deviations from the ordinary displacement relations. Oxidant persisted in the exit gas for 5 days, after many hours of flushing. T h e flushing process was in-
terrupted twice and the reactor was allowed to stand with the stopcocks closed. I n each case, the oxidant concentration present in the carboy gas rose. These data showed that oxidants were being liberated from the glass, and that if the flushing was stopped equilibrium was reached between the gas and surface oxidant concentrations. The amount of oxidant on the glass was calculated. T h e logarithm of the quantity of adsorbed oxidant decreased linearly with the flushing time (Figure 4. B ) . Thus the liberation rate was proportional to the quantity of adsorbed oxidant, the initial rate constant being 0.004 min.-' and the half life of liberation 3 hours. Further evidence that the liberated oxidants were reaction products, and not ozone, was obtained by application of the kinetic colorimetry technique to the samples of run 190. By accurate spectrophotometric measurements of the amounts of iodine liberated from the reagent a t times u p to 1 hour after sampling. and a graphical procedure more fully described elsewhere (Q), the amounts of instantly liberated and slowly liberated iodine and the liberation rate constant of the latter were determined. T h e sensitivity of this technique is indicated by the fact that many samples represented less than 0.25 y of active oxygen. T h e fraction of slowly liberated iodine increased with flushing time, varying from 20 to 1007,. Because ozone yields only about 10% slow color, the oxidants were clearly not ozone. This was further confirmed by the fact that the oxidants did not give the nitrogen dioxide equivalent test.
0 , 03
I
06
I
I
INLET
3
6
OXIDANT,
IO
PPM
3r
60
Figure 2. Nitrogen dioxide equivalent data for the reaction of ozone with 1 -hexene Inlet hexene concentrations. Series 111, 7.07 p.p.rn.; IV, 11.8; V, 1.41; VI, VI-A, X, 35.9 Space velocity: 0.0490 m h - 1 (except IV, 0.0294) VOL. 51,
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Interpretation of D a t a KEY SERIES -
4 A.
A
Series Ill, IV, V, VI, VI-A, X
The interpretation of the kinetic data required a mathematical treatment involving only the entering hexene concentrations, as it was impractical to determine the final concentration of this reactant. I t was also necessary to determine the significance of the data for the reacted mixtures as determined by the two oxidant methods. The previously reported ( 7 ) initial relationship, first order with respect to both ozone and hexene, was assumed to apply to the entire reaction. A hexeneozone consumption ratio, r , which might not be a constant was also assumed. A material balance yielded the following equations for the consumption of ozone and hexene :
- x ) = kVxy F(yo - y ) = rkVxy F(x0
I
0.6
0.3
INLET
3
6
IO
OXIDANT,
P.P.M.
30
60
(11 (2)
where
F is the flow rate x , is the ozone concentration entering
KEY SERIES 0
VI1
A
VIII
the reactor x is the ozone concentration in the
reactor, and also leaving the reactor y o is the hexene concentration entering
4 B.
0'31
0.1
I
0.3
Series VII, VIII, IX. Inlet hexene concentrations 10.0, 2.02, and 37.2 p.p.m., respectively. Space velocity0.1763 min.-1
I
0.6
I
I 3
INLET
I 6
I
I
30
IO
OXIDANT,
P.P.M.
4 C.
C
Figure 3.
14 18
Series X-A. Inlet hexene concentration 35.9 p.p.m., space velocity 0.0490 min.-'
Iodine equivalent data for the reaction of ozone with 1 -hexene
INDUSTRIAL AND ENGINEERING CHEMISTRY
Equation 2 was solved for y as follows:
Substituting this value in Equation 1 and rearranging :
B
I
the reactor y is the hexene concentration in the reactor, and also leaving the reactor k is the kinetic rate constant Vis the reactor volume I is the hexene-ozone consumption ratio
This form was convenient for plotting. The left side consisting of known experimental quantities was plotted against the experimental term (L'x/F) on the right. The intercept for zero value of abscissa is the term 1, k . and the value of r at a given point is given by the slope of the chord connecting the intercept to the same point. If r is a constant, a straight line may be expected. Kinetic data were taken from smooth curves drawn through the experimental points in Figures 2 and 3, A and B, to give a clearer picture and reduce the experimental variance as much as possible. Plots in the form of Equation 3 are given in Figure 5. il, for the nitrogen dioxide equivalent data, and in Figure 3, B, for the iodine equivalent data. The bulk of the nitrogen dioxide equivalent data converges to a single intercept of about 74. corresponding to k = 0.0135 p.p.m.-'min.-'. Each series a t a constant hexene feed concentration plotted as a practically straight line. Series V, a t a very low hexene-ozone
O Z O N E REACTION WITH 1-HEXENE
4 S c I
A.
a’
k-0.5
z 4
-Px
A
00.2
I-
W $0. I 3 0
0.05
Oxidant analyses of reactor exit gas after flushing with pure air. The breaks in the curve at 250 and 750 minutes represent standing without flushing for 63‘/2 and 16 hours respectively. The dash-dot line represents the theoretical relationships for simple displacement from a turbulent reactor with no adsorption
0
t
100
Vx/F
200
300
PP.M. MIN.
x-A
5001
0.02
500
0
1000
0
I00
Vx’IF
4
Figure 5. 6.
-21
I
0
50 0
FLUSHING TIME, M I N .
ratio, was atypical and exhibited a slower rate. T h e hexene-ozone consumption ratios indicated by the slopes were as follows for various hexene feed concentrations: 1.41 p.p.m., 0.2; 7.07 p.p.m., 0.9; 11.8 ~ . p . m . 1.3; ~ 35.9 p.p.m., 1.0. Deviations were noted a t very lo\v values of x, due to the blank errors. T h e iodine equivalent data in Figure 5, B, show a series of straight lines: not converging to a definite intercept. All rates were slower than those indicated for the nitrogen dioxide data, except for the atypical Series V. This suggested that the iodide oxidant included substances other than ozone. T h e difference in rates should thus give the rate of formation of organic oxidants. For the sake of clarity the term x is reserved for nitrogen dioxide equivalent oxidant, and the iodine equivalent oxidant denoted by x’. T h e seemingly complex pattern shown by the iodine results may be resolved and made consistent with the nitrogen dioxide data on the basis of the simple assumption that a fixed fraction of the products of the ozone-hexene reaction consists of oxidants which continue to give the iodine test, but not the nitrogen dioxide test. Thus the analytical data for aged ozone-hexene mixtures should show the following relationship : x’
- x = f(Xo
-
x)
(4)
1000
Calculated amounts of adsorbed oxidant
Figure 4. Surface adsorption of synthetic smog oxidant on reactor surface is clearly demonstrated
where f is the molar yield fraction of the oxidant products. The bracketed term on the right side represents the amount of ozone consumed by the reaction. The term x ’ - x on the left represents
A. 6.
200
300
P.PM M I N .
Plots of kinetic functions
Nitrogen dioxide equivalent Iodine equivalent data
the difference in analyses obtained by the iodide and nitrogen dioxide methods, respectively, and may be regarded as representing “synthetic smog oxidants.” The plot in Figure 6 represents the experimental data for Series VI, \,.I-A, and X. T h e differences, x ’ - x, were too small in the other series for accurate results. T o improve the accuracy of this plot, certain analytical corrections for the blanks and for incomplete conversion were made to the nitrogen dioxide equivalent data obtained at the outlet of the reactor. The value of xo
Calculations based on analyses of a g e d ozanehexene mixtures
Figure 6. The reaction yield of synthetic smog oxidants remains approximately constant at 0.17 to 0.25 VOL. 51, NO. 11
NOVEMBER 1959
14 19
was taken from the iodine data to avoid the necessity of corrections. Figure 6 shows that the value off remains approximately constant a t 0.17 to 0.25 over a hundredfold range of concentrations. As the yield increases rather than decreases a t high ozone concentrations, the synthetic smog oxidants appear to be stable toward ozone. T h e values of f and k may also be obtained readily from the iodine intercepts in Figure 5, B. For convenience. these intercepts are denoted by I;
I
lim = (V.x’/F) + 0
cI
(definition) ( 5 ) T h e relationships are derived by combining Equations 3 and 4 to eliminate x; the bracketed term on the right side of Equation 3 is taken as zero for this limiting case. T h e function on the right side of Equation 5 is then constructed by manipulating the terms of the combined equation, which is finally rearranged into the following graphical form :
I n Figure 7, the values of the iodine intercepts for all the series are plotted as ordinates against the values of the bracketed terms as abscissas. T h e slope of the line gives the value o f f = 0.17, and the intercept gives the same value of k as obtained from the nitrogen dioxide equivalent data, 0.0135 p.p.m.-’min.-’ T h e agreement of the points with the line is good, except for the atypical Series V. T h e amounts of oxidants adsorbed on the glass, as plotted in Figure 4, B, were calculated on the basis of a n oxidant material balance :
where t is the time of flushing with pure air and G is the quantity of adsorbed oxidant a t time t. I n this equation the terms on the left side represent, respectively, the oxidants on the glass, in the gas phase of the reactor, and those already flushed out. These are equated to the integral term on the right side, which represents the total amount of volatile oxidants. T h e equation is solved for G;
T h e integral term was obtained graphically from the semilog plot of data in Figure 4, A . Assuming a straight line between two points, x f r and x f r + , , then 1’
1420
=
e-m(t-tr)
(8)
IAV
I
500 (It y,V/F)
1000
P.P.M. M I N .
Figure 7. Plot of intercept functions for iodine equivalent data Agreement is goad, except for atypical Series V
where rn is the average graphical slope measured between x ’ , and x f p l i . Thus the integral could be calculated in a stepwise manner from the values of x ’ and the slopes connecting them on the graph, by means of the simple fraction on the right side of Equation 9. I t was assumed that infinite time had been reached for all practical purposes a t the end of the experiment, since there had been 20 hours of flushing, and the exit concentration of oxidant was down to 0.02 p.p.m. The results are given in Figure 4, B. Interesting calculations were made of the oxidant quantities in the reactor a t the moment the flushing began. By extrapolating the line in Figure 4, B to zero flushing time, it was found that about 100 pl. (liters x p.p.m.) were adsorbed. T h e conditions in the gas phase of the reactor were obtained from the analytical data, which showed the iodine equivalent of the oxidants in the reactor was 35.4 p.p.m. and the nitrogen dioxide equivalent 20.3 p.p.m. Correcting the latter figure for incomplete conversion (Figure 1). x was found to be 22 p.p.m. and the concentration of snythetic smog oxidants in the gas phase, x f - x . was 13.4 p.p.m. T h e total quantities of oxidants in the gas phase, obtained by multiplying the parts per million by 10.21 liters (volume of reactor). were thus 360 ml. of iodine oxidants and 136 ml. of smog oxidants. The total quantity of smog oxidants generated during the 3-hour adsorption period prior to flushing was obtained by multiplying the parts per million by 90 liters (flow rate times time), giving 1200 ml. I t was thus determined that the amount of synthetic smog oxidants adsorbed on the glass represented 28% of the iodine oxidants and 74y0 of the smog oxidants present in the gas phase of the reactor when the flushing began, and 8% of the
INDUSTRIAL AND ENGINEERING CHEMISTRY
total amount of smog oxidants generated in the 3 hours prior to flushing. T h e surface adsorption effect may explain some of the abnormally low reaction rates observed a t the conclusion of the study. As the apparatus was operated for many hours at high organic oxidant concentrations, it seems reasonable to expect that appreciable amounts of oxidized and polymerized hexene would be deposited on the reactor surface. This surface could then slow the reaction by reacting with either the hexene or active intermediary compounds, removing them from the vapor phase. The rate observed in Series X-A (Figure 3, B ) was less than half of that expected. Most of the low concentration points in Series X also showed abnormally low rates, compared with similar runs for the earlier Series V I . However, the surface adsorption effect apparently was not important for most of the work, as a successful plot was obtained in Figure 5, A . Acknowledgment
Sincere thanks for encouragement and support of the work are due R. G. Keenan, D. H. Byers, H. E. Stokinger, L. J. Cralley, and W. C. Cooper, U. S. Public Health Service. literature Cited (1) Cadle, R. D., Schadt, C., J . Am. Chem. SOC.7 4 , 6002-4 (1952). ( 2 ) Darley, E. F., Stephens, E. R., Middleton, J. T.. Hanst, P. L., “Oxidant Plant
Damage from Ozone-Olefin Reactions,” Am. Petroleum Inst., Div. of Refining, St. Louis, Mo., May 15, 1958. ( 3 ) Haagen-Smit, A. J., Darley, E. F., Zaitlin, M., Hull, H., Noble, W.. Plant Physiol. 27, 18-34 (1952). (4) Hanst, P. L., Stephens, E. R., Scott, W. E., “Reactions Involving Ozone, Nitrogen Dioxide, and Organic Compounds at Low Concentrations in Air,” .4m. Petroleum Inst., Div. of Refining, St. Louis, Mo., May IO, 1955. 5) Hanst, P. L., Stephens, E. R., Scott, W. E., Doerr, R. C., “Atmospheric Ozone-Olefin Reactions,” Franklin Institute, August 1958. G ) Saltzman, B. E., Anal. Chem. 26, 194955 (1954). 7) Saltzman. B. E., IND.ENG.CHEM.5 0 , 677-82 (1958). 5) Saltzman, B. E., Ph.D. thesis, University of Cincinnati, 1958. ( 9 ) Saltzman. B. E., Gilbert, N.. Anal. Chem. 31, 1913 (1959). (10) Saltzman. B. E., Gilbert. N., J. Am. Ind. Hyg. Assoc., 20, 379-86 (1959). (11) Scott, W. E., Stephens, E. R., Hanst, P. L., Doerr, R. C., “Further Developments in the Chemistry of the Atmosphere,” Am. Petroleum Inst., Div. of Refining, Philadelphia, Pa., May 14, 1957. RECEIVED for review February 24, 1959 ACCEPTED June 15, 1959 American Institute of Chemical Engineers. Annual Meeting, Cincinnati, Ohio, December 10, 1958. From Ph.D. thesis, 1958, University of Cincinnati, by Bernard E. Saltzman.
