Advanced Propellant Chemistry

26 PhysicalPropertiesof the Liquid Ozone—Fluorine System Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 13, 2016 | http://pubs.acs.org Publication Date: January 1, 1966 | doi: 10.1021/ba-1966-0054.ch026

A. J. GAYNOR and C H A R L E S K. H E R S H IIT Research Institute, Chicago, Ill.

The density, viscosity, and surface tension of liquid ozone -fluorinemixtures were determined at —183° and —195.8° C. At the two temperatures investigated, the density can be de termined from the following equations: ρ -183°C. = 0.1009 (wt. fraction O ) + 1.4704 and ρ -195.8°C. = 0.0534 (wt. fraction O ) + 1.5611. The viscosity of solutions at —183° C . varies linearly (on a log scale) with the composi tion from 1.55 cp. for 100% ozone to 0.208 cp. for 100% fluo rine. A similar relationship exists at —195.8° C., where the viscosity varies from 4.15 cp. for 100% ozone to 0.344 cp. for 100% fluorine. The ozone-fluorine mixtures are Newtonian fluids. Vapor pressure and vapor liquid equilibria data are also presented for pressures up to 20 atm. 3

3

Τ Ttuizing the energetic oxidizers—ozone and fluorine—has been an aim ^ of rocket technologists for many years. The physical properties of pure ozone and pure fluorine have been characterized well. Mixtures of ozone with oxygen ( I ) and fluorine with oxygen have also been charac terized. The latter system is ideal while the former is not. It occurred to us that the physical properties of ozone-fluorine mixtures should be characterized so that this system could be evaluated more completely by liquid propellant technologists. Further, we expected that the mixtures might have superior properties. W i t h this intent we measured the density, surface tension, viscosity, and vapor pressure of the ozone-fluorine system at l i q u i d oxygen and liquid nitrogen temperatures. Experimental Density. A n apparatus and procedure similar to that described else where (1 ) was used for the density measurements. A borosilicate glass 279

Holzmann; Advanced Propellant Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1966.

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 13, 2016 | http://pubs.acs.org Publication Date: January 1, 1966 | doi: 10.1021/ba-1966-0054.ch026

280

ADVANCED PROPELLANT CHEMISTRY

U-tube, 4 mm. i.d. and 10 cm. long, was used for the density measurement. The volume of the U-tube was determined as a function of the distance from a reference mark at the bottom of the tube. Calibrations were made at room temperature, initially with water and carbon tetrachloride, and again at cryogenic temperatures with l i q u i d oxygen. A measured amount of liquid ozone was transferred to the U-tube, and the procedure was re peated with enough liquid fluorine to result i n a solution of the desired concentration. T w o techniques were used to aid i n mixing the ozone and fluorine. One technique consisted of bubbling helium through the mixture. T h e second technique consisted of closing the valves separating the legs of the U-tube, raising the temperature of the gas slightly (less than 5 degrees), equalizing the pressure, and repeating the procedure. Equilibrium between the liquid and vapor was noted b y observing the pressure and color of the solution. Fluorine is pale yellow-green while liquid ozone is blue-black, and the color can therefore give a fair measure or solution uniformity. Pressure equilibrium was usually achieved with three heatings on alternate arms. The fourth heating was used to give the pressure differential for manometrically determining the density. The temperatures of the liquid oxy gen and nitrogen were obtained using an oxygen vapor-pressure ther mometer. The densities obtained i n this way are given i n Table I ; they represent an average of at least four independent measurements. Table I. Temperature °C.

Density of Liquid O z o n e - F l u o r i n e Mixtures Ozone Concentration

wt. %

Density, grams/cc. Calculated* Measured

-183

0.0 31.0 84.6 100.0

1.472 1.499 1.557 1.571

1.470 1.502 1.556 1.571

-195.8

0.0 23.0 61.8 100.0

1.561 1.573 1.595 1.614

1.561 1.573 1.594 1.615

» From Equations 1 and 2.

These data were then reduced to straight-line functions on a Univac 1105 computer b y the method of least squares. Equations 1 and 2 were used to determine the density of liquid ozone-fluorine mixtures at the two temperatures investigated. P - i 8 3 ° o = 0.1009 (wt. fraction 0 ) + 1.4704 (deviation = ± 0 . 0 0 1 3 )

(1)

P-i66.8°c. = 0.0534 (wt. fraction 0 ) - f 1.5611 (deviation = ± 0 . 0 0 2 4 )

(2)

3

3

Viscosity. The viscosity of ozone-fluorine mixtures was determined i n a modified Ostwald viscometer ( I ) which was used with a variable volume of liquid. T h e viscometer was made from precision-bore glass tubing (4 m m . i.d.) w i t h a capillary section 0.203 m m . i n diameter and 12 cm. long.


26.

GAYNOR

A N D HERSH

Liquid Ozone-Fluorine

281

T o force the liquid to a convenient height above the capillary section, either helium pressure was used or the metal tubes containing the equilib rium vapor over each leg were heated after the valves had been closed. Then the valve isolating the two arms of the viscometer was opened, and the readings of the height, h, of liquid as it fell through the capillary were taken as a function of time. The driving pressure was proportional to the difference between the liquid and the equilibrium levels (h — h ) and i n uniform bore tubing the rate of flow was proportional to dh/dt. Hence, for a liquid following Poiseuilles law, log (h — h ) should be proportional to the time of flow. In every case a linear relation between log (h — h ) and time was obtained, which showed that ozone^fluorine solutions are Newtonian fluids. The half time (ti ) , which is the time required for the liquid to fall one-half the distance from the initial level to the equilibrium level, was determined from graphs of the time-height functions. The viscosity was calculated from Equation 3. e

e


e

2

η ='Cp*i/iL

(3)

where η = viscosity, ρ = density of the fluid, grams/cc., and C = an ap paratus constant determined w i t h liquids of known viscosity ( 1.289 X 10~ centipoise-cc./sec-gram). Calibration fluids were water, ethylene glycol, and liquid oxygen. The results shown i n Table II represent at least two independent measure ments for each viscosity reported. 2

Table II.

Viscosity of Ozone-Fluorine Mixtures

Ozone Concentration, mole 100.0 79.1 70.5 30.5 26.8 0.0

Viscosity, cp. - 183°C. 1.55 ± 0 . 0 1 0.905 ± 0 . 0 1

-195.8°C. 4.15

±

0.04

1.95

± 0 . 0 1

0.343 ± 0 . 0 3 0.208 ±

0.01

0.682 ± 0.344 ±

0.02 0.01

Surface Tension. The surface tension of various ozone-fluorine mix tures was determined b y the capillary rise method i n the apparatus used for the viscosity measurements ( I ) using Equation 4. (4)

where: Τ = surface tension r = radius of capillary, cm. h = capillary rise, cm.

ρ = density of solution, grams/cc. g = gravitational constant, cm./sq. sec.

Results at —183° and —195.8° C . are given i n Table III. Again, the pro cedure and equipment are calibrated b y determining the surface tension of known materials—e.g., liquid oxygen.


2 8 2


Table HI.

Surface Tension of Ozone-Fluorine Mixtures

Ozone

_

Concentration, mole %


100.0 79.1 70.5 30.5 26.8 0.0

Surface Tension - 183°C.

39.9 30.2 19.1 12.3

-195.8 °C.

43.5

35.6 22.4 15.5

1400·

Fluorine Cone,molt %

Figure I . Vapor pressure of liquid ozone-fluorine mixtures Vapor Pressure. T w o different techniques ( 1 , 2 ) were used to deter mine the vapor pressure of various liquid ozone-fluorine mixtures, depend ing on the pressures to be measured. T h e first technique was developed



26.

GAYNOR

0

Î0

Figure 2.

283

Liquid Ozone-Fluorine

A N D HERSH

20

30

40

50

60

Ozone Cone, mole %

70

BÔ

90

IOC

Vapor-liquid equilibrium diagram of ozone-fluorine system

for measurements at low pressures (1.5 atm.). The liquid ozone, which was condensed at liquid oxygen temperature ( —183° C . ) into a calibrated glass tube, was pumped on at reduced pressure to remove any residual oxygen; then the total volume was measured with a cathetometer. The measured amount of ozone Was then transferred quantitatively to a glass tube by distillation. The above procedure was repeated with liquid flu orine condensed at liquid nitrogen temperature, and the two liquids were allowed to come to equilibrium before a vapor pressure reading was taken. In this apparatus both color and constant pressure were used to determine equilibrium. Readings were taken at bath temperatures of 75.7°, 77.7°, and 90.2° K . These temperatures were measured with an oxygen vapor pressure thermometer. After the initial values had been determined, ad ditional known amounts of fluorine were admitted to the U-tube, and va por pressure readings were taken again. The data obtained i n this way




2 84

for a series of ozone-fluorine mixtures are given i n Figure 1. A total of 16 experimental points were used to determine each curve. It was thought that a stirring bar would ensure a homogeneous solu tion of the two liquids i n the modified apparatus. However, i n each of the three attempts to use a Teflon-coated stirring bar on the greater than 90 mole % ozone mixtures, the apparatus was destroyed by an explosion. Apparently, the mixtures which have high ozone concentrations are as sensitive to the w i p i n g action of the stirring bar along the glass surface of the reservoir as is 100% ozone (from previous experience). In the second technique (to 20 atm.), the apparatus was an all-metal system similar to that used for measurements on ozone-oxygen mixtures (2). The test chamber was constructed of stainless steel. It consisted of 1-inch bar stock ( l - / inches long), Swagelok fittings, a pressure gage, and a copper-constantan thermocouple. The system had a volume of 20.1 cc. The experimental procedure consisted of determining the liquid lines. The results are shown i n Figure 2. W h e n the volume of vapor i n a closed system is kept small relative to the volume of liquid, the amount of liquid that must be vaporized to give a 20-atm. pressure is small. Thus, the com position of the liquid w i l l be changed by only a negligible amount. F o r these determinations the composition of the ozone and fluorine charge was known accurately, and a provision was made for agitating the test bomb. Over 100 separate measurements were used to obtain the liquid lines. As determined by this method, the vapor pressure of pure fluorine agreed with the value reported by L a n d a u (4), and the vapor pressure of oxygen agreed w i t h the value reported by Hilsenrath et at. (3). This verified the fact that the pressure and temperature indicators were correct relative to each other. 1

Results and

2

Conclusions

These studies indicate that liquid ozone-fluorine mixtures are homo geneous and do not form a two-phase region as does the ozone-oxygen system. Mixtures of 3 0 % ozone i n fluorine require very few handling pre cautions over those observed with 100% liquid fluorine. The 1- and 20-atm. vapor lines, as shown i n Figure 2, were con structed from the liquid data and the vapor pressure of pure ozone using Equation 5: ν = xP/Pt

(5)

where y is the mole fraction of ozone i n the vapor, % is the mole fraction of ozone i n the liquid, Ρ is the vapor pressure of ozone, and P is the total pressure. Thus, Figure 2 represents the vapor-liquid equilibrium diagram of the ozone-fluorine system although the diagram is of course subject to the errors associated with the use of Raoults and Daltons laws. The viscosity of the solution decreases rapidly as fluorine is added. A semilog plot of viscosity of the mole fraction gives a straight line at both temperatures which is typical of a nonassociated liquid. The surface ten sion of ozone is approximately three times that of oxygen. t


26.

GAYNOR AND HERSH

Liquid

Ozone-Fluorine

i*5

Acknowledgment This work was supported at I I T Research Institute b y the National Aeronautics and Space Administration under Contract N o . NASw-76.


Literature Cited (1) Hersh, C. K., Berger, A . W., Brown, J. R. C., A D V A N . C H E M . SER. 21, 22 (1959). (2) Hersh, C. K., Brabets, R . I., Platz, G. M., Swehla, R . J . , Kirsh, D. P., ARS J. 30, 264 (1960). (3) Hilsenrath, J . et al. Nat. Bur. Std. (U.S.), Circ. 564 (1955). (4) Landau, R., Rosen, R., "Preparation, Properties, and Technology of Fluo rine and Organo-Fluoro Compounds," Chap. 7, C. Slesser, ed., McGraw-Hill Book Co., New York, 1951. RECEIVED

May 3,

1965.





Advanced Propellant Chemistry

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