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A new method of preparation and some properties of chlorine pentafluoride
Notes
655
J. Inorg. Nucl. Chem., 1966, Vol. 28, pp. 655 to 657. Pergamon Press Ltd. Printed in Northern Ireland
A new method of preparation and some properties of chlorine pentafluoride (Received 30 July 1965) WHEREAS the pentafluorides of bromine and iodine have been known and investigated for a long time, very little has been known until now about chlorine pentafluoride. In a recent paper ~1~ SMrrt-i describes a method for preparing this substance. According to him, a 14:1 mixture of fluorine and chlorine trifluoride is heated for 1 hr at 350°C at a pressure of 250 atm. However, this rather complicated method did not give very satisfactory results. The efficiency is not very high, and apparently, the author did not obtain the pure compound. Whilst studying the kinetics of some chlorine and fluorine containing sulphur compounds we observed the formation of chlorine pentafluoride through the addition of fluorine atoms to chlorine trifluoride. Basing ourselves on this reaction we developed a method of preparation of chlorine pentaftuoride and determined some of its physical constants. Chlorine pentafluoride is a colourless liquid which solidifies to a white solid at --93°C. The pure compound is very stable; in the gas phase, and at room temperature, we did not observe any decomposition even in 10 hr. It is of great importance that the system be free of reactive substances and specially water. We observed that even traces of adsorbed water favoured the formation of some undetermined compounds which induced a rather rapid decomposition of the C1Fs. When condensed these compounds were deeply red coloured. In the gas phase C1F5 is monomeric. The determination of its mol. wt, by the gas density method, gave a value of 129.5 (theoretical 130"46). The vapour pressure of liquid C1F5 can be represented by the equation: logpmm = 7'71-1257/T. Its boiling point is --12-9°C, the heat of evaporation 5"74 kcal and the Trouton constant 22.0 cal/°K. The vapour pressure of the solid at --100°C is 1"5 mm. C1F~ dissolves rapidly in a 0"5 ~o solution of sodium hydroxide. The u.v. spectrum of C1F5 is continuous. Absorption begins rather weakly at about 3250 and increases quickly towards shorter wavelengths. Table 1 shows some of the experimentally determined absorption coefficients, e is defined by the equation: log (lo/It)= e.p.d.; d is given in cm and p in mm of Hg at 0°C. The infra-red spectrum of C1F5 was measured in the NaC1 region (Fig. 1). Eight bands appeared, a very strong one at 732 cm -x and a strong one at 786 cm -1, both already reported by Src,Irn and, furthermore, four weak bands at 980, 1216, 1272 and 1447 cm -1 and two very weak ones at 822 and 1103 cm -1. EXPERIMENTAL
Preparation of CIF6 An all quartz apparatus was used for the reaction system; stopcocks were replaced by aluminum valves with Teflon packings. A 600 cm 3 quartz bulb served as reaction chamber and a quartz spiral manometer (Bodenstein type) was used as zero instrument. The reaction vessel was submerged in a Pyrex glass water thermostat which served, at the same time, as a light filter absorbing all radiation of wavelengths shorter than 3100/~. The apparatus was connected with the vacuum line and absorber. It was provided with T junctions which could be used to connect the absorption cells and other parts necessary for determining the physical properties of the substance. The light source was a high-pressure mercury lamp, type Osram 500, radiation of which was concentrated on the reactor by means of a condenser. The CIFs used was prepared, according to usual methods, by heating in a flow system a 3:1 mixture of F2 and C12 at 250°C and fractionating the products. Fluorine was furnished by the Matheson Co. Before starting each experiment the apparatus was heated and well evacuated. It was then filled several times with dry nitrogen, heated, and again evacuated. As a rule we worked at 30°C with 2:1 mixtures of F2 and C1F3 and a total pressure of approximately 1 atm. The formation of C1F5 is
~1~D. F. SMnna Science 141, 1039 (1963). Editor's Note. See also BEGUN, FLETCHERand SMITrl, J. Chem. Phys. 42, 2236 (1965).
656
Notes TAnLE 1.--THE EXTINC"nON COEFFICIENTSOF GASEOUS CIF5 A
e
A
t
3147 3083 3020 2960 2894
0.60.10 -s 1.06.10 -s 1.87.10 -5 3 ' 9 4 . 1 0 -s 6.59.10 -s
2831 2767 2704 2640
1-36.10 -4 2.20.10 -4 4"03 . 10-4 7.65 . 10 -4
characterized by a pressure decrease and, under our conditions, finished within 4 hr. Later we illuminated for 2 more hr with light of 365 m # wavelength which is not absorbed by the CIF6 formed. The excess of fluorine and the oxygen formed during the reaction by attack of fluorine atoms on the quartz walls were eliminated by evacuation at liquid air temperature; small amounts of SiF, were pumped Off at --140°C. When the system was free of impurities there remained practically pure C1Fs. Different samples were distilled into a small trap at temperatures between --100 ° to --90°C and studied. Molecular weight
To determine the gas density we used a 330 cm s quartz bulb with two capillaries soldered opposite to each other. The bulb was filled, at 20°C, with a pressure of about 250 mm of CIFs.
I / a _ ppressure our About ½cm s of liquid C1F8 was distilled into a small trap. The pressures between --100 ° to --30°C were measured with a quartz manometer.
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Fie. 1.--I.r. spectrum of CIFs. a. 16.3 ram; b. 46.0 mm, and c. 99.5 m m Hg o f CIF=.
Notes
657
U.v. spectrum The u.v. spectrum was registered with a Beckman Spectrophotometer Type D K 2. The quartz absorption cell was 10 cm long. The pressures of CIF5 used were 30.5 and 143.8 mm at 21°C. Lr. spectrum The spectra were measured with a Perkin-Elmer Type 221 Spectrophotometer using a 10-cm quartz cell with NaCI windows. Acknowledgement--This work was supported by the United States Air Force. "Grant AF-AFSOR 800-65 ; Air Force Office of Scientific Research of the Office of Aerospace Research. lnstituto Superior de lnvestigaciones Facultad de Quimica y Farmacia Universidad Nacional de La Plata La Plata
J.
R. GATTI R . L . KRIEGER J . E . SICRE H . J . SCHUMACHER
lnorg. Nucl. Chem., 1966,Vol. 28, pp. 657 to 658. PergamonPress Ltd. Printedin Northern Ireland
Studies on silver vanadate in acidic media (Received 18 May 1965) IN ALKALINEmedium vanadium (V) exists as a monomeric species designated by orthovanadate. Certain insoluble varmdates like those of silver and lead can be precipitated in alkaline medium having composition corresponding to the structure Ms(1)VO4. In acidic medium, however, vanadic acid exists in many polymeric forms and there is considerable uncertainty regarding the extent of polymerisation of vanadium (V) species at lower pH. The work of ROSSOTTIand RossoTn tl) indicates that in the pH range 0'5-6-5 the polymeric vanadium (V) species contain ten vanadium atoms. It was observed during the present studies on the effect of pH on the precipitation of silver vanadate that whereas in alkaline medium a precipitate of the composition 3AgzO. V~O~ was obtained the composition changed as the medium became more and more acidic. The ratio Ag20:V2Os kept on changing gradually in compounds precipitated at different pH. One of such compounds was precipitated at pH 3.7 having the composition 3Ag20.5V205. These observations indicate that V1002s8type species exists in solution and corresponding silver salt could be obtained thus confirming the conclusions drawn by RossoTa7 and ROSSOTTI.(1) EXPERIMENTAL All solutions were prepared in double-distilled conductivity water using B.D.H. reagents. The solutions were kept out of contact from the atmospheric carbon dioxide. Sodium orthovanadate solutions of exactly 0-1 M, 0"66 M and 0.05 M strength were prepared after standardising them with a previously standardised ferrous ammonium sulphate solution. 0-5 M silver nitrate and 1.0 M nitric acid solutions were prepared from their respective AnalaR reagents. A Cambridge bench pattern pH meter was used for performing the potentiometric titrations. The electrode system consisted of a saturated calomel half-cell and a thick silver plate indicator electrode. The connection between the calomel half-cell and the titration cell was made with saturated potassium nitrate solution. The conductivity measurements were made with a LBR model B177 measuring bridge operated on 220¥/50 cycles a.c. mains having a magic eye electronic detector. All systems were kept in an electrolytically maintained thermostat maintaining temperature at 25.0 ± 0.1°C. To an aliquot sample of the vanadate solution a varying quantity of nitric acid solution was added to keep the pH of the solution at 3-7. The final volume of the solution was kept the same in each (1) F. J. C. ROSSOT-rXand H. RossoTrl, Acta Chem. Scand. 10, 957 (1956). 2.3
655
J. Inorg. Nucl. Chem., 1966, Vol. 28, pp. 655 to 657. Pergamon Press Ltd. Printed in Northern Ireland
A new method of preparation and some properties of chlorine pentafluoride (Received 30 July 1965) WHEREAS the pentafluorides of bromine and iodine have been known and investigated for a long time, very little has been known until now about chlorine pentafluoride. In a recent paper ~1~ SMrrt-i describes a method for preparing this substance. According to him, a 14:1 mixture of fluorine and chlorine trifluoride is heated for 1 hr at 350°C at a pressure of 250 atm. However, this rather complicated method did not give very satisfactory results. The efficiency is not very high, and apparently, the author did not obtain the pure compound. Whilst studying the kinetics of some chlorine and fluorine containing sulphur compounds we observed the formation of chlorine pentafluoride through the addition of fluorine atoms to chlorine trifluoride. Basing ourselves on this reaction we developed a method of preparation of chlorine pentaftuoride and determined some of its physical constants. Chlorine pentafluoride is a colourless liquid which solidifies to a white solid at --93°C. The pure compound is very stable; in the gas phase, and at room temperature, we did not observe any decomposition even in 10 hr. It is of great importance that the system be free of reactive substances and specially water. We observed that even traces of adsorbed water favoured the formation of some undetermined compounds which induced a rather rapid decomposition of the C1Fs. When condensed these compounds were deeply red coloured. In the gas phase C1F5 is monomeric. The determination of its mol. wt, by the gas density method, gave a value of 129.5 (theoretical 130"46). The vapour pressure of liquid C1F5 can be represented by the equation: logpmm = 7'71-1257/T. Its boiling point is --12-9°C, the heat of evaporation 5"74 kcal and the Trouton constant 22.0 cal/°K. The vapour pressure of the solid at --100°C is 1"5 mm. C1F~ dissolves rapidly in a 0"5 ~o solution of sodium hydroxide. The u.v. spectrum of C1F5 is continuous. Absorption begins rather weakly at about 3250 and increases quickly towards shorter wavelengths. Table 1 shows some of the experimentally determined absorption coefficients, e is defined by the equation: log (lo/It)= e.p.d.; d is given in cm and p in mm of Hg at 0°C. The infra-red spectrum of C1F5 was measured in the NaC1 region (Fig. 1). Eight bands appeared, a very strong one at 732 cm -x and a strong one at 786 cm -1, both already reported by Src,Irn and, furthermore, four weak bands at 980, 1216, 1272 and 1447 cm -1 and two very weak ones at 822 and 1103 cm -1. EXPERIMENTAL
Preparation of CIF6 An all quartz apparatus was used for the reaction system; stopcocks were replaced by aluminum valves with Teflon packings. A 600 cm 3 quartz bulb served as reaction chamber and a quartz spiral manometer (Bodenstein type) was used as zero instrument. The reaction vessel was submerged in a Pyrex glass water thermostat which served, at the same time, as a light filter absorbing all radiation of wavelengths shorter than 3100/~. The apparatus was connected with the vacuum line and absorber. It was provided with T junctions which could be used to connect the absorption cells and other parts necessary for determining the physical properties of the substance. The light source was a high-pressure mercury lamp, type Osram 500, radiation of which was concentrated on the reactor by means of a condenser. The CIFs used was prepared, according to usual methods, by heating in a flow system a 3:1 mixture of F2 and C12 at 250°C and fractionating the products. Fluorine was furnished by the Matheson Co. Before starting each experiment the apparatus was heated and well evacuated. It was then filled several times with dry nitrogen, heated, and again evacuated. As a rule we worked at 30°C with 2:1 mixtures of F2 and C1F3 and a total pressure of approximately 1 atm. The formation of C1F5 is
~1~D. F. SMnna Science 141, 1039 (1963). Editor's Note. See also BEGUN, FLETCHERand SMITrl, J. Chem. Phys. 42, 2236 (1965).
656
Notes TAnLE 1.--THE EXTINC"nON COEFFICIENTSOF GASEOUS CIF5 A
e
A
t
3147 3083 3020 2960 2894
0.60.10 -s 1.06.10 -s 1.87.10 -5 3 ' 9 4 . 1 0 -s 6.59.10 -s
2831 2767 2704 2640
1-36.10 -4 2.20.10 -4 4"03 . 10-4 7.65 . 10 -4
characterized by a pressure decrease and, under our conditions, finished within 4 hr. Later we illuminated for 2 more hr with light of 365 m # wavelength which is not absorbed by the CIF6 formed. The excess of fluorine and the oxygen formed during the reaction by attack of fluorine atoms on the quartz walls were eliminated by evacuation at liquid air temperature; small amounts of SiF, were pumped Off at --140°C. When the system was free of impurities there remained practically pure C1Fs. Different samples were distilled into a small trap at temperatures between --100 ° to --90°C and studied. Molecular weight
To determine the gas density we used a 330 cm s quartz bulb with two capillaries soldered opposite to each other. The bulb was filled, at 20°C, with a pressure of about 250 mm of CIFs.
I / a _ ppressure our About ½cm s of liquid C1F8 was distilled into a small trap. The pressures between --100 ° to --30°C were measured with a quartz manometer.
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Fie. 1.--I.r. spectrum of CIFs. a. 16.3 ram; b. 46.0 mm, and c. 99.5 m m Hg o f CIF=.
Notes
657
U.v. spectrum The u.v. spectrum was registered with a Beckman Spectrophotometer Type D K 2. The quartz absorption cell was 10 cm long. The pressures of CIF5 used were 30.5 and 143.8 mm at 21°C. Lr. spectrum The spectra were measured with a Perkin-Elmer Type 221 Spectrophotometer using a 10-cm quartz cell with NaCI windows. Acknowledgement--This work was supported by the United States Air Force. "Grant AF-AFSOR 800-65 ; Air Force Office of Scientific Research of the Office of Aerospace Research. lnstituto Superior de lnvestigaciones Facultad de Quimica y Farmacia Universidad Nacional de La Plata La Plata
J.
R. GATTI R . L . KRIEGER J . E . SICRE H . J . SCHUMACHER
lnorg. Nucl. Chem., 1966,Vol. 28, pp. 657 to 658. PergamonPress Ltd. Printedin Northern Ireland
Studies on silver vanadate in acidic media (Received 18 May 1965) IN ALKALINEmedium vanadium (V) exists as a monomeric species designated by orthovanadate. Certain insoluble varmdates like those of silver and lead can be precipitated in alkaline medium having composition corresponding to the structure Ms(1)VO4. In acidic medium, however, vanadic acid exists in many polymeric forms and there is considerable uncertainty regarding the extent of polymerisation of vanadium (V) species at lower pH. The work of ROSSOTTIand RossoTn tl) indicates that in the pH range 0'5-6-5 the polymeric vanadium (V) species contain ten vanadium atoms. It was observed during the present studies on the effect of pH on the precipitation of silver vanadate that whereas in alkaline medium a precipitate of the composition 3AgzO. V~O~ was obtained the composition changed as the medium became more and more acidic. The ratio Ag20:V2Os kept on changing gradually in compounds precipitated at different pH. One of such compounds was precipitated at pH 3.7 having the composition 3Ag20.5V205. These observations indicate that V1002s8type species exists in solution and corresponding silver salt could be obtained thus confirming the conclusions drawn by RossoTa7 and ROSSOTTI.(1) EXPERIMENTAL All solutions were prepared in double-distilled conductivity water using B.D.H. reagents. The solutions were kept out of contact from the atmospheric carbon dioxide. Sodium orthovanadate solutions of exactly 0-1 M, 0"66 M and 0.05 M strength were prepared after standardising them with a previously standardised ferrous ammonium sulphate solution. 0-5 M silver nitrate and 1.0 M nitric acid solutions were prepared from their respective AnalaR reagents. A Cambridge bench pattern pH meter was used for performing the potentiometric titrations. The electrode system consisted of a saturated calomel half-cell and a thick silver plate indicator electrode. The connection between the calomel half-cell and the titration cell was made with saturated potassium nitrate solution. The conductivity measurements were made with a LBR model B177 measuring bridge operated on 220¥/50 cycles a.c. mains having a magic eye electronic detector. All systems were kept in an electrolytically maintained thermostat maintaining temperature at 25.0 ± 0.1°C. To an aliquot sample of the vanadate solution a varying quantity of nitric acid solution was added to keep the pH of the solution at 3-7. The final volume of the solution was kept the same in each (1) F. J. C. ROSSOT-rXand H. RossoTrl, Acta Chem. Scand. 10, 957 (1956). 2.3