Hydrogen fluoride physical properties

Physical Properties. Physical properties of anhydrous hydrogen fluoride are summarized in Table 1. Figure 1 shows the vapor pressure and latent heat of vaporization. The specific gravity of the Hquid decreases almost linearly from 1.1 at —40°C to 0.84 at 80°C (4). The specific heat of anhydrous HF is shown in Figure 2 and the heat of solution in Figure 3. 

Properties. Lithium fluoride [7789-24-4] LiF, is a white nonhygroscopic crystaUine material that does not form a hydrate. The properties of lithium fluoride are similar to the aLkaline-earth fluorides. The solubility in water is quite low and chemical reactivity is low, similar to that of calcium fluoride and magnesium fluoride. Several chemical and physical properties of lithium fluoride are listed in Table 1. At high temperatures, lithium fluoride hydroly2es to hydrogen fluoride when heated in the presence of moisture. A bifluoride [12159-92-17, LiF HF, which forms on reaction of LiF with hydrofluoric acid, is unstable to loss of HF in the solid form. 

Vlayl fluoride [75-02-5] (VF) (fluoroethene) is a colorless gas at ambient conditions. It was first prepared by reaction of l,l-difluoro-2-bromoethane [359-07-9] with ziac (1). Most approaches to vinyl fluoride synthesis have employed reactions of acetylene [74-86-2] with hydrogen fluoride (HF) either directly (2—5) or utilizing catalysts (3,6—10). Other routes have iavolved ethylene [74-85-1] and HF (11), pyrolysis of 1,1-difluoroethane [624-72-6] (12,13) and fluorochloroethanes (14—18), reaction of 1,1-difluoroethane with acetylene (19,20), and halogen exchange of vinyl chloride [75-01-4] with HF (21—23). Physical properties of vinyl fluoride are given ia Table 1. 

TABLE 8.5.1 Physical Properties of Hydrogen Fluoride CAS Registry Number 07664-39-3... 

Although the gas-phase hydrogen-bonded dimer (MeF)2H" is held by a strong hydrogen bond (McMahon and Kebarle, 1986) this is a rare exception to the previous statement regarding covalently bonded fluoride. More typical are the perfluorocarbons, which are among the weakest hydrogenbonding substances known, as their physical properties and uses clearly demonstrate. 

Considerations of mechanism despite their difficulties are extremely valuable and productive. The discovery of the catalytic properties of hydrogen fluoride for condensation reactions came about from considering the mechanisms of certain organic reactions coupled with a knowledge of the chemical and physical properties of hydrogen fluoride. That fundamental acidity is involved in the catalytic properties of hydrogen fluoride is confirmed by the fact that hydrogen chloride under appropriate conditions can catalyze some of the same reactions (Simons and Hart, 81). 

Is fluorine an element 1 Since fluorine had never been previously isolated, it remained for H. Moissan to prove that the gas he found to be liberated at the positive pole is really fluorine. Many of its physical and chemical properties, as will be shown later, agree with those suggested by the analogy of the fluorides with the chlorides, bromide, and iodides. It was found impossible to account for its properties by assuming it to be some other gas mixed with nitric acid, chlorine, or ozone or that it is a hydrogen fluoride richer in fluorine than the normal hydrogen fluoride. 

Although no attempt will be made to describe the chemistry of all of the nonaqueous solvents listed in Table 5.4, the survey to this point has included ammonia as a basic solvent and liquid hydrogen fluoride as an acidic solvent. Another solvent that has been extensively utilized in both inorganic and organic chemistry is sulfur dioxide. Accordingly, we will give a brief survey of the chemistry of liquid sulfur dioxide for which the physical properties are presented in Table 5.8. 

Toxic chemicals tliat could potentially cause a major problem if accidentally released into tlie atmosphere include clilorine, hydrogen fluoride, hydrogen chloride, ammonia, chloropicrin, gasoline lead additives, vinyl cliloridc. and benzene. Hiis chapter addresses the process application of some chemicals from the foregoing list, as well as some others that are considered to be highly toxic hydrogen cyanide, sulfuric acid, and etliylene. Process considerations, physical and chemical properties, healtli effects, and metliods of manufacture of tliese chemicals are discussed in conjunction with potential causes of release. 

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