Gaseous hydrogen

Bonds with characteristics intermediate between ionic and covalent can also be represented by, for example, two imaginary structures, I and II both of which contrihute to the true structure III. Consider gaseous hydrogen chloride ... 

Chlorination may be performed either in carbon tetrachloride with SOCU (418) or by passing gaseous hydrogen chloride through an aqueous solution (419). 

Fep2 was first prepared by the action of gaseous hydrogen fluoride over FeCl2 ia an iron boat (2). The reaction of anhydrous FeCl2, FeCl2 4H20, or FeSO and anhydrous HF in plastic reaction vessels such as vessels of polyethylene, polypropylene, or Teflon results in quantitative yields of very... 

Anhydrous FeF is prepared by the action of Hquid or gaseous hydrogen fluoride on anhydrous FeCl (see Iron compounds). FeF is insoluble in alcohol, ether, and ben2ene, and sparingly soluble in anhydrous HF and water. The pH of a saturated solution in water varies between 3.5 and 4.0. Low pH indicates the presence of residual amounts of HF. The light gray color of the material is attributed to iron oxide or free iron impurities in the product. 

The hquid remaining after the solvent has been recovered is a heavy residual fuel called solvent-refined coal, containing less than 0.8 wt % sulfur and 0.1 wt % ash. It melts at ca 177°C and has a heating value of ca 37 MJ/kg (16,000 Btu/lb), regardless of the quaUty of the coal feedstock. The activity of the solvent is apparently more important than the action of gaseous hydrogen ia this type of uncatalyzed hydrogenation. Research has been directed to the use of petroleum-derived aromatic oils as start-up solvents (118). 

Ra.don Sepa.ra.tion, Owing to its short half-life, radon is normally prepared close to the point of use in laboratory-scale apparatus. Radium salts are dissolved in water and the evolved gases periodically collected. The gas that contains radon, hydrogen, and oxygen is cooled to condense the radon, and the gaseous hydrogen and oxygen are pumped away. 

Table 4. Physical and Thermodynamic Properties of Gaseous Hydrogen ...

Standard of Gaseous Hydrogen Systems at Consumer Sites, Nad. Eke Protect. Assoc, pamphlet no. 50A (ANSI Z292.2), 1973. 

Table 3. Thermal Stability of Gaseous Hydrogen Chloride...

Gaseous Hydrogen Chloride. Cast Hon (qv), mild steel, and steel alloys are resistant to attack by dry, pure HCl at ambient conditions and can be used at temperatures up to the dissociation temperature of HCl. The corrosion rate at 300°C is reported to be 0.25 cm/yr and no ignition point has been found for mild steel at 760°C, at which temperature HCl is dissociated to the extent of 0.2%. 

Ballard Power Systems, in conjunction with the province of British Columbia and the government of Canada, have converted a diesel bus for Vancouver, B.C. Transit (43). This 9.1-m vehicle is powered by a 105-kW fuel cell. Gaseous hydrogen, stored on board the bus in DOT-approved glass-wound composite cylinders operating at 20.7 MPa (3000 psi), provides the necessary fuel requited for the 150-km projected vehicle range. 

The hexahydrate of aluminum chloride is a deUquescent, crystalline soHd soluble in water and alcohol and usually made by dissolving aluminum hydroxide [21645-51 -2] A1(0H)2, ia concentrated hydrochloric acid. When the acid is depleted, the solution is cooled to 0 °C and gaseous hydrogen chloride is introduced. Crystalline aluminum chloride hexahydrate, AIQ 6H20, is precipitated, filtered from the Hquor, washed with ethyl ether, and dried. 

The heat of formation of ammonium chloride from the elements is 317 kJ /mol (75.8 kcal/mol) it is 175 kJ /mol (41.9 kcal/mol) from gaseous ammonia and gaseous hydrogen chloride. The heat of formation of ammonium bromide from the elements, bromine in the Hquid form, is 273 kJ /mol (65.3 kcal/mol) for ammonium iodide, the corresponding heat of formation is 206 kJ /mol (49.3 kcal/mol). Iodine is in the soHd state. 

Titanium trifluoride may be prepared ia 90% yield by the reaction of gaseous hydrogen fluoride, ia practice ia a 1 4 ratio of hydrogen HF, with either titanium metal or titanium hydride at 900°C. 

Other preparative methods include direct synthesis from the elements, reaction between gaseous hydrogen fluoride and titanium tetrachloride, and decomposition of barium hexafluorotitanate [31252-69-6] BaTiF, or ammonium, (NH 2TiFg. 

Titanium tetraiodide can be prepared by direct combination of the elements at 150—200°C it can be made by reaction of gaseous hydrogen iodide with a solution of titanium tetrachloride in a suitable solvent and it can be purified by vacuum sublimation at 200°C. In the van Arkel method for the preparation of pure titanium metal, the sublimed tetraiodide is decomposed on a tungsten or titanium filament held at ca 1300°C (152). There are frequent hterature references to its use as a catalyst, eg, for the production of ethylene glycol from acetylene (153). 

In the CVD coating process, the tools are heated in a sealed reactor with gaseous hydrogen at atmospheric or lower pressure volatile compounds are added to the hydrogen to supply the metallic and nonmetaUic constituents of the coating. For example, TiC coatings are produced by reaction of TiCl vapors with methane (CH and hydrogen (H2) at 900 to 1100°C. The reaction is... 

Recovery of iodine hy action of sulfur dioxide on aqueous sodium iodate Hydrogenation of vegetable oils with gaseous hydrogen Desulfurization of gases by scrubbing with aqueous ethauolamiues... 

Problems sometimes occur in trying to minimize the temperature difference at the cold end of the heat exchanger, particularly if the specific heat of the warm fluid decreases with decreasing temperature as is the case with gaseous hydrogen. 

---