The chain reaction of 1,2-dichloroethane induced by a CW CO, laser has been studied in the presence of SF, as a sensitizer. Vinyl chloride and hydrogen chloride are the main products. The photosensitized decomposition of 1,2-dichloroethane mainly depends on the irradiated laser frequency and is governed by the excitation of the vibrational mode and collisional energy transfer. Arrhenius plots show two distinct regimes, corresponding to the respective activation energies: 96.3 kJ mol-' for the low-temperature regime and 50.2 kJ mol-' for the high-temperature regime. The inhibiting and promoting effects of propene and chlorine, respectively, on the chain reaction are examined. The kinetics proposed for the chain reaction are in agreement with the observed data, and mechanisms for molecular excitation and intramolecular energy transfer have been discussed. By using an IR laser, active centres can be generated, and initiation and propagation of a chain reaction at lower temperatures than is possible thermally can be achieved. This may be a way to decrease the energy expenditure and reduce the number of by-products in the chain reaction.

Ammonination technique for dehydration of hydrated magnesium chloride is a special kind of method for preparation of high-pure anhydrous magnesium chloride, which is requisite for electrolytically manufacturing metal magnesium. The technique has been developing for decades in the west world. China has now been exploiting the technique for his magnesium ore, especially the magnesium resource in the west of China. We started investigation of the method for several years, and several new progresses were arrived for preparation of anhydrous magnesium chloride. From our study, ethanol, methanol and water solution can be used for the method, and each had an advantage over the others; the ammonia used in the technique for preparation of anhydrous magnesium chloride is less corrosive for the equipment, and friendly for environment. The method gives great potential application in industry of metal magnesium and magnesium matrix materials.

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