and chlorine are combined to form a liquid, ethylene dichloride
(i) which is then heated to give vinyl chloride (ii) which is then
distilled off and gives hydrogen chloride gas;
H2C=CHCl + HCl
reactions also occur to form organochlorine compounds some of which
are collected as they have a commercial use. The remaining by-products
are burnt to reclaim hydrogen chloride, which can be recycled and
reacted with more ethylene to form new ethylene dichloride.
chloride gas is less harmful than chlorine however a liver cancer
called angiosarcoma has been linked with people who worked with
vinyl chloride. Workers exposed to it are now protected and leaks
and losses of vinyl chloride gas in plants are reduced to an absolute
minimum and residual traces in the product PVC are removed as far
as possible. These improvements ensure that the general public is
at no risk at all from this chemical.