DIAGRAM VII
CHLORINE GAS PRESSURES AT VARIOUS TEMPERATURES
In practice it is found impossible to utilise all the gas contained in the containers; when the cylinders are almost empty the pressure necessary for the operation of the regulating device cannot be obtained and full cylinders must be attached. When sufficient heat is provided the weight of chlorine in the cylinder can be reduced to 1 - 11⁄2 pounds before the tank pressure becomes too low.
Liquid chlorine machines will operate, with ordinary care, for long periods. The various parts are made of such metals as experience has demonstrated to be best able to resist the corrosive action of the dry gas and the apparatus is designed to prevent the access of moisture which would otherwise produce corrosion and impede the flow of gas. Stoppages are sometimes caused by brown deposits derived from impurities in the liquid chlorine. These are primarily due to variations in the graphite electrodes used in the electrolytic process for the manufacture of chlorine from salt.
Fig. 8.—Dunwoodie Chlorinating Plant Treating 400,000,000 Gallons Per Day
for New York City.
To convey the dry gas from the apparatus to the point of application, copper or iron pipes may be used; for aqueous solutions, flexible rubber hose must be employed. Chlorine water is exceedingly active, chemically, and rapidly attacks all the common metals; ordinary galvanised iron pipe is eroded in a few days and should never be used.
Liquid chlorine, for water disinfection, possesses several marked advantages over the ordinary bleach process.