A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

^4 SEA WATER DISTILLATION. meter (its pressure, whether equal to 3 inches head of water, or only 1 inch head of water, is immaterial) the consumer is charged for the number of cubic feet at atmospheric pressure. Thus, say that after the gas has passed through the meter it is allowed to escape into an inverted rccoivor, open sit flic bottom, tli6 interior dimen sions of which are 10 feet by 10 feet by 10 feet high, equalling 1,000 cubic feet. Gas, being about half the weight of air, will rise in the inverted receiver, and fill it with gas, the air being expelled downwards, and in a short time we shall have 1,000 cubic feet of gas at atmo- spheric pressure. This is the rate at which the gas is charged for. If the gas entered the receiver with a pres- sure of, say, 3 inches head of water behind it, it would obviously fill ths receiver in a shorter time than if the pressure behind the gas was only 1 inch head of water, but the quantity would be the same. It may be taken that the volume of the gas is practically unaffected by the ordinary pressure of supply in town mains. 20. A simple manner of ascertaining the pressure of the gas is to take a piece of india-rubber tube, having a short piece (say 6 inches) of glass tube at one end. If the rubber end is then put on an unlighted gas burner, and the glass tube dipped into a tumbler of water, the gas (when passing into the glass tube) will depress the water for, say, 3 inches out of the glass tube below the level in tumbler, and this will show there is a pressure of 3 inches head of water. —Before leaving the subject of gas, it may be interesting to compare its cost as against that of coal. For this purpose it is necessary to compare their following heating powers.