Between 60 and 70 per cent of the common fuels are utilized in the generation of steam for heating purposes. TABLE SHOWING GENERATION OF HEAT ===========+====================+================ AMOUNT | FUEL | B. T. U. -----------+--------------------+---------------- 1 lb. | Anthracite coal | 13,200-13,900 1 lb. | Bituminous coal | 12,000-15,000 1 lb. | Lignite coal | 8,500-11,400 1 lb. | Wood | 8,200- 9,200 1 cu. ft. | Natural gas | 900- 1,000 1 cu. ft. | Illuminating gas | 500- 600 1 lb. | Kerosene | 18,000 1 lb. | Alcohol | 12,000 1 lb. | Gasoline | 19,000 1 K.W.-hr. | Electricity | 3,400 -----------+--------------------+------------ One pound ice in being melted will absorb 144 B. T. U. CHAPTER XXXIX GAS PLANTS =278. Gasoline-Gas Plants.= Gasoline-gas plants are devices for generating gas from gasoline. The gas is a mixture of air and gasoline vapor. It is made by air being forced thru gasoline. There are small plants which can be installed in private homes (Fig. 155). Gasoline vaporizes at ordinary temperature. The vapor or gas produced can be used for heating, lighting and running gas engines. [Illustration: FIG. 155. Gasoline gas plant.] One gallon of gasoline, when entirely vaporized, produces about thirty-two cubic feet of gas. Its heating power depends upon the character of the gasoline utilized and the temperature at which it is kept during vaporization. The plant is a device for forcing air thru the gasoline to make it vaporize as fast as wanted. Combined with the carburetor is a storage tank for the gas. A weight, or water motor, furnishes the power most commonly used in forcing the air thru the gasoline and forms a part of the plant. Air cannot flow thru the gasoline when the storage tank is full of gas so that the power is only in operation when the gas is being used or the tank is not quite full. =279. Acetylene-Gas Plant.= Acetylene is often used in rural homes when gas or electricity are not available. The operation of the plant often has to be attended to by a member of the family. A capable woman can do this, but she must be careful and must thoroly understand the plant (Fig. 156). [Illustration: FIG. 156. Acetylene gas plant.] The materials used in making acetylene are calcium carbide and water. Calcium carbide (_A_, Fig. 156) is made from lime and coke fused together in an electrical furnace. It must be kept stored in a dry place. The plants for making acetylene are inexpensive enough to be installed in individual homes of moderate means. Calcium carbide for making the gas can be transported without difficulty.