Lavoisier discovered in 1793 that when steam, unmixed with air, is passed through glowing coke, the coke is oxidised; carbonic oxide and hydrogen are produced theoretically pure, and in equal volumes ; practically the product contains 3 to 8 per cent. of carbonic acid and 4 to 9 per cent. of nitrogen. The yield is, from coke (7,000,000 calorics per ton), about 35,000 cubic feet, with a heating value of about 75,000 calorics per 1,000 cubic feet, or, on the whole, about 40 per cent of the heat value of the coke; from coal (7,800,000 calorics per ton), about 42,000 cubic feet at 95,000 calorics, or about 49 per cent.

When the by-product - "the producer gas" - which may be generated in large quantities by regulating the supply of air while the coke glow is being worked up, is used for boilers or gas engines, the net cost of making simple water gas is between 5d. and 6d. per 1,000 cubic feet, or about 8d. per 1,000 less than coal gas.

Water gas gives on combustion an extremely high temperature, which saves time in furnace work; gold, silver, and copper, and even an alloy of 70 per cent. of gold and 30 per cent. of platinum, are readily melted in quantity by it; hence for bringing objects such as Fahnehjelms combs (a series of rods of magnesia) into brilliant luminous incandescence, for welding or for metallurgical operations inducing high temperature, it is very suitable. Unfortunately, its high percentage of carbonic oxide, which is odourless, has caused a high death roll.