Acetylene is a heavy, combustible gas with a strong odor, and was first made by Davy in 1837. It is produced by the reaction between water and calcium carbid according to the formula CaC2+H2O = C2H2+CaO2

The principal impurities of the freshly generated gas are ammonia and hydrogen phosphid and sulphid. These are removed by washing the gas in different solutions which will react upon these gases.

Acetylene is endothermic. So that the great heat of its combustion is the sum of its endothermic factor and the factor for carbon monoxid or dioxid. For this reason acetylene burns with tremendous heat with oxygen. The intense white light of combustion in air is attributed to the nascent carbon particles.

Mixed with air, acetylene is explosive between the range of 2 per cent, gas, 98 per cent, air; and 49 per cent, gas, 51 per cent air. This is a very wide range and makes the gas a troublesome one unless used with care. The odor, which is attributed to a small proportion of hydrocarbons, is offensive, but helps to detect leakage. Though there are instances of asphyxiation by this gas, it has been shown that pure acetylene is not a poisonous gas.

Fig. 43a. - Diagram of carbid-feed acetylene generator. (Davis Acetylene Company).