BUTANE (C4Hio) is the fourth in the series of paraffin hy dro-carbons of the general formula and has one isomer. Normal butane boils at about the freezing point of water and has a Beaume gravity of 109. Both crude petroleum and natural gas come from wells and in most cases a mixture of oil and gas is ob tained simultaneously. Butane lies in the border zone and occurs in considerable quantities in both products. In the early days of petroleum refining most of the butane was lost in both the field and refinery operations since it was too volatile to condense in ordinary condensers. To-day both field and refinery gases are being scrubbed with oil or compressed to recover the butane as a liquid, in which form it has more value than as a gas. In order to utilize liquid butane commercially it is necessary to free it from dissolved gases, such as the lower members of the same series— ethane and propane, as their presence increases the volatility of the butane to such an extent that its storage and use becomes almost impossible.
The modern development of the butane industry has come about through the perfection of processes for the manufacture of "nat ural gasolene" from natural gas and refinery gases and in particular for the fractionation of this hydro-carbon mixture into its com ponents. In modern natural gasolene plants practically all of the butane is extracted from the gas and used either as part of the gasolene or as liquid butane. When propane is absent butane has a sufficiently low vapour pressure at ordinary temperatures to enable it to be shipped safely in tank cars or other containers and yet will completely evaporate when the pressure is relieved to give a gas of about four times the heating power of ordinary manufactured gas. It has been successfully tried out as a sub stitute for gas oil for the enrichment of illuminating gas and its uses as a solvent have been studied. Mixed with propane it is sold in cylinders for household heating and for isolated illumi nating plant. Butene, the corresponding unsaturated hydro-carbon found in gases from cracking stills, shares all the properties listed above for butane and in addition serves as the starting point for the manufacture of synthetic alcohols.