ISOMERIC • DICTIONARY ONE.COM • Definition of Isomeric

... economically by acting as diluents to the acetylene and, by having little or no illuminating value of themselves, causing the gas to emit less light than it should per unit of volume consumed, more particularly, of course, when the acetylene is not burnt under the mantle. Also, not being acetylene, or isomeric therewith, they require, even if they are combustible, a different proportion of oxygen for their perfect combustion; and a good acetylene jet is only calculated to attract precisely that quantity of air to the flame which a gas ...

— Acetylene, The Principles Of Its Generation And Use • F. H. Leeds and W. J. Atkinson Butterfield