Note 28 — Chapter VIII · CARBON AND THE HYDROCARBONS

As, for example, in the saturated series of hydrocarbons CnH2n+2, the lowest member (n = 0) must be taken as hydrogen H2, a gas which (t.c. below -190°) is liquefied with great difficulty, and when in a liquid state has doubtless a very small density. Where n = 1, 2, 3, the hydrocarbons CH4, C2H6, C3H8 are gases, more and more readily liquefiable. The temperature of the absolute boiling point for CH4 = -100°, and for ethane C2H6, and in the higher members it rises. The hydrocarbon C4H10, liquefies at about 0°. C5H12 (there are several isomers) boils at from +9° (Lvoff) to 37°, C6H14 from 58° to 78°, &c. The specific gravities in a liquid state at 15° are:—

C₅H₁₂ C₆H₁₄ C₇H₁₆ C₁₀H₂₂ C₁₆H₃₄

0·63 0·66 0·70 0·75 0·85