Chem. [f. TRI- 5 + METHYL.] a. A formative denoting the presence of three methyl groups, CH3, in a compound, as trimethyl-arsine, As(CH3)3, trimethyl-phosphine, P(CH3)3: see also Trimethylamine below. b. spec. denoting the substitution of 3 methyl groups for 3 hydrogen atoms, in the substance designated by the rest of the name; e.g., trimethylbenzene, C6H3(CH3)3, in which 3 methyl groups have taken the place of 3 H atoms in benzene, C6H6; so trimethyl-methane, CH(CH3)3, from methane, CH4, trimethyl-carbinol, C(CH3)3.OH, etc. Also used attrib. as trimethyl phosphate, (CH3)3.PO4. Hence Trimethylic a. = trimethyl attrib.
1866. Roscoe, Elem. Chem. xxxi. 281. Trimethylarsine is a colourless liquid.
1868. Watts, Dict. Chem., IV. 608. Trimethylphosphine is a transparent, colourless, mobile liquid, heavier than water, having a strong refracting power, and an indescribably nauseous odour.
1873. Watts, Fownes’ Chem. (ed. 11), 767. Trimethyl-benzene is susceptible of three isomeric modifications. Also Trimethylamine, the tertiary amine of methyl, N(CH3)3, in which all the 3 hydrogen atoms of ammonia, NH3, are replaced by 3 methyl groups; a volatile liquid with a penetrating fishy odor; formerly also called Trimethyl ammonia and Trimethylia. Trimethylene, [formula], a colorless gas; trimethylene-diamine, a poisonous ptomaine.
1857. Miller, Elem. Chem., III. 210. Trimethylia.… This alkali … is found in considerable quantity in the roe of herrings.
1866. Odling, Anim. Chem., 87. Trimethylamine (CH3)3N, a frequent constituent of stale brine in which herrings and other fish have been pickled.
1872. Garrod & Baxter, Mat. Med. (1880), 408. The Hydrochlorate of Trimethylamine is a stable compound, in long needle-shaped crystals, very deliquescent, soluble in water and in alcohol.
