Defn: Having the same percentage composition; — said of two or more different substances which contain the same ingredients in the same proportions by weight, often used with with. Specif.: (a) Polymeric; i. e., having the same elements united in the same proportion by weight, but with different molecular weights; as, acetylene and benzine are isomeric (polymeric) with each other in this sense. See Polymeric. (b) Metameric; i. e., having the same elements united in the same proportions by weight, and with the same molecular weight, but which a different structure or arrangement of the ultimate parts; as, ethyl alcohol and methyl ether are isomeric (metameric) with each other in this sense. See Metameric.
ISOMERIDE
I*som"er*ide, n. (Chem.)
Defn: An isomer. [R.]
ISOMERISM
I*som"er*ism, n. (Chem.)
Defn: The state, quality, or relation, of two or more isomeric substances. Physical isomerism (Chem.), the condition or relation of certain (metameric) substances, which, while chemically identical (in that they have the same composition, the same molecular weights, and the same ultimate constitution), are yet physically different, as in their action on polarized light, as dextro- and lævo-tartaric acids. In such compounds there is usually at least one unsymmetrical carbon atom. See Unsymmetrical.
ISOMEROMORPHISM
I`so*mer`o*mor"phism, n. Etym: [Isomer + Gr. ism.] (Crystallog.)
Defn: Isomorphism between substances that are isomeric.
ISOMETRIC; ISOMETRICAL
I`so*met"ric, I`so*met"ric*al, a. Etym: [Iso- + Gr.
1. Pertaining to, or characterized by, equality of measure.
2. (Crystallog.)