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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 dif…

ut has no action on polarized light, and thus malic acid is a remarkable case of physical isomerism.

Connection with, or affinity to, one variety of isomerism, characteristic of the benzene compounds; -- contrasted with meta- or para-; as, the ortho position; hence, designating any substance showing such isomerism; as, an ortho compound.

ed at once to four different atoms or radicals. This condition usually occasions physical isomerism, with the attendant action on polarized light.