isomerismn.

1838 T. Thomson Chem. Org. Bodies 58 This is one of the most extraordinary examples of isomerism at present known.

1851 T. Wright & G. F. Richardson Introd. Geol. (new ed.) v. 78 Isomerism, discovered by Berzelius, is a principle which is somewhat vague and doubtful in its application.

1880 E. Cleminshaw tr. C. A. Wurtz Atomic Theory 291 Isomerism is due to the difference in molecular grouping.

1884 E. Frankland & F. R. Japp Inorg. Chem. 111 Allotropy stands in the same relation to elements that isomerism does to compounds.

1892 H. F. Morley & M. M. P. Muir Watts' Dict. Chem. (rev. ed.) III. 81/1 Berzelius never intended that polymerism should be regarded as a form of isomerism.

1896 I. Remsen Introd. Study Compounds of Carbon 163 Bodies may conduct themselves chemically in exactly the same way, and yet differ in some of their physical properties, as in their action towards polarized light. To distinguish this kind of isomerism..it is called physical isomerism... The branch of chemistry which has to deal with the kind of isomerism just referred to, is called stereo-chemistry.

1938 R. W. Lawson tr. G. von Hevesy & F. A. Paneth Man. Radioactivity (ed. 2) x. 124 This isotope of silver..has two half-value periods, 24·5 m. and 8·2 d., the former being associated with positron emission, and the latter with the emission of β- and γ-rays... Here we are confronted with the phenomenon of nuclear isomerism.

1950 S. Glasstone Sourcebk. Atomic Energy x. 276/1 Over seventy examples of nuclear isomerism have been discovered, and the phenomenon of decay by isomeric transition, that is, by the spontaneous conversion of one nuclear isomer into another, has been elucidated. In most instances there are isomeric pairs only, but triple isomerism has been observed in a few cases.