metamerism

...However, after further investigation, it became clear that although the two compounds have the same composition within the margin of error, they have completely different properties. In 1930, J. J. Berzelius confirmed that tartaric acid and racemic acid have the same composition, and defined several concepts to encompass them, such as isomerism, which means having the same molecular formula; heteropolymerism, which means having the same composition but different molecular weights (e.g., ethylene C ₂ H ₄ and butylene C ₄ H ₈ ); and metamerism, which means having the same composition but different components. Initially, all of these were considered to be isomerism in the broad sense, but gradually the concept of isomerism in the narrow sense came to be used. ...

*Some explanations of terms that mention "metamerism" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…しかし，再検討の結果，この二つの化合物が誤差の範囲で組成は同一なのに，まったく性質が異なる化合物であることが明白となった。　30年J.J.ベルセリウスは，酒石酸とラセミ酸とが同一組成をもつことを確認したうえで，これらを包括するいくつかの概念，すなわち同一分子式をもつ〈異性〉，同一組成をもつが分子量が異なる〈異量polymerism〉(たとえばエチレンC₂H₄とブチレンC₄H₈)，同じ組成をもつが異なる構成部分をもつ〈メタメリズムmetamerism〉などを定義した。当初はこれらのすべては広義の異性とみなされたが，しだいに狭義の異性の概念が用いられるようになった。…

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