combining weight


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combining weight,

the proportion (by weight) in which a chemical element combines with other elements to form compounds. The determination of combining weights was a very important part of early chemical endeavor. The atomic theory of John DaltonDalton, John
, 1766–1844, English scientist. He revived the atomic theory (see atom), which he formulated in the first volume of his New System of Chemical Philosophy (2 vol., 1808–27).
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 (see atomatom
[Gr.,=uncuttable (indivisible)], basic unit of matter; more properly, the smallest unit of a chemical element having the properties of that element. Structure of the Atom
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) was based in part on his determinations of combining weights, which he called atomic weights. Combining weights were usually measured by early chemists on a scale in which hydrogen had a combining weight of 1. See equivalent weightequivalent weight.
The equivalent weight of an element or radical is equal to its atomic weight or formula weight divided by the valence it assumes in compounds. The unit of equivalent weight is the atomic mass unit; the amount of a substance in grams numerically equal to the
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.

combining weight

[kəm′bīn·iŋ ‚wāt]
(chemistry)
The weight of an element that chemically combines with 8 grams of oxygen or its equivalent.