Long ago, people did not investigate the chemical composition of stones.
很久以前，人们对宝石的化学成分没有研究。
That part of the atmosphere in which the chemical composition is homogenous (uniform).
化学成分是均匀的一部分大气。
Chemical formula: Expression of the composition or structure of a chemical compound.
化学式：化合物的组成或结构的任何一种表达式的总称。
Chemical formula: Expression of the composition or structure of a chemical compound.
化学式：化合物的组成或结构的任何一种表达式的总称。
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