Some ionic compounds form crystals that in-corporate a definite proportion of molecules of water as well as the ions of the compound itself.

一些离子化合物形成含一定比例的水分子和离子化合物的晶体。

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Thus, when the elements lead and sulfur are combIned In the proper proportion, they form a compound called lead sulfide.

因此，当铅和硫以适当的比例结合在一起时，它们便形成了一种叫铅硫化物的化合物。

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Their Aw property added in water is investigated and the proportion for the compound phosphate ester is optimized by means of four - ball tester.

利用四球试验机考察了添加到水溶液中的抗磨性能，并优化了复合磷酸酯的配比。

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