书城教材教辅科学读本(英文原版)(套装1-6册)
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第166章 第二册(83)

"This piece," he added, "is sheet zinc. How was that made?""It was rolled or hammered out," said Norah, "so zinc must be malleable.""Yes," said Fred, "it is like lead and tin in this respect. And, like them too, it is not good for making wire. It is neither ductile nor tenacious.""It is mostly used as sheet zinc. The reasons are that it is malleable, and can be easily rolled out; it is lighter and harder than lead, and, at the same time, cheaper, and it bends easily.

"It is largely used for the roofs and gutters of houses, and for rainwater pipes, as well as for baths, cans, and vessels of all kinds for holding water. The reason is that water and air do not rust zinc, except on the surface.""Do you know, Norah, that zinc saws are always used for sawing up blocks of salt?" said Fred. "Iron or steel saws would rust, but zinc does not rust.

"Now look at mother" s new pail. It looks exactly like zinc; it is the colour of zinc. But it is not zinc. It is made of iron. We call it galvanized iron.

"It was made just as the "tinned ware" was made. The iron was dipped into melted zinc, and this formed a coat all over it, to keep the iron from rusting."SUMMARY