crustn.外壳；坚硬的外壳；面包皮vt.盖以硬皮vi.结硬皮crustedadj.生了外皮的；(酒)有沉淀的；陈年的；古老的动词crust的过去式和过去分词形式.

1. Leaching of arsenic from arsenic and iron slag obtained from cobalt metallurgy with sodium hydroxide has been studied.
   研究了用氢氧化钠浸出钴冶金过程中产出的高砷铁渣中的砷。
2. The best presidents are like magnets below a piece of paper, invisibly aligning iron filings into a new pattern of their making.
   最好的总统，就像放在纸下面的一块磁铁，虽然看不见，但会吸引铁渣形成新的图案。