来自《耶鲁大学开放课程：新生有机化学 第1集 第1集》

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  I just wanted you to know what's coming up.
  我只是希望你们了解接下来要做些什么
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  Incidentally, this thing about the problems set
  顺带一提 关于问题集
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  that has to do with the mathematics
  必须使用到数学
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  that Newton and Pepys were working on there,
  就是牛顿和佩皮斯所做的那些
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  has to do with isotope ratios.
  计算同位素比例
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  You know, chlorine has a funny atomic weight.
  你知道 氯的原子量很有趣
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  Why? What is the atomic weight, does anybody know?
  为什么 原子量是多少 有人知道吗
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  Thirty-five and a half.
  三十五点五
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  Thirty-five and a half.
  三十五点五
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  Why a half?
  为什么有个零点五
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  Most of the elements are pretty near integers.
  大多数元素的原子量相当接近整数
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  It's because it's a mixture of isotopes.
  这是因为它是一个含同位素的混合物