This is just as well, for if oxygen were corn bustible, each time you lit a match all the air around you would bur into flame. 这倒还不错，要说氧是可燃的话，你每次划一根火柴周围的空气就会一下子燃烧起来。

　　Hydrogen gas, on the other hand, is extremely corn bustible, as the dirigible Hindenburg demonstrated on May 6, 1973 in Lakehurst, New Jersey, 另一方面，氢气的可燃性极强，“欣登堡”号飞艇事故就说明了这一点。1937年5月6日，在新泽西州的莱克赫斯特，

　　when its hydrogen fuel burst explosive) into flame, killing thirty-six people.) 使该飞艇升空的氢突然爆炸，燃起熊熊大火，造成36人死亡。）

　　Odder still in combination are sodium, one of the most unstable of all elements, and chlorine, one of the most toxic. 更奇特的是钠和氯的化合物。钠是最不稳定的元素之一，氯是最毒的元素之一。

　　Drop a small lump of pure sodium into ordinary water and it will explode with enough force to kill. 要是把一小块纯钠放进水里，它会爆炸，具有置人死地的威力。

　　Chlorine is even more notoriously hazardous. 毒性很大的氯是非常危险的。

　　Though useful in small concentrations for killing microorganisms (it's chlorine you smell in bleach), in larger volumes it is lethal. 虽然低浓度的氯可以用来杀死微生物（你在漂白粉里闻到的就是氯的气味），但量大了就可以致命。

　　Chlorine was the element of choice for many of the poison gases of the First World War. 第一次世界大战期间，许多毒气就含有氯的成分。

　　And, as many a sore-eyed swimmer will attest, even in exceedingly dilute form the human body doesn't appreciate it. 许多患眼痛的游泳运动员可以作证，即使在浓度极低的情况下，人体也不大喜欢氯。

　　Yet put these two nasty elements together and what do you get? 然而，要是你把这两种讨厌的元素放在一起，你会得到什么来着？

　　Sodium chloride—common table salt. 氯化钠——普通的食盐。

　　By and large, if an element doesn't naturally find its way into our systems—if it isn't soluble in water, say—we tend to be intolerant of it. 总的来说，要是一种元素不是自然地进入我们的系统——比如说，如果它不能溶解于水——我们往往就不会接受它。

　　Lead poisons us because we were never exposed to it until we began to fashion it into food vessels and pipes for plumbing. 铅之所以会使我们中毒，是因为我们向来不接触铅，直到我们开始把它用于盛食品的器皿以及水管。

　　(Not incidentally, lead's symbol is Pb, for the Latin plumbum, the source word for our modern plumbing.) （铅的符号是Pb，代表拉丁语Plumbum，现代“管道”（plumbing）这个名词就源自该词，这不是偶然的。）