The Development of Rubber k4 B+ g2 W3 I3 `
Here is the story of rubber. From the earliest time it was __1__ common knowledge to the Peruvians that when a cut was made in the outside skin of a rubber tree, a white liquid __2__ milk came out, and that __3__ this a sticky mass of rubber might be made. This rubber is soft when warm, so that it is possible to give it any __4__. The Peruvians made the discovery that it was very good for keeping out __5__. Then in the early 1800's, the Americans made use of it for the first time. First they made overshoes __6__ their feet dry. Then came a certain Mr. Mackintosh, who made coats of cloth covered with natural rubber. From that day to this we have been coating cloth with rubber as Mr. Mackintosh __7__, and our raincoats are still named after him.' U6 p8 e) m8 B+ m7 C$ Z
But these first rubber overshoes and raincoats were all soft and sticky in summer, and __8__ and inelastic in the winter when it was cold. But the rubber we have today is soft and elastic, though very strong---even in the __9__ summer and the coldest winter. This was made __10__ by a man called Goodyear. __11__ experiments, he found that nitric acid (HNO3) made the rubber much better, but it is not hard and strong enough. Then strange thing took place. A friend of __12__, Nicholas Hayward, had the idea in his sleep that rubber might be made hard and strong if mixed with sulphur and put in the sun. Goodyear put this idea __13__ the test, and saw that it did have more or less the desired effect---though somewhat less than more. The only effect it had was on the outside of the rubber. It is common knowledge now that the way to make rubber hard and strong is __14__ sulphur. It took Goodyear four more years to find this method. When at last he did it, he had nothing at all. Everything of the smallest value __15__ to get money, even his sons' school-books.3 s- v# `. I. L- H1 U
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发表于 2012-8-15 23:30:26
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