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加助熔剂的目的

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改变反应热降低渣的熔点,使熔渣易与被还原金属分离低温合成和分离将局部的温度降低到低于环境温度的操作,成为制冷。

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(7)------中偏难题

People generally use spices (香料) every day when preparing meals.Most of these spices are readily available in local supermarkets.However, in the 15th and 16th centuries, spices were as valuable as gold or diamonds.Spices are small plants or parts of plants, such as ginger, pepper, vanilla, and cinnamon, which are used to add flavor to our food. 1   Such a use for spices actually goes all the way back to Roman times.The Romans used spices such as cumin and coriander to help preserve food.

The spices came to Europe from countries to the east, such as the islands in the East Indies, Sri Lanka, and India. 2   Because of the long journeys involved, they were very expensive.

European sailors began to look for routes to these countries themselves in order to bring back the spices by sea.In 1498, a Portuguese explorer named Vasco Da Gama reached an East Indies island called Calicut. 3   In 1519, another Spanish explorer, Ferdinand Magellan, found a new trade route by sailing west across the Atlantic Ocean, around the southern tips of both South America and Africa, and back to Europe.

4   Portugal was the leader until the end of the 16th century.Spain was in control during much of the next 100 years.Then, Holland took over.The Dutch controlled the East Indies, but, in 1780, England defeated them in a famous war. 5   They treated the people there badly and made them submit to the British government.

India finally became independent from Britain in the 1940s.Today, it is still called “the land of spices”.In fact, at present India produces 2.5 million tons of spices each year and produced more types of spices than any other country.

A.For centuries, Arab traders had carried the spices over land and sold them to European countries.

B.For the next four centuries, Western countries raced each other for control of the spice trade in these new countries, which they called the “New World.”

C.Though they might not be as valuable today as gold or diamonds, spices are still big business around the globe.

D.Six years earlier, Spanish explorer Christopher Columbus had been looking for spices when he discovered America.E.The English then moved from the islands into India.

F.The history of spice is almost as old as human civilization.

G.In those times, spices also helped keep meat from spoiling.