Dmitri Mendeleev, |
So good were the Egyptians at making them that some of their colored glass and tile have been dug up from the earth where they were buried for thousands of years — and the colors are as bright as when the glass and tile decorated the palaces of Egyptian pharaohs. Egyptian pictures in colored tile show ships with bright-colored stripes dyed in their sails, and nobles, both men and women, wearing beautifully colored clothes. All these facts are still more evidence that the Egyptians knew how to do things that required the use of chemistry. The Romans knew how to make cement. They made such good cement that some of their roads and aqueducts, built of cement two thousand years ago, can still be used today. The hardening of cement is a chemical process. This shows that the Romans, too, knew how to make materials that required the use of chemistry. An ancient Greek wise man named Empedocles taught that all materials are made of four things called elements: earth, air, water and fire. For two thousand years after Empedocles, certain men tried to make different kinds of materials by combining these four elements in different ways. Fortunately, for the future of chemistry, these men thought of earth as including anything solid, such as ore, metal, salt, glass or wood. Also, they counted any kind of gas as air and any liquid as water
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