X. Переведите текст с учетом выполненных заданий. Третий и четвертый абзацы переведите письменно.

1. Titanium is a silvery-white metal which melts at approximately 1668°C and has a specific gravity of 4.505. Commercially pure titanium possesses high strength properties.

2. The story of titanium is extraordinary. To begin with, it was discovered twice. A British scientist, William Gregor, found it first and called it menachanite, and six years later, in 1797, M.H. Klaproth, a German chemist, also found it and gave it its present name.

3. For many years, titanium was of interest only to research chemists -- it was considered too brittle to be of any practical value. Yet it was the impurities with which it was usually associated (it forms compounds easily with nearly every known element) that made it brittle.

4. It cost the chemists in many countries endless efforts to isolate pure titanium and even more to start producing it commercially. In 1948 the world stock of pure titanium was only ten tons. Today the output is much larger.

5. Titanium has one surprising property -- it is completely inert in biological media. It is being used to make artificial joints and many other things necessary in surgery (traumatology and orthopedics). Titanium instruments do not corrode, and are thirty per cent lighter than instruments made of stainless steel.

6. Titanium's high standard of corrosion resistance, lightness, tensile strength, and the ease of forging, rolling and stamping are finding it more and more uses. Titanium alloys are very useful in mechanical engineering, and for chemical and refractory apparatus. Titanium helped Russian design engineers to surmount the sound and heat barriers in supersonic and high-altitude aircraft designing. On earth, it shows good work at chemical plants, in the pulp-and-paper and food industries. However, even very small amounts of oxygen and nitrogen in titanium alloys sharply reduce the ductility. A carbon content of more than 0.2% reduces both the ductility and impact strength of a titanium alloy.

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XII. Подготовьте сообщение о цветных металлах на примере любого цветного металла, о котором не говорилось в рассмотренных текстах.

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