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Indium lies between iron and tin in the electromotive series (2).
Two reactions are possible with concentrated sulphuric acid (3).
Several methods of extracting indium from its ores arc possible (2).
Ex. 13. Answer the following questions:
I. What is the occurrence of indium in nature? 2. What properties docs indium exhibit? 3. What can you say about commercial applications of indium? 4. What kind of oxide docs indium form? 5. What compounds of indium and the halogens arc known? 6. In what way docs indium react with sulphuric acid? 7. What docs the spcctral analysis show?
Scction II
Упр. 1. Прочтите заглавие текста 10 В. Скажите, знаете ли вы что-IIII6)71ь по этому вопросу?
Упр. 2. Назовите значения следующих интернациональных слов:
material, medicine, pharmaceutical, thallium, platinum, busmuth, temperature, corrosion, discomfort, patient, dentist, amalgamate, diffuse, uniform, porous, attack, diffuse
Упр. 3. Определите значения выделенных слов по контексту. Сино нимы в скобках помогут вам.
1. Sometimes chemists add indium to obtain desirable (needed) properties of substances. 2. Indium forms alloys (mixtures of metals) with lead, tin, silver, gold, platinum and others. 3. Unique properties of indium enable (give the possibility) it to be used in medicine. 4. Indium alloys arc very corrosion-resistant (unaffected by corrosion). 5. Indium can be deposited on the article (thing) coated with zinc or cadmium.
Слова к тексту:
purpose — цель; jewellery — ювелирные изделия; mordant — веще ство, закрепляющее краску; dyestuff — краситель; braze— паять; insert — вставка; cast — форма (для отливки)', limbs — конечности; molten — рас плавленный; filling — пломба (зубная); conventional — обычный; plate— покрывать металлом; bake — запекать; chip — откалываться; рее! — ше лушиться
Text 10 В
Прочтите текст про себя (контрольное время чтения — б минут).
Uses of Indium
Indium finds most of its uses as an addition to other materials for the purpose of obtaining more desirable properties.
Indium and its compounds also find uses in jewellery, pharma-ccuticals, mcdicincs, mordants for dycstuffs, and also in low-mclting-point alloys.
Indium forms alloys with many metals; some of them arc lead, thallium, tin, silver, gold, platinum, mercury, bismuth, and sodium. Alloys of Au-In have good brazing characteristics. For example, the alloy of 77.S per cent Au and 22.5 per cent In has a working temperature of about 500°C. This enables the alloy to be used on metal pieces with glass inserts. Indium alloys arc very corrosion-resistant.
Low-melting alloys could also be used in making casts for broken limbs; a form is made around the broken member and the molten alloy poured into it. The alloy would be at a temperature which would cause no discomfort to the patient.
In dental work, indium amalgamated with mercury was frequently used. In fact, this must have been the first commercial use of indium. The resulting fillings were harder, more resistant to corrosion and discoloration than conventional fillings and looked little different.
Indium cannot be plated on ferrous metals directly. However, by first coating the iron or steel with a metal such as zinc, cadmium, or some similar metal which has a higher clcctrodc potential than the iron or steel and indium plate could be deposited successfully. After such a plate is deposited the article is baked at a temperature slightly above the melting point of indium for several hours. The indium and the other non-ferrous metal diffuse into one another, to producc a uniform plate which would not chip or peel and which would be non-porous.
Indium can be plated directly on non-ferrous metals. Generally, the plate is diffused into the base metal by the method mentioned above. Such coatings are more resistant to certain kinds of chcmical attack than the base metal and arc usually harder.
Упр. 4. Что нового вы узнали из текста 10 В?
Упр. 5. Разделите текст на тематические части и озаглавьте каж дую часть.
Упр. б. Скажите, что говорится в тексте:
другими металлами; 3) о применении индия в медицине.
Упр. 7. Найдите в тексте место, т е говорится об особенностях нане сения слоя индия иа металлы. Переведите этот отрывок на русский язык.
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