Text 10

( - ). 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, pharmaceuticals, medicines, mordants for dyestuffs, and also in low-melting- 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 77.5 per ccnt Au and 22.5 per ccnt 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 wrhich would cause no discomfort to the patient.

In dental work, indium amalgamated widi 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 can not 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 produce 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 ccrtain kinds of chemical attack than the base metal and arc usually harder.

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Section

Ex. 1. Think of the situations with the following expressions. Mind the difference in the word-order.

Here is the pen.( .)Here it is.( .) Here are the books.( .)Here they are.( :)

Example: - Give me your copy-book, please. ( , .) - Here you are. / Here it is. ( .)

Ex. 2. Translate the following questions or requests and react to them. Use expressions from exercise 1.

1. , , . 2. ? 3. , , . 4. 쳿? 5. , ? . , , . 7. . 8. ? 9. , , . 10. , , .

Ex. 3. up sentences or short stories with the following words:

1) seldom, mineral, indium, occur, 0.1 per ccnt, quantity; 2) form, compound, indium, various, most, be, they, water, soluble; 3) can, ore, several, indium, extract, method; 4) react, indium, nitric acid, reaction, possible, concentrated, two, be, sulphuric acid

Ex. 4. Give detailed answers to the following questions:

1. Why was not indium used commercially before 1934? 2. What methods of extracting indium from its ores do you know? 3. What compounds can indium form? 4. In what way docs indium react with acids? 5. What arc the main uses of indium?

Ex. 5. Discuss the following topics:

1. The Occurrcncc of Indium.

2. The Properties of Indium.

3. The Uses of Indium.

DO YOU KNOW THAT ...

In 1863 Reich and Richtcr, in an effort to tracc thallium in zinc blende observed two new blue lines in the spectrum. The zinc blende had been roasted to remove most of the arsenic and sulphur. The residue had been dissolved with hydrochloric acid and evaporated to dryness. This residue of crude zinc chloride was submitted to a spectrum analysis. They discovered the new element, indium, so named from its characteristic blue lines.




Text 9 | Fluorine | Fascinating Phosphorus | Modifications of Phosphorus | Lesson 12 | Chemical Symbols for Representing Compounds | Weight of 12 atom of carbon 12 | Lesson 13 | Text 13 A The History of Chemistry | Text 13 |

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