Task 1. Give Ukrainian equivalents to the following words and word combinations.

Ductile, melting point, isolation, acidic solution, to encounter, capacitor, tungsten, to separate, fusing, to extract, molten fluoride, resultant mixture, to be immune to, conversion, high strength, to remain, reduction, to line, suture, stamping, scoring, rubber, slippage, punch, to spring back, acceptable, fine wire, thickness.

Task 2. Fill in the correct words and word combinations from the list below. Use each word only once.

Extraction, widespread, repair plates, present, slipping, mixture, high index, extract, close, immune to.

1. to be … chemical attack 6. … adherence

2. … of the metal 7. … technique

3. to … from the ores 8. … of refraction

4. to … no difficulties 9. … use

5. the resultant … 10. cranial …

Task 3. Fill in the gaps with the verbs from the list below used in the proper tense form.

To be, to remain, to involve, to be, to have, to contain, to use, to take.

1. Form stamping techniques … similar to those used with mild steel, except that precautions should be taken to prevent seizing or tearing of the metal.

2. Tantalum minerals usually … both niobium and tantalum.

3. Annealed tantalum … a permanent set of forming and does not spring back from the dies.

4. Current methodology … the separation of tantalum from these acid solutions using a liquid-liquid extraction technique.

5. The oxide … to make special glass with a high index of refraction for camera lenses.

6. The niobium … in the solution.

7. Therefore, tantalum … widespread use for surgical use.

8. Tantalum … very inert and so useful in the chemical and nuclear industries to line reactors.

UNIT 18 NON-FERROUS METALS. SILVER

History of Silver. A major watershed of silver production was the discovery of the New World in 1492, after which time major silver mines in Mexico, Bolivia, and Peru were opened leading to a rapid rise in the annual world production of silver. This rise, coupled with improved techniques for extracting silver from ore, broadened both the quality and quantity of ore that could be exploited. Later improvements, particularly in the late 19th and early 20th centuries, vastly enhanced the base of silver production and accelerated the exploitation of silver as a byproduct of base-metal mining.

A variety of advances in the early part of the last century allowed for increased production worldwide. This was critical, as many of the high-grade ores throughout the world had been largely depleted by the end of the 19th century. These advances included:

• Bulk mining methods, both at the surface and underground, capable of handling large amounts of lower grade base-metal ores that contained byproduct silver.

• Refinement of extraction techniques capable of separating various base-metal concentrates from ores.

• Improved techniques in ore separation, notably froth flotation (since 1910) that allowed for concentration of silver in lead, zinc, and copper concentrates.

• Improvements in electrorefining techniques allowing for the easy separation of silver and other base metals from refinery slimes, thus providing an increasingly important source of silver.

Symbol: Ag Atomic number: 47 Group number: 11 Number of neutrons: 61 Number of Protons/Electrons: 47 Mass: 107.868 Density 293 K: 10.5 g/cm3 Atomic volume: 10.3 cm3/mol Hardness: 3.25 mohs

Heat of fusion: 11.30 kJ/mol Heat of vaporization: 250.580 kJ/mol Melting Point: 961.93C (1235.1 K) Boiling Point: 2212 C (2428 K) Classification: Transition Metal Crystal Structure: Face-centered Cubic Color: silver Characteristics: soft, ductile, tarnishes

In order to fully understand how silver came to be where it is today, and where it might be going, it is useful to review silver market trends since the 1950s. By looking at the larger trends that have swept silver supply, demand, and prices upward and downward since 1950, a much fuller understanding emerges of where silver stands today.

Silver is a Precious Metal. Although silver is relatively scarce, it is the most plentiful and least expensive of the precious metals. Precious metals are valued for their beauty and relative scarcity in the Earth's crust, and their superior properties. They are very malleable, highly resistant to corrosion, superior reflectors of light and are unsurpassed as conductors of heat and electricity.

Besides signifying status and wealth, silver has been one of the most romantic and sought after of all the precious metals. Mystified by its beauty from the beginning of time, people have been drawn to remote areas of the world in search of this white, reflective metal.

Silver has often been surrounded by mystery. The Incas of Peru called it “the tears of the moon” because they were awed by silver’s strange gleam, and the Chinese believed that a silver locket hung around a child’s neck would ward off evil spirits.

Uses. Demand for silver is built on three main pillars; industrial and decorative uses, photography and jewelry and silverware. Together, these three categories represent more than 95 % of annual silver consumption. In 2003, 351 million ounces of silver were used for industrial applications, while over 196 million ounces of silver were committed to the photographic sector, and 266 million ounces were consumed in the jewelry and silverware markets.