Question

Define: (a) roasting; (b) smelting; (c) flotation; (d) refining.

Short answer

a. Roasting: It is a metallurgical process in which a sulfide is heated in presence of air. Roasting converts a metal sulfide to a metal oxide or to a free metal. Example: Mercury obtained from roasting mercury sulfide.

b. Smelting: It is a type of extractive metallurgy to extract metals from their ores, which includes silver, iron, and other base metals. In order to decompose the ore, it uses heat and reducing agent which drives off other elements as gases or slag and leaves behind the metal base.

Heating an oxide ore with coke is called smelting.

c. Flotation: In this process, an oil-detergent mixture is stirred with pulverized ore in water to form slurry. To some extent the surface of mineral and of gangue becomes wet. Further, mixing them with air produces an oily, mineral-rich froth that floats, but silicate particles sink. Finally, removal of solvent by skimming isolates the concentrated mineral fraction.

d. Refining: It is a process of purifying the elements. There are three methods of refining such as electrorefining, distillation, and zone refining.

Step-by-step solution

Metallurgy

The process of extraction of metals from its ore is discussed in detail in metallurgy. A metal in its pure state can be obtained by following various steps like roasting, smelting, flotation, refining etc.

(a) Roasting

Roasting is a metallurgical process that involves heating a sulfide in the presence of air. Roasting transforms a metal sulfide into a metal oxide or a free metal. Mercury obtained by roasting mercury(II) sulfide as an example.

(b) Smelting

Smelting: This process is used to extract metals from their ores, such as silver, iron, and other base metals. It uses heat and a reducing agent to decompose the ore, which drives off other elements as gases or slag and leaves behind the metal base. Heating an oxide ore with coke is called smelting.

(c) Flotation

Flotation: An oil-detergent mixture is stirred with pulverised ore in water to form a slurry in this process. The surface of the mineral and gangue becomes wet to some extent. When they are mixed with air, they form an oily, mineral-rich froth that floats, but silicate particles sink. Finally, skimming isolates the concentrated mineral fraction by removing the solvent.

(d) Refining

The process of purifying the elements is known as refining. Electro refining, distillation, and zone refining are the three refining methods.