Metallurgy

According to various findings it is found that our predecessors were very advanced in this sector that ancient Indians excelled in metallurgical science. This is a proven fact since we all know about the iron pillar at Delhi. It is 1600 yr. old pillar and uses the same iron material as was manufactured in ancient India. It is rust free despite the weather conditions. Other examples of metallurgical science might be of Dhar in Madhya Pradesh and Kodachadri hill in coastal Karnataka.

With advancement and the coming up of iron beams they were widely used in many Indian temples. For example, Jagannathan of Puri in Odisha of 12 th century and that of sun temple in Konark.

A specialist or a person who practices metallurgical science is known as a Metallurgist.

Metallurgy studies has been divided into two broad sectors these are as follows -:

1) Physical metallurgy – It is based of physical, chemical and mechanical properties of metals

2) Chemical metallurgy – It is based on the performance of metals, basically the chemical one and is concerned with redox reactions of metals. Redox reactions are the oxidation and reduction reactions. Metallurgy deals with science of metals while considering and using technology into play. 

Concentration of ore

Ore contains a lot of impurities which are known as gangue. Various processes are done to concentrate the ore, these are briefly discussed as follows -:

Hydraulic washing – based on the difference in gravities of the ore and its gangue. It is basically a gravity separation process wherein an upward stream of water is used to wash the ore. The lighter gangue washes away and heavier stay behind.

Magnetic separation – based on the difference in magnetic properties of the components. It is used if either the ore or the gangue is having some metallic properties

Froth floatation method –In this gangue is removed from sulphide ores. Various substances like collectors and froth stabilizers are used. Main examples of collectors are pine oil, fatty acids and xanthates while to enhance the non-wettability stabilizers like cresols and aniline are used.

Leaching

It is used if ore is soluble in a solvent. like in the case of bauxite or the case of silver or gold

Extraction of crude metal from concentrated ore

For extraction of the metal it should be in a fork suitable for reduction like the oxide ore is preferred usually because it is easier for reducing it .So the sulphide ores are converted to oxide ore.

So, the process of isolation of metal from its concentrated ore has two steps, the first one being conversion to oxide and then reduction of oxide to metal.

Further the conversion to oxide ore can be done by calcination or roasting.

Refining

A metal extracted usually has some minor impurities that are removed during the refining process. For providing metals of high purity there are alot of techniques used to refine the metal. Based on the properties of the metal and the difference between the properties of big metal and impurity a particular method is chosen.

Some of the methods if refining are as Follows -:

1) Distillation

2) liquation

3) Electrolysis

4) zone refining

5) Vapour phase refining

6) chromatographic methods.

A) Distillation-: This is the process which depends on the difference in boiling point of the impurity and the metal. For example, for low boiling metals like zinc.

B) Liquation-: This is based on the principle of melting point that is the impurity and the metal have a difference in melting point. For example, in the case of Tin

C) Electrolytic Refining-:In this method impure metal is made anode and pure form is made cathode and is put in an Electrolytic bath containing salt and the same metal. Various metals like copper, zinc may be refined in this way.

D) Zone Refining-It is based on the principle of solubility wherein the solubility of impurity is different from that of the metal This is useful for extracting metals with high purity. Examples of metals that are extracted by zone refining are – germanium and boron.

E) Vapor phase refining- for this method we need a volatile metal and it should be easy. Basically what we do in this method is that we convert the metal to a volatile state and extract it and then get pure metal from it. For example, Mond’s process for nickel and Van Arkel process for zirconium are examples.

F) Chromatographic methods-this is based on the property of adsorption that is different components adsorb differently in the adsorbent.

Conclusion

Metallurgy is a crucial process that helps in extracting metals. These metals find its use in a variety of purposes like Aluminium foils for chocolate and wrappers, copper is used for making wires, zinc is used to make batteries and alloys and gold silver are used as jewellery.