General Principles and Processes of Isolation of Elements Test - 5

Using dilute solution of NaCN or KCN in presence of air, CN^- forms complex with gold or silver, from which the metal is obtained later by replacement.

The low melting metal like tin is made to flow on a sloping surface. Thus it can be separated from higher melting impurities.

This method is very useful for producing semiconductor and other metals with very high purity, e.g., Ge, Si, B, In etc.

Al is generally used in paints and lacquers, since it adds sparkle to the paint.

Hall-Heroult process is used for extraction of Al from bauxite. It is usually carried out at a temperature of 980 °C.

Nitride ores not found in earth's crust.

Metal halides ores occur in sea and oceans, since they are soluble in water.

Cassiterite is a tin dioxide mineral. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today.

HgS is brick red form of sulphide ore of Hg from which it can be profitably extracted. It resembles quartz in symmetry.

In the metallurgy of aluminium, purified Al₂O₃ is mixed with Na₃AlF₆ which lowers the melting point of mixture and improves conductivity.