Read about the main constituent of brass and answer the questions to the text

Zink

Zinc is a silvery white metal with a relatively low melt-Ing point (419.5°C) and boiling point (907°C). When unalloyed its strength and hardness is greater than that of tin or lead, but appreciably less than that of aluminium or cop­per and it cannot be used in stressed applications. Except when very pure, zinc is brittle at ordinary temperatures but malleable above 100°C and can then be readily rolled. When alloyed with 4 per cent aluminium its strength and hardness is increased considerably. Small additions of copper and titanium appreciably improve the creep resistance of rolled sheet and the use of this material is growing. With additions of 20-22 per cent aluminium, superplasticity can be developed, the alloys produced flowing readily at temperatures of 220°C under vacuum.

One of the most useful characteristics of zinc is its re­sistance to atmospheric corrosion, one of its main applications thus being for the protection of steelwork. The electro-negative character of zinc also leads to its use in consid­erable quantities in dry batteries.

Zinc, cadmium and mercury constitute Group IIB of the periodic table.

Zinc is divalent only and can give up the two outer electrons to form an electrovalent compound, for example, zinc carbonate ZnCO₈. It may also share those electrons as in zinc chloride ZnCl₂, in which the bonds are partly ionic and partly covalent.

8. Answer the following questions:

1. When did the production of zinc occur? 2. When was lead produced? 3. What is brass? 4. What characteristics of zinc do you know? 5. What chemical properties of zinc do you know?