Page 17 - Curriculum Visions Dynamic Book

corrosion: the slow decay of a substance resulting
from contact with gases and liquids in the environment. The term is often applied to metals. Rust is the corrosion of iron.
inert: nonreactive.
precious metal: silver, gold, platinum, iridium, and palladium. Each is prized for its rarity. This category is the equivalent of precious stones, or gemstones, for minerals.
pyrite: “mineral of fire”. This name comes from the
fact that pyrite (iron sulphide) will give off sparks if struck with a stone.
Lead containers
Why would you want to make a container out of one of the world’s heaviest metals? The answer lies in a key property of lead: it will not corrode. So, for just the same reason as it was once useful for making water pipes, lead was traditionally used to make containers.
When a container is made from lead, the surface atoms of the lead react with the oxygen in the air to make lead oxide. When lead comes into contact with sulphuric acid, it makes an inert coating of lead sulphate.
Normally, it is very difficult to find containers for sulphuric acid because it dissolves them, but because lead reacts
very slowly to form a protective coating of lead sulphate, sulphuric acid can readily be kept in lead. In fact you may well find a lead-lined tub of sulphuric acid in some school metal workshops, where the acid is used for removing the oxide from most metals.
Lead chamber process
The lead chamber process was the earliest method of preparing sulphuric acid. Its development was one of the landmarks in the development of industrial chemistry because it allowed a valuable raw material, sulphuric acid, to be produced in large quantities for the first time. This, in turn, allowed the acid to be produced much more economically than previously and so brought down the price of chemicals and the processes and products that depended on them.
The lead chambers were the size of rooms. In this process a mixture of sulphur or pyrite and potassium nitrate was placed in a ladle and ignited. The floor of the chamber was covered with water. As the mixture burned, the gases produced condensed on the inside of the lead-lined chamber and were absorbed by the water.
The process produced about two-thirds purity sulphuric acid. The purpose of the lead chambers was simply to act as an inert container (since the lead forms an insoluble sulphate coating when in contact with the sulphuric acid).
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