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Dust has many unlikely uses and effects

Posted in Farming, Geography, Geology, Minerals, Nature on Friday, 6 April 2012

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This edited article about dust originally appeared in Look and Learn issue number 684 published on 22 February 1975.

Brick dust seller, picture, image, illustration

Brick dust seller in Portman Square; it was used for cleaning knives and cost a penny a quart

Most of us think of dust as just dirt that has to be swept up in the house or as something that gets into your eyes on a windy day.

But dust is much more than gritty dirt or an irritating speck in the eye. It is one of the most important things in our lives. It can do us good and it can do us harm.

Without dust, we would have no food, because the shape and size of dust particles making up soil decide whether or not crops will grow. This is because particles of earth, which are really dust, can hold, on their surface, a lot of moisture, heat and air. Without these three things, plants could not grow.

The dust particles in the earth attract specks of the minerals that plants need. The moisture on the dust then dissolves the minerals to feed the plant roots.

If, however, the earth is dry and the dust particles cannot collect moisture, the ground then becomes a desert. That happened many thousands of years ago in China and Africa. What were once vast areas of good agricultural land became trackless deserts, because there was no rainfall. The same thing is happening today over thousands of square miles in western and middle-western America.

In contrast to the beneficial effect of moist dust, dry dust can be very dangerous. If dust from coal, sugar, wheat or flour mix with the air in a small space, they collide or rub against each other. In doing this, they generate electricity which may set off an explosion. Even without this explosive effect, dry dust is dangerous. Lead dust can slowly poison whoever breathes it, and the dust in quarries and stonemasons’ yards can seriously injure the lungs.

Fortunately, there are dry dusts that are lifesavers. Respirators or gas masks contain powdered charcoal. This absorbs harmful gas in the air and lets the oxygen through. Dust from kaolin clay is used as a dressing for certain skin diseases. Ulcers are treated with aluminium dust and weak heart muscles are strengthened by injections of talcum dust.

In industry, too, dust is beneficial. Tin, copper and graphite dust, mixed with oil, can be made into a material which can be cast into machinery bearings that never need oiling.

Powdered copper and carbon made into devices called brushes are a vital part of an electric motor. And there is useful dust in radio or television receivers which use valves and not transistors. The filaments of valves are made from tungsten dust melted down and then drawn into fine hair-like valves. The insides of valves and the back of television screens are coated with metal dust.

We may live in a dusty world but, as you have seen, dust has its uses.

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