The Basics of Shielding in Chemistry

The Basics of Shielding in ChemistryFor many students, shielding in chemistry might be a little confusing. A shielding material is typically a substance that is chemically bonded to the surface of a gas or liquid (hence the term 'gas shield'), so that the gas or liquid will not flow past the surface without passing through an impenetrable barrier of the material.The most common examples of this are for gases and liquids, but the principle is applicable to the chemical reactions that take place between substances. Commonly, the barrier is made up of an impenetrable oxide film, where the gas or liquid is passed through a specific medium in order to reach the surface.The simplest form of a gas shield is a thin film of carbon dioxide, which is good for high pressures and temperatures. This is because its surface is very reactive - it is very likely to absorb most of the gas. It also absorbs light, so that you have to be careful when using it near any lamps or bright sunlight.A second bas ic form of a gas shield is silver halide. This shield is used in photoconductivity experiments. In this type of experiment, silver halide is combined with iodine, which is extremely reactive. But this reaction does not take place at the same rate as in some other experiments.Of all these forms, the most complex and most versatile is the hydrogen peroxide (H2O) gas shield. This chemical is used to block radiation, and to form molecular bonds.Hydrogen peroxide is commonly found as a solid; however, it can also be dissolved in chloroform, which is a gas, or in helium. When dissolved in helium, the gas is called 'helium peroxide', and the substance has become known as 'Helium'.Anotherimportant form of shielding is the silver nitrate, which is used to form a chemical bond between two other compounds. One such compound is bromine, which is used as a catalyst to destroy hydrocarbons, making them simpler to process into fuel. Other forms of shielding are employed in the chemical reactions t hat remove metals from gas.A further form of shielding is the use of an inert gas, such as argon, to protect a sample from unwanted chemical reactions. One example of an air-filled shield is the nitrogen mask used by those who operate an aircraft in a no-fly zone.