Stirrers

Stirrers are laboratory devices or instruments used to mix compounds to ensure even distribution. They can vary in size from a small stick to a complex piece of machinery. One of the most frequently used pieces of laboratory equipment is the stirring rod. Usually made of Pyrex, this solid glass rod is slightly longer and thicker then a drinking straw. It is 10-40 centimetres long, half a centimetre thick and flame polished. It provides controlled agitation and can limit the rate of flow. The magnetic stirrer is a laboratory device that employs a rotating magnetic field to cause a stir bar immersed in a liquid to spin very quickly. The rotating field is created by a rotating magnet or a set of stationary electromagnets. It is considered to be quicker and more efficient then motorised stirrers as there are no moving external parts. The sample is contained in glass vessels since this does not affect the magnetic field. It can only be done with relatively small experiments of less then four litres. Stirrers are used in all laboratories, whether they are research, industrial or educational. Stirring rods can be used to induce crystallisation or to break up emulsion during extraction.