Michael Faraday is one of the great names of British scientific history, with notable achievements in the fields of physics and chemistry to his credit. Born at Newington Butts in Surrey in the year 1971, he had little in the way of formal education. His father was a blacksmith and by the time he was 11 the young Michael Faraday was apprenticed to the bookbinding trade. Reading the many volumes on which he was working, however, gave him a thirst for scientific knowledge. One day he went to the lectures of the great Sir Humphry Davy and later entered his service, first as a manservant, afterwards as his secretary.
Michael Faraday’s interest in chemistry and physics grew and by the time he was 31 he was reading his own scientific papers at the Royal Institution in London (where Davy worked). He was appointed the Director of the Laboratory there in 1825 and in 1833 he became the Institution’s Fullerian Professor of Chemistry, a post which he helps until his death in 1867.
Michael Faraday’s talents covered many fields. He was the first to liquefy chlorine, carbon dioxide and other gases. He investigated electromagnetic induction. He developed the idea of lines of force around a magnet. And in many ways the most important feat of all, he established his laws of electrolysis.
Electrolysis is a method of splitting up a chemical compound by passing through it an electric current. Perhaps the simplest laboratory experiment demonstrating the principle is the electrolysis of water (a compound of hydrogen and oxygen). By passing a direct current through the water (to which a small amount of acid has been added) bubbles of oxygen and hydrogen gases are formed at the electrodes (the electrical contacts in the water). Electrolysis has a great many practical applications today, for example the electroplating of cutlery with ‘nickel silver’, the electroplating of car bumpers with chromium and the extraction of metals such as aluminium from the ores.
The laws of electrolysis which Michael Faraday put forward were as follows.
- First he said that the weight of a substance set free during electrolysis is proportional to the size of the current which passes and the time for which is passes.
- Secondly, the weight of a substance set free during electrolysis is proportional to the equivalent weight of a substance.
The first part is not difficult to understand. A strong current flowing through the electrolyte for a long time causes more of the substance (e.g. oxygen, hydrogen) to be released at the electrodes than would a weak current flowing for a short time.
The second part means that with the same current flowing for the same time, the amount of the substances released will depend on their equivalent weights. The equivalent weight of a substance is the number of units of weight of a substance that will combine with hydrogen weighing one unit. In a molecule of water, two atoms of hydrogen, each weighing one unit are combined with one atom of oxygen weighing sixteen units. So two units of hydrogen are combined with sixteen units of oxygen; one unit of hydrogen then would combine with eight units of oxygen. The equivalent weight of oxygen as hydrogen by weight is set free during the electrolysis of water. The larger the equivalent weight of the element involved, the greater the weight of it that will be set free during electrolysis.
Michael Faraday was responsible for introducing many of the technical terms connected with electrolysis. Electrolyte is the liquid through which the current is passed. Anode and cathode are the names for the positive and negative electrodes respectively. These terms were invented for Michael Faraday by a friend, William Whewell.