General Information (A)

Aclinic — The aclinic is a magnetic equator.

Actinide — An actinide is an element with an atomic number between 89 and 103.

Actinium — Actinium is a radioactive element with the symbol.

Adit — An adit is the horizontal entrance to a mine.

Aerated Water — Aerated water (soda water) is a solution of carbonic acid in water. It was discovered by Priestly and suggested as a prevention of scurvy, a paper being presented to the Admiralty in 1773. Certainly sailors drank aerated water on board ship as a bottle was found from the Royal George which sank in 1780.

Aggry Beads — Aggry Beads are glass beads prized by West African natives as ornaments and having magical and medicinal powers.

Agma — Agma is a tradename for calcined magnesite.

Alchemy — Alchemy was the medieval forerunner to chemistry. It was the supposed technique of transmuting base metals, such as lead and mercury, into silver and gold by the philosopher's stone, a hypothetical substance, to which was also attributed the power to give eternal life. This aspect of alchemy constituted much of the chemistry of the Middle Ages.

More broadly, however, alchemy was a system of philosophy that dealt both with the mystery of life and the formation of inanimate substances. Alchemy was a complex and indefinite conglomeration of chemistry, astrology, occultism, and magic, blended with obscure and abstruse ideas derived from various religious systems and other sources. It was practised in Europe from ancient times to the Middle Ages but later fell into disrepute when chemistry and physics developed.

Alchemy probably began in Egypt, where it is mentioned in very early records. Many legends developed regarding the origin of this mystical science, which is variously attributed to Hermes Trismegistus, to the fallen angels of the Book of Genesis, and yet again by revelation to Moses and Aaron. The origin through Hermes was most generally accepted, and has affected chemical language down to the present day (for example, hermetically sealed).

During the 4th and 5th centuries the writings of the alchemists continued increasing until by the end of the 5th century speculative alchemy had reached its highest point in the Alexandrian schools. During the Islamic conquests, many Arabs and Persians became notable alchemists. One of the best known was Jabir ibn Hayyan, known to western Europe as Geber. His ideas were very similar to those of the old Alexandrian philosophers, and he also believed in the influence of the planets on metals.

The theory of transmutation, which can be traced quite easily in the writings of the Greek philosophers, continued to exist amongst the alchemists of the Middle Ages and men such asSt Albertus Magnus, Roger Bacon, and Vincent of Beauvais all believed in it. Even well into the 17th century alchemistic ideas were still held, at least from the academic point of view, by the chemists of the period. Among them may be mentioned Johann Glauber, Robert Boyle, and, for some time Isaac Newton and Gottfried Leibniz who were interested in chemistry.

Alkakarb — Alkakarb is a tradename for sodium" bicarbonate.

Alkali — An alkali is a chemical substance.

Alloy — An alloy is a mixture of a metal and other metals or non-metals.

Alluvium — Alluvium is river transported deposits of mud, sand and gravel which accumulate to form distinctive features such as levees, flood plains and deltas.

Alpha Particles — Alpha Particles are the nuclei of the atom of helium, comprising two neutrons and two protons, and thus exhibiting a positive electric charge.

Alpha Rays — Alpha Rays are a stream of swiftly moving alpha particles. An alpha ray is capable of ionizing gases and of producing fluorescence in certain substances.

Alundum — Alundum is a form of aluminium oxide used in the manufacture of thermionic valves.

Americium — Americium is a synthetic chemical element with the symbol Am that is the most frequently used element for superconducting devices. It is artificially produced from plutonium, and is used commercially in gauges, distance-sensing devices, and smoke alarms. Americium was first synthesized in a nuclear reactor in 1944 by Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso.

Anatomical Alloy — Anatomical alloy is a fusible alloy consisting of 53.5 per cent bismuth, 19 percent tin, 17 per cent lead and 10.5 per cent mercury.

Andricite — Andricite is a tradename for anhydrous calcium sulphate.

Asphalt — Asphalt is a material used for road coverings.

Assay — Assay is the testing of an alloy or an ore to determine the proportion of a given metal. An assay officer is someone who certifies the fineness of gold, silver and platinum.

Astatine — Astatine is an element with the symbol At.

Asteroid — An asteroid is a minor planetary body.

Atom — An atom is the smallest quantity of a chemical element which can enter into combination or take part in a chemical reaction.

Atoms — see "atom"

Atrium — The atrium was the entrance hall to a Roman house.

Avoirdupois — The avoirdupois scale is a measurement of weight.