A pencil is a long-haired brush terminating in a point and used by artists and sign writers.
Pencil is short for 'lead pencil', an instrument consisting of a thin, usually wooden, tube enclosing a thin rod of some substance, usually graphite. Research Pencil
Edward Goodrich Acheson was an American chemist and inventor. He was born in 1856 at Washington, Pennsylvania, and died in 1931. From 1880 to 1881 he did research on electric lamps as an assistant to Thomas Edison. After 1884 he worked independently to develop the electric furnace for the conversion of carbon into diamonds, without success. In 1891 he invented carborundum (silicon carbide) and artificially prepared graphite. Research Edward Acheson
The Acheson process is an industrial process for the manufacture of graphite by heating coke mixed with clay. The reaction involves the production of silicon carbide, which loses silicon at 4150°C to leave graphite. The process was patented in 1896 by the American inventor Edward Acheson. Research Acheson Process
Atmolysis is a method of separating the constituent gases of a compound gas (such as air) by causing it to pass through a vessel of porous material (such as graphite). The process was discovered by Graham and made known in 1863. Research Atmolysis
Carbon is a non-metallic, chiefly trivalent element found native (as in diamond and graphite) or as a constituent of coal, petroleum, and asphalt, of limestone and other bicarbonates, and of organic compounds or obtained artificially in varying degrees of purity especially as carbon black, lampblack, activated charcoal and coke. It has the symbol C and is contained in all life forms.
The diamond is the purest form of carbon; in the different varieties of charcoal, in coal, anthracite, etc, it is more or less mixed with other substances. Pure charcoal is a black, brittle, light, and inodorous substance. It is usually the remains of some vegetable body from which all the volatile matter has been expelled by heat; but it may be obtained from most organic matters, animal as well as vegetable, by ignition in close vessels. Carbon, being one of those elements which exist in various distinct forms, is an example of what is called allotropy. The compounds of this element are more numerous than those of all the other elements taken together. With hydrogen especially it forms a very large number of compounds, called hydrocarbons, some of which have latterly become of the greatest economic importance. With oxygen carbon forms only two compounds, but union between the two elements is easily effected. Research Carbon
In a nuclear electricity generating installation the heat required for raising steam is provided by a nuclear reactor instead of a coal or gas furnace. A reactor consists of a strong steel pressure vessel enclosing a core made of graphite bricks. This graphite core has a number of vertical channels which are filled with rods of uranium. Interspersed among the uranium rods are a set of boronsteel rods (the control rods) which may be raised or lowered in similar channels in the graphite. The uranium used in the reactor consists of a mixture of two different kinds of atoms, of which the most important are U-235. Quite spontaneously, some of these U-235 atoms explode or disintegrate to form other atoms of smaller mass. When this happens, energy is radiated from the central core or nucleus of the atom together with small high-speed particles called neutrons. If one of the neutrons happens to strike the nucleus of a neighbouring atom this may also disintegrate, with a further evolution of energy and the production of more neutrons. This
splitting up of the nucleus is called fission. The graphite of which the core is composed is called a moderator, and its function is to slow down the speed of the neutrons, as it is found that fission of U-235 is more likely to occur with slow neutrons than with fast ones. In a small piece of uranium mixed with moderator most of the neutrons escape through the surface. If, however, the amount of material is increased the chances that a neutron will collide with an atomic nucleus will also increase, since there are more atoms present. Each nuclear fission which occurs produces two or three fresh neutrons which are, in turn, capable of promoting the fission of further nuclei. When the lump of uranium and moderator is above a certain critical size the fission process proceeds cumulatively in what is called a chain reaction. This is where the boronsteel rods play their part. Before the uranium rods are loaded into the graphite core the boron rods are already in position, and these have the property of being able to absorb neutrons which are shot out from the uranium, and so prevent the chain reaction from starting. When sufficient uranium rods have been added to effect critical conditions the pressure vessel is sealed and the boron rods raised out of the core. The uranium rods are now freely bombarded by one another's neutrons and the chain reaction begins. The rate at which fission occurs can be controlled by raising or lowering the boron rods. If these are fully inserted into the graphite core the reaction shuts down completely, and only the normal spontaneous nuclear fission takes place. The heat energy released by the fission process is carried away in a stream of high-pressure carbon dioxide gas which is continuously pumped through the pressure vessel. This hot gas circulates through a special steamboiler, and the steam so raised is used to drive an electric turbo-generator in the usual way. Research Nuclear Energy
Graphite (also known as Plumbago, Black-lead, and as Wad) is pure carbon with a relative hardness of 2, occurring naturally and often confused with the heavier molybdenite. Graphite occurs not infrequently as a mineral production, and is found in great purity at Borrowdale in Cumberland, and in large quantities in Canada, Sri Lanka, and at Bohemia. Graphite has an iron-grey colour, a metallic lustre, and a granular texture, and is soft and unctuous to the touch. It is formed from organic materials or by the presence of hydrocarbons in a metamorphic region. Graphite may be heated to any extent in close vessels without change and is exceedingly unchangeable in the air and as such has been used in the manufacture of crucibles, as a lubricant when mixed with oils, and as 'lead' for pencils when mixed with clay. Graphite is also used in burnishing iron to protect it from rust, for giving a smooth surface to casting moulds, for coating wax or other impressions of objects designed to be electro-typed, and for counteracting friction between the rubbing surfaces of wood or metal in machinery. Since the start of the 20th century artificial graphite has been produced by the electric furnace. Research Graphite
GEM is an abbreviation for Giotto Extended Mission
GEM is an abbreviation for Graphics Environment Manager
GEM is an abbreviation for Gimbal Electronics Module
GEM is an abbreviation for Goddard Earth Model
GEM is an abbreviation for Graphite Epoxy Motor
GEM is an abbreviation for Ground Effects Machine
GEM is an abbreviation for Guidance Evaluation Missile Research GEM
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
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