Karl Ferdinand Braun was a German physicist who made improvements to Guglielmo Marconi's system of wireless telegraphy. He was born in 1850 at Fulda, and died in 1918. He and Marconi shared the 1909 Nobel Prize for Physics. Braun also discovered crystal rectifiers (used in early radios), and invented the oscilloscope in 1895. He was educated at Marburg and Berlin. He held academic posts at a number of German universities, ending his career as professor and from 1895 director of the Institute of Physics at Strasbourg. In an attempt to increase the radio transmitter range to more than 15 km, Braun devised a system in which the power from the transmitter was magnetically coupled (using electromagnetic induction) to the antennacircuit. He patented this invention in 1899, and the principle of magnetic coupling has since been applied to all similar transmission systems. Later Braun developed directional antennas. In 1874 Braun discovered that some mineral metal sulphides conduct electricity in one direction only. These were later used in the crystal radio receivers that preceded valve circuits. Braun's oscilloscope was an adaptation of the cathode-ray tube. A laboratory instrument to study high-frequency alternating currents, it was the forerunner of television and radar display tubes. Research Karl Braun
Fluorescence is the process of emission of electromagnetic radiation resulting from the absorption of certain types of energy. Fluorescent paints are usually the sulphides of calcium, barium and strontium which glow in the dark after having been exposed to light for a while. Research Fluorescence
Arsenic is a trivalent and pentavalent, solid, poisonous common element usually found combined with metals as arsenides, the commonest of which is arsenical pyrites, FeAsS. It has a steel colour and high metallic lustre, and tarnishes on exposure to the air, first changing to yellow, and finally to black. In hardness it equals copper; it is extremely brittle, and very volatile, beginning to sublime before it melts. It burns with a blue flame, and emits a smell of garlic. Its specific gravity is 5.76. It forms compounds with most of the metals. Combined with sulphur it forms or-piment and realgar, which are the yellow and red sulphides of arsenic. Orpiment is the true arsenicum of the ancients. With oxygen arsenic forms two compounds, the more important of which is arsenious oxides or arsenic trioxide (As40e), which is the white arsenic, or simply arsenic of the shops. It is usually seen in white, glassy, translucent masses, and is obtained by sublimation from several ores containing arsenic in combination with metals, particularly from arsenical pyrites.
Of all substances arsenic is that which has most frequently occasioned death by poisoning, both by accident and design. The best remedies against the effects of arsenic on the stomach are ferric hydroxide or magnesic hydroxide, or a mixture of both, with copious draughts of bland liquids of a mucilaginous consistence, which serve to procure its complete ejection from the stomach. Oils and fats generally, milk, albumen, wheat-flour, oatmeal, sugar or syrup, have all proved useful in counteracting its effect. Like many other virulent poisons it has been described as a safe and useful medicine, especially in skin diseases, when judiciously employed. Arsenic was also employed by men during the Victorian era to enhance sexual prowess However, arsenic is also addictive and the body becomes dependent upon it, not receiving enough when dependant can cause heart failure.
Arsenic is used as a flux for glass, and also for forming pigments. The arsenite of copper (Scheele's green) and a double arsenite and acetate of copper (emerald green) were formerly largely used to colour paper-hangings for rooms, but as poisonous gases are liable to be given off, the practice was abandoned. Arsenic compounds have in the past been used for colouring confectionery, and other articles, bright green. It is found in crude oil of vitriol, and occasionally in the past in products such as grape-sugar, beer, etc, in the manufacture of which oil of vitriol was employed. Arsenic tablets were formerly worn as protection against the plague. Research Arsenic
Barite or baryte is major ore of barium. It has a high specific gravity for a light coloured mineral and is a common gangue mineral in hydrothermal veins or as a replacement mineral in veins of limestone and dolomite. It is associated with lead, silver and antimonysulphides. It has the formulae BaSO4 and a relative hardness of 3. It was the first mineral to be found to be luminescent when heated, and led to the discovery of the luminescence of minerals. It is used as an ore of barium, for refining sugar, in the paper industry and as a pigment. Research Barite
Bismuth is a common metal element occurring in oxides, sulphides and carbonate compounds and also in its natural state. Bismuth has some unusual properties. It expands on freezing, and it exhibits diamagnetism - it pulls away from a magnet. Research Bismuth
Glance is a name given to some sulphides, mostly dark-coloured, which have a brilliant metallic lustre, such as the sulphide of copper which is called copper glance. Research Glance
Malachite is a native hydrous carbonate of copper, usually occurring in green mammillary masses with concentric fibrous structure. It is a widely distributed copperore. Found in the oxidized portions of copper veins and is often associated with cuprite, native copper, iron oxides, and sulphides of copper and iron. It often occurs in copper veins that are found in limestone. Green malachite, or malachite proper, admits of a high polish, and is sometimes used for ornamental work. Blue malachite, or azurite, is a related species of a deep blue colour.
Malachite has the formulae Ci2(CO3)(OH)2 and a relative hardness of 4. Research Malachite
Marcasite is one of the sulphides of iron. It often shows a white colour on a fresh surface. It is found in iron metallic veins and frequently with lead and zinc ores, and is also found in sedimentary rocks. Marcasite most frequently occurs as a replacement deposit in limestone and often in concretions imbedded in clays, marls, and shales. It has a relative hardness of 7. Research Marcasite
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Abbreviations
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