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400 MERCHANT MERCURY Lancaster, the former in 1853 and the latter in 1871. The college was merged with Frank- lin college, and is now known as Franklin and Marshall college. MERCHANT, Commission. See FACTOR. MKRUA, the largest kingdom of the Saxon heptarchy in the island of Britain. The name is derived from mark, meaning frontier, as this was the most western of the three kingdoms of the Angles. It was situated inland, being bounded N. by Cambria and Northumbria, E. by East Anglia and Essex, S. by Wessex, and W. by Wales, and included the modern coun- ties of Chester, Derby, Nottingham, Lincoln, Salop, Stafford, Leicester, Rutland, Northamp- ton, Huntingdon, Hereford, Worcester, War- wick, Gloucester, Oxford, and Buckingham, and parts of Hertford and Bedford. It was founded by Crida, an Angle, about 585, was subject for a time to the Northumbrians, and afterward subdued East Anglia and Kent. Its more important kings were Penda, Ethelred, Kenred, and Wiglef, who was finally conquered by Egbert, king of Wessex, in 827. MERCK, Johann Heinrioh, a German scholar, born in Darmstadt, April 11, 1741, died June 27, 1791. He officiated in various public func- tions in his native town, translated Addison's "Cato" and other works from the English, cooperated with Lavater in the publication of his work on physiognomy, and took an active part in the Frankfurter gelehrte Anzeigen, DeutecJier Merkur, and other leading periodi- cals, and in various other literary enterprises. His select works were edited long after his death by Stahr, and published in Oldenburg in 1840. He is chiefly remembered in German literature on account of his intimate association with Goethe, Herder, and other eminent men, npon whose intellectual development he ex- erted a great influence by his literary criticism. The latter part of Merck's life was saddened by domestic and pecuniary misfortunes, which led him to shoot himself. The letters ad- dressed to him by Goethe, Herder, Wieland, and others, were published by Wagner (Darm- stadt, 1835) ; and another edition of his cor- respondence, including both letters received and written by him, appeared in 1838. MERCURY, or Qoleksilver, a metal of the color and lustre of silver, and fluid at ordinary temperatures, whence its ancient name of ar- gentum vivum, and that by which it was called by Aristotle and Theophrastus, who made the earliest mention of it, &pyvpos X vr6^ fluid silver. It was also known as hydrargyrum, and from this its chemical symbol, Hg, is derived. The equivalent of the metal is 200 ; and its specific gravity, which varies somewhat with the tem- perature, is given by Kopp as 13*557 at 62-6 F. At 39 or 40 below zero F. the metal be- comes solid and crystallizes in regular octahe- drons, contracting in bulk and assuming the density of 14; the mass is malleable, and re- sembles lead. Its boiling point is 662 F., at which it forms an invisible, transparent vapor, the density of which is 6,976, air being 1,000. Before assuming this form, if exposed to the air at high temperatures, it absorbs oxygen and is converted into the red oxide, which is decomposed at the boiling point. Above 40 F. mercury is somewhat volatile, as may be shown by holding an iodized daguerreotype plate, that has been submitted to the action of light in the camera, over a bath of mercury, when the picture will be brought out by the vapor. Gold leaf is also affected by the vapor when suspended in a vial containing mercury and kept at ordinary temperatures. Strong nitric acid dissolves mercury ; but hydrochloric acid, hot or cold, does not affect it. It is oxidized by heated concentrated sulphuric acid, and is soluble in a solution of common salt. Exposed for a long time to the air, mercury gathers a film of gray oxide upon its surface, which adheres to the glass in which the metal is contained ; glycerine is employed to prevent the formation of this film. When mercury contains dissolved in it lead, zinc, or other extraneous oxidizable metals, these may be removed by covering the surface of the metal, placed in a shallow vessel, with dilute nitric acid, and stirring frequently. The acid attacks and takes up the foreign matters, and may also form a crust of nitrate with a small portion of the mercury. This is a more efficient method of purification than that of distillation when zinc is present, as this is distilled over with the mercury. Impurities mechanically mixed with mercury may often be removed by strain- ing the metal through paper perforated with a very small hole, or squeezing it through wash leather. But if a film of oxide still adheres to the mercury, this may be removed by agitating it violently in a bottle in which some powdered white sugar has been introduced, then blowing air into the bottle, repeating the shaking and blowing several times, and then filtering. Mer- cury unites with various metals, as gold, sil- ver, tin, lead, zinc, and bismuth, forming com- pounds which are noticed under the head of AMALGAM. In some cases the cheapest of the metals named have been used to adulterate mercury. The effect of this mixture is to produce an amalgam, the presence of which is easily detected by the fluid, when poured upon a plate of glass or porcelain, not flowing freely, but leaving a trace behind it. Mercury occurs native in globules scattered through masses of rocks or ore, and also (rarely) in the form of a silver amalgam; but chiefly as a sulphide of mercury. (See CINNABAK.) It seldom if ever occurs in fissure veins, though sometimes it im- pregnates or constitutes well defined deposits. It is found in geological formations of almost all ages, and particularly in talcose and argil- laceous slates. The most important deposit in the world is that of Almaden in Spain, from which, according to Pliny, the Romans annually obtained about 700,000 Ibs. of cinnabar. The matrix of the ore consists of quartz and quartz- ose sandstone, intermixed with cinnabar in