GOLCONDA, India, a fortress and ruined city of the Hyderabad state, situated on a granite ridge, five miles west of Hyderabad, India. In its immediate neighborhood are the ruins of an ancient city, once the metropolis of the powerful kingdom of Gol conda, which reached its height at the close of the 16th century and endured till 1687. The place itself is still strong; and about half mile to the north are the solid mausoleums of its former sovereigns. The fort is held by a small garrison from Hyderabad. Golconda is pro verbially famous for its diamonds; but they were merely cut and polished here, as no diamonds are found in the vicinity.
GOLD (chemical symbol, Au, atomic weight, 197.3); a metal distinguished from other common metallic elements by its beau tiful characteristic yellow color which it pre serves untarnished on exposure to the atmos phere under nearly all conditions. Many alloys of copper with zinc, tin and aluminum have also a more or less golden-yellow color, and are used as substitutes for and imitations of gold, being sold under various fanciful names, such as Dutch metal, Mannheim gold, Abys sinian gold, etc. Some of the bronzes have also a golden color. None of these resist atmospheric action like gold, but some are fairly permanent under ordinary conditions. Pure gold has a high metallic lustre, but is in ferior in this respect to steel, platinum and silver. The metal possesses a higher specific gravity than any common metal, but is exceeded in this respect by platinum. The specific gravity varies from 19.2 to 19.4, and the metal is thus one and one-half times heavier than lead and nearly twice as heavy as silver, bulk for bulk. Gold melts at 1,045° C., being somewhat less fusible than silver and more fusible than copper. It does not melt in a common fire. At high tem peratures the metal is sensibly volatile, and in the intense heat of the oxyhydrogen blowpipe or electric furnace may be vaporized. The vapor is purple.
The pure metal is somewhat harder than lead, but softer than copper, silver, platinum, zinc or iron. It is consequently too soft, in the pure state, for the purposes to which it is gen erally applied. For practical application it is
alloyed with copper or silver, and both these metals are often present. The former renders the gold redder and the latter paler than its true color. The proportion of gold contained in an alloy is expressed in degrees of fineness, or as °carats)); fineness is expressed in parts per thousand, for example 916.6, or decimally, .9166; the carat value of the gold is expressed in parts of -24, pure gold being 24 carats fine. Thus 9-carat gold contains 9 parts of pure gold and 15 of some alloy. Sovereign gold consists of 11 parts gold and 1 copper; guinea gold, of 11 parts gold, Y2 part of copper and V2 part of silver. Standard and guinea gold are thus 22 carats fine (the legal standard for coins in the United Kingdom and colonies), and contain only two parts of alloy. The German, American and Italian standard is 21.6 carat, and is composed of one part copper and nine gold. The follow ing table shows the relative amounts of gold and baser metal in alloys commonly employed: The lowest recognized standard is nine carat, but much gold of inferior quality is worked up into ornaments and commonly sold as real gold. Derby gold is also a common name for this poor material. In the United Kingdom articles of jewelry, plate, etc., are stamped with certain marks known as hall marks, or plate marks, as a guarantee that they have the quality they pro fess to have. Tampering with hall-marked arti cles is an indictable offense. Many specious imi tations of hall marks are put upon sham jewelry, but always differ in some essential feature. Gold alloys of a red character are frequently colored. This consists in treating the article chemically in such a manner as to dissolve out the base metal constituting the alloy, leaving a covering of purer gold, paler than the original. For this purpose the articles are boiled with one part of salt, one of alum, two of saltpetre dis solved in four parts of water, for 20 minutes. Rolled gold is produced by applying thin sheets of gold to a plate of alloy and rolling down.