![]() It has also been shown that gold volatilizes when a gold-amalgam is distilled. Copper and zinc increase the volatility far more than lead, while the greatest volatility is induced, according to T. The volatility is barely appreciable at 1075° at 1250° it is four times as much as at 1 roo°. Elsner, and, in the presence of other metals, by Napier and others. Its volatility has also been studied by L. Macquer and Lavoisier showed that when gold is strongly heated, fumes arise which gild a piece of silver held in them. At still higher temperatures it volatilizes, forming a reddish vapour. Daniel Berthelot gives 1064° C., while Jaquerod and Perrot give 1066.1-1067.4° C. The melting-point has been variously given, the early values ranging from 1425° C. The specific gravity of cast gold varies from 18.29 to 19.37, and by compression between dies the specific gravity may be raised from 19.37 to 19.41 by annealing, however, the previous density is to some extent recovered, as it is then found to be 19.40. The specific gravity of gold obtained by precipitation from solution by ferrous sulphate is from 19.55 to 20.72. Gold can be readily welded cold the finely divided metal, in the state in which it is precipitated from solution, may be compressed between dies into disks or medals. The presence of minute quantities of cadmium, lead, bismuth, antimony, arsenic, tin, tellurium and zinc renders gold brittle, 2 ' 0 15th part of one of the three metals first named being sufficient to produce that quality. in length, and an ounce of gold covering a silver wire is capable of being extended more than 1300 m. It is also extremely ductile a single grain may be drawn into a wire 500 ft. When pure, it is the most malleable of all metals (see Goldbeating). It is nearly as soft as lead and softer than silver. When the gold is finely divided, as in " purple of Cassius," or when it is precipitated from solutions, the colour is ruby-red, while in very thin leaves it transmits a greenish light. ![]() Gold has a characteristic yellow colour, which is, however, notably affected by small quantities of other metals thus the tint is sensibly lowered by small quantities of silver, and heightened by copper. Vitruvius also gives a detailed account of the means of recovering gold, by amalgamation, from cloth into which it had been woven. With regard to the history of the metallurgy of gold, it may be mentioned that, according to Pliny, mercury was employed in his time both as a means of separating the precious metals and for the purposes of gilding. 10 " More to be desired are they than gold, yea, than much fine gold "). Gold ornaments of great variety and elaborate workmanship have been discovered on sites belonging to the earliest known civilizations, Minoan, Egyptian, Assyrian, Etruscan (see Jewelry, Plate, Egypt, Crete, Aegean Civilization, Numismatics), and in ancient literature gold is the universal symbol of the highest purity and value (cf. GOLD ] Au, atomic weight 1 95.7(11 = I),1972(O =16)], a metallic chemical element, valued from the earliest ages on account of the permanency of its colour and lustre.
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