1911 Encyclopædia Britannica/Amber (resin)

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1911 Encyclopædia Britannica Amber (resin)

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AMBER, a fossil resin much used for the manufacture of ornamental objects. The name comes from the Arab. anbar, probably through the Spanish, but this word referred originally to ambergris, which is an animal substance quite distinct from yellow amber. True amber has sometimes been called karabe, a word of oriental derivation signifying "that which attracts straw," in allusion to the power which amber possesses of acquiring an electric charge by friction. This property, first recorded by Thales of Miletus, suggested the word " electricity," from the Greek, ήλεκτρον, a name applied, however, not only to amber but also to an alloy of gold and silver. By Latin writers amber is variously called electrum, sucinum (succinum), and glaesum or glesum. The Hebrew hashmal seems to have been amber.

Amber is not homogeneous in composition, but consists of several resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. The average composition of amber leads to the general formula C₁₀H₁₆O. Heated rather below 300°C. amber suffers decomposition, yielding an "oil of amber," and leaving a black residue which is known as "amber colophony," or "amber pitch"; this forms, when dissolved in oil of turpentine or in linseed oil, "amber varnish" o "amber lac."

True amber yields on dry distillation succinic acid, the proportion varying from about 3 to 8%, and being greatest in the pale opaque or "bony" varieties. The aromatic and irritating fumes emitted by burning amber are mainly due to this acid. True Baltic amber is distinguished by its yield of succinic acid, for many of the other fossil resins which are often termed amber contain either none of it, or only a very small proportion; hence the name "succinite" proposed by Professor J. D. Dana, and now commonly used in scientific writings as a specific term for the real Prussian amber. Succinite has a hardness between 2 and 3, which is rather greater than that of many other fossil resins. Its specific gravity varies from 1·05 to 1·10.