GOLD 



2523 



GOLD 



In medieval times it played a great part in 

 history, for a whole science was built around' 

 it the science of alchemy. Gold was the most 

 perfect substance in the world, the alchemists 

 declared, and they used their science and their 

 magic in vain attempts to find some means of 

 turning other metals into it. With the growth 

 of science and the understanding of the prin- 

 ciples of chemical elements, it became clear 

 that such transformation could not be brought 

 about. The knowledge of the properties of 

 gold acquired by the alchemists in their vain 

 search has served as a basis for a more scien- 

 tific study of this very interesting and useful 

 metal. 



Its Properties. First of all, it is a chemical 

 element ; that is, it cannot by any known means 

 be separated into simpler components. It is a 

 bright yellow, lustrous, very heavy metal (19.31 

 times heavier than water), and it melts at a 

 temperature of about 1945 F. If subjected to 

 a much higher temperature it gives off a vapor 

 with a greenish-yellow color. It has been 

 estimated that the boiling point would be 

 4585 F. Electricity and heat both pass 

 through it readily; in other words, it is a good 

 conductor, but needless to say it is seldom put 

 to any of the practical everyday uses to which 

 any of the cheaper metals are equally well 

 suited. No other metal has ever been found 

 which is so satisfactory for coins of high value, 

 for jewelry and ornaments and for dentistry, 

 and most of the gold mined is used for these 

 purposes, for gilding or lettering, and for col- 

 oring glass and chinaware. About one-fourth 

 of each year's production of gold, it is esti- 

 mated, is used for coins. 



In its pure state gold has one quality which 

 unfits it for hard usage it is soft; and conse- 

 quently it is almost always mixed with a harder 

 metal, the mixture being known as an alloy. 

 A finger ring of pure gold would not hold its 

 shape well; a coin of pure gold would wear 

 away quickly; so in making the former a mix- 

 ture of silver is used, and for the latter about 

 eight to ten per cent of copper. Copper 

 deepens and reddens the color, while silver 

 lightens it, and the proportion of either of 

 these metals used in an alloy is determined in 

 part by the color desired. The pureness of 

 gold used for jewelry is measured in carats, 

 and "twenty-four carats" is the standard of 

 measurement, for it means absolute pureness. 

 In nearly all countries gold coins are made 

 nine-tenths pure. The Austrian ducat has 98.6 

 per cent of gold and 1.4 per cent of copper. 



The British sovereign, which is 91.7 per cent 

 gold and 8.3 per cent copper, contains twenty- 

 two carats; the American gold coin of ninety 

 per cent gold and ten per cent copper contains 

 21.6 carats. Most twenty-carat gold has 

 twenty parts of gold to four of a harder metal ; 

 eighteen-carat gold has two less; but articles 

 made of this alloy have a right to be called 

 "solid gold," for this simply means that they 

 are of gold or the gold alloy all through, rather 

 than having a plating of gold over a basis of 

 some cheaper material. 



Gold has two properties which are far more 

 interesting than any of those mentioned above. 

 It can be hammered out into a sheet of incred- 

 ible thinness, or, to speak technically, it is 

 the most malleable of the metals (see subheads 

 Gold-Beating and Gold Leaf below) ; and it is 

 extremely ductile that is, it can be drawn out 

 to a great length without breaking. As re- 

 gards this latter quality, skilful operators have 

 drawn gold out into such a tiny wire that it 

 takes 680 feet of it to weigh one grain or about 

 900 miles to weigh a pound avoirdupois. But 

 the gold, to be thus treated, must be pure. If 

 one two-thousandth of its weight of lead, for 

 instance, be added to the gold, the wire can- 

 not be made. 



Gold in Chemistry. Like every other ele- 

 ment, gold has its chemical symbol, or "nick- 

 name," for it would be unwieldly in speaking 

 of chemical compounds always to use the full 

 name of every element; and since the Latin 

 name for gold is aurum, its symbol is the 

 abbreviation Au. In the paragraph above, 

 mention is made of some of the alloys of 

 gold, and the article ALLOY has more to say 

 on the same subject. Now many of the alloys 

 are mixtures and not chemical compounds; 

 that is, each substance which enters into the 

 alloy keeps its own individuality and proper- 

 ties. This is true of the alloys of gold with 

 silver and copper and also of gold amalgam 

 (the alloy with mercury). But gold does com- 

 bine with certain substances to make real 

 compounds. With aluminum it forms a brittle 

 purple, and with zinc a brittle violet, com- 

 pound. Alloys with iron, used in jewelry in 

 France, are known as gray gold and blue 

 gold on account of the modifications of the 

 yellow color resulting from the formation of 

 alloys. 



Looking at gold and touching it, it would 

 seem that so solid and heavy a substance could 

 not be dissolved, and indeed most acids or 

 other liquids have no more effect on it than 



