2 72 THE POPULAR SCIENCE MONTHLY 



to the ancients, who called it "liquid or live silver'' (whence our 

 modern name, quicksilver), and they found but little use for it. Zinc 

 was also one of the mysteries of the olden times. The Greeks and 

 Romans knew of it as a troublesome impurity, often associated with 

 lead ores, and in some way the very desirable alloy now called "' brass," 

 which is composed of tin and zinc, was discovered and produced by 

 them to a limited extent, but the metal zinc remained unknown* 



Through medieval times practically no progress was made in a 

 knowledge of the metals. The science of chemistry was unknown, but 

 its precursor, alchemy, flourished. The alchemists recognized many 

 of the natural substances that are now known as ores of the metals, but 

 were unable, except by accident, to decompose them. However, about 

 the 3'ear 1450, antimony and bismuth became articles of commerce, and 

 in 1520 pure zinc was j^roduced, though it did not come on the market 

 in any quantity until 17-1:3. In 1694 arsenic was isolated and recog- 

 nized. Thus, up to a little- more than 200 years ago, the world knew 

 of but eleven of the metals, and of these, arsenic and antimony are not 

 now regarded as such, being classed as semi-metals. 



Chemistry, as a science, began to arise during the eighteenth cen- 

 tury, as a result mainly of the perfection of the laboratory balance to a 

 point where delicate operations in weighing could be carried on. In 

 this period the list of the metals was doubled by the discovery of co- 

 balt and platinum in 1735-6, of nickel in 1751, of manganese in 1774, 

 of tungsten and molybdenum in 1781, of titanium, uranium and 

 zirconium in 1789, and of chromium and yttrium in 1792. All of 

 these excejDt zirconium and yttrium are now fairly familiar names to 

 us, but none of them were produced in any quantity, or put to any 

 commercial use as metals, for a long time after their discovery. Plat- 

 inum for a century was merely a curiosity. Certain compounds of 

 cobalt and of uranium found considerable use in the ceramic arts, and 

 of chromium and manganese in the laboratory as reagents, in the crude 

 chemical research of the dav. But with the opening of the ninteenth 

 century, and the advance of chemistry to the condition of an exact 

 science, the metal elements began to come to light. Cerium, iridium, 

 osmium, palladium, rhodium and tantalum became known in 1804 ; 

 in 1807 potassium and sodium were recognized; in 1808 barium, cal- 

 cium, magnesium and strontium, and in 1817 cadmium and lithium. 

 Between 1828-1830 aluminum, glucium, thorium and vanadium were 

 added to the list, and in 1839 lanthanum. Then came didymium, 

 erbium, terbium, columbium and ruthenium in the five years between 

 1842 and 1846. In the sixties caesium, indium, rubidium and thal- 

 lium were discovered; in the seventies gallium: in the eighties ger- 

 manium, and since then the chemists have added gadolineum, scandium, 

 samarium, thulium, ytterbium, and finally radium. 



