Page:The American Cyclopædia (1879) Volume XI.djvu/432

 420 METAL ORDER OF TENACITY. ORDER OF MALLEABILITY. ORDKR OF DUCTILITY. Lead .. -1 Gold. Silver. Copper. Platinum. Iron. Tin. Zinc. Lead. Gold. Silver. Platinum. Iron. Copper. Zinc. Tin. Lead. Tin 1-8 Gold 0-6 Zinc 8 Silver 8-9 Platinum 18 Conner IT ln 26 CONDUCTIVITY FOR HEAT. CONDUCTIVITY FOR ELECTRICITY. LINEAR EXPANSION BY HEAT BETWEEN 0* AND 1000 C. (Fran* and Wiede- mann.) Silver -1000 (Matthiessen.) Silver =1000 Copper. ... 774 Gold 552 Lead 0-00301 Tin 0-00273 Zinc (forged). 0-00220 Silver 0-00199 Gold 0-00188 Wr'ht iron 0-00119 Platinum.. 0-00068 Copper 786 Gold. 682 Zinc. . . . 190 Zinc. Iron. Tin 274 144 Tin 145 Iron 119 115 Lead 86 Platinum 84 Lead 78 Mercury ... 16-8 THERMO-ELECTRIC ORDER. SPECIFIC HEAT. Antimony. Arsenic. Iron. Zinc. Gold. 23" Tin. Silver. Cobalt Palladium. Platinum. Nickel. Mercury. Bismuth. (Water = 1 ) Lithium 0-9408 Sodium 0-2934 Aluminum 0*2143 Iron 0-1188 Copper 0-0952 Zinc 0-0956 Silver 0-0570 Tin 0-0562 Antimony 0-0608 Gold 0-0824 Platinum 0-0324 Mercury ... . 0-0338 Lead. 0-0814 Bismuth 0-0308 The physical properties of the metals are large- ly dependent on their purity and molecular condition, and on temperature. Hammered, rolled, or drawn metal generally has a higher specific gravity than cast metal. The state of molecular tension often induced by mechanical working, especially when cold, is resolved by annealing, i. e., heating and slow cooling. Most of the metals are more malleable and ductile at high temperatures. Commercial zinc is only malleable between 100 and 150 C. ; at 200 it is so brittle that it can be pul- verized. The conductivity for electricity is greatly diminished at high temperatures, and also by the presence of impurities in the metal. The addition of a small amount of a foreign substance often makes a metal harder, more rigid, and less susceptible of elongation. This is notably the case with iron, which when pure is soft and stretches considerably under strain before breaking, while steel, which is iron with a small amount of carbon, may be rigid and brittle. If reference be had to the origi- nal area of section, the rigid metal will show the greatest strength under a gradually applied tensile strain ; but if to the fractured area, the purer metal is the strongest. The tenacity of metals generally decreases as the temperature is raised. The fusing points of the more re- fractory metals given in the above tables are approximate only, since trustworthy methods for determining high temperatures are want- ing. The metals vary greatly in hardness. The alkaline metals are as soft as wax, while some, as chromium, will scratch glass. It is not improbable that extreme hardness in metals is produced by the presence of some foreign body, and is not inherent in the metal itself. Most of the metals are capable of assuming a distinctly crystalline form, generally belonging to the regular or isometric system. Some, as antimony and arsenic, crystallize in rhombo- hedrons. A few of the metals occur native ; these are gold, platinum, palladium, iridium, and rhodium, which are almost exclusively found in the metallic state, and silver, cop- per, mercury, bismuth, arsenic, and antimony. Generally, however, the metals occur mineral- ized in combination with oxygen or sulphur. The specific heats of the metals, as will be noticed in the above tables, are inversely as their atomic weights, or, in other words, the specific heats of the atoms of the metals are equal. Chemically, the metals present very varied characters. As a class they are distin- guished by the formation of compounds with oxygen which have basic characters, while the non-metals as a class form oxides which have acid characters. These two classes of oxides are capable of combining to form salts. While the oxides of the non-metals never form bases, the higher oxides of many of the metals have distinctly acid properties, and indeed a few of the metals form only acid oxides. The most stable compounds of tellurium, arsenic, anti- mony, tungsten, titanium, molybdenum, and vanadium with oxygen are acid in character and capable of combining with basic oxides. Those metals which seem to hold a position in- termediate between the two classes have been termed half metals or metalloids. The latter term, as now generally used, includes all the non-metallic elements, viz. : hydrogen, oxygen, bromine, chlorine, iodine, fluorine, boron, ni- trogen, phosphorus, selenium, silicon, sulphur, and carbon. Tellurium is closely related to sulphur and selenium, and is often classed with the metalloids; but its metallic appearance, and the analogy which its compounds bear to those of antimony, render its association with the metals equally appropriate. Hydrogen, although a gas and the lightest body known, resembles the metals in its chemical proper- ties, and is capable of replacing them in com- bination. The formation of salts is regarded in modern chemistry as the replacement of hydrogen in the acid by a metal. The metals are variously classified. A natural grouping, and one in common use, is : 1, metals of the alkalies ; 2, metals of the alkaline earths ; 3, metals of the earths proper; 4, oxidable metals proper, whose oxides form powerful bases ; 5, oxidable metals, whose oxides form weak bases or acids ; 6, metals proper, whose oxides are reduced by heat, called noble metals. The strength of affinity of the different metals