Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/76

Rh 66 METALS relations between E and temperature, we quote the results of Kohlrauscli and Loomis, who found the following relations between the modulus E for C. and the value E for +t C. : Iron : E =E (1- 000483 &amp;lt;- 00000012&amp;lt;2). Copper : E&amp;lt; =E (1 - 000572 &amp;lt;- -00000028^). Brass : E =E (l--000485f- 00000136* 2 ). Thus, for these three metals at least, the value of E diminishes, when temperature increases, at pretty much the same rate per degree of temperature. Specific Gravity. This varies in metals from 594 (lithium) to 22 48 (osmium), and in one and the same species is a function of temperature and of previous physical and mechanical treat ment. It has in general one value for the powdery metal as obtained by reduction of the oxide in hydrogen below the melting point of the metal, another for the metal in the state which it assumes spontaneously on freezing, and this latter value again, in general, is modified by hammering, rolling, or wire-drawing, &c. These mechanical operations do not necessarily add to the density ; stamping, it is true, does so necessarily, but rolling or drawing occasionally causes a diminution of the density. Thus, for instance, chemically pure iron in the ingot has the specific gravity 7 844 ; when it is rolled out into thin sheet, the value falls to 7 6 ; when drawn into thin wire, to 7 75 (Berzelius). The follow ing table gives the specific gravities of all metals (except a few very rare ones) according to the most trustworthy modern de terminations. Where special statements are not made, the numbers may be assumed to hold for the ordinary temperature (15 to 17 or 20 C.), referred to water of the same temperature (specific gravity = 1) as a standard, and to hold for the natural frozen metal. Name of Metal. Specific Gravity. Authority. Lithium 594 Bunsen. Potassium 875 Haumhauer. Sodium 9735 Rubidium 1 52 Bunsen. Calcium 1-578 Bunsen and Matthiesen. Magnesium 1-743 Bunsen. Caesium 1-88 Setterberg. Beryllium 2-1 Debray. Strontium 2-5 Aluminium, pure, ingot 2-583 at 4* Mallet, 1880. Aluminium, ordinary, hammered Barium 2-67 Clarke. Zirconium 4-15 Troost. Vanadium, powder 5-5 Hoscoe. Gallium 5-9 Lecoq de Boisbaudran. Lanthanum 6-163 Didymium 6-544 Hillebrandt and Norton. Cerium 6-728 Antimony 6-715 at 16* Marchand and Scheerer. Chromium 6-81 Wohler. Zinc, ingot 6-915 Karsten. ,, rolled out 7-2 Manganese 7 14 to 7-2 lirunner. Tin, cast 7-29 to 7-299 crystallized by galvanic cur- ) rent from solutions ) 7-178 V. H. Miller. Indium 7-42 Iron, chemically pure, ingot ,, thin sheet 7-844 7-6 Berzelius. ,, wrought, high quality Nickel, ingot 7-8 to 7-9 8-279 Richter. .. forged 8-666 Cadmium, ingot 8-546 ,, hammered 8-667 Cobalt 8 5 to S 7 Molybdenum, containing 4 to 5 ) per cent, of carbon ) 8-6 Debray. 8 94 cast. 8-92 Marchand and Scheerer. 8-94 to 8 95 ,, electrotype, pure 8-945 9-823 at 12&quot; 10 4 to 10 5 ,, stumped 10-57 G. Rose. Lead, very slowly frozen 11-254 Deville. ,, quickly frozen in cold water Palladium 11-363 11-4 at 22 5 11-86 Khodium 12-1 Ruthenium 12 -2C at 13-595 at Deville and Debray. solid 14-39 below 40 Tungsten, compact, by H 2 from ) chloride vapour ) 16-54 Wohler, 1855. as reduced by hydro- ) gen, powder ) 19-13 Roscoe. 18-33 Pe ligot 1868 Gold, ingot 19-265 at 13&quot; ,, stamped 19-31 to 19 34 powder, precipitated by ) ferrous sulphate ) 19-55 to 19-72 Platinum, pure 21-46 Indium 22 40 Osmium 22-477 Deville and Dcbray,1876. Thermic Properties. The specific heats of most metals have been determined very carefully by Regnault. The general result is that, conformably with Dulong and Petit s law, the &quot;atomic heats&quot; all come to very nearly the same value (of about 6 4); i.e., atomic weight by specific heat = 6 4. Thus we have for silver by theory 6-4/108= 0593, and by experiment 0570 for 10 to 100 C. The expansion by heat varies greatly. The following table gives- the linear expansions from to 100 C. according to Fizeau (Comptcs- Eendus, Ixviii. 1125), the length at being taken as unity. Name of Metal. Platinum, cast Gold, cast Silver, cast Copper, native, from Lake Superior Copper, artificial Iron, soft, as used for electromagnets reduced by hydrogen and compressed Cast steel, English annealed Bismuth, in the direction of the axis at right angles to axis mean expansion, calculated Tin, of Malacca, compressed powder Lead, cast Zinc, distilled, compressed powder Cadmium, distilled, compressed powder Aluminium, cast Brass (71-5 per cent, copper, 28-5 per cent, zinc) Bronze (86-3 per cent, copper, 9-7 per cent, tin, 4-0 per cent. zinc). Expansion to 100. 000 907 001 451 001 936 001 708 001 869 001 228 001 208 001 110 001 642 001 239 001 374 002 269 002 948 002 905 003 102 002 336 001 879 001 802 The coefficient of expansion is constant for such metals only as- crystallize in the regular system ; the others expand differently in the directions of the different axes. To eliminate this source of uncertainty these metals were employed as compressed powders. The cubical expansion of mercury from to 100 C. is &quot;018153- = Tro-W (Regnault). Fusibility and Volatility. The fusibility in different metals is very different, as shown by the following table, which, besides including all the fusing points (in degrees C. ) of metals- which have been determined numerically, indicates those of a selection of other metals by the positions assigned to them in the table. Of the temperatures given, those above (say) 500 C. must be looked upon as rough approximations. Name of Metal. Fusing Point. Authority. -S8-8 +26 to 27 30-1 38-5 62-5 95-5 180-0 176 228 264 290 320 325 425 415 412 525 700 1,040 1,100 1,100 1,200 1,300 to 1,400 higher 1,400 1,600 1,500 to 1,600 st wind-furnace 2,000 2,870 s yet infusible. B. Stewart. Setterberg. L. de Boisbaudran. Bunsen. ? Richter (?) Rudberg. Lamy. Rudberg. Person. Daniel!. Pouillet. Pouillet. Becquerel Pouillet. Pouillet. heat. The following Bunsen. Gallium Tin Thallium Zinc Cheivy Red Heat Silver Gold Cobalt Nickel Dazzling White Heat Palladium is barely fusible at the highe melt only in the oxyhydrogen flame: Max. Temp, of Oxyhydrogen Flame.... Osmium does not melt at 2,870, i.e., is a Of the volatility of metals we have little precise knowledge only the following boiling points are known numerically : Name of Metal. Boiling Point. Mercury 357-3 Cadmium ! 860 Zinc : 1,040 Potassium below 1,040 Sodium : above 1,040 Authority. Regnault. Deville and Troost. Dewar and Dittmar. For practical purposes the volatility of metals may be stated as- follows: 1. Distillable below redness: mercury. 2. Distillable at red heats : cadmium, alkali metals, zinc, mag nesium. 3. Volatilized more or less readily when heated beyond their fusing points in open crucibles : antimony (very readily), lead,, bismuth, tin, silver. i Bunsen, Jahresb./. Chem, 1867, p. 41 ; Phil. May., xxxiv. 489.