Page:The American Cyclopædia (1879) Volume I.djvu/359

 ALLOUEZ ALLOY 335 allotropism was only applied to elements ; later it was also applied to compounds. Tartaric acid which turns the plane of polarization of light to the right, tartaric acid which turns it to the left, and that which does not deviate it at all, are considered by some chemists to be the same compound in several allotropic states. (See ISOMEBISM.) ALLOUEZ, Claude Jean, one of the earliest Jes- uit explorers of the northwest, born in France in 1620, died in 1690. He went to Quebec in 1 658, and, after some years' training in the Al- gonquin missions on the St. Lawrence, founded the mission of the Holy Ghost at Chegormegon on Lake Superior in 1665, collected data as to the Mississippi, explored Green bay, where he founded the mission of St. Francis Xavier, and labored among the Foxes, Mascoutins, Miamis, and Illinois. In 1676 he permanently estab- lished at Kaskaskia in Illinois the mission begun by Marquette; but in 1679 he retired on the approach of La Salle, who was bitterly opposed to the Jesuits. His latest field of labor was among the Miamis on St. Joseph's river, where he died. His contributions to the Jesuit Rela- tions are among the most valuable records as to the ideas and manners of the Indians at the time. ALLOY (Fr. aloi, standard of coin, from d la loi, according to law), a compound of two or more metals fused together. When one of the metals is mercury, the compound is called an amalgam. (See AMALGAM.) By the alchemists metals were called "noble" and "base," and when one of the latter was brought into com- bination with one of the former, the nobility of this was said to be "allayed" or "alloyed," and assayers at the present day still use the term in this sense. Most alloys are mixtures of no exact proportions ; the metals dissolve in one another indefinitely, as sulphuric acid unites with water. Some, however, appear to be combinations in equivalent proportions, and of these there are found examples in nature, as of the native gold, which occurs combined with silver 4, 5, 6, or 12 atoms of gold to one of silver, but never a fractional part of an atom of gold. The tendency of some alloys to take crystalline forms also indicates definite com- binations. This is verified by cooling a melted mixture slowly, and when partially solidified pouring off the liquid remnant, when crystals are left which are always combinations in the proportion of the atomic weights of the met- als ; for instance, in the mixtures of copper and tin (bronze), copper and zinc (brass), copper and nickel (German silver), or copper and alu- minum (aluminum bronze), the proportions of the crystals are found to be either in the ratio of the numbers 64, 118, 65, 59, 27, which are the respective atomic weights of copper, tin, zinc, nickel, and aluminum, or of a multiple the one of the other. The metals of many alloys are with difficulty brought into com- bination, and even tend to separate from each other while in the melted state, and in some instances form layers which contain dif- ferent proportions of the metals. The changes in the physical properties of metals effected by their combinations are of great variety, and cannot before experiment be at all anticipated. Even slight variations in the proportions of the metals involve great changes in the prod- uct of their union. The specific gravity of the alloy may be greater or less than the mean of that of the component parts. In the alloy of gold and tin it is greater ; also of silver with zinc, lead, tin, bismuth, or antimony; copper with zinc ; lead with palladium ; bismuth with antimony ; lead with bismuth ; and zinc with antimony. The specific gravity is less in the alloy of gold with silver, lead, iron, copper, nickel, or iridium ; also of iron with bismuth, zinc, antimony, or lead ; tin with lead ; zinc with palladium or antimony; and zinc with antimony. The alloy of silver and copper as used in coins is also of less specific gravity when cast; but Karnmarsch found that by rolling and coining it is so far compressed that the specific gravity is the same as the mean obtained by calculation. Alloys are always more fusible than the metal most difficult to melt that enters into their combination, and gen- erally more so than the most easily melted one. The fusible metal discovered by Sir Isaac New- ton melts at different temperatures between 198 and 210 F. It is composed of bismuth 5 or 8 parts, lead 2 or 5 parts, and tin 3 parts. These metals melt, the first at a temperature of 476, the second at about 600, and the last at 442. The addition of one part of mercury lowers the melting point of this alloy to 167. Wood's fusible alloy, discovered in more recent times, consists of 2 parts cadmium, 2 tin, 1 lead, and 3 bismuth ; it melts at the low temperature of 150 F. The alloy fusible at the lowest tem- perature is that of sodium and potassium ; the first melts at 194, the second at 128, while the alloy melts at 80, and is thus liquid at the common summer temperature. Alloys conduct heat and electricity less perfectly than their pure metals; they are also gen- erally more brittle. But their power of cohesion is usually greater than that of either of the metals, the alloy resisting more strongly the force applied to draw a bar apart than does a bar of either one of the metals composing it. The color which the alloy will take is as uncer- tain as any of its other properties. A large addition of zinc will not make its alloy with copper whiter, but will give it the rich pinch- beck hue. Tin makes copper more pale, but especially nickel, the addition of one eighth of which is sufficient to make it almost white. Aluminum acts in a similar way, while silver possesses the power of destroying the red color of the copper in so high a degree, that it may be largely alloyed with it without materially impairing its whiteness. Alloys composed of metals of different degrees of fusibility may sometimes be separated into their distinct metals by heating to the melt-