alloys, such as brass, German silver, etc. form of sheets, worked into a variety of s iron from rusting, as in galvanised-iron; it positive element in many batteries; and fine dust it is obtained in large quantitie oxide, and forms a valuable reducing agent It Cadmium. In the process of zinc ext served that a volatile vapour, in some case with the first portions of zinc; this was metal cadmium. It possesses a tin-white c structure, and takes a high polish. It is malleable, ductile, and readily volatile. 86; it melts at about 320° C., and boils vapour is of a dark-yellow colour, with a di Like tin it emits a crackling sound when in alloys to produce a fusible metal, which C.; and an amalgam of cadmium is employ for teeth, such amalgam being soft when f soon becomes hard. Magnesium. This metal possesses colour, but soon tarnishes when exposed to the formation of magnesium oxide. It is great tensile strength, being nearly equal to t bronze. Its specific gravity is 1.74. At 450° C. it can be rolled and worked into a Screws and threads made of this metal are s exact than those made of aluminium. W flame it burns with a dazzling white light, have been seen at sea from a distance of tw This light is used for purposes of photo sium occurs abundantly in nature in combin elements forming compounds, such as ma dolomite MgCa(CO3)2, etc. ALUMINIUM § 11. Aluminium.-With the exception used in the it prote the electr he form with it was - than t It is used ir, due t erature c of forms and mor is said t Magne ith other MgCO gen and silicon, this is the most widely distributed of the elem and contained in the largest quantity in the solid cr the earth. It occurs in a variety of forms as oxide more generally in combination with other metals, suc zinc, iron, magnesium, etc., forming aluminates; as si in all clays, and as fluoride in cryolite (6NaF, Al,F). Aluminium is a white metal which takes a fine p It has no taste or odour. It is soft, very malleable ductile, with an elasticity and tenacity about equal to of silver. Its specific gravity is 2.5, which is increase hammering; it melts at a temperature a little above th zinc, and is not volatile when strongly heated out of co with air. Its conductivity for heat and electricity is sa be very high; but, according to Mr. Roby, it is very and diminishes the conductivity of copper considerably alloyed with it. It does not oxidise in air or combine sulphur; it is insoluble in cold nitric acid; sulphuric has no action on it; but hydrochloric acid and all dissolve it readily. Aluminium is valuable for making articles where ness is an important feature; this, combined with its l unalterability in air and sulphuretted hydrogen, non-poise properties, and ease of working, gives it a widespread int It is, however, in its alloys that its greatest value app In some cases it imparts strength, in others it modifie colour, while in others it promotes soundness in casting ALKALINE-EARTHY METALS § 12. The term "earth" was formerly used to denote bodies which are insoluble or but slightly soluble in v and unaltered by exposure to a high temperature. So these were found to have an alkaline reaction, and to neutralise acids; hence the term "alkaline earth." oxides-viz. baryta, strontia, lime, and magnesiafound to be composed of metals in combination oxygen. Barium is a pale yellow metal, malleabl a red heat. It rapidly tarnishes in air, and at a red heat forming barium oxide. It according to Frey, is above that of cast-iron. water rapidly at the ordinary temperatu gravity is 4. Strontium is similar to barium in colour fusible at a red heat, quickly oxidises on burns brilliantly in air when heated, and poses water. Its specific gravity is 2.58. Calcium is a yellow metal, tenacious ar melts at a red heat, oxidises in air, and buri it decomposes water rapidly. Its specific g The alkaline-earthy metals, although thei widely distributed, do not occur in nature state, and the isolated metals have little ap arts, on account of their easy oxidation. Th in removing oxygen from other metals and th ALKALI METALS. SODIUM, POTASSIUM, § 13. The word "alkali was originall name of a soluble salt obtained from the ashe and is now applied to a well-defined class of the following properties: They turn red completely neutralise acids, are soluble in w solutions exert a caustic action upon animal alkalies proper are the oxides of sodium, pota rubidium, and cæsium. To these is added t metal ammonium NH4, which is called the in contradistinction to potash and soda. the alkalies are soft, readily fusible, volatile oxidised on exposure to air, and they rapi water at ordinary temperatures. Sodium. This metal melts at 96° C. and v ing a dark blue vapour. It rapidly oxidises in strongly heated burns with a yellow light. water rapidly at ordinary temperatures. It is a white metal, with a specific gravity of 98. Sodium i for the preparation of aluminium, magnesium, boror silicon. As an amalgam it is used in the extraction of and in the laboratory as a reducing agent. It occur abundantly in nature in a state of combination; in the of chloride, nitrate, borate, carbonate, and silicate. Potassium.-This element is very similar to sodi appearance and properties. It is a silver-white lu metal, having a specific gravity of 86; it is brittle at but at 15° C. it becomes soft, malleable, and weldab melts at 62.5° C., forming a liquid like mercury in appea at a red heat it boils, emitting a green-coloured vapou has a strong affinity for oxygen, and decomposes water evolution of great heat. It is used for similar purpo those of sodium, and occurs abundantly in nature in ana forms. Lithium. This is a widely diffused element, being in many micas and felspars, in the ashes of plants, a sea-water. It has the colour and lustre of silver, is so weldable, melts at 180° C., is volatile at a high temper burning with a white flame, and rapidly oxidises in c with air at ordinary temperatures; its specific gra 58, and it is therefore the lightest of all solid and bodies. Rubidium and Cesium.-These rare metals so resemble potassium that they cannot be distinguished that metal by many of the ordinary tests. Their pr is detected by means of spectrum analysis. NATURE OF ALLOYS § 14. When two or more metals are caused perma to unite the resulting mixture is termed an alloy. mercury is an essential constituent the mixture is then t an amalgam. The general method of effecting combi is by the agency of heat, but with certain soft metal alloys may be formed by subjecting the c siderable pressure, even at the ordinary te Alloys, such as those briefly referred sketch, were doubtless first discovered by treatment of mixed ores, from the simulta which, alloys would be formed; or in som of gold and silver, naturally formed alloys by a simple melting process. The dire alloys by the simple melting together o metals has been enormously developed in the attention which mixed metals are chemists is far greater than in any period o Comparatively few of the metals possess render them suitable to be employed alone turer; but most of them have important the form of alloys. Even among the met used independently, it is often found ex portions of other metals, to improve or o their physical properties. Thus gold is made to resist wear and tear, as well a cost, by the addition of copper; silver is li by alloying it with copper; and the br formed of an alloy of copper, zinc, and reasons. The purposes for which metals are alloye as the uses of the metals themselves, but, combination is employed to harden, render mo the colour, or to reduce the cost of producti class of alloys known as solders, which are u the several parts of a body or bodies together as to possess melting-points below that of the soldered. The well-known class of alloys to furnishes a good illustration of the effect of a ducing different shades of colour. These bodie of the metals copper and zinc in varying p colour depending to a great extent on the quar present. When the copper predominates the co |