welded by -n by any s directly soft for Iver and iring its lead are esent in ; highly adily be it only the oxy- cids, its d with en and ន copper, the relative hardness being as 4:5:7.2. extremely malleable and ductile, with a tenacity of a tons per square inch; its specific gravity is 10.5, whi be slightly increased by the operations of coining, hammering, etc.; it melts at about 1000° C.; is on best conductors of heat and electricity; is volatile temperatures, and at the temperature of the electri may be boiled and distilled. When heated in a cu hydrogen it volatilises at 1330° C. It does not when heated in air, but molten silver mechanically oxygen and emits it on solidifying; this is termed "sp Silver in a finely divided state is oxidised when heat certain metallic oxides, such as cupric oxide, ma dioxide, red lead, etc., these bodies being reduced t oxides. Silver is soluble in nitric and sulphuri Silver unites readily with sulphur when heated, silver sulphide Ag2S, which is a dark gray cry body, with feeble lustre, somewhat soft and ma When heated in air it does not form oxide or sulpha most other metallic sulphides, and at a red heat is posed into metallic silver and sulphurous acid. hydrochloric acid has no action on silver sulphide, strong acid attacks it. Lead, copper, or iron decon when the two bodies are fused together. Whe sulphide is heated with common salt, in the pres moist air, silver chloride is formed. Silver and all its salts dissolve in sodium thios forming a soluble double thiosulphate (Na,S,O +A when the sodium salt is in excess. Silver combines with chlorine to form silver chloride AgCl. Th substance is formed by adding hydrochloric aci AgNO3 + NaCl = AgCl + NaNO3 Silver chloride fuses at a low red heat to and readily volatilises at a strong red heat. in acids, but soluble in ammonia, sodium thiosulphate, and potassium cyanide. It ma hydrogen, carbonate of soda, zinc, iron, an metals, and partially by sulphur. It unites lead in all proportions, and partially so W lead and some other sulphides. Silver occurs in nature in the metallic sta in silver glance, which is often associated wit of lead, antimony, and iron; as bromide chloride in horn silver; in many lead, zinc, a and sometimes in iron pyrites. Silver is too soft to be worked by itself for pure silver being only used in special cas presence of another metal would exert an i In most cases, silver is alloyed with copper, a with other metals, as in silver solders. COPPER GROUP. COPPER, MERCURY, I § 7. Copper has a red colour; is highly ma tough, and tenacious; it melts at about 11 sensibly volatile, except at very high tem specific gravity is 8.96, which may be slig by hammering and rolling. Copper is one of ductors of heat and electricity, but this considerably interfered with by the presence of impurities. When a bar of pure copper is it exhibits a fibrous silky fracture, of a light It readily unites with oxygen at a red heat, both of the two oxides, known respectively as oxide, in virtue of their colour. The red or is highly basic, and unites with acid substances, forming copper salts. Cuprous oxide is solu copper, making it dry in appearance and brittl ductile, is not es; its creased st conrty is traces proken colour. one or nd red oxide silica, holten acter. This may be remedied by remelting the copper little charcoal, and stirring with a pole of green Commercial or tough-pitch copper is never pure, E impurities are neutralised by the presence of a little If the poling referred to above be continued too neutralising oxygen is removed and the other im present act on the copper prejudicially, making it The copper is then said to be over-poled. Copper unites directly with sulphur when the two are heated together forming cuprous sulphide, which dark bluish-gray colour, shows a finely-granular fr surface when broken, and has a metallic lustre. Phosphorus is highly injurious to copper when alle remain in it, but a small quantity may, under certain stances, exert a refining influence, provided the whole afterwards removed. The element silicon, when reduced from sand by th of carbon, unites with copper, making it much hard causing it somewhat to resemble gun-metal in colo diminishes its toughness and malleability. Lead, arsenic, and antimony have a very injurious on copper, making it hard, brittle, and cold-short. The common impurities in copper are iron, antimony, and cuprous oxide; sometimes tin, bismu phur, lead, nickel, and cobalt are present. The var commercial copper are :—rosette or Japan copper, the of which presents a peculiar red colour, due to a co oxide, formed by throwing water on the surface of th while in a heated state. Bean-shot and feather copper, which are obtained in the form of globules an respectively, by running the metal into hot or cold Tough-cake is a variety cast into rectangular slabs, con for rolling, etc. Best-selected is the name applied purest variety of commercial copper, special care taken to free it from sulphur, arsenic, antimony, ai Russian-copper, which generally contains traces of i is otherwise very pure. Chili-bars. This variety, as i into this country, is prepared in bars weighi each; the copper being in a raw state, requ before it is ready for use. Mercury. This is the only one of th which is liquid at ordinary temperatures; quicksilver, and has been known from the m It has a silver-white colour with a brilliant of taste or odour when pure; at a tempera boils, and at 39.4° C. it solidifies, formin malleable mass, exhibiting a granular structu fractured surface. It has a high and fairly r of expansion for heat, which renders it su mometers and similar instruments; its specif and its density at 4° C. is 13-59. Liquid n oxidise in air, except when near its boiling po a ready means of detecting the presence of ba as lead and antimony, added as adulteration impurities. Impure mercury, when exposed t becomes coated with a gray film, due to the impurities. At its boiling point mercury is to mercuric oxide HgO. It combines directly forming an important compound, mercuric s milion HgS. Mercury unites with most metals forming some of which are liquid, others semi-liqu solid. The solid amalgams are regarded compounds, while the liquid amalgams maj of compounds in excess of mercury, but feeble, as the mercury is partially expelled and completely so, in most cases, by heat are formed-(1) by rubbing the metal in a state with mercury, an increase of tempera ing the amalgamation; (2) by dipping a n solution of a mercury salt; (3) by voltaic ad a metal is placed in contact with mercury and by mixing a metal, such as gold, with an a highly positive metal, such as sodium. ut 200 le > be refined ful metals also called of 360° it! · does not Oxygen, on of the oxidised sulphur, or ver algams, d some hemical lutions mity is essure, algams divided cilitat to the when 1; (4) m of Mercury sometimes occurs in the metallic state, som as an amalgam with silver, and occasionally as ch bromide, and iodide of mercury. The chief source metal is the sulphide HgS, known as cinnabar. Lead. This metal has a bluish-gray colour, and pos considerable lustre; it is malleable, ductile, and toug has a feeble tenacity. The lustre of a freshly cut s soon becomes dim when exposed to the air, owing t formation of a film of suboxide of lead. Pure lead e dull sound when struck, but the presence of imp renders it more sonorous; also when the pure metal i in the form of a hollow sphere it becomes somewhat son Its specific gravity is 11:45, and all base metals, alloyed with it, lower its density. Its melting point is 330° C., and it is not well adapted for castings, since i tracts considerably on solidifying. It is so soft that easily be cut with a knife, and squirted into the for tubes or rods; two clean surfaces of lead can easi welded together by pressure in the cold, and also wher finely divided state, the metal can be pressed into a co mass. Its specific heat between 0° and 100° C. is · and its coefficient of expansion is 00003 for each between 0° and 100° C. If lead is boiled with water containing oxygen it is pa dissolved, and the liquid affords an alkaline reaction. metal is oxidised when exposed to moist air; it is some volatile when heated in air, forming lead oxide PbO this oxide acts as an oxidising agent on many metals. as copper, zinc, iron, etc. Lead and sulphur unite heated together, forming lead sulphide PbS, which bluish-gray, brittle, and crystalline body. Commercial lead is often nearly pure, but it generally tains some silver, copper, antimony, tin, and sulphur occasionally iron, arsenic, zinc, and manganese. Bismuth is a hard, grayish-white metal with a re tint and bright metallic lustre. Its specific gravity i which may be reduced by pressure; it melts at 270° C |