METALS METALLURGY. 



and in some the workmen require to protect the 

 face with a towel, and stop up the nostrils with 

 cotton-wool. 



Two sulphides of arsenic, namely, realgar (disul- 

 phide) and orpiment (trisulphide), occur native ; 

 but, for commercial purposes, they are prepared 

 artificially by heating together arsenious acid and 

 sulphur, or by their sublimation. Realgar is of a 

 beautiful red colour, and, when refined, forms red 

 arsenical glass. Cups, teapots, and similar articles 

 are made of it by the Chinese ; and it is one of 

 the ingredients in "white Indian fire. Orpiment is 

 the colouring substance in king's yellow. 



Like antimony, metallic arsenic is very brittle, 

 and may be easily reduced to powder in a mortar. 

 When heated, it passes at once from the solid state 

 into vapour without fusing. It performs an import- 

 ant function as an alloy in certain metallurgical 

 operations, but the metal is not used for any pur- 

 pose by itself. Several compounds of arsenic are, 

 however, extensively employed. Combined with 

 copper, it forms Scheele's green, and with acetic 

 acid in addition, emerald green, both beautiful 

 colours used by painters, paper-stainers, and dyers. 

 Arsenate of sodium has been much used of late 

 years as a dung-substitute in calico-printing. 

 Arsenious acid in minute quantities is a useful 

 medicine. It gives an opaque white colour to 

 flint-glass, so as to make it resemble porcelain. 

 A great deal of it has been consumed of late years 

 in the manufacture of rosaniline. Another use of 

 it is found in preserving seeds and fruits. For 

 such purposes as poisoning rats, it can now only 

 be purchased, under certain restrictions, coloured 

 with indigo. 



Bismuth. 



Bismuth is nearly all obtained from the native 

 metal, which generally occurs in veins in crystal- 

 line rocks, associated with ores of silver, cobalt, 

 lead, and zinc. It is chiefly found in Saxony and 

 Bohemia, but it also occurs in Norway and 

 Sweden, as well as in Cornwall, Devonshire, and 

 Cumberland, in England. It is likewise obtained 

 in South America and the United States, but is 

 not an abundant metal. 



Bismuth is extracted from the ores and minerals 

 which usually form its matrix, by simply heating 

 them on a hearth till it melts and runs out, its 

 point of fusion being about 260 C. Within the 

 last ten or twelve years, bismuth has risen greatly 

 in price, being now more than one-third the value 

 of silver. Some artificially crystallised specimens 

 of the metal, with fret-like modifications of cubes, 

 are objects of great beauty. 



There are not many uses to which bismuth can 

 be applied, though some of them are important. 

 It increases very much the fusibility of other 

 metals with which it is alloyed, and for this 

 reason it is used in the formation of pewter, 

 solder, and type-metal. Several alloys of bismuth, 

 lead, and tin, called fusible metal, melt under the 

 temperature of boiling water. Nitrate of bismuth 

 is used in the manufacture of white sealing-wax, 

 and in medicine. Formerly, it was extensively 

 consumed as a cosmetic. 



Cobalt. 



The two closely allied metals, cobalt and nickel, 

 can scarcely be distinguished from each other by 



the eye, and their ores are nearly always found 

 together. Botlr much resemble iron in appear- 

 ance, as well as in hardness and tenacity, but arc 

 whiter in colour. Although cobalt is not employed 

 in the metallic state, yet its property of forming 

 blue colours when in combination with other sub- 

 stances, especially silica and potash, confers much 

 value on its compounds. Smalts and zaffre are 

 both the powder of cobalt glass. A mixture of 

 alumina and phosphate of cobalt, heated to red- 

 ness, yields a fine blue like ultramarine. Since 

 the discovery, about thirty years ago, of Mr 

 Askin's process for the separation of cobalt from 

 nickel, oxide of cobalt has been largely made in 

 Birmingham, for the purpose of imparting a blue 

 colour to pottery and glass. Curiously enough, 

 his process did not aim at this application of the 

 oxide at all, being used at first simply to eliminate 

 the cobalt from the nickel, as its presence was 

 injurious to the latter. For some time, accord- 

 ingly, it was looked upon as a waste product ; but 

 on its value as a colouring substance being dis- 

 covered, potters bought it at the rate of two guineas 

 a pound, thereby amassing a large fortune to the 

 makers. Its price is, however, much lower now. 



Nickel. 



The name of this metal is from the German, 

 and signifies something of little worth. Nickel is, 

 however, both an important and an interesting 

 metal. It first began to be made on a manufac- 

 turing scale about forty years ago, Mr Askin of 

 Birmingham having then discovered an efficient 

 way of refining it. Its chief ore is knpjer-nickel 

 'false copper' so called by the German miners 

 from its resembling but not yielding copper. When 

 pure, it consists of arsenic 56, and nickel 44, and 

 is found in Saxony and Hungary, occasionally in 

 Cornwall ; and of late years some has been raised 

 from the old Hilderston silver mine, near Bath- 

 gate, in Scotland. Another ore, a sulphide of iron 

 and nickel, has been largely worked in Norway, 

 and, to a less extent, near Inverary, in Scotland. 

 Nickel also occurs as a constituent of many com- 

 plex ores. The processes employed for the reduc- 

 tion of the metal are, for the most part, kept 

 secret. 



Pure nickel is a hard, not easily tarnished 

 metal. Its whiteness is between that of silver and 

 polished steel. It is malleable and ductile, and 

 has a higher tenacity than wrought-iron, but has 

 hardly as yet been employed alone, except in .1 

 recent application as an electro-deposit on brass 

 or iron furniture, for which its hardness and 

 non-liability to tarnish render it very suitable. 

 Nickel is most in demand to form the important 

 alloy known as German silver, of which a vast 

 number of articles, such as table-plate of all 

 kinds, are now made in Birmingham. These are 

 very often plated with silver, for which this alloy is 

 singularly well suited. It consists of copper, nickel, 

 and zinc in various proportions. Other alloys 

 of nickel are used in the coinage of some foreign 

 countries, and the late Master of the Mint was 

 strongly in favour of its being introduced into the 

 new copper coinage of Great Britain. A new- 

 alloy, formed of 1000 parts of copper, 700 of 

 nickel, and 50 of tungsten, under the name of 

 ' min-argent,' has of late been extensively employed 

 in Paris as a substitute for silver. 



415 



