96 
THE PRINCIPAL FLOOR, 
Nickel and German Silver. 
Table Case 33. — The metallurgy of nickel is usually kept a 
secret by the manufacturers. In Case 18 will be found some 
specimens illustrating the extraction of nickel in Sweden. Of 
late years nickel has been prepared on a large scale from the rich 
silicate ores of New Caledonia, and from the nickeliferous 
pyrrhotite of Sudbury, Ontario, in Canada. 
The metal is produced in large quantities to meet tha 
demands of the makers of German silver. Several white 
metals, bearing different names, such as nickel 'silver, p albata 
plate, &c., are only varieties of German silver. 
Smalts and other Cobalt Colours. 
Table Case 33. — The preparation of the beautiful cobalt-blues 
was discovered in Saxony about 1540, and it has since that time 
been carried on extensively in that country. The cobalt in the 
ores is converted into oxide by roasting, and the oxide of cobalt 
thus produced is vitrified, with the addition of pure potash and 
silica. The product called smalt is really a double silicate of 
cobalt and potash. Smalt is, therefore, simply a cobalt glass ; 
this ground to fine powder and carefully washed is applicable to 
all purposes in which a cheap and durable blue is required as a 
paint, and for giving a blue tint to paper or linen. For 
colouring earthenware the roasted ore, with an addition of 
powdered flint and nitre, is sent into the market under the 
name of Zaffre or Saflor (a corruption from sapphire) ; and 
the colour required is developed in the process of firing the 
glazed ware. In this case will be found a large series of the 
colours produced by chemical treatment from cobalt. Whilst 
the silicate of cobalt and potash forms smalt and cobalt or 
Licknor's blue ; oxide of cobalt and oxide of zinc form Rinman’s 
green ; and phosphate of cobalt with alumina, Thenard’s blue : 
arsenite of cobalt produces a purple, and silicate of cobalt a 
pink , colour. 
Arsenic, &c. 
Table Case 33. — Arsenic is employed in commerce mainly in 
the form of white arsenic or arsenious oxide. Large quantities 
of this oxide are now prepared in Devon and Cornwall by 
roasting ores of copper and tin. In 1894 the production 
amounted to 4,754 tons, and the previous year it reached 5,976 
tt>ns. The arsenic exists in the ore as mispickel or “ arsenical 
mundic ” — a compound of arsenic, sulphur, and iron (p. 73). 
The ores are placed on the hearth of a reverberatory furnace, 
through which a current of air is allowed to play. The sulphur 
present is converted into sulphurous acid gas, while the arsenic 
volatilises as an oxide, which is readily condensed in the flues. 
To obtain pure arsenious oxide the first products thus directly 
obtained are subjected to a second sublimation. 
