.854 ?KINCIPLES OF -CHEMISTRY 



preparation of cobalt compounds ; they are first sorted by discarding 

 the rocky matter, and then roasted. During this process most of the 

 sulphur and arsenic disappears ; the arsenious anhydride volatilises 

 with the sulphurous anhydride and the metal also oxidises. 32 It is a 

 simple matter to obtain nickel and cobalt from their oxides. In order 

 vto obtain the latter, solutions of their salts are treated with sodium 



52 The residue from the roasting of cobalt ores is called zqfflor, and is often met with 

 in commerce. From this the purer compounds of cobalt may be prepared. The ores of 

 nickel are also first roaste'd, and the oxides dissolved in acid, nickelous salts being then 

 obtained. 



The further treatment of cobalt and nickel ores is facilitated if the arsenic can be 

 almost entirely removed, which may be effected by roasting the ore a second time with a 

 small addition of nitre and sodium carbonate 5 the nitre combines with the arsenic, 

 forming an arsenious salt, which may be extracted with water. The remaining mass is 



Dissolved in hydrochloric acid, mixed with a small quantity of nitric acid. Copper, iroa, 



'manganese, nickel, cobalt, &c., pass into solution. By passing hydrogen sulphide 

 through the solution, copper, bismuth, lead, and arsenic are deposited as metallic sul- 

 phides ; but iron, cobalt, nickel, and manganese remain in solution. If an alkaline solu- 

 tion of bleaching powder be then added to the .remaining solution, the whole of the 

 manganese will first be deposited in the form of dioxide, then the cobalt as hydrated 

 cobaltio oxide, and finally the nickel also. It is, however, impossible to rely on this 

 method for effecting a complete separation, the more so since the higher oxides of the 



three above-mentioned metals haye all a black colour; but, after a few trials, it will be 

 easy to find how much bleaching powder is required to precipitate the manganese, and 

 the amount which will precipitate all the cobalt. The manganese may also be separated 



* from cobalt by precipitation .from a mix! ure of the solutions of both metals (in the form ol 

 the ' ous ' salts) with ammonium sulphide, and then treating the precipitate with acetic 

 acid or dilute hydrochloric acid, in which manganese sulphide is easily soluble and cobalt 

 sulphide almost insoluble. Further particulars relating to the separation of cobalt from 

 nickel may be found in treatises on analytical chemistry. In practice It is usual to rely on 

 the rough method of separation founded oirthe fact that nickel is more easily reduced and 

 more difficult to oxidise than cobalt. The New Caledonian ore is smelted with CaS0 4 

 end CaC0 3 on coke, and a metallic regulus is obtained containing all the NI, Fe, and 8. 

 This is roasted with Si0 2 , which converts all the iron into slag, whilst the Ni remains 

 combined with the S ; this.residue on further roasting gives NiO, which is reduced by the 

 carbon to metallic Ni. The Canadian ore (a pyrites containing 11 p. c. Ni) is frequently 

 treated in America (after a preliminary dressing). by smelting it with NagSC^ and 

 charcoal ; the resultant fusible Na-jS then dissolves the CuS and FeS ft while the NiS la 

 obtained in a bottom layer (Bartlett and Thomson's process) from which Ni is obtained 

 in the manner described above. 



For manufacturing purposes somewhat impure cobalt compounds are frequently used, 

 which are converted into smalt. This is glass containing a certain amount of cobalt 

 oxide ; the glass acquires a bright blue colour from this addition, so that when powdered 

 it may be used as a blue pigment; it is also unaltered at high temperatures, so 

 that it used to take the place now occupied by Prussian blue, ultramarine, &o. At 

 present smalt is almost exclusively used for colouring glass and china. To prepare 

 emalt, ordinary impure cobalt ore (zaffre) is fused in a crucible with quartz and potassium 

 carbonate. A fused mass of cobalt glass is thus formed, containing silica, cobalt oxide, 



i and potassium oxide, and a metallic mass remains at the bottom ol the crucible, con- 

 taming almost all the other metals, x arsenic, nickel, copper, silver, &o. This 'metallic 

 niass is called speiss, and is used as nickel ore for the extraction of nickel. Smalt usually 

 contains 70 p.c. of silica, 20 p.c. of potash and soda, and about 5 to 6 p.o. of cobaltous 

 <mde; the remainder consisting of other metallic oxides. 



