COBALT. 



COBALT ORES. 



1000 



sulphides of arsenic, copper, bUmuth, and tin, are thoroughly pre- 

 cipitated. The filtered liquid U now boiled to expel excess of sulphu- 

 retted hydrogen, little nitric acid introduced to peroxidisc iron, and 

 carbonate of soda added till the oxide of iron and carbonates of nickel 

 and cobalt are all precipitated. The precipitate U now, after washing, 

 diverted in strong solution of oxalic acid and again well washed on a 

 filter; in this way the soluble oxalate of iron is entirely removed. The 

 oxalatos of nickel and cobalt are finally dissolved in strong solution of 

 ammonia, and the liquid exposed for several days, when the oxalate of 

 nickel is deposited, oxalate of cobalt remains in solution, and on 

 evaporating to drynrss and heating in an open crucible, the pure oxides 

 of cobalt are obtained. 



Another process consists in adding one part of roasted cobalt ore by 

 small portions at a time, to three parts of fused bisulphate of potash, 

 and then increasing the heat till no more fumes are given off; in this 

 way excess of bixulphate of potash is converted into neutral sulphate, 

 sulphate of nickel is decomposed and arseniate of iron formed ; the 

 latter remains undissolved when the cooled broken up mass is digested 

 in water. From the aqueous solution antimony, bismuth, or copper 

 are precipitated by sulphuretted hydrogen and pure basic carbonate of 

 cobalt precipitated by carbonate of potash. 



Pure protoxide of cobalt may be obtained by washing, drying, and 

 igniting the carbonate, or from the mixed oxides produced in the first 

 process by solution in boiling hydrochloric, precipitation by carbonate 

 of potash and reduction of the carbonate by heat as just described. 

 It is an ash-gray powder that in contact with air gradually absorbs 

 oxygen, becomes brown, and ultimately black : heat causes the same 

 change but more rapidly. 



Ilydrated oxide of cobalt (CoO, HO) is a rose-coloured precipitate, 

 formed when either of the fixed alkalies are added to a solution of a 

 salt of cobalt: when first formed it is pale blue (a subsalt). It is 

 soluble in ammonia and most ammoniacal salts. 



Haiti of the protoxide of cobalt are formed by dissolving the basic 

 carbonate, already described, in acids. 



Sulphate of cobalt (CoO, SO, + 7 aq.) crystallises from a solution, 

 concentrated by evaporation, in carmine-coloured oblique rhombic 

 : :.-:..-. 



Xitrate of cobalt (CoO, NO, + 6 aq.) forms red deliquescent crystals. 

 A solution of this is used in blowpipe operations. A small quantity 

 of the substance under examination is moistened with the solution, 

 and heated in the blowpipe flame in any convenient manner ; a pink- 

 coloured mass indicates the presence of magnesia ; a green residue, 

 zinc ; and a blue, alumina. 



Pkotpkate of cobalt (3CoO, PO S ) is precipitated in violet flakes when 

 ordinary tribasic phosphate of soda is added to a soluble cobalt salt. 



Carbonate of cobalt (CoO, CO,) U formed by digesting the basic car- 

 bonate 3(CoO, HO) + 2(CoO, CO,), described under oxide of cobalt, in 

 an alkaline bicarbonate. 



Chloride of cobalt (Co CD U obtained in ruby-red octohedra, when a 

 solution of the carbonate of cobalt in hydrochloric acid is evaporated. 

 It does not deliquesce. 



ftitljAide of cobalt (CoS) is precipitated when sulphide of ammonium 

 is added to a solution of a salt of cobalt. Two other sulphides also 

 exist, K*iaitulfltidc (Co,S,), and bitulfhide (CoS,), but they are com- 

 paratively unimportant. 



Saguioxide of cobalt (Co,O,) is a brownish black powder, formed on 

 passing chlorine gas through a dilute solution of potash in which oxida 

 of cobalt is suspended ; or by adding solution of chloride of lime to 

 moist hydrate of cobalt 



Salts of sesquioxide have not been obtained in a definite state. 



A mmmiaeal compound* of cobalt. According to M. Fremy, when an 

 ammoniacal solution of oxide of cobalt is exposed to the air that the 

 protoxide may, by absorbing oxygen, be converted into the sesquioxide, 

 there are formed combinations of four, five, or six equivalents of 

 ammonia with one equivalent of sesquioxide of cobalt. These bodies 

 combine with acids to form salts, in which the jwwer of the ammonia 

 for saturating acids U not exerted in the slightest On account 

 difference in colour of their salt* he has named the base* 



Fucotaltia . 

 Roteocob.ltlt 

 LuteoeobtlUa . 



Co,0,, 4NII, (brown) 

 Co.O., 4NII, (red) 

 00,0,, 6MI , (yellow) 



Ckmdet's unmoniocal salt of nitrate of cobalt (Co O,, 5NH,)3NO, 

 u an example of a salt of roseooobaltia. For further information 

 regarding these interesting compounds, see a paper by M. Fremy, in 

 Ann. de Chimie, 1 III., xxxv. 257. 



Thenard't blue U a pigment that owes its delicate pale blue colour to 

 cobalt It is prejiored by adding phosphate of potash to nitrate of 

 cotlt, and mixing the resulting precipitate with gelatinous alumina 

 nbuined from carbonate of soda and solution of alum ; the whole i* 

 finally evaporated to dryness and exposed to a dull red heat 



BMMMTI grttn is produced by adding carbonate of soda to mixed 

 solutions of the sulphates of cobalt and zinc. 



ic if I: A dilute solution of chloride of cobalt has such a 



pale pink tint that characters written on paper with it an , wl 

 invisible. On gently heating, however, the anhydrous chlori.lc is 

 formed, and this has a sufficiently deep blue colour -t> n-n<l. i th 

 writing perfectly legible. On exposure to air, the pajwr absorbs 



moisture, and the figures or characters again become invisibl 

 mixing the cobalt solution with a small quantity of a zinc salt, letters, 

 &c. , may be described, that when heated appear of a red colour ; or with 

 a persalt of iron, a green colour ; with copper, yellow. 



The use of oxide of cobalt in the manufacture of porcelain, Ac., has 

 already been referred to. It is, however, well known, that from the 

 difficulty of thoroughly disseminating the oxide, spots of a colour 

 darker than the surrounding parts are apt to be formed. To obviate 

 this, M. Carre 1 , of Sevres, recommends the substitution of oxide of 

 cobalt by a solution of one of the salts of cobalt ; the latter can 1 

 easily mixed with the porcelain mass, or with greater facility :i]>: 

 any desired portions. 



A tea. jar cobalt, in addition to the precipitation of the sulphide, 

 oxide, carbonate, and phosphate, already described, consists in heating 

 a fragment of the suspected substance with borax, supported on plati- 

 num wire in the blowpipe flame ; if cobalt is present, the resulting 

 bead has an intense blue colour. 



Quantitative analylit of cobalt. Cobalt is always estimated in the 

 metallic state. The oxide is first obtained by taking advantage of any 

 of the processes already mentioned, and is then reduced in a current of 

 dry hydrogen with the aid of heat, and finally weighed. 



COBALT ORES. Cobalt is not found in the native state, and its 

 ores, though not numerous, require a more minute examination than 

 they have hitherto received. We shall notice those which are best 

 known. 



Bright white cobalt, or white cobalt, occurs crystalline and massive; 

 the primary form is a cube, the planes of which are usually striated ; 

 colour silver-white ; streak grayish-block ; lustre metallic ; hardness 

 fr.">, yielding with difficulty to the knife, and not very frangible ; specific 

 gravity 6'3-6 - 5 ; fracture uneven ; cleavage parallel to the faces of the 

 cube; before the blowpipe on charcoal gives arsenical fumes; and 

 tinges borax of a deep blue. 



It is found in fine crystals at Tunaberg in Sweden, in Norway, 

 Silesia, and Cornwall. 



It is met with also amorphous, arborescent, botryoidal, and sta- 

 lac titic. 



Analysis of the crystals from Tunabuerg by 



Klaproth. 



Cobalt 44 



Arsenic 55 



Sulphur ..... GO'S 



Stromcycr. 

 867 

 49-0 



5-6 



6-5 



i,,,. - o7*a 



. . . > i ' i -. 



Tin-white cobalt, or hard tchite cobalt, occurs massive and crystallised 

 in cubes and octohedrons ; colour tin-white, but sometimes externally 

 tarnished ; fracture fine-grained and uneven ; lustre metallic ; it yields 

 with difficulty to the knife, and is hard and brittle ; specific gravity 

 Y-ariously stated, from 674 to 77; yields arsenical vapour when heated 

 with the blowpipe, and tinges borax deep blue. 



The massive is amorphous, arborescent, botryoidal, &c. The amor- 

 phous occurs in Cornwall, and the crystallised at Skutterud in Norway. 

 Analysis of the crystals by Stromcycr : 



Cobalt 33-10 



Arsenic 43'46 



Iron 3-:;;{ 



Sulphur 20-00 



99-79 



Gray cobalt occurs massive and crystallised ; primary form a cube ; 

 colour grayish tin-white; streak grayish black; lustre metallic; hard- 

 ness 6'5 ; specific gravity 6-466 ; fracture uneven ; cleavage intli 



The mossiY-c occurs amorphous and reticulated. It is found princi- 

 pally at Schneeberg in Saxony, and is used in the manufacture of 

 smalt. 



Earthy cobalt occurs massive, amorphous, botryoidal, pulverulent, 

 Ac. ; colour yellowish-brown and bluish-black ; specific graY-ity - 

 the fracture of the massive is earthy and dull, but polished by friction , 

 and yields to the knife readily; when heated on charcoal gi\ 

 arsenical odour, and a deep-blue colour with IK mix. It is found in 

 Hesse, Saxony, Bohemia, and also in Cheshire and Cornwall. 



Sulphide of cobalt occurs yrlliiwixh-white and steel-gray; streak 

 gray; it is amorphous or botryoidal, and externally brilliant; fracture 

 uneven. According to Hisinger it consuls of 



Cobalt 43-2 



Copper Ill 



1 1 on : 



Sulphur 38-50 



Karthy matter '33 



99-96 



Anenintc of cobalt Oobalt bloom Red cobalt occurs fibrous, 

 massive, and crystallised; primary form an oblique rhombic prism; 

 colour various shades of red passing into crimson ; sometimes grayish ; 

 translucent, transparent ; it is soft, light, and flexible ; specific gravity 

 2-918 ; the massive variety amorphous, botryoidal : structure fibrous, 



