381 



NATURAL-PHILOSOPHICAL COLLECTIONS. 



FaoU relative to the History qf Cobalt i by M. Lampadius. 

 1 . Preparation qfpwre cobalt. 



A. To obtain the oxide in a state of purity, recourse has hitherto been had to 

 die rather complicated method of M. Laugier. 



B. A less complicated preparation of pure peroxide was the following : The 

 hydrated oxide of commerce was dissolved in sulphuric acid. There remained 

 a little iron. The solution was then treated with sulphuretted hydrogen, Jiltered 

 and treated by carbonate of soda. The precipitate which resulted was dried and 

 brought to a red heat. After this the peroxide was redissolved in concentrated 

 acetic acid, precipitated again by carbonate of potass, and lastly dried and 

 heated. 



C. A part of the oxide of commerce was triturated with water and treated by 

 chlorine gas, by which there was obtained a black precipitate of pure peroxide. 



During all these experiments, no oxide of nickel could be discovered in the 

 oxide of cobalt of commerce ; but there was foimd a little oxide of iron, oxide of 

 copper and bismuth, and arsenic acid. 



Each of the peroxides, obtained according to the methods A, B, and C, was 

 put in the form of a paste with oil in a crucible, and covered with a thin layer of 

 a flux, which had been prepared with three parts of calcined borax, one part of 

 lime, one part of silica, and one part of alumina. Then each of the three cruci- 

 bles was exposed for three hours to a heat which was sufficient to melt crude 

 iron, steel, and nickel. Notwithstanding, there were only obtained some metal- 

 lic grains of the size of a pin's head. All the rest of the reduced metal was in the 

 Form of a black powder, which was readily attracted by the magnet. The expe- 

 riment was repeated, and the same products were again exposed for three hours 

 to a heat quite as intense ; but the result was the same. It was therefore found 

 flecessary to collect the metallic powder by means of the magnet, to put it in 

 small paper capsules, about four grains in each, (that it might not be blown 

 away by the blast,) and to melt it gradually on charcoal by means of oxygenated 

 gas. In this manner, there were obtained grains of the size of a lentil, and whose 

 exterior was covered by a small layer of oxide which could be removed. More 

 than 200 ^^^ins of pure cobalt were thus obtained. 



2. Properties qf Pure Cobalt. 



Colour greyish-white, intermediate between that of silver and steel. 



Specific gravity, 8.710. 



Lustre bright, strongly reflecting light, and remaining unaltered by exposure 

 to the air. 



Hardness moderate, not offering more resistance to the file than copper. 



Extensibility equally moderate, bearing some blows of the hammer, and after- 

 wards separating in the form of lacerated lamellas ; the same when the metal is 

 heated ; fracture fine and granular. 



Fusibility between nickel and platina, about 143° of Wedgwood's pyrome- 

 ter. 



The magnetic force being taken as one, the magnetism of cobalt is 0.701. 



3. Oxides of CobalL 



The oxide, which is obtained on burning the metal with oxygen, is the first of 

 these oxides. It is pure, and when melted, appears under the form of an opaque 

 black glass. It dissolves in hydrochloric acid without disengagement of gas, 

 and with an indigo-blue culoux. In powder, and slowly submitted to a red heat, 



