209 Miscellaneous Intelligence, 



procured in a definite and crystalline condition. — Ann, de Chimie, 

 xlii. 225. 



11. Preparation of Pure Oxide of Cobalt. — I treat the ore of 

 cobalt (unroasted) with nitric acid, evaporate to dryness, and re- 

 dissolve in water. I precipitate with carbonate of potash, until 

 I perceive that arseniate of cobalt begins to fall. I separate the 

 arseniate of iron by a filter, and pour an acid oxalate of potash 

 into the solution. In the course of some hours, all the oxalate 

 of cobalt precipitates ; the iron, arsenic, and nearly all the nickel 

 remaining in solution. The precipitate, well washed, is then to 

 be treated with ammonia, according to M. Laugier's process, 

 and it will be sufficient to use but little ammonia with heat, 

 which will then first dissolve the oxalate of nickel. If this be not 

 thought necessary, (and the quantity of nickel present is very 

 small,) nothing remains but to decompose the oxalate by heat, 

 in an open vessel. The oxide of cobalt thus obtained will con- 

 tain no iron or arsenic, and only minute traces of nickel. — Ques- 

 neville. — Journ. de Pharmacie, xv. 



12. Properties of Cobalt. — The following are, according to 

 Lampadius, the properties of pure cobalt, obtained with great 

 difficulty in pieces the size of a pea. Colour greyish-white, 

 between steel and silver j specific gravity 8.71; lustre con- 

 siderable, strongly reflecting light, and being unaffected by the 

 air ; hardness moderate, not more to the file than that of copper ; 

 malleability moderate : the metal bears a few blows with a ham- 

 mer, and then gives way in scales ; when heated, the effect is the 

 same ; fracture fine and granular ; fusibility between nickel 

 and platina; magnetism, the magnetic force (of iron?) being 

 taken as unity, that of cobalt is 0.701. — Bull. Univ. A. xii. 455. 



13. Preparation and Properties of the Bi-iodide of Mercury. — 

 The following details are extracted from M. A. Hayes's account. 

 Boil a mixture of 125 parts of iodine, 250 parts of clear iron filings, 

 and 1000 parts of distilled water in a flask. When the colour 

 from brown has become light green, decant the clear fluid, wash 

 the residue, and add the washings to the former liquor; a solution 

 of 272 parts of corrosive sublimate, in 2000 of warm water, is to 

 be added, and the resulting precipitate washed and collected. 



This salt, either in crystals or in powder, presents two distinct 

 and beautiful colours. If the precipitate be heated in a small 

 subliming apparatus, or in a glass tube, it melts and sublimes 

 copiously, and the vapour is condensed in large transparent rhom- 

 bic tables, of a fine sulphur yellow colour. These crystals are 

 permanent in the air, and unaltered by the direct solar rays ; but 

 the slightest friction, or the contact of a fine point, is sufficient to 

 alter their interior arrangement. The point of contact instantly 

 becomes of a rich scarlet, and the same colour spreads over the 



