382 NaUiraUPhilosopJdcal Collections. 



it passes into the state of peroxide. The vitrified peroxide is still attracted by 

 the magnet vith a fate* eq^ to 0^02. 



4. Action of Cobalt on some other Metals. 



Cobalt mi gold readily melt together, and fmnlsh A wry h«d but extensible 

 alloy. The gold colour disappears, and the alloy has the colour of cobalt itself. 

 The magnetic force of this mixture was 0.507*. 



Cobalt and platina readily united by fusion. The aUoy, which was rather 

 soft, possessed a moderate extensibility, and, after some blows of the hammer^ 

 broke. The colour approached that of silver. Magnetism = 0"509. 



Cobalt and silver readily united in fluxion. The alloy broke under the first 

 blows of the hammer. The colour was intermediate between that of iron and 

 silver. Magnetism = 0.508. 



Cobalt and copper combined, and in so dotng intumesced and enlarged in vo- 

 lume. The mixture, which was softer than copper^ had a considerable degree of 

 extensibility, and a magnetic force = 0.509. 



Cobalt and iron melted together, but a considerable portion of the iron burnt 

 in this case, and the mixture was enveloped with a crust of oxide of iron. The 

 mixture was of a grayish-white colour, pretty hard, and slightly malleablel 

 Magnetism = 0.780. 



Cobalt combines with sulphur and phosphorus. When combined with the 

 latter substance if does not act on the magnet. 



Nitric acid, of the specific gravity of 1.30, immediately attacks the metal in 

 the cold state. There is disengagement of nitrous gas, and the solution has a 

 fine deep rose colour. 



Hydrochloric acid has little action in the cold state, but acquires a blue tint, 

 and some bubbles of hydrogen are disengaged. With the aid of heat, the ac- 

 tion becomes energetic, and the solution assumes a deep indigo colour. 



Sulphuric acid of the specific gravity of I.7OO, has no action in the cold state, 

 and only attacks the metal feebly by means of heat. The solution at first as^ 

 sumes a purple colour, and when the ebullition is continued, the whole of the 



cobalt dissolves. The solution evaporated yields a rose-coloured salt Bullet. 



des Sciences Chimigues. 



Decrepitating Common Salt — Condensation of Gas in it. — .M. Dumas has 

 examined and described a very curious effect which occurred when some rock- 

 salt, obtained from the mine of Wieliczka, in Poland, and given to him by M. 

 Boue, was put into v/ater. It decrepitated as it dissolved in water, and gradu- 

 ally evolved a sensible portion of gas. The bubbles of gas were sensibly larger 

 when the decrepitations were stronger, and the latter frequently made the glass 

 tremble. This salt owes its property of decrepitating to a gas, which it contains 

 in a strongly-compressed statCj although no cavities are sensible to the eye. 

 When the experiment was made in perfect darkness no light was disengagetl. 

 The gas disengaged is hydrogen slightly carbonated ; when mixed with aij it 

 burns by the approach of a light. 



This disengagement of gas will assist in explaining the numerous accidepyi 

 which have happened from fire-damp in salt mines. Several portions of the salt 

 were nebulous, others were transparent. The nebulosities indicated the existence 

 of numerous minute cavities, probably filled with condensed gas, and, in fact, A 

 nebulous fragment, dissolved in water gave more gas than an equal-sized frag- 

 ment of the transparent salt. 



• The author made two compound alloys, one of 10 coltalt and 90 gold, the 

 other of 5 cobalt and 95 gold. Each of these alloys was still remarkably har^, 

 so as to render it difficult to bend a piece of the form of a ducat. The two mix- 

 tures had a fine gold colour, were perfectly malleable, susceptible of a fine po- 

 .iish, and insensible to the a^ion of thempfrnet. There would result from tfii* 

 that cobalt might be employed in alloy with gold. 



