t 313 ] 



LI I. InlelUgence and Miscellaneous Articles. 



burni>;g of metals. 



JVl. Vauquelin has cominunicatod to the French Institute an 

 account of the results of sorne recent experiment •, which are high- 

 ly interestinij: to assayists, gold- and silver-smiths, and cill work- 

 ers in the precious metals. Tliis chenjist, placing four grains of sil- 

 ver in a cavity of ignited charcoal, ob^served ihat, when he directed 

 a current of oxygen gas on the metal, it produced a conical 

 ilame, the base of which had a yellow colour, the middle purple, 

 and the top blue ; and that, by collecting the disengaged vapour 

 in a bell glass, he found the receiver covered with a brownish 

 yellow crust, which was almost wholly dissolved in cold very dilute 

 i»itric acid. In this experiment the four grains of metal disap- 

 peared in less than a minute. M. Vauquelin thinks that the 

 silver burned at the same time with the charcoal, and that it is 

 to this cause the yellow-coloured flame of the latter must be 

 ascribed. 



ON THE PHOSPHORESCENCE OF THE COMPRESSED GASES. 



M. Dessaigne has addressed the following letter on this sub- 

 ject to M. de ia Metherie. — " Several years ago, M. Mollet of 

 Lyons made known the curious fact of a light appearing at the 

 mouth of an air gun, when it is discharged in the dark. In 1810, 

 in a memoir on phosphorescence by collision, which I read to 

 the Institute, after having made known several facts in which the 

 luminous appearance is produced by the separation of bodies 

 only, I had concluded that there were, with respect to the light 

 concealed in bodies, two modes of excitation ; the one which is 

 the result of a pressure, and the other which is produced in the 

 expansion. 



" Subsequently the French chemists have made us acquainted 

 with two mixtures, in which the luminous excitation also takes 

 place by a7i expansive movement at the instant of their decom- 

 position. 



" I took a cylindrical glass vessel, and closed its upper orifice 

 with a wet bladder, which I stretched and firmly tied down around 

 it. I allowed this bladder to dry in the air until no appearance 

 of humidity remained ; after which I placed the vessel on the 

 itand of an air piunp, and made a vacuum in the dark. At the 

 moment when the air by its pressure burst the bladder, in order 

 to precipitate itself into the vacuum, a very brisk flask uj I'lglit 

 llluminuted the interior of I lib receiver. 



'* This experiment had a pleasing effect when made at night : 

 the light omitted is white and intense, like that of the combus- 

 tion 



