148 Intelligence and Miscellaneous Articles. 



powder is to be put into a moderately large tube, and the bromine is 

 to be poured upon it. Combination takes place rapidly with a noise 

 similar to that produced by immersing red-hot iron in water j much 

 heat is given out, and the mixture becomes instantaneously solid : 

 the compound has a red brown colour, similar to that of iodide of 

 phosphorus ; and some parts are yellowish like chloride of iodine ; it 

 gives out vapour when exposed to the air, which has an odour similar 

 to that of chloride of sulphur. It is entirely soluble in water, except 

 some particles of selenium, which precipitate. The filtered solution 

 is colourless when there is no uncombined bromine -, it is strongly 

 acid, and consists of selenic and hydrobromic acids. The solution when 

 saturated by potash, gives, by evaporation, a crystallized mixture of 

 seleniate and hydrobromate : on the addition of muriatic acid, either 

 before or after saturation with potash, the selenium is precipitated in 

 particles of a fine red colour. 



When a bar of iron or zinc is kept immersed in the solution of 

 bromide of selenium, rapid action occurs, and especially with the 

 zinc j hydrogen gas is abundantly evolved, and the metallic bar is 

 covered with selenium, which adheres in the same manner as one 

 metal precipitated by another j by agitation the selenium is detached, 

 and bubbles of hydrogen gas, which had also been retained, are given 

 out. The selenium being separated by filtration, the hydro-bromate 

 of zinc may be decomposed by carbonate of potash, by which car- 

 bonate of zinc is precipitated and hydro-bromate of potash remains in 

 solution. This action of zinc or iron, in the solution of bromide of 

 selenium, is similar to that which occurs when either of these metals 

 is put into a mixture of selenic and muriatic acids ; the selenium is 

 deoxidized, and hydrogen evolved by the decomposition of water. 

 Is the whole of the hydrogen evolved, or is part of it employed in re- 

 ducing the selenic acid ? Or is there, as with the metals, a voltaic cir- 

 cuit formed ? A slight smell of decayed cabbage is perceptible, which 

 is one of the characteristics of oxide of selenium. When bromide of 

 selenium is strongly heated, a portion of it sublimes, and assumes a 

 yellow appearance, the remainder is decomposed into bromine and 

 selenium. — Ibid. p. 349. 



ELECTRICITY OF GASES AND THE ATMOSPHERE. 



M. Pouillet concludes from numerous experiments : 1st, That 

 gases give out electricity, when they combine together, or when they 

 unite with solid or fluid bodies ; and in these combinations, oxygen 

 always gives out positive electricity, and the combustible body, what- 

 ever it may be, gives out negative electricity ; and reciprocally, when 

 a compound is decomposed, each of the elements then requiring the 

 electricity which it had given out, is in the opposite state of electricity. 

 This reciprocity shows in what consists the difference of the nascent 

 state of a body from its ultimate condition. 



2ndly. The action of vegetables upon the oxygen of the air is one 

 of the most permanent and powerful causes of atmospheric electricity ; 

 and when it is considered on one hand that a gramme (about 15*5 

 grains) of charcoal, in becoming carbonic acid, gives out sufficient 



electricity 



