SCIENTIFIC HEWS. 383 



oxide of arsenic is deposited on the sides of the vessel, ff portions of 



it be mixed with twice its volume of atmospheric air, the oxl 8 en - 



product of the combustion is arsenious acid and water. 



With six times its bulk of atmospheric air it will not take 



fire. A mixture of it with an equal part of atmospheric 



air cannot be fired by the electric spark. With an equal 



bulk of oxigen gas it detonates violently, and the products 



are water and arsenious acid: with only half, or a third, 



of oxigen gas, oxide of arsenic likewise is formed, and 



part of the metal is reduced. With five parts of oxigen 



gas it burns without detonation. Arsenic acid is formed 



in none of these processes. The combustion having been 



tried with various proportions of the two gasses in VoIta r s 



eudiometer, the mean of the experiments gave 0*72 of a 1 pait requires 



cubic inch of oxigen gas as the proportion required to burn t0 Dum it? ° 



1-inch of arsenicated hidrogen gas, in which the hidrogen 



is fully saturated with arsenic at the common temperature. 



All acids, in which the oxigen is feebly combined, de- Action of acid?, > 

 compose arsenicated hidrogen gas. This phenomenon is 

 very striking with nitric acid. While part of the hi- Nitric. 

 drogen, being condensed by the oxigen of the acid, is con- 

 verted into water, another part is set free. At the same 

 time the whole [?] of the arsenic is separated in the me- 

 tallic form, but is very quickly oxided by the nitric acid ? 

 and at length acidified. The nitric acid acquires a yellow- 

 colour, and bubbles of nitrous oxide gas are extricated 

 from it. The gas that ultimately remains is pure hidrogen 

 mixed with nitrous oxide. Prof. Stromeyer employ* the 

 action of nitric acid on the arsenicated hidrogen gas, to 

 calculate the proportion of its principles, -which, ac- 

 cording to him are 10*600 arsenic, and 0*219 hidrogen. 



Nitrous acid decomposes it instantaneously, and arse- xi' rju ,s. 

 nious acid is deposited. 



Oxigenized muriatic acid decomposes it, part of the lw- Oxigeniz.»d 

 drogen and arsenic undergoing combustion, and the other l^ttnatu;. 

 being separated. Oxigenized muriatic acid gas brought 

 into contact with it in narrow tubes acts upon it in the 

 same manner as the liquid acid : but if the two gasses be 

 mixed in a wide jar, the whole of the arsenic is instantly 

 converted into arsenious acid, appearing as a white va- 

 pour ; 



