ARSENIETTED HYDROGEN. 631 



Chlorides of arsenic. A ter chloride, As C1 3 , corresponding 

 with arsenious acid, is formed when arsenic is introduced into 

 chlorine gas, in which it takes fire and burns spontaneously. 

 The same compound is obtained by distilling a mixture of 1 part 

 of arsenic, with 6" parts of corrosive sublimate, as a colourless, 

 oily, and very dense liquid. It is resolved by water into arse- 

 nious and hydrochloric acids. A lower chloride of arsenic ap- 

 pears to be formed when a mixture of arsenic and calomel is 

 distilled ; it is obtained as a dark brown sublimate, mixt with 

 calomel. No chloride corresponding with arsenic acid is known. 

 The bromide of arsenic, As Br 3 , is formed by the direct com- 

 bination of its elements. The iodide of arsenic, As I 3 , is 

 formed, according to Plisson, by digesting 3 parts of arsenic 

 with 10 of iodine, and 100 of water, so long as the odour of 

 iodine is perceived. The liquid yields by evaporation red 

 crystals of the iodide. The fluoride of arsenic is obtained by the 

 distillation of a mixture of fluor spar and arsenious acid with 

 sulphuric acid. It is a fuming colourless liquid ; the density of 

 its vapour is 2730 (Unverdorben). 



Arsenic and hydrogen. A solid arseniuret of hydrogen was 

 obtained, by Davy, by using metallic arsenic as the negative 

 pole (the chloroid), in decomposing water. Gay-Lussac and 

 Thenard have also shewn that the same compound precipitates, 

 when arseniuret of potassium is dissolved in water. It is a 

 chestnut brown powder, which may be dried without change. 

 Its composition is not certainly determined. Arsenietted hy- 

 drogen, As H 3 , a gas analogous in constitution to ammonia, is 

 obtained by dissolving an alloy of equal parts of zinc and arsenic 

 in sulphuric acid, diluted with three times its weight of water. 

 It is a dangerous poison, when inhaled even in the most minute 

 quantity, and should, therefore, be prepared with the greatest 

 caution. The density of this gas is 2695, according to M. 

 Dumas. It is liquefied by a cold of 40. When passed 

 through a glass tube, heated to redness by a spirit lamp, this 

 gas is decomposed and deposits metallic arsenic. The flame of 

 this gas, when burned in air, also deposits metallic arsenic upon 

 a cold object exposed to it. No combination of arsenietted 

 hydrogen is known with either acids or bases. It precipitates 

 many of the metallic solutions, which are precipitated by sul- 

 phuretted hydrogen, but not oxide of lead ; its hydrogen alone 

 being oxidated by the common metallic oxides, and the arsenic 



