ARSENIATED HIDROGEN GAS. fJQO 



cipitalion of metaliic arfenlc. The coUefled metal yielded 

 nitrous gas, by the affufion of nitric acid, and on adding to 

 this mixture muriatic acid, arfenic acid was produced. The 

 arfanic depofited in the manner ftated before, when laid on 

 ignited coals, became volalihzed in thick white fumes, yield- 

 ing arfenious acid. The precipitation of metallic arfenic mutt 

 be afcribed to the decompofition of the oxiginized muriatic aci4 

 gas; the oxigen of this gas uniting with part of the hidrogen 

 of the arfeniated hidrogen, and forming water, and thus fe- 

 parating the arfenic. For the arfenic is capable of being ox- 

 ided by the muriatic acid. Should it be imagined, that arfenic 

 esifted in arfeniated hidrogen, in the oxidized ftate, and that 

 it became precipitated by the oxiginized muriatic acid robbing 

 it of its oxigen, we fuppofe things analogically erroneous, for 

 the oxiginized muriatic acid rs more capable of giving out oxi- 

 gen than of taking it. The experiments of Chenevix feems 

 perhaps hofiile to this aflertion; but the experiments of this 

 philofopher merely prove that the oxiginized muriatic acid is 

 capable of combining with an additional dofa of oxigen, and 

 conftituting with it a hyperoxiginized muriatic acid. This 

 certainly cannot be the cafe in the prefent inftance, as will 

 appear more evident from what I (hall ftate prefently. 



I filled a cylinder in the mercurial pneumatic trough, with Further expcri- 

 arfeniated hidrogen, and fent up into it as expeditioufly as pof- ^"" w^ t^^'* 

 fible, a quantity ot oxiginized muriatic acid gas. 1 he relult fiiyer. 

 was evolution of heat, diminution of volume, and the inner 

 fides of the cylinder became covered with a kind of dew. A 

 formation of water had therefore a61ually taken place in this 

 experiment. Into another dry cylinder half filled over mer- 

 cury, with arfeniated hidrogen, I introduced dry muriatic 

 acid gas. In this cafe no diminution of bulk, no feparation 

 of arfenic enfued ; no change at all took place. Repeating the 

 fame experiment, I introduced into the cylinder a fmall quan- 

 tity of water; the muriatic acid gas was abforbed, and the re- 

 lidue was arfeniated hidrogen unaltered. 



Into a cylinder half filled with oxiginized muriatic acid gas, 

 I paffed gradually arfeniated hidrogen in fmall bubbles at a 

 time; in this cafe no metallic arfenic was feparated, but thick 

 white clouds appeared. On continuing the addition of arfe- 

 niated hidrogen till no more white fumes appeared, metallic 

 ffirfenic was depofited, Jt follows from this experiment, that 



when 



