360 Further Experiments and Observations on Iodine. 



gas in water is formed, and it is slowly decomposed by heat alone, 

 affording a deep red-brown easily fusible substance^ which seems 

 to be a compound of hvdroionic gas and iodine. 



When condensed in water, it is instaritl)- decomposed by so- 

 lution of nitric acid and iodine precipitated. 



The sohition of hydroionic acid rapidly absorbs oxygen Irom 

 the air, and becomes yellow, and at last deep tawny orange ; 

 and this absorption is assisted bv light and heat, the hydrogen 

 is attracted by the oxygen to form water, and the iodine formed 

 is dissolved in the remaining acid. 



The concentrated hydroionic acid will probably form a good 

 eudiometrical substance ; it does not render the vessels in which 

 it is used cloudy like the hvdrosulphurets by the deposition of 

 solid matter, and it does not enlarge the volume of the residual 

 air like some other substances. 



The solution of the hydroionic acid is decomposed by being 

 heated with the hAperoxymuriate of potassa, and iodine is pro- 

 duced. 



Hvdroionic acid gas, as I have mentioned in my last paper, 

 is decomposed by all the metals I have exposed it to, except 

 gold and platinum ; and the same metals that decompose it in 

 its ga?eous state, likewise decompose it when it is in solution, 

 requiring, however, in some cases, the assistance of heat. The 

 fluid hydroionic acid tarnishes silver at common temperatures, 

 and dissolves mercury slowly when boiled in contact with it. 



2. It dissolves the alkaline and common earths, and forms 

 with them compounds very analogous in their properties to the 

 compounds they produce when acted on by muriatic acid. 



I heated dry quick -lime in a small tube filled with hydroionic 

 acid gas, a yellow fluid immediately formed, which was coloured 

 by dissolving hydroionic gas and iodine, and a fusible compound 

 soluble in water, and which had a bitter taste similar to muriate 

 of lime, was produced. 



I made the same compound by dissolving marble in the hy- 

 droionic acid ; the compound when heated to redness became 

 fluid, and when kept in fusion in contact with air eu^.itted iodine, 

 gradually lost it fusibility, and from being neutral became alka- 

 line, so that at a high temperature iodine is partly expelled 

 from calcium by oxygen. I proved this still moie distinctly by 

 fusing the compound in a close vessel, in which it v.as confined 

 by mercury. There vvas no change. I admitted a little oxy- 

 potassame, and caused it to give off oxvgen by heating it : as 

 soon as the calcareous compound was fused in contact with oxy- 

 gen, it instantly emitted iodine, and lime vvas formed on the sur-- 

 face. 



The compound'^formed from hydroionic acid and baryta is an 



acrid 



