24 Mr. Grove on the Decomposition of Water by Heat. 



by electrolysis : no change in properties was perceptible in 

 the oxygen after its exposure to the ignited wire. This con- 

 traction I incline to attribute to a slight portion of hydrogen 

 present, which view will, I think, be considered as strengthened 

 by the effect of the ignited wire on hydrogen, to be presently 

 detailed. I at one time thought that the contraction might be 

 due to a slight oxidation of the wire, but it never went beyond 

 a very limited point; nor was the wire altered in size or weight, 

 though it was kept ignited for many hours. 



Chlorine over water gave dense white fumes; a grayish- 

 yellow insoluble powder accumulated on the sides of the tube 

 near the platinum wire, which appeared of the same nature 

 as the vapours ; the deposit was insoluble in cold nitric, sul- 

 phuric, or muriatic acid, but dissolved by the last when boiled. 

 The fumes did not, as far as I could judge, affect litmus paper ; 

 a barely perceptible tinge of red was indeed communicated to 

 it, but this, I had every reason to believe, was attributable to 

 a slight portion of muriatic acid not absorbed by the water. 

 I have not yet woi'ked out this result, as it is probable, con- 

 sidering the number of experiments that have been made on 

 heated chlorine, that it is a known product, though I cannot 

 find, in several books to which I have referred, any substance 

 answering to it in description, and the field opened by voltaic 

 ignition is so new that each result demands a separate and 

 prolonged examination ; if I find that this is an unknown 

 compound I shall probably resume its investigation*. 



Cyanogen gave, though in very minute quantities, a some- 

 what similar deposit, but at its then very high temperature it 

 began to act rapidly on the mercury, and I was obliged to 

 give up the experiment after an hour's ignition. Both these 

 gases require peculiar and novel apparatus for examination 

 by voltaic ignition. It will presently be seen that my whole 

 attention and disposable time were necessarily occupied with 

 certain phaenomena to which this class of experiments ulti- 

 mately led me. 



Hydrogen gave a very notable contraction, amounting in 

 some cases to one-tenth of its volume. This was an unex- 

 pected result, and I examined it with care. It took place 

 both over water and over mercury; rather more with the 

 former than with the latter. It obtained equally with hydrogen 

 procured by electrolysis from carefully distilled water and pure 

 sulphuric acid ; with that procured from common zinc and 

 pure sulphuric acid diluted with distilled water; and with 

 that obtained from distilled zinc and pure diluted sulphuric 

 acid. The contraction was less when the water from which 

 * See Supplemental paper. 



