1902.] Chemical Change, Electrical Conduction in Gases, etc. 99 



using phenol phthalein as indicator. In Experiment 7 the solution 

 was mixed with excess of caustic soda before warming it to decompose 

 the per-salts, and the excess was subsequently determined. No 

 hydrogen peroxide was present except in solution 5, in which case the 

 amount was determined by permanganate and allowed for. 



The following are the results obtained in terms of decinormal 

 solutions : — 



Caro's acid. Perdisulphuric acid. Acid liberated. 



Found. Calculated. 



1 41-54 1-05 22-1 21-8 



II 38-8 5-91 26-6 25-3 



III 35-0 2-77 20-2 20-3 



IV 39-24 2-24 21-3 21*8 



V 37-3 1-56 21-5 20-2 



VI- 49-8 3-43 28-7 28*3 



VIII 23-3 0-71 12-2 12-4 



" The Conditions determinative of Chemical Change and of 

 Electrical Conduction in Gases, and on the Phenomena of 

 Luminosity." By Henry E. Armstrong, V.P.E.S. Eeceived 

 March 13— Eead May 1, 1902. 



In his communication to the Chemical Society on the union of 

 oxygen and hydrogen, read at the meeting on February 19,* Mr. H. 

 Brereton Baker has added another to his brilliant series of proofs that 

 interactions supposed to take place between two substances are in 

 reality of a more complex character ; and having successfully demon- 

 strated, in the case of the gases referred to, that water alone does not 

 determine the interaction, he has, I believe, carried the investigation 

 to the final stage which it was essential it should reach to make it a 

 complete discovery of the nature of the process. 



Mr. Baker has shown that when a mixture of hydrogen and oxygen 

 [most carefully prepared by electrolysing a solution of barium hydrate] 

 is enclosed in a chamber of hard Jena glass [cleansed in the most 

 careful manner possible], and the mixture is dried as thoroughly as 

 may be [by means of phosphoric anhydride which has been carefully 

 purified by distilling it in a current of air], no appreciable interaction 

 takes place between the gases, even on heating the tube to redness. 

 If the drying be not carried too far, however, water is gradually but 

 very slowly formed — finally in sufficient quantity to be visible : and 

 yet, even when water is visibly present, no explosion takes place. 



The interpretation I would give of these observations is as follows : — 

 * ' Chem. Soc. Proc., 5 1902, p. 40. 



