EVOLUTION OP GASES FROM HOMOGENEOUS LIQUIDS. 259 







investigations also point to the conclusion that the rate of decomposition of ammonium 

 nitrite in solution, into nitrogen and water, is also conditioned by the presence of free 

 nitrous acid. The decomposition of potassium chlorate into potassium chloride and 

 oxygen has been studied by TEED and P. F. FEANKLAND with DINGWALL,* whose 

 investigations were published while the present research was being carried on. The 

 results show that of the two changes commonly represented in the text-books, namely 



(i.) 2KC10 S = KC10, + KC1 + 2 ; 

 (ii.) KC10 4 = KC1 + 2O 2 



the former at the temperature of boiling sulphur is incomplete, not more than 6 '3 to 

 876, instead of 13'05, parts of oxygen being evolved for every 100 parts of potassium 

 chlorate originally taken. FRANKLAND and DINOWALL noticed that when the chlorate 

 is mixed with half its iveight of powdered glass the decomposition of the chlorate 

 according to equation (i.) is practically realised. The effect of certain metallic oxides 

 in favouring the evolution of oxygen from potassium chlorate has been studied by 

 W. A. MILLER and by MERCER. The former writes.t " Other oxides produce a similar 

 effect (to that of manganese peroxide) ; thus, I find when the chlorate is mixed with 

 ferric oxide it requires a temperature of about 260 C., with plumbic oxide a somewhat 

 higher temperature is needed, whilst magnesia and zinc oxide do not aid the decom- 

 position at all. I have found also that powdered glass and pure silica are equally 

 inert." 



Mr. HARCOURT, in the course of his investigations on the rate of chemical change 

 made several years ago, studied the decomposition of hydrogen peroxide into water 

 and oxygen, of ammonium nitrite in aqueous solution into water and nitrogen, 

 of oxalic acid into carbonic oxide, carbonic anhydride, and water, and of the formation 

 of nitric oxide from a gently warmed mixture of potassium nitrate, ferrous sulphate, 

 and dilute sulphuric acid. The observations made in the course of these unpublished 

 investigations, and those especially on the effect of roughened surfaces on the decom- 

 position of hydrogen peroxide, led to several experiments detailed in this paper, and 

 will be alluded to in the sequel. 



III. The Apparatus used. 



The method adopted in most of the experiments for collecting a definite quantity of 

 gas, taken as the measure of the velocity of the chemical change, may briefly be 

 designated " the tivin \J-tube method." Though described in my paper "On the Rate of 

 Decomposition of Ammonium Nitrate," it will be convenient here to add a brief des- 

 cription. The apparatus consists of two inverted U-tubes (U fig. 1, page 288), made 



* ' Chem. Soc. Jonrn.,' 1887, pp. 274-286. 

 t ' Elements of Chemistry,' fifth edition, vol. 2, p. 847. 

 2 L 2 



