yU REPORT— 1888, 



purpose four bulbs were filled witli a mixture of hydrochloric acid and 

 oxygen ; a known quantity of chlorine was added to three of them. The 

 four bulbs were exposed for the same length of time and the chlorine was 

 then estimated, when it was found that the mixture to which no free 

 chlorine had been added contained 75 "9 per cent, free chlorine, whilst the 

 bulbs containing free chlorine in the first instance gave 100"93, 105'37, 

 and 1:'7"29 per cent, of free chlorine. Further experiments are being made 

 in this direction ; it appears, however, likely that the presence of chlorine 

 renders the mixture less transparent to those rays which promote the 

 oxidation of the acid. 



Influence of bromine. — A weighed quantity of bromine was added to a 

 mixture of hydrochloric acid and oxygen, and exposed in bulbs, together 

 with those just described; when the gas was analysed it was found that 

 onlylO'85 percent, of chlorine had been liberated in one bulb, and 5'05 per 

 cent, in the other (the latter contained a larger quantity of bromine). It 

 does not appear likely that this retarding action of the bromine can be due 

 to its union with the chlorine liberated m the presence of excess of hydro- 

 chloric acid, and it will be interesting to observe the influence of bromine 

 vapour on the oxidation of hydrobromic acid. 



Influence of moisture. — It has already been stated that a mixture of 

 dry hydrochloric acid and oxygen is unacted on in sunlight, and it was 

 at first supposed that the partially dry mixture was completely stable in. 

 the light ; at has, however, been found that a very prolonged exposure 

 brings about slow oxidation, the rate depending on the amount of 

 moisture present. The results obtained after four months' exposui'e 

 show that when two-thirds of the gas was dried 236 per cent, of chlorine 

 is set free ; when one-third only of the gas was dried 42'8 per cent, is 

 liberated ; in the case of both gases saturated, as nearly as possible, 88 per 

 cent, of chlorine is liberated. 



Decomposition of chlorine water. — Experiments have been made on 

 the action of light on chlorine water and chlorine and aqueous vapour; 

 the results given on Table III. show that the amount of decomposition 

 increases wiiii the volume of water taken ; the ultimate strength of acid, 

 however, varies in each case, becoming more concentrated as the volume 

 of water taken diminishes. On the other hand, the volume of oxygen 

 set free diminishes with the water. With a dilute solution of chlorine 

 water the decomposition is arrested by a comparatively large volume of 

 oxygen acting on a weak solution of acid ; with a strong solution a small 

 volume of oxygen is tending to decompose a concentrated acid. These 

 results can be represented graphically in the form of a curve by mapping 

 the percentage of combined chlorine found after exposure against the 

 volume of water taken. 



Chlorine gas and water vapotir. — A known volume of carbon dioxide 

 saturated with water vapour was mixed with enough chlorine to theore- 

 tically decompose all the water ; after exposure for thirty-three days l'3f» 

 per cent, of chlorine had been converted into hydrochloric acid. In a 

 second experiment oxygen was substituted for carbon dioxide. In this 

 case 3 per cent, of chlorine was found to be present as chloride. 



Further experiments are being made in which a large volume of moist 

 gas is taken, the gas being only partially saturated, as it is possible 

 that condensation took place on the sides of the flask. 



Some preliminary experiments have been made with chlorine water 

 exposed to light in coloured solutions. From these it appears that decora- 



