ON THE ATOMIC WEIGHT OF CHLORINE. 



171 



in the globe, which was kept cool by ice. A little hydrogen chloride was formed by 

 the action of the water-vapour on the chlorine in the flame, a corresponding amount 

 of oxygen being liberated. This oxygen was determined in the analysis of the 

 residual gases, which contained, besides traces of air, the small quantity of hydrogen 

 which filled the capillary tube between the tap and the jet when the flame was 

 extinguished, and any that might escape unburnt from the flame. 



The chlorine remaining in the globe unburnt, as gas and in solution, was determined 

 by breaking a thin glass bulb containing potassium iodide. The residual gases having 

 been pumped out (and any iodine vapour caught by a wash-bottle), the liberated 

 iodine was determined by standard thiosulphate in an atmosphere of carbonic acid. 

 In calculating the unburnt chlorine from the iodine, the atomic weight of chlorine 

 was assumed to be 35'195 and the atomic weight of iodine 126'015.* In each 

 experiment we burnt about 11 litres of hydrogen and 11 litres of chlorine. The 

 volume of chlorine left unburnt was about 2 per cent, of the volume burnt. 



The balance (by OERTLING) was fixed on a stone pedestal in an underground cellar. 

 The vibrations of the pointer were read by a telescope, GAUSS' method of reversals 

 being used. The chlorine and the hydrogen bulbs were counterpoised on the balance 

 by bulbs of the same glass and of nearly the same displacement, and the small 

 weights used in the weighings were reduced to a vacuum standard. 



In the following table are given the corrected weights of hydrogen and of chlorine 

 burnt in the several experiments the weights of hydrogen being rounded off to 



1 milligramme : 



TABLE I. 



In the whole of these experiments 9'1786 grammes of hydrogen combined with 

 323 "0403 grammes of chlorine ; hence the atomic weight of chlorine, calculated in mass, 

 is 35-195. 



* G. P. BAXTER, 'Proc. Amer. Acad.,' xl., 419. 

 z 2 



