DR. EDWARD C. EDGAR ON THE ATOMIC WEIGHT OF CHLORINE. 3 



DIXON and EDGAR, burning hydrogen in chlorine, found the equivalent of chlorine 

 to be 35'4630'0019 from their nine experiments. 



The concordance of the two sets of experiments is thus exceedingly close, and the 

 number 35'462 may be taken as representing the result of the whole work'. 



On the other hand, NOTES and WEBER* have recently effected a complete 

 quantitative synthesis of hydrogen chloride by passing a known weight of hydrogen 

 over weighed potassium chlorplatinate, noting the loss in weight of the salt, and 

 condensing and weighing in water the hydrogen chloride formed. The mean number 

 they have thus obtained for the atomic weight of chlorine is 35'4520 - 0008 

 (H = 1-00762). 



In view of the promised recalculation of the Atomic Weights by the International 

 Committee, I have not attempted to correlate my results with the recent determi- 

 nations of silver, nitrogen and chlorine. 



The inception of this work is due to Prof. DIXON, and I gladly take this opportunity 

 of thanking him for the searching, yet kindly, criticism to which he has subjected 

 these experiments. 



To the Government Grant Committee I am indebted for two grants, which have 

 largely covered the cost of the apparatus employed. 



PART II. DETAILS OF EXPERIMENTS. 



1. Preparation of Hydrogen. The preparation of hydrogen and its occlusion in 

 palladium have been fully described in the previous paper, t The only alterations I 

 introduced in the arrangement of the apparatus were these : Four phosphorus 

 pentoxide drying tubes instead of three were used, and a water reservoir was attached 

 to one arm of the electrolysis vessel. The whole apparatus, including the bulb 

 containing palladium, was made of boro-silicate glass. 



In the preparation of the hydrogen, the gas passed through two U tubes containing 

 platinised pumice, kept at 400 C., instead of 220 C., to remove any oxygen diffusing 

 from the + electrode. 



The purity of the hydrogen is evidenced by the fact that the residual gases from 

 the combustion of all the hydrogen about 15^ grammes burnt in my eight 

 experiments and of the corresponding weight of chlorine yielded less than half a cubic 

 centimetre of nitrogen. If it be assumed that all this nitrogen came from the 

 hydrogenised palladium bulb (which is not likely), the maximum weight of nitrogen 

 present in the hydrogen was 1 part in 25,000. 



2. The Palladium Bulb. The palladium bulb, of which a sketch is given in fig. 1, 

 differed little from that described in the former paper. It was made of boro-silicate 

 glass, and terminated, not in a jet, but in the inner portion of a ground joint. 



* 'Jour. Amer. Chem. Soc.,' 30, 13, 1908. 

 t 'Phil. Trans.,' 1906, vol. 205, p. 172. 

 B 2 



