170- PEOFESSOE H. B. DIXON AND ME. E. C. EDGAE 



found 100 of silver equal to 69'119, and in his latest work to 69'123 of potassium 

 chloride. Therefore, although STAS' value 35'457 (0 = 16) is in satisfactory agreement 

 with CLARKE'S value 35 '447 re-calculated from all the best determinations, it is 

 possible that some constant error may occur in some part of the long chain connecting 

 the value of hydrogen with that of chlorine, an error which would be repeated from 

 link to link, and would become evident only when the two ends of the chain were 

 connected up. 



A direct comparison between hydrogen and chlorine might not only serve to detect 

 any systematic error in this chain of ratios, but such a comparison, inasmuch as it 

 does not involve the probable error of other ratios, would be cceteris paribus more 

 exact. Again, the closing of the chain between hydrogen and chlorine with 

 reasonable accuracy would permit the accidental errors to be distributed and prevent 

 their accumulation at the unconnected end. The accumulated "probable error" in 

 CLARKE'S recalculated value for chlorine is '0048 ; the " probable error" of our nine 

 experiments is '0019. 



The suggestion to carry out this work was made to us by Professor EDWARD W. 

 MORLEY, who happened to visit our laboratories when pure chlorine was being 

 prepared by the electrolysis of fused silver chloride. He suggested that we should 

 burn weighed hydrogen and chlorine in a closed vessel, just as he had burnt weighed 

 hydrogen and oxygen. After some discussion we decided to make the attempt an 

 attempt which was rendered possible by the fact that one of us was enabled, by a 

 research scholarship, to devote his whole time to the investigation. 



A year was spent in designing, making and testing the several parts of the 

 apparatus. In the second year we put together the pieces and carried through 

 preliminary experiments, which led to some modifications and further trials. In the 

 third year the apparatus was got into Avorking order and the determinations made. 

 After the three years' work we are painfully aware how far our attempt falls short of 

 the precision of Professor MORLEY'S own determination, but the relation we have found 

 between hydrogen and chlorine seems worthy of record on account of the directness 

 of the method of comparison. 



Our method was, briefly, as follows : Chlorine prepared by the electrolysis of 

 fused silver chloride (with purified carbon poles in a Jena-glass vessel) was condensed 

 and weighed as a licpuid in a sealed glass bulb. This was attached to a vacuous 

 " combustion globe " and the chlorine allowed to evaporate slowly .nto the globe. 

 The hydrogen prepared by the electrolysis of barium hydrate was dried and absorbed 

 by palladium in a weighed vessel. The palladium on being warmed gave off the 

 hydrogen, which was ignited by a spark and burnt at a jet in the combustion globe 

 previously filled with chlorine. The gases were regulated so as to maintain the 

 hydrogen flame until nearly all the chlorine had been combined ; then the palladium 

 was allowed to cool and the hydrogen was turned off just before the flame died out. 

 The hydrogen chloride, as it was formed in the flame, was dissolved by water standing 



