DISCOVERY AND PROPERTIES OF BADIUM 149 



viz. the conversion of radium chloride into radium bromide by 

 heating it in a current of hydrogen bromide and vice versa ; 

 there was no transference and only gaseous reagents were used." 



The material used by Ramsay and Gray was obtained from 

 Cornish pitchblende through the Radium Corporation, and 

 consisted of 330 mgrms. of anhydrous radium barium bromide, 

 containing about 70 per cent of radium bromide. These bromides 

 were purified by the authors by treatment first with sulphuretted 

 hydrogen whereby a small black precipitate, probably lead 

 sulphide, was formed and removed. The solution was then 

 acidified with sulphuric acid so as to precipitate the sulphates, 

 which were dried and heated to redness in a mixture of carbon 

 tetrachloride vapour and gaseous hydrogen chloride, whereby 

 they were converted into chlorides. The chlorides were next 

 converted into bromides by heating to redness for some hours 

 in a current of hydrogen bromide. 



The bromides thus obtained were submitted to fractional 

 crystallisation whereby the barium was removed and the purified 

 radium bromide was divided into a number of separate portions 

 which were used for determining the equivalent. This was done 

 as already indicated by determining the loss 1 of weight which 

 ensued on converting a weighed quantity of bromide into 

 chloride, and the gain 1 on converting the chloride into bromide. 

 As the result of all this experiment, with the calculations follow- 

 ing, the final result for the atomic weight of radium was 226-36, 

 which is identical with the number found by Madame Curie. 



These then are some of the most striking facts which have 

 become known to us about radium, and during the first year or 

 two after the isolation of this curious substance no explanation 

 was forthcoming which seemed to satisfy both chemists and 

 physicists, for the simple reason that nothing of the kind had 

 previously been dreamt of in their philosophy. 



The results of Madame Curie's work showed that the pheno- 

 mena exhibited by radium salts were due not to the molecule as 

 a whole, but to the atom of the new element independently of 

 the other elements with which it was associated. Thus equivalent 

 quantities of chloride, bromide, and sulphate of radium show 

 equal activity electrically. 



It was immediately found that the radiations of radium are 



1 The quantities to be weighed being very small, usually 2 to 3 mgrm., a 

 special balance was used, one form of which was described, p. 78, Part I. 



