938 



ADVENTURES IN RADIOISOTOPE RESEARCH 



ScHOENHEiMEE,, whosG Untimely and tragic death is much to be de- 

 plored. The discussion of the numerous important results obtained by 

 ScHOENHEiMEE and RiTTENBERG and their collaborators*^*^ lies, how- 

 ever, beyond the scope of this lecture. 



HEAVY WATER 



In 1931, Urey discovered deuterium, an isotope of hydrogen. ^^^^ 

 This important discovery made possible the labelling of hydrogen. 

 Deuterium is not an ideal indicator, its properties differing appreciably 



60 



80 



100 



120 



mm. 



jTjct, 2. — Percentage distribution ratio of labelled sodium, potassium 

 and deuterium oxide between plasma water and muscle water of 



equal weight. 



from those of hydrogen. The latter has a unique position : it is the 

 sole element met with, though only transitorily, as a naked nucleus in 

 chemical reactions. Chemical forces do not suffice to remove all electrons 

 from any other element. Differences in the structure of the nucleus will 

 therefore make themselves more noticeable in the chemical behaviour of 

 hydrogen isotopes than in the case of any other element. Furthermore, 

 the difference between the mass of the hydrogen atom and that of the 

 deuterium atom amounts to as much as 100 per cent, while, for example, 



