DEEP-SEARADIUM 115 



a fair and nearly constant amount of dissolved 

 uranium — according to measurements by Berta Kar- 

 lik and others ^ about 1.3 X 10 '' gram of uranium per 

 liter of ocean water of normal salinity, 35% c.^ Ac- 

 cording to the "equilibrium ratio" t between uranium 

 and radium found in undisturbed rock samples, 

 U:Ra = 3,000,000: 1, there should be .6 X 10 ^^ 

 gram of uranium-supported radium present in each 

 liter of sea water. According to our measurements, the 

 average radium content of ocean water, which is more 

 variable with locality and depth than is the uranium 

 content, is only a fraction, on an average one-eighth of 

 the equilibrium value. In order to explain the relative 

 scarcity of radium in ocean water and its abundance in 

 deep-sea deposits the author in 1937 suggested that an 

 intervening element in the uranium-radium dynasty — 

 namely ionium, the immediate parent substance of 

 radium — is being removed from solution in sea water 

 through precipitation together with iron. From this 

 assumption it would follow that the precipitated ionium 

 will at its disintegration breed its offspring radium. 



* The usual abbreviation for expressing small fractions is 

 used here, viz. 1 x 10"'^ for units of the 6th decimal place, 

 or millionths, 1 X lO-^- for millionths of millionths, etc. The 

 notation 35%c may also be written 3.5% . 



t Radioactive equilibrium between succeeding members of 

 the same dynasty of radioactive elements is attained in the 

 course of time and is characterized by an equal number of 

 atoms from each element being born and disintegrated in a 

 unit of time. 



