PROTIUM DEUTERIUM TRITIUM TAYLOR 123 



the evolved hydrogen (containing deuterium) and oxygen gases are 

 recovered as water and passed back to the preceding stage of elec- 

 trolysis. The experimental arrangement is shown in plate 2. The 

 successive stages handle successively smaller volumes of water, the 

 concentration of deuterium in which rises by steps from 1 percent 

 to 4, 13, 35, 95, and 100 percent D2O. The electrolytic fractionation 

 factor is about 5, that is to say, the gas evolved is about one-fifth 

 as concentrated in deuterium as the water from which it is evolved. 

 Hence the separation that is achieved. 



The product has unique and characteristic properties. Its density 

 relative to ordinary water at 25° C. is 1,1079. It melts at 3.82° C. 

 and boils at 101.42° C. It has a maximum density, not at 4° C. as 

 with ordinary water, but at 11.6° C. It is 25 percent more viscous 

 than ordinary water at 20° C. but has a smaller surface tension. 

 Salts are less soluble in it by about 10 percent, and the electrical 

 conductance of salt solutions is less than in light water. 



There are three kinds of hydrogen molecules that can arise from 

 light and heavy hydrogen atoms, namely, H2 molecules, Do molecules, 

 and the mixed molecule HD. To analyze mixtures of such gases a 

 special mass spectrograph has been developed by Dr. Bleakney, of 

 the Princeton Physics Department. It is evident that the molecules 

 just discussed will give rise to ions of masses 2a(H2"^), 3a(IID'"), 

 and 4a(D2''). In addition to these, atomic ions of masses 1 and 2 

 (H"" and D"") can also arise and, from these, triatomic ions (IIHH'^) 

 of mass 3, (HHD^) of mass 4, (HDD^) of mass 5 and (DDD^) of 

 mass 6. Bleakney's method permits him to sort out these various 

 possibilities so that he can estimate how much protium (H) and 

 how much deuterium (D) is present in a given sample. Figure 1 

 shows the results of one such analysis of a deuterium-rich sample. 



Using such a method of analysis it has been found that the deute- 

 rium content of normal rain water is 1 part in 5,000 of the total hydro- 

 gen present. This is a much greater abundance of deuterium than is 

 present in the chromosphere of the sun as spectra at the last eclipse 

 definitely showed ; it points to a tremendous preferential loss of light 

 hydrogen during the earth's formation. The announcement by Lord 

 Rutherford of the synthetic production of hydrogen of mass 3, tritium 

 (T) by bombardment experiments of deuterium with highspeed 

 deutons lent considerable interest to a determination by the Princeton 

 Physics Department of the tritium content of the purest deuterium 

 oxide water prepared in the Frick Chemical Laboratory. With a new 

 and specially refined mass spectrograph it has now been shown that 

 our purest heavy water contains approximately 1 tritium to 200,000 

 deuterium atoms. This means that, in ordinary water, the tritium con- 

 tent is not more than 1 part in a billion. Tritium, therefore, becomes 

 the youngest and rarest of all the isotopes yet discovered in naturally 



