264 



ISOTOPIC TRACERS AND NUCLEAR RADIATIONS 



[Chap. 8 



review by Urey and Teal [20], in which references to the original data may 

 be found. The values for density and the temperature of maximum density 

 have been changed in accordance with more recent data [30-32]. 



Water has its maximum density at 3.98°C. The volume of 0.001 liter of 

 water at this temperature is, by definition, 1 milliliter. Density measure- 

 ments are commonly expressed as grams of weight per milliliter and there- 

 fore are called "density (or specific gravity) relative to water at 4°C." The 

 notation d\ signifies that the weight of a given volume at the temperature 

 indicated by the superscript is referred to that of water at 3.98°C, and there- 

 fore also indicates the weight per milliliter directly. These values are slightly 

 different from those of absolute density, which conform to the cgs system 

 and express density as grams of mass per cubic centimeter. Similarly, the 

 notation d\\ indicates that the weight of a certain volume of the sample at 

 25°C is referred to that of the same volume of water at 25°C. 



Table 28. Some Properties of H 2 and D 2 

 Abstracted from Urey and Teal [1935], [20]. 



Property 



Density, d\\ 



Temperature of maximum density 



Molar volume at temperature of maximum density. 



Surface tension 



Viscosity in millipoises: 



10°C 



20°C 



30°C 



Refractive index, 20°C Na D line 



Melting point 



Boiling point 



H,0 



D 2 



* More accurate values than in original table [30-32]. 



The molar volume is, of course, the volume of a gram-molecular weight. 

 If the molar volume of deuterium oxide and water were equal, the d\\ of 

 deuterium oxide would be 1.1116 instead of 1.10764. 



Table 29 presents the combined data of Longsworth [33], Swift [31,34], 

 and Tronstad et al. [30], with Longsworth's values for mole fraction recalcu- 

 lated to conform to a pure deuterium oxide d\\ of 1.10764. The values 

 of d\ b are the experimental values obtained by Swift and by Longsworth. 

 The corresponding dll's were calculated from these. The final column 

 gives the density of each dilution at its temperature of maximum density. 



These data may be used to show that D2O-H2O mixtures form almost 

 ideal solutions, i.e., there is a negligible volume change upon mixing (the 

 density of an ideal solution is not necessarily a linear function of the mole 



