BRIDGMAN. — WATER UNDER PRESSURE. 



543 



> 



TEMPERATURE 



Figure 38. The relation 

 between voliune and temper- 

 ature for a normal liquid. 



the abnormality at low pressures followed 

 by normal behavior at high pressures. No 

 previous measurements seem to have been 

 made within this region, although the 

 principal effects are within the reach of 

 previously attainable pressures. At at- 

 mospheric pressure the study of water 

 at low temperatures is prevented by the 

 accident of freezing. It will pay us, how- 

 ever, to imagine what would be the relation 

 between temperature and volume on the 

 present theory of polymerization if it were 

 possible to subcool the water indefinitely. 

 At high temperatures we evidently expect 

 the water to behave normally, for its mol- 

 ecules are all single molecules of the same 

 kind, and similarly at very low tempera- 

 tures, where the molecules are all double 

 molecules, we should expect the behavior 

 to become normal again. The curve 

 connecting volume with temperature for a 



normal liquid is of the form shown in 

 Figure 38, the dilatation becoming 

 more rapid at high temperatures. 

 These considerations lead us to pre- 

 dict, therefore, a curve of the shape 

 shown in Figure 39 for water. Ex- 

 perimentally it has been found pos- 

 sible to follow this only as far as 

 —10°, not far enough to reach the 

 first point of inflection. The effect 

 of increasing pressure must be to 

 change in some continuous way the 

 curve of Figure 39 into that of 

 Figure 38. 



The data indicate very strikingly 

 the way in which the abnormality is 

 effaced. Figure 40 shows this. In 

 this figure the relation between vol- 

 ume and temperature for various 

 constant pressures is plotted directly from the data of Table XXXL 

 Each separate curve is drawn to scale, but the curves for different 



TEMPERATURE 



Figure 39. Hypothetical rela- 

 tion between volume and temper- 

 ature for liquid water if it could 

 be subcooled indefinitely without 

 freezing. 



