BRIDGMAN. — WATER UNDER PRESSURE. 



511 



-5 



h 



<: 



LiJ-15 

 Q. 



:e 



-20 



•25 



These were 9/16 inch o. d. and about 3/64 inch thickness of wall. 



In fact, it seems rather surprising that 



the effect did not prove troublesome on 



more than these two occasions. 



The regular apparatus for the middle 



temperature range was used in finding 



these points. Some skill in manipulation 



was necessary to arrive on the curve at all. 



The procedure was to start with the water bJ 



impregnated with glass splinters and raise § "10 



the pressure at a temperature somewhere 



between —10° and —20°. On sufficiently 



overpassing the unstable VI-L curve, VI 



would separate out. After some little 



while V would appear. With the first 



signs of its appearance, indicated by a rise 



of pressure, the pressure was increased as 



rapidly as possible, in a few seconds, to 



the V-VI curve, where the automatic 



change of volume was sufficient to ensure 



retaining of the equilibrium pressure after 



freezing of the remaining mass of liquid. 



This method of procedure was made neces- 

 sary by the fact that at the temperatures 



at which it is easy to obtain V, it is possi- 

 ble to pass from either side of the V-VI curve into the region of 



instability on the other side, without the reaction running. At higher 



temperatures, nearer the triple 

 point, it is not possible to carry 



V so far into the region of VI, 

 corresponding to the fact already 

 noted that at the triple point 

 itself it is impossible to carry 



V any distance at all into the 

 region of VI. 



The equilibrium pressures and 

 temperatures are shown in Table 

 XXIV. and Figure 28. The 

 equilibrium line is nearly at con- 

 stant pressure, but there is an 

 unmistakable though slight in- 

 crease of pressure at the higher temperatures. Within the limits of 

 error, the equilibrium curve is a straight line. 



6300 6400 . 



PRESSURE, KGM.CM? 



Figure 28. The equilib- 

 rium curve V-VI. 



-15 -10 



TEMPERATURE 



Figure 29. The change of volume 

 when VI passes to V. 



