504 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



in the meantime the data required for the mercury paper were 

 finished. 



On taking the matter up again, the only difference that presented 

 itself between the two runs, one giving V and the other not, was that 

 in the former run water had been in the presence of glass. The appa- 

 ratus as set up again was 

 made to differ from the for- 

 mer set up, therefore, only 

 in the fact that splinters 

 of Jena chemical glass were 

 placed in the water, which 

 was again included in a 

 copper shell The very first 

 attempt at —10° was suc- 

 cessful. Pressure was in- 

 creased beyond the VI-L 

 line, the reaction VI-L had 

 started, and the equilibrium 

 pressure had been reached, 

 when the phase V put in an 

 appearance, displacing VI. 

 Briefly, the mere addition or 

 subtraction of the fragments 

 of glass appeared to be the 

 determining factor. When it was desired to work on VI in the sub- 

 cooled region, the glass was omitted ; when V was desired, the glass 

 was added. Even then the appearance of V was under surprising 

 conditions. V was never formed directly out of the water, but always 

 in the presence of the phase VI. Furthermore, V showed a preference 

 for appearing only when VI, water, and glass were present together, 

 usually during determinations of the equilibrium pressure Vl-water, 

 either during increasing or* decreasing pressure. The facility with 

 which V might replace VI was the source of some annoyance. Once 

 a day's work was lost because V had successfully come in without 

 being noticed V might, however, form directly fi:om the solid VI, as 

 described above. All this holds only for the initial appearance of V, 

 it being very much easier, as already explained, to produce it after it 

 had appeared once. It was possible in this way to get V to separate 

 directly from the liquid, if it had appeared recently before. 



Figure 23, plotting piston displacement against pressure, shows well 

 the way in which V might appear. With increasing pressure, the 

 water froze regularly to VI, as shown at A. The point F shows the 



PRESSURE. 



Figure 23. Shows the* way in which V 

 may appear. The dotted line C-D indicates 

 the sudden transition from VI to V. 



