certain High-temperature Boiling-points. 



151 



10. Table V. contains results for bismuth. In the first 

 part of the Table temperature does not change with pressure. 

 Hence a boiling-point is not reached. In the second part of 

 the Table temperature certainly oscillates with pressure. 

 Hence the temperature corresponding to the lower values of 

 pressure (3 centim. to 4 centim.) are boiling-points. The 

 temperature corresponding to the higher values of pressure 

 (9 centim. to 10 centim.) are below the corresponding boiling- 

 points ; for I found that on further increasing pressure the 

 temperature did not increase. The temperatures observed 

 are therefore the limit of the heating-power of the furnace. 

 At least 5 minutes must be allowed for each observation. 

 The top of the crucible should be filled with asbestos to 

 diminish loss of heat by radiation. 



Table Y. — Boiling-points of Bismuth. 



P. 



T. 



P. 



T. 



P- 



T. 



centim. 



°C. 



centim. 



°C. 



centim. 



°C 



26 



1152 



3-2 



1199 



95 



1236 



5-8 



1164 



86 



1211 



3-4 



1207 



26 



1165 



97 



1207 



4-0 



1217 



8-1 



1182 



3-2 



1206 



9-7 



1260 



8-8 



1186 



37 



*12 2 



3-4 



1206 



2-7 



1183 



4-2 



1215 



39 



1221 



98 



1194 



37 



1247 



96 



tl258 



2-4 



1186 



39 



1213 



3-3 



1215 







3-4 



1204 



42 



1233 



* Flame intensified ; B.P. criterion satisfied, 

 t Limit of burner-power. 



11. In the above Tables I. to V., the criterion of boiling- 

 point has been change of temperature with pressure. When 

 this was not observed the data were rejected. The method 

 of obtaining low boiling-points from liquids is a priori ob- 

 jectionable, because of the liability to superheating. In 

 special measurements made with zinc*, however, I found the 

 error thus introduced to be negligible. There seems to be 

 less superheating in case of metals and high temperatures, 

 supposing the temperature of the environment to be reason- 

 ably near the boiling-point (say 200° or 300° above it) . In 

 case of bismuth and metals of higher boiling-points, the 

 difficulties of experiment are such that I do not think a 

 capacious vapour-bath for low pressures feasible. 



Experiments with antimony failed from breakage of 

 crucible. 



* Bull. U.S. G. S. no. 54, pp. 108, 109, 1889. 



