526 Mr. E. C. C. Baly on the 



This result very nearly lies on the curve of Olszewski's 

 smoothed results. 



The two points jt?=760 mm. T=77°'54 and p = 2805 mm. 

 T = 90 o, 96 were plotted by Ramsay and Young's method, and 

 the vapour-pressure curve drawn. 



The vapour-pressures of chemical nitrogen were also deter- 

 mined. These were carried out similarly to those of atmo- 

 spheric nitrogen with some intermediate points taken in 

 liquid air. The boiling-point was not actually measured 

 owing to the difficulty of preparing a sufficient quantity of 

 liquid chemical nitrogen. The Ramsay and Young ratios 

 were calculated and extrapolated to 760 mm., and from the 

 straight line the vapour- pressures were obtained. The values 

 obtained from the complete curve are given in the second 

 column. Olszewski's values are continued up to 12-4° 

 absolute. 



The measurement of the vapour-pressure of oxygen was 

 carried out very similarly to that of nitrogen. A large 

 quantity of liquid nitrogen was made, and a small bulb con- 

 nected with a, store of pure oxygen from KMn0 4 was sur- 

 rounded with it. When the bulb was about a quarter full of 

 liquid oxygen, it was connected with a gauge and the pressure 

 read. Two series of measurements were made with one prepa- 

 ration of oxygen, and a third with fresh oxygen prepared with 

 the greatest care. All three agreed absolutely to a tenth of a 

 millimetre. Great pains were taken with these measurements 

 on account of their disagreement with both Olszewski's and 

 Estreicher's. The result obtained was/>== 171* 7mm. T = 78°'08. 

 Olszewski's and Estreicher's measurements were about 157 mm. 

 at the same temperature. A very extraordinary faculty for 

 being superheated was shown by the liquid nitrogen in these 

 experiments. Although it was to all intents boiling, that is 

 to say it was in actual ebullition, the temperature was o, 8 

 above the true boiling-point. By dropping in pieces of copper 

 wire or glass the temperature at once fell to the normal 

 boiling-point, but if left the nitrogen rapidly superheated 

 itself, and the temperature rose to exactly the same point as 

 at first. It appears, therefore, that unless these liquefied 

 gases are in a state of extremely rapid ebullition, they become 

 superheated to a very considerable extent. This may possibly 

 be the explanation of Estreicher's and Olszewski's results for 

 vapour-pressures of oxygen being so much lower than the one 

 1 have obtained. It is true that Estreicher and Olszewski 

 agree very well in their values at low pressures, but this may 

 be quite easily accounted for, because they used the same 

 thermometer, and because in my results the superheating is 



