54 



The Boiling Point of Liquid Hydrogen. 



The following table shows what alterations would be required for 

 each of the thermometers, in the values of t, P, P , and x to alter the 

 boiling point of oxygen or that of hydrogen by 1/10 or 1/100 of a 

 degree. The table is calculated for t = 13° ; and in the cases of P and 

 P the initial pressure is taken to be about 1/wth of an atmosphere. 



Table II. 





Thermometer 

 No. 1. 



Thermometer 

 No. 2. 



Alteration 

 of T. 





fat B.P. of .. 

 .at B.P. of H .. 



8*° 

 7i° 



6° 

 17° 



1 9 

 100 



H 



'at B.P. of . . 

 , at B.P. of H .. 



0-280 



mm. 



n 



0-285 



mm. 



n 



0-280 

 mm. 



n 



0-282 

 mm. 



n 



1° 



To 



H 



'at B.P. of .. 

 .at B.P. of H 



0-842 

 mm. 



n 



3-79 



mm. 



n 



0-839 

 mm. 



n 



3-76 



mm. 



n 



i° 



10 



H 



fat B.P. of 

 [at B.P. of H . . 



• 88 per cent. 

 2-57 



2 -00 per cent. 

 5 -81 



l ° 



100 



Thus, for example, if the initial pressure in either thermometer were 

 about half an atmosphere an error of 1/7 mm. in reading P would alter 

 T by a tenth of a degree. 



If we take the average values given by these experiments as being 

 the most probable, then the boiling point of oxygen is - 182° -5 and 

 that of hydrogen is - 252°-5, or 20 o- 5 absolute. The temperature 

 found for the boiling point of oxygen agrees with the mean results of 

 Wroblewski, Olszewski, and others. If the boiling point of oxygen is 

 raised to - 182°, which is the highest value it can have; then an equal 

 addition to the hydrogen value must follow, making it then - 252° 

 or 21° absolute. In a future communication the temperature of solid 

 hydrogen will be discussed. 



I am indebted to Mr. J. D. H. Dickson, M.A., of St. Peter's College, 

 Cambridge, for help in the theoretical discussion of the results, and to 

 Mr. Eobert Lennox, F.C.S., for able assistance in the conduct of the 

 experiments. 



