480 



Prof. Dewar on Solid Hydrogen. [Apr. 6, 1900. 



Densities. 



Liquid 

 Melting-point. 



Hydrogen 



Nitrogen 



Oxygen 



0-OSG 



11 



1-27 



Gas, 

 3000 Atmospheres. 



Limiting Value, 

 4000 Atmospheres. 



0-097 

 0-833 

 1127 



0-12 

 0-12 

 1-25 



It will be noted that the density of gaseous hydrogen at 8000 

 atmospheres is actually greater than the maximum density of the 

 liquid state ; but neither in the case of nitrogen nor oxygen does 

 the density at the same pressure reach the fluid density. Amagat's 

 limiting vulue for oxygen under 4000 atmospheres would, however, 

 be almost identical with mine. 



During the courso of my inquiries sufficient data have been ac- 

 cumulated to coustruct Waterston Formulae giving the approximate 

 densities of liquid hydrogen, nitrogen and oxygeu in each case through 

 a wide range of temperature. The equation for each substance 

 is given in the following tahle : — 



Liquid Atomic Volumes. 



Hvdrogen = 23-3 - 8-64 log (32° - t) 

 Nitrogen =30-0-11-00 log (127° - 

 Oxygen = 32-6 - 10-22 log (155° — t) 



Atomic volume of hydrogen 



Absolute Observed at 

 Zero. Melting-point. 



= 10-3 



nitrogen .. .. = 12 "8 

 oxygen =10-20 



11-7 



13-1 

 12-0 



From these formulae we find the respective hypothetical atomic 

 volumes of hydrogen, nitrogen and oxygen at the absolute zero to bo 

 10*3; 12*8 and 10*2. My observed minimum fluid volumes were 

 11*7; 13 and 12*6. The coefficients of expansion of the liquids, 

 taken in the same order at their respective boiling-points are 0*024 ; 

 0*0056 and 0*0046. Thus liquid hydrogen has a coefficient of expan- 

 sion five times greater than that of liquid oxygen. Further inquiry 

 will enable the constants in these equations to be determined with 

 greater accuracy. In the meantime, however, they give us general 

 ideas of the order of magnitude of the quantities involved. 



I have to thank Mr. Robert Lennox for efficient aid in the arrange- 

 ment and execution of the difficult experiments you have witnessed. 

 Mr. Heath has also heartily assisted in the prej)arations. 



[J. D.] 



LONDON : PRINTED BY WILLIAM CLOWES AND t~ONS, LIMITED, 

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