260 



SOLID HYDROGEN. 



volume — the nine hundred and ninety-nine being chiefly nitrogen — yet 

 the low temperature method of separation can be successfully applied. 

 Now that we know definitely the approximate values of some of the 

 more important physical constants of liquid hydrogen, it is interesting 

 to look back at the values that have been deduced — say for such a 

 constant as the density — by various workers using entirely different 

 methods. The following table gives some of the more important 

 values of the density of hydrogen under the different conditions in 

 which it enters into organic and inorganic bodies: 



Densitij of hydrogen in different conditions. 



Kopp Organic bodies 0. 18 



Amagat Limit of gaseous compression 0. 12 



Wroblewski Van der Waals's equation (critical density) ' 0. 027 



Van der Waals. .Superior limit of density 0. 82 



Graham Palladium alloy 2. 



Dewar Palladium alloy 0. 63 



Dewar Liquid hydrogen at boiling point 0. 07 



My density at the boiling point agrees substantially with that which 

 can be deduced from Wroblewski's form of the Van der Waals equa- 

 tion. The deduced densities of Kopp for organic bodies and Amagat 

 for gaseous compression are both about the same value, and may be 

 taken as a mean to be twice the observed density of hydrogen in the 

 liquid state. The conclusions of Graham and myself touching the 

 density of the hydrogen in the so-called alloy of palladium, must be 

 regarded as altogether exceptional. Even my value would exceed the 

 density of the stuff' constituting the real gas molecule, according to 

 the theory of Van der Waals. In order to harmonize the palladium 

 hydrogen results with those deduced from the study of organic bodies, 

 we must assume that, during the formation of the so-called hj^droge- 

 nium, a condensation of the palladium suflicient to increase its density 

 by one-fifth must take place. This is by no means an unreasonable 

 hypothesis. The mode of determining the density of hydrogen at its 

 melting point has been previously described, and found to be 0.086. 

 In the same way the approximate values for the densities of nitrogen 

 and oxygen at their melting points have been found, their respective 

 values being 1.07 and 1.27. The following table shows the compari- 

 son between my results and those given by Amagat for high gaseous 

 compressions: 



Densities. 



Hydrogen 

 Nitrogen . 

 Oxygen... 



Limiting 

 value 4,000 

 atmos- 

 pheres. 



0.12 

 0.12 

 1.25 



