266 LIQUEFACTION OF HYDROGEN AND HELIUM. 



and measuring the gas produced, thereby ascertain iug its weight. In 

 this way 8.15 liters at 14° 0. and 753 millimeters were collected over 

 water from between 9 and 10 cubic centimeters of liquid hydrogen. 

 It appears, therefore, that the density of the liquid is about 0.07, using 

 whole numbers as the calculation works out to 0.068 nearly. Liquid 

 hydrogen is therefore a very deceptive fluid so far as appearance goes. 

 The fact of its collecting so easily, dropping so well, and having such a 

 well-defined meniscus induced me to believe that the density might be 

 about half that of liquid air. It was a great surprise to find the density 

 only one-fourteenth of water. Liquid marsh gas was the lightest known 

 liquid, the density at its boiling point being 0.417, but liquid hydro 

 gen has only one-sixth the density of this substance. The density of 

 occluded hydrogen in palladium being 0.62, it is eight times denser 

 than the liquid. 



Hydrogen in the liquid state is one hundred times denser than the 

 vapor it is giving off at its boiling point, whereas liquid oxygen is two 

 hundred and fifty-five times denser than its vapor. It appears, therefore, 

 that the atomic volume of liquid hydrogen at its boiling point is 14.3, 

 as compared with 13.7 for oxygen under similar circumstances. In 

 other words, they are nearly identical. From this we can infer that the 

 critical pressure need not exceed 15 atmospheres. The extraordinary 

 properties theory requires hydrogen should possess, especially as regards 

 specific and latent heat, become more intelligible from the moment we 

 know that the density is so small. In other words, when we compare 

 the properties of equal volumes of liquid hydrogen and air under similar 

 corresponding temperatures, they do not differ more than might be 

 anticipated. 



