522 



On the Limit of the Liquid State. [Mar. 10, 



curves have been drawn to show the slight depression of the critical 

 temperature with increase of pressure, and these lines have been con- 

 tinued down the curve of vapour pressure to show the break at the 

 critical point." This will be clearly seen in the annexed fig. 1. 



The consideration of these results yields a novel mode of looking at 

 the states of matter which I have shown at fig. 2. From this, it 

 appears we might classify matter under four states : First, the 

 gaseous, which exists from the highest temperatures down to an 

 isothermal passing through the critical point, and depending entirely 

 upon temperature or molecular velocity. Second, the vaporous, bounded 

 upon the upper side by the gaseous state, and on the lower by absolute 

 zero, and depending entirely upon the length of the mean free path, 

 because shortening of the mean free path alters the state. Third, the 

 liquid state, bounded upon the upper side by the gaseous, and on 

 the lower by the solid or absolute zero. Fourth, the solid state. 



Fig. 2. 



The gaseous state is the only one which is not affected by pressure 

 alone, or in which the molecular velocity is so high that the collisions 

 cause a rebound of sufficient energy to prevent grouping at any pres- 

 sure. Another distinction between the gaseous and vaporous states 

 is, that the former is capable of acting as a solvent of solids, while the 

 latter has not that power. 



The two conclusions arrived at are : — 



" 1st. The liquid state has a limit which is an isothermal passing 

 through the critical point. 



" 2nd. The vaporous state can be clearly defined as a distinct state 

 of matter." 



