HEAT OR CALORIC. 



9. AERIFORM STATE DEPENDENT ON PRESSURE. 



FIG. 1. 



Proof that some Liquids would always be aeri- 

 form, were it not for the Pressure of the 

 Atmosphere. 



"A glass flask, fig. 1, being nearly filled 

 with water, and having the remaining space 

 occupied by sulphuric ether, is inverted in a 

 glass jar, covered at bottom by a small quan- 

 tity of water, to prevent the air from entering 

 the neck of the flask. The whole being placed 

 upon the air pump plate, under a receiver, 

 and the air exhausted, the ether assumes the 

 aeriform state, and displaces the water from 

 the flask. Allowing the atmospheric air to re- 

 enter the receiver, the ethereal vapor is con- 

 densed into its previous form, and the water 

 reoccupies its previous situation in the flask." 



FIG. 2. 



" The return of the ether, to the fluid state, 

 is more striking, when mercury is employed, as 

 in fig. 2 ; though, in that case, on account of 

 the great weight of this metallic liquid, the 

 phenomenon cannot be exhibited on so large a 

 scale, without endangering the vessels, and 

 risking the loss of the mercury."* 



* It is pleasing to see so dense a fluid as mercury, especially as it is also brilliant 

 andopake, becoming a truly transparent, invisible, and elastic vapor, and then by a 

 slight depression of temperature, returning again to the fluid state. The boiling of 

 the mercury in the thermometer ball and tube, during the construction of that in- 

 strument, exhibits this fact in perfection. 



