236 Intelligence and Miscellaneous Articles. 



ness, becomes plane, loses its sharpness, is progressively effaced ; 

 at last the liquid entirely disappears. The tube then appears 

 filled with a homogenous body which henceforth resists all pressure 

 as a liquid would do. 



If now the pressure be slowly diminished, at a pressure which 

 is constant for determinate temperatures the liquid suddenly re- 

 appears ; a thick mist is produced, which expands, vanishes in a 

 moment, and marks the level of the liquid which has just re- 

 appeared. 



The following numbers indicate the course of the phenomenon : — 

 The mixture operated on being formed of approximately 5 vols, of 

 carbonic acid and 1 vol. of air, the liquid carbonic acid reappears at 

 a tin. 



132 at the temperature of -J- 5*5 



124 „ „ 10 



120 „ „ 13 



113 „ „ 18 



110 „ „ 19 



The carbonic gas compressed above 350 atm. 



is no longer liquefied at 21 



This phenomenon of the disappearance of the liquid cannot be 

 explained by the heat which the compression evolves ; for in this 

 experiment the tube dips in water, which keeps it at a constant 

 temperature, and the compression takes place with sufficient slowness 

 for the cooling to be always complete. 



In reality every thing goes on as if at a certain degree of com- 

 pression the carbonic acid spread into the gas which surmounts it, 

 producing a homogeneous body without sensible alteration of 

 volume. There is therefore nothing to prevent us from assuming 

 that the gas and the liquid have dissolved in one another. I have 

 essayed to verify this hypothesis by colouring the liquefied carbonic 

 acid. Of all the substances tried, iodine alone could be dissolved 

 in the acid ; but, unfortunately, in this experiment the mercury is 

 rapidly attacked, and the phenomenon is immediately masked by 

 the iodide of mercury which is deposited on the wall of the tube. 



It might, however, be supposed that the disappearance of the 

 liquid is only apparent, that, the index of refraction of the com- 

 pressed air increasing more quickly than that of the liquid carbonic 

 acid, a moment arrives when, the two indices becoming equal, the 

 surface of separation between the liquid and the gas ceases to be 

 visible. But if the pressure of the system were then augmented 

 by some hundreds of atmospheres, the surface separating the gas 

 from the liquid would become again visible, the index of refraction 

 of the gas continuing, by hypothesis, to increase more rapidly than 

 that of the liquid. 



Now the experiment, tried up to 450 atmospheres, gave only 

 negative results. We may, then, suppose that under high pres- 

 sures a gas and a liquid can be dissolved in one another so as to 

 form a homogeneous whole. — Comptes Renclus de VAcademie des 

 Sciences, Feb. 2, 1880, t, xc. pp. 210, 211. 



