480 Intelligence and Miscellaneous Articles. 



from the part which has not been heated. I have made spongy pla- 

 tinum inactive by plunging it red-hot into boiling water which had 

 been for some time kept boiling. 



IV. Solid bodies which have not been in contact with air are 

 without action on supersaturated gaseous solutions. 



When a fragment of any salt, soluble or not, is immersed in a su- 

 persaturated gaseous solution (of alum, for instance, in Seltzer water), 

 carbonic acid is disengaged. Is this effect due to the presence of the 

 solid body ? The following experiment shows that it is not. 



A supersaturated solution of alum is prepared and placed in a 

 tube ; when it is cooled, Seltzer water is carefully poured on it, 

 forming on its surface a distinct layer. A fine rod is then taken, the 

 end of which has touched a piece of alum, and it is dipped through 

 the Seltzer water as far as the supersaturated solution of alum ; an 

 octahedron of alum forms on the rod and rapidly increases ; on re- 

 moving it and placing it in Seltzer water, no disengagement of gas 

 is perceived on its circumference. 



V. Air and gases set up the disengagement of dissolved gases. 

 The preceding experiments show that the disengagement of gas is 



not to be ascribed to solids. On the other hand, bodies which have 

 become inactive by a lengthened stay in water or by the action of 

 heat, and those which, like the crystal of alum, had not been in con- 

 tact with air, resume the property when they have been in the air for 

 some time. This result led me to inquire what was the action of air on 

 the gaseous solution ; and with this view, in a supersaturated aqueous 

 solution of carbonic acid, I introduced an almost capillary tube, closed 

 at one end, and inverted like a gas-jar, and containing air. I had 

 previously deprived this tube of the property of setting up a disen- 

 gagement of gas. Immediately after immersion, gas adhered to the 

 column of air which the tube contained, forming quickly a large 

 bubble, which was disengaged; then another was produced, and so 

 on. The gas formed, then, only at the point where the liquid touched 

 the column of air. From this experiment, which I have varied in 

 several ways, it may be concluded that air sets up the disengagement 

 of carbonic acid. Now, in the case of supersaturated saline solutions 

 and of superposed solids, I have proved that a molecule of the sub- 

 stance itself, or one isomorphous with it, is necessary, in determinate 

 conditions of temperature, for setting up the separation. Was there 

 here something analogous, and was it the carbonic acid of the air 

 which acted on the aqueous solution ? in other words, had the na- 

 ture of the gas any influence on the phenomenon ? To clear up this 

 point I varied the gaseous solutions, and used a supersaturated so- 

 lution of nitric oxide along with atmospheric air. Experiment showed 

 that the phenomenon was still produced, although no trace of nitric 

 oxide can exist in air. Hence the nature of the gas does not come 

 into play in these phenomena, and supersaturated solutions lose their 

 gas under the influence of any gas-bubbles whatever. 



Now, how is it that solid bodies which have been exposed to the 

 air produce in gaseous solutions the effects they are known to pro- 

 duce ? It may be accounted for if we remember that a solid, whatever 



