190 Action of Solid Bodies on [Gaseous] Supersaturated Solutions. 



tuents is indeed always connected. Only in the case in which the 

 gas in solution unites chemically with the solid so as to form a 

 gaseous body, could there be a separation of gas-bubbles. 



There are many bodies which have for gases a strong conden- 

 sing force or power of absorption, such, for example, as charcoal 

 for carbonic acid. But their great porosity and numerous points 

 and roughnesses (which soon exhaust their absorbing powers) 

 render them scarcely available for experiments of this kind. I 

 have endeavoured to prepare a piece of charcoal by plunging 

 it red-hot into previously boiled water and keeping it immersed 

 some days with occasional heating. On plunging it into highly 

 impregnated water, only a few solitary bubbles appeared on its 

 surface, while a silver wire similarly immersed was completely 

 covered with them. The graphite from a common lead pencil 

 or roughly dressed strips of the same material prepared as 

 above, and plunged into the same highly impregnated solution 

 of carbonic acid, produced no bubbles, notwithstanding the 

 roughness of the surface. The non-appearance of the bubbles 

 can only be ascribed to the condensation of the gas within the 

 pores of the graphite. 



I have prepared the charcoal in another way, namely by tri- 

 turating it while thoroughly wet. The wet powder was then 

 shaken into a test-glass; and after standing some days, the su- 

 pernatant water was drawn off and soda-water carefully poured 

 upon it. The result was as before, scarcely a bubble was to be 

 seen ; while in another test-glass, which instead of charcoal- 

 powder contained the finest quartz sand, numerous bubbles ap- 

 peared on it ; and these being released by shaking, others took 

 their place. Pieces of stone-coal with brilliant surfaces and 

 one piece with polished sides were covered with bubbles. 



The remarkable condensation of the mixed gases on a clean 

 platinum surface, the condensation of oxygen alone, and even 

 the less marked condensation of hydrogen on such a surface, 

 may be made the subject of experiments with water sufficiently 

 impregnated with these gases. A small glass cylinder 9 centims. 

 in height and 1^ centim. in width, was one evening filled with 

 boiled water, and five or six drops of strong sulphuric acid added ; 

 a strip of zinc was then put in and the glass left in a cool place. 

 The gas came off so quietly that on the following day it was still 

 escaping. What was left of the zinc was taken out, and a well- 

 cleaned platinum and silver wire inserted. The platinum had 

 scarcely any action ; but numerous bubbles appeared on the silver 

 wire, the number and size of which increased, especially after 

 warming the glass, while on the platinum wire not a bubble was 

 to be seen. 



For the investigation of the first case (preponderance of attrac- 



