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 LXII. Intelligence and Miscellaneous Articles. 



ON THE DISENGAGEMENT OF GASES FROM THEIR SATURATED 

 SOLUTIONS. BY M. GERNEZ. 



r PHE researches I have for some years pursued on supersaturated 

 saline solutions have led me to investigate the supersaturated 

 solutions of gases in certain liquids. Solutions of this kind are easily- 

 obtained. The gas may be dissolved in water under a definite pres- 

 sure, and the temperature then be gradually raised ; and if (as is ge- 

 nerally the case) the gas is less soluble at a higher temperature, the 

 solution remains for some time supersaturated ; or the pressure may 

 be diminished without altering the temperature, and the liquid re- 

 tains the gas dissolved for some time. Under these circumstances, 

 if the solution is thrown into any vessel, a multitude of gas-bubbles 

 are seen to form on the sides, which increase there, then rise 

 through the liquid and burst on the surface. A solid body introduced 

 into the liquid is in like manner surrounded by gas-bubbles. There 

 is no one who has not observed this phenomenon with solution of 

 carbonic acid, whether as Seltzer water, or in an alcoholic liquid in 

 the state of sparkling wine. The formation of gas-bubbles is gene- 

 rally attributed to the roughnesses of solid substances wetted by the 

 liquid, and the following explanation of it is given : — A molecule of 

 gas in the solution is equally acted on by all the liquid molecules 

 uniformly distributed about it, and there is no reason for its disen- 

 gagement. Near the side, on the contrary, it is on the one hand at- 

 tracted by the liquid, and on the other by the solid molecules : these 

 latter, it is assumed, act less energetically than the others, and hence 

 the predominating action causes it to take the gaseous state ; it is 

 thus the layer in contact which will abandon the dissolved gas. 

 Solid bodies introduced into the liquid act in the same manner. The 

 attentive investigation of the phenomenon has led me to observe that 

 this view of it is contradicted by experiment. 



I. Solid substances round which are disengaged bubbles of gas 

 lose this property after some time. 



I bring any solid rod into a supersaturated solution; and it becomes 

 covered with gas-bubbles. I stir it to facilitate their rising ; new 

 bubbles form, in less quantities. After several operations of this kind 

 all disengagement ceases ; the solid no longer acts ; but if the por- 

 tion of the rod hitherto not immersed be plunged into the liquid, it 

 produces an effervescence. 



II. A lengthened immersion of a body in the water deprives it 

 of action. 



A body which has been for a long time in water becomes inactive, 

 while the part of the same substance which has remained outside the 

 liquid is immediately covered with gas-bubbles on immersion. 



III. Solids lose the property under the influence of heat. 



Heat produces the same effect as continued contact with water. 

 A metal rod passed for a few seconds through a spirit-lamp soon 

 becomes inactive ; thus, of a platinum wire which sets up a brisk 

 effervescence, the part heated has no effect, and the gas only starts 



