158 Intelligence and Miscellaneous Articles* 



When the gas is one which is very soluble in the liquid, we can, 

 by operating in tubes prepared as I have indicated, bring the solu- 

 tions to a pressure sufficiently feeble, or to a temperature high 

 enough, for the quantity of gas held by the liquid to be very con- 

 siderably more than the normal quantity. If a gaseous atmosphere 

 be then introduced to the interior of the liquid, a sort of ebullition 

 will be determined. The experiment can very readily be realized 

 with ammonia solution. The ordinary solution is put into a pre- 

 pared tube, surrounded with a freezing-mixture, and is satu- 

 rated by passing for a long time a current of gaseous ammonia. 

 The tube containing the solution is then taken out and allowed to 

 return to the surrounding temperature, say, of 20° C. ; no gas is 

 liberated within the liquid ; but if the end of a glass tube, formed 

 at the lamp into a small bell, containing air be put into it, ammonia 

 gas escapes in that atmosphere, and seems to issue from the bell, 

 in bubbles the more frequent the more pronounced the supersatu- 

 ration. In this case the experiment resembles the ebullition excited 

 in a liquid by the same process. Besides, when after some time it 

 slackens, the liberation of the gas is made more active by raising the 

 temperature a little, 



In the Note above mentioned, I had already compared the pheno- 

 menon in question to the decomposition, under the same influence, 

 of substances such as oxygenated water. The preparation of very 

 concentrated oxj^genated water being a delicate thing to execute, 

 I will indicate how a known reaction (studied formerly by Schon- 

 bein*) may easily be made use of for the same demonstration. 



Into a glass tube from 6 to 20 millims. in diameter, closed at one 

 end, and recently prepared as I have said above, from 5 to 10 cen- 

 tims. depth of distilled water is introduced, having been filtered to 

 rid it of the solid particles held in suspension. The tube is cooled 

 to zero ; and then some liquid hyponitric acid, previously cooled, is 

 dropped in. This liquid, gliding along the side of the tube, passes 

 through the water without liberating any gas, and collects at the 

 bottom of the tube in the form of a blue liquid which is regarded 

 as containing nitrous acid ; at the same time nitric acid remains in 

 solution in the water. The tube can then be taken out of the freez- 

 ing-mixture and allowed to return to the surrounding temperature, 

 of 15° for example, without a single bubble of gas escaping from 

 the interior of the liquid. Tubes thus prepared I have kept 15 

 days in a medium the temperature of which has varied from 7° to 

 15° : the blue liquid had been gradually diffused, without liberation 

 of gas, in the superposed layer of water, a certain thickness of 

 which remained colourless. If a body without chemical action 

 upon nitric acid, and disaerated, such as a platinum wire which has 

 been used for some minutes to maintain the ebullition of some 

 water, be introduced to the surface of the lower layer of the liquid, 

 it produces no effect upon it ; whiJe the otter end of the wire, 

 which has not been cleared of the adhering layer of air, is hardly 

 brought into contact with the nitrous acid before it excites an abun- 

 * Pogg. Ann. vol. xl. p. 382. 



