346 Messrs. C. Tomlinson and G. Van der Mensbrugghe [May 16, 



water being =4*5, and that of an aqueous solution of benzoic acid falling 

 within the limits 4 and 5 % the difference in tension is too small to produce 

 a rupture of equilibrium. The same remark applies to a solution of soap 

 and of bicarbonate of soda, which had no nuclear action. 



Action of Vapours. — It has been shown by recent researches that the 

 presence of vapours in the air of a room, even in minute quantity, has a 

 marked influence in lowering the tension of water and other liquids, so as 

 to account for the discordant values of various careful measurements of the 

 capillary heights of such liquids. As to the nuclear action of the vapours 

 of certain volatile liquids upon supersaturated saline solutions, many obser- 

 vations had been made by one of us, leading to the conclusion that such 

 vapours are strongly nuclear when they become condensed into the form of 

 films on the surface of the solutions, as when the latter is of a lower tem- 

 perature than the former. In order to ascertain whether vapours, as such, 

 that is, without forming films, have any nuclear action, the following ex- 

 periments were contrived. The vapour was presented to the surface of the 

 solution by means of a bit of sponge tied to the end of a glass rod, wetted 

 with the volatile liquid and carefully passed down the neck of each flask, 

 so as to avoid touching the side, and bringing the sponge close upon the 

 surface to avoid touching that also*. The sponge was held over the solution 

 several minutes, then carefully withdrawn and the flasks covered, leaving 

 the interior charged with vapour. The liquids used were ether, absolute 

 alcohol, chloroform, bisulphide of carbon, wood-spirit, and benzole. The 

 solutions were of all three strengths, and the temperature from 40° to 47° F. 

 After many hours and even days the flasks had a strong odour of the 

 vapours in question, but there was no separation of salt. 



Vapour of camphor was also tried in the following manner : — 



Experiment 7. A quantity of camphor was placed in a small retort, the 

 beak of which, made chemically clean by being heated in the flame of a 

 spirit-lamp, was passed into a flask containing a solution of 2 parts salt 

 to 1 of water. The camphor in the belly of the retort was then boiled so 

 as to produce a powerful jet of vapour upon the surface of the solution. 

 The camphor condensed upon such surface in the form of a fine white 

 powder without any nuclear action. 



In this case a portion of the vapour of camphor or of the powder would 

 dissolve in the solution without producing in it a notable diminution of 

 surface-tension. The same remark applies to the other vapours, to the 

 action of solid camphor and benzoic acid, of heat, &c. 



So also, as stated in Part II., glycerine mingles with the solution without 

 any nuclear action. Now the surface-tension of glycerine =4*2 ; so that it 

 can have no effect in lowering the surface-tension of a solution =4, and does 



* In a few cases the wet sponge did touch the solution for an instant, so as to take 

 up a small portion, which immediately crystallized upon the sponge ; but the crystalli- 

 zation thus produced, not being in contact with the solution, the latter retained its 

 liquid state. 



