on Supersaturated Saline Solutions. 227 



the nuclear action of the vapours of certain volatile liquids upon su- 

 persaturated saHne solutions, many observations 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 temperature 

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

 (that is, without forming films) have any nuclear action, the following 

 experiments 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, avoiding also touching that"^. The 

 sponge was held over the solution several minutes, then carefully with- 

 drawn and the flasks covered, leaving the interior charged with va- 

 pour. 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 efl*ect in lowering the surface-tension of 

 a solution = 4, and does not sufficiently lov/er the tension of a solution 

 = 5*2 to produce a rupture of equilibrium. 



It was also stated that bisulphide of carbon ^ = 3 '3 to 3° 5, and 

 chloroform =2-98 to 3*12, formed lenses on the surface of the solu- 

 tion, and that on gently agitating the flask they fell to the bottom, 

 where they remained permanently without any luiclear action. Creo- 

 sote ( = 3) behaves in the same manner. Now, in any one of these 

 cases, the tension t-\-c must be greater than 4*5, and hence there 

 can be no separation of the salt. 



We now pass on to consider the second proposition — namely, that 

 if on the surface of a supersaturated saline solution there be depo- 



* 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 crystallization thus produced not being in contact with the solution, 

 the latter retained its liquid state. 



Q2 



