226 Royal Society : — Mr. Tomlinson andYan der Mensbrugglie 



seven-atom salt at the bottom of the flask was moved over the flame 

 of a spirit lamp in a line from the bottom of the flask to the neck, so 

 as to heat one part only of the flask. The only effect was to convert 

 a portion of the surface of the seven-atom salt into the anhydrous ; 

 but there was no crystallization. After some hours the anhydrous 

 portion had again taken up its water of crystallization. 



Experiment 3. A solution of 2 salt to 1 water that had been 

 in the open air during twenty-four hours was uncovered, and water 

 nearly boiling was dropped upon it. A slight cloudiness came over 

 the solution, but there was no crystallization. 



Next day a very weak solution of Glauber's salt nearly boiling 

 was dropped upon the surface, with no nuclear action. 



Experiment 4. An eight-ounce globular flask had the globe filled 

 with a solution of 2 salt to i water. Solutions of two difi'erent strengths, 

 namely 1 salt to 1 water, and 3 salt to 1 water, at a nearly boiling 

 temperature, were dropped upon it, but with no nuclear action. 



Experiment 5. A solution of 1 salt to 1 water had filtered into 

 it a nearly boiling solution of 3 salt to 1 water. The drops descended 

 to the bottom of the flask in beautiful rolling rings, but there was 

 no nuclear action. 



Experiment 6. The neck of a flask was inclined over the flame 

 of a spirit-lamp, so as to boil the upper part of the solution, while 

 the lower part remained cold. Water was driven off in vapour, so as 

 to leave a crust of salt in the neck. This, when the flask was left to 

 itself, gradually absorbed moisture and trickled down, and was also 

 washed down into the solution ; but there was no nuclear action either 

 from this or from the heat. 



These experiments on the action of heat lead to the conclusion 

 that, however much it may diminish the superficial tension of the 

 solutions, it does not apparently disturb the state of supersaturation. 

 This result may be explained by reference to the feeble tension of 

 the solution ( = 4), and to the fact that heat locally applied does not 

 greatly diminish it. Moreover heat tends to oppose crystaUization 

 by increasing the solubility. 



Numerous experiments were tried as to the action of newly sub- 

 limed camphor and benzoic acid on the solutions. The flasks con- 

 taining these bodies floating on the solutions were plugged with cotton- 

 wool and kept for some months, during which time they were re- 

 peatedly shaken ; but there was no separation of salt. The camphor 

 and benzoic acid formed weak solutions with the supersaturated 

 solutions ; but the tension of camphorated water being = 4*5, and 

 that of an aqueous solution of benzoic acid falling within the limits 

 4 and 5*2, the diff'erence 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 quan- 

 tity, 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 Hquids. As to 



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