1872.] 



on Supersaturated Saline Solutions. 



345 



Experiment 1. Four flasks, each about half full of a supersaturated 

 solution of Glauber's salt (2 salt to 1 water), were exposed to a tempera- 

 ture of 32° F. for an hour. A red-hot poker was then passed down the 

 neck of each flask, and in two of them the hot metal was brought into 

 contact with the surface of the solution so as to raise a volume of vapour. 

 There was no separation of salt in any one case. 



Experiment 2. A solution containing a considerable mass of the 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 1 water. Solutions of two different 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 ab- 

 sorbed 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 with 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 crystallization by increasing the solubility. 



Numerous experiments were tried as to the action of newly sublimed 

 camphor and benzoic acid on the solutions. The flasks containing these 

 bodies floating on the solutions were plugged with cotton-wool and kept for 

 some months, during which time they were repeatedly 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 



