1873.] 



Supersaturated Saline Solutions. 



211 



not have been derived from the walls of the flask, because the solution 

 had been briskly boiled in it, so that steam escaped with considerable 

 force from the neck after the small beaker had been put on. Hence 

 I am compelled to fall back on my former statement * — namely, that the 

 oil acted as a nucleus by the flattening of one or more of the globules 

 against the wall of the flask into the form of film. 



A globular flask, containing the same solution and the same oil, was 

 corked, and the oil dispersed in globules. It was left some hours, with 

 occasional shaking, so as to rattle the solution against the side. The 

 rattling motion was purposely less energetic than in the former case, 

 to avoid splashing against the cork. This solution crystallized after 

 it had been left a short time at rest ; and it did so in large flat crystals, 

 described in my second paper, very different from the minute radial ac- 

 tion noticed when crystallization sets in from a point t. 



A similar flask, containing the same solution, was treated with oil of 

 bergamot, a drop of which was allowed to trickle down the side of the 

 flask. As soon as the oil touched the solution, crystallization set in, 

 the radiant-point coinciding with such point of contact, and the whole 

 surface was covered with fine lines diverging from this point alone. 



In another case a drop of the oil of rosemary was deposited on the 

 centre of the solution. On shaking the flask, the solution assumed the 

 solid state. 



Two flasks, containing the same solution, crystallized under the influ- 

 ence of oil of lavender. 



Tive flasks, with the same solution, crystallized under the action of 

 sperm-oil. 



Experiment 2. Sodic sulphate — 2 salt, 1 water. In three flasks the 

 solution crystallized on the addition of olive-oil, the first immediately, and 

 the other two after being shaken. 



Experiment 3. Sodic sulphate — 3 salt, 1 water. This solution crys- 

 tallized under the action of the oils of bergamot, almonds, colza, rape, and 

 sesame. 



Experiment 4. Sodic sulphate — 3 salt, 1J water, in six flasks, all of 

 which crystallized under the action of sesame oil. 



Experiment 5. Potash alum — 8 salt, 3 water. The solution crystal- 

 lized suddenly, as with a flash, on being shaken up with oil of olives. 

 This is the more remarkable, as the usual action of a nucleus is to pro- 

 duce a solitar} 7 " octahedron, which grows rapidly until the solution becomes 

 solid. This last effect was produced by a less violent shaking of the solu- 

 tion in contact with oil of lavender. 



Experiment 6. Ammonia alum — 8 salt, 7 water. On shaking the 

 solution with olive-oil it suddenly became solid, and of an opaque chalky 

 white. 



This selection from a large number of experiments may be sufficient to 

 * Phil. Trans. 1871, p. 52 et seq. t Ibid. p. 54. , 



