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Mr. C. Tomlinson on the Action of Solid Nuclei [Jan. 21, 



suspended in hot oil are said to have been raised to from 110° to 1/8° C. 

 without boiling ; but the moment they were touched with a solid they burst 

 into steam. Porous bodies acted best because, it is said, they carried down 

 air to the globules. 



Such is a very brief notice of a few of the numerous memoirs that have 

 been published on the subject of boiling. The writers are all more or less 

 disposed to adopt the following conclusions: — (1) that liquids boil with 

 difficulty, or produce only sudden flashes of steam, as soon as the air which 

 had been dissolved in them is expelled by heat ; (2) that those liquids that 

 have the weakest affinity for air, such as sulphuric acid, alcohol, ether, &c, 

 boil with the greatest difficulty ; (3) that the adhesion of the liquid to the 

 vessel, and the mutual cohesion of its own molecules, cause the liquid to 

 boil in bursts, and produce souhresauts ; (4) that the action of solid sub- 

 stances in preventing souhresauts is by carrying down air. 



My object in introducing a new set of experiments on boiling is (1) to 

 show the action of solid nuclei in liberating vapour from liquids at or near 

 the boiling-point ; (2) to define the conditions under which souhresauts 

 take place ; and (3) to show what is the best remedy for the same. 



Definition.— & liquid at or near the boiling-point is a supersaturated 

 solution of its own vapour, constituted exactly like soda-water, Seltzer-water, 

 champagne, and solutions of some soluble gases. 



Action of Nuclei. — If the above definition be admitted, the behaviour of 

 solid substances in liberating vapour on some occasions, and remaining 

 "inactive" on others, becomes clear. If the solid be chemically clean, the 

 solution of vapour will adhere to it as a whole, and there will be no libe- 

 ration of vapour. If, on the contrary, the solid be unclean, the adhesion 

 between the vapour and the solid will remain the same as before, while the 

 adhesion between the liquid and the solid will be more or less diminished, 

 according to the nature of the impurity and the liquid operated on ; and 

 hence there will be a separation of vapour. 



But not only is it necessary to distinguish bodies as chemically clean or 

 unclean, but also as porous or compact. The same force by which one 

 volume of charcoal absorbs 98 volumes of ammoniacal gas, enables charcoal 

 and some other porous bodies, when thrown into a boiling liquid, to sepa- 

 rate the vapour from it, and thus to act as most efficient nuclei. 



The liquids operated on were water, alcohol, ether, wood-spirit, naphtha, 

 carbonic disulphide, benzole, paraffine oil, oil of turpentine, rosemary, and 

 a few other essential oils. 



The liquids with low boiling-points are convenient for illustrating the 

 phenomena in question. Any one of them in a tube about one-third or one- 

 half filled may be raised to the boiling-point by putting the tube into hot 

 water contained in a six- or eight-ounce German flask standing on the ring 

 of a retort-stand. The tube should fit loosely into the neck, and rest on 

 the bottom of the flask. In reheating the water a small spirit-lamp flame 

 may be applied, not directly under the tube, but on one side of it, the 



