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XXIII. On the Action of Solid Bodies on [Gaseous] Supersatu- 

 rated Solutions. By F. C. Henrici*. 



NO. 52 of the Naturforscher (1869) gave a short account 

 of numerous experiments by Mr. Tomlinson on the action 

 of solids on supersaturated solutions, as brought before the Che- 

 mical Society. The views which Mr. Tomlinson has founded 

 thereon, and which in their exposition called forth some objec- 

 tions, do not appear to me to follow from the phenomena ; and 

 as some experiments of my own strengthened my objections, I 

 determined to investigate the matter fully. I have limited my 

 numerous experiments to gas-impregnated water, a limitation 

 which can have no injurious effect on the inquiry. 



It is necessary first of all to define accurately what we mean 

 by a supersaturated solution. If we consider how difficult it is 

 to free water from air, even by boiling or by the action of the 

 air-pump, there must evidently be between air and water an at- 

 traction, or so-called adhesion. The volume of air in solution 

 must depend on this adhesion, and also on the atmospheric pres- 

 sure at the time. The temperature has also considerable influ- 

 ence, since heat diminishes the adhesion and increases the ex- 

 pansive force of the air-molecules. There is also under the 

 given conditions an equilibrium of pressure between the exterior 

 and the dissolved air, which does not exist when these conditions 

 are wanting. Hence, if the water contain too little air, it will 

 absorb more, and in the opposite case part with it. In the 

 latter case, therefore, the water is supersaturated with air, which 

 is nearly always the case with spring-water. As respects gases 

 which are not found in the atmosphere, or only in minute quan- 

 tities (such as hydrogen, carbonic acid, and ammonia), the equi- 

 librium of pressure does not obtain. Each of these gases, with 

 respect to the quantity brought into contact with water, pro- 

 duces supersaturation more or less. 



With respect to equality of pressure, the air particles in a gas- 

 holding liquid are under the same conditions in all directions. 

 If supersaturated, air particles continually escape from the sur- 

 face, and others follow from the interior, their tendency to expand 

 being thereby assisted. But this condition is entirely changed 

 when the continuity of the liquid is interrupted by a solid body, 

 as indeed it already is by the boundary walls of the containing 



* Translated by Charles Tomlinson, F.R.S., from Poggendorff's Annalen, 

 No. 12 (1872). The translator has made a number of critical remarks on 

 this interesting paper, which he proposes to send in time for the April 

 Number of the Philosophical Magazine. In the mean time he begs to refer 

 to two papers by him on the same subject in the Philosophical Magazine 

 for August and September 1 867- 



