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VI. On certain Phenomena of Capillary Attraction exhibited 

 by Chloroform, the Fixed Oils, and other Liquids : with an 

 inquiry into some of the causes which modify the form of the 

 mutual surface of two immiscible liquids in contact with the 

 walls of the vessel in which they are contained. By William 

 Swan, F.R.S.E., Teacher of Mathematics, Edinburgh*. 



DR. GEORGE WILSON has recently noticed a curious 

 class of phenomena depending upon capillary attraction, 

 which he has described in a paper which will appear in the 

 Quarterly Journal of the Chemical Society of London for July 

 1848. The following are the principal facts he has observed. 



When chloroform, bisulphuret of carbon, Dutch liquid 

 (C 4 H 4 Cl 2 ), bromine, and several of the volatile oils whose 

 specific gravity is above 1*000, are placed in glass vessels 

 under water or acids, they assume a highly convex surface ; 

 while, on the other hand, under solutions of potash, soda or 

 ammonia, their surface is sensibly flat. The object of this 

 paper is to describe some results of a similar nature which I 

 have obtained with other liquids, and also to inquire into the 

 probable cause of the phasnomena which have been observed. 



Before attempting any explanation of the flattened surface 

 of chloroform under alkaline solutions, it was natural to ascer- 

 tain whether its surface might be considered as absolutely flat, 

 or only apparently so ; and at Dr. Wilson's request I under- 

 took the examination of this point. Perfect flatness was 

 scarcely to be expected ; for among all possible relations of 

 the mutually attractive forces of the two liquids and the walls 

 of the containing vessel, the chance was evidently small that 

 the particular relation necessary to produce a perfectly flat 

 surface should actually exist; and even supposing the requi- 

 site conditions to be fulfilled, the slightest particle of foreign 

 matter adhering to the glass might vitiate the result. 



In order to avoid any fallacious appearances which might 

 arise from the irregular transmission of light through ordinary 

 glass vessels, I ground the ends of a tube of glass, about an 

 inch in length and half an inch in internal diameter, and ce- 

 mented to them pieces of parallel plate glass by means of 

 Canada balsam. The axis of the tube being placed horizon- 

 tally, it was half-filled with chloroform, and solution of caustic 

 potash was added. On looking through the glass plates, the 

 surface of the chloroform was seen to be sensibly flat, except 

 close to the glass, where it was convex. At the points of 

 contact of the tube with the glass plates the surface was con- 

 cave; but this reversal of its curvature was evidently due to 

 * Communicated by the Author. 



