M. Donny on the Cohesion of Liquids. 293 



the salt ceased to lose weight, it was thereafter found to con- 

 sist of — 



Experiment. With one equivalent of 

 , • ■ A • > water. 



Sulphate. of zinc . 20-42 89*20 90*03 



Water .... 2'46 10-75 9-97 



22-88 100- 100- 



It is sufficiently evident, therefore, that sulphate of zinc, 

 which is admitted by M. Pierre to contain seven equivalents 

 of water, retains one equivalent of water by a stronger affinity 

 than the other six, contrary to his observation ; while, more- 

 over, this strongly retained atom of water is absent in the 

 double sulphate of zinc and potash, the last containing only 

 six atoms of water — the experimental data on which the view 

 of the constitution of these salts controverted by that chemist 

 is founded. 



XLVIII. On the Cohesion of Liquids and their Adhesion to 

 Solid Bodies. By M. F. Donny, Agrege a V Universite de 

 Gand, Pre'parateur du Cours de Chimie. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



THE twenty-sixth volume of your valuable Magazine 

 (p. 541) contains an account of two communications 

 made by Prof. Henry to the American Philosophical Society, 

 on the 5th of April and 17th of May 1844, both relative to 

 the cohesion of liquids. 



I have been investigating the same subject from the begin- 

 ning of 1841 to the end of 1843, when I gave a full descrip- 

 tion of my experiments on cohesion and adhesion in a written 

 communication addressed to the Academie Royale de Brux- 

 elles. The reception of this memoir is recorded in the Bul- 

 letin de la Seance du 2 Decembre 1843 (tome x. p. 457), and 

 the memoir itself is printed in the Memoires Couronnees et des 

 Savants Etra?igers, tome xvii. I beg leave to direct your at- 

 tention to the contents of this communication. 



Having discovered, in 1841, as Prof. Henry did in 1844, 

 that the cohesion of liquids is a powerful attraction, entirely 

 misrepresented in the works on natural philosophy, I en- 

 deavoured to find out the cause of this misrepresentation. 

 With this object I constructed a very simple instrument, which 

 enabled me to observe accurately how the separation of water 

 from water is effected, in the well-known experiment of a 



X2 



