IS 14.] Proceedings of Philosophical Societies. 22/ 



Article XII. 

 Proceedings of Philosophical Societies. 



IMPERIAL INSTITUTE OF FRANCE. 



Account of the Labours of the Class of Mathematical and Physical 

 Sciences of the Imperial Institute of France during the Year 1813. 



{Continued from p. 154.) 



Physics and Chemistry. By M. le Chevalier Cuvier. 



It will he seen in our analysis of 1S11 how hy accelerating 

 evaporation by a vacuum, and hy the presence of a body which very 

 readily absorbs water, Mr. Leslie, of Edinburgh, succeeded in 

 freezing water at all seasons of the year. This philosopher after- 

 wards contrived an apparatus, which was shown to the Class by M. 

 Pictet, a corresponding member, by means of which we may 

 instantly, and at pleasure, either freeze water or restore it again to 

 its liquidity. For this purpose water is placed under the receiver of 

 an air-pump, in a vessel famished with a lid, which may be lifted 

 up, and let down again, by menus of a wire passing through the 

 top of the receiver. When the lid is taken off, the water, by the 

 action of the sulphuric acid and the vacuum, congeals ; and 

 when the lid is put on again, the surrounding heat soon restores its 

 liquidity again. 



Our associate M. Gay-Lussac, who repeated the experiment of 

 Mr. Leslie before the Class, stated a well known fact of the same 

 kind; namely, the cold produced in certain machines when con- 

 densed air is allowed to escape. He has shown that in every season 

 it is sufficient that air be condensed into half its bulk in order to 

 produce ice ; and he conceives that ice might easily he procured in 

 this way in hot climates, by condensing air by means of a fall of 

 Meter. 



We may, by employing bodies more evaporable than water, 

 arrive at degrees of- cold really astonishing} and noi only freeze 

 mercury, hut the purest alcohol. This has been done by Mr. 

 Hutton, of Bklinburgh ; who observed on the occasion, that in the 

 heal rectified alcohol, congelation still separates differenl rices. 



M. ConBgliacchi, Professor -it Pavia, i i in! mercury bj the 

 evaporation of water alone. Wi i ted for the first comniu- 



Dtcatioii of these experiments to M. Pictet. 



It was supposed that the pressure of air. the influence of which 

 i powerful in retarding evaporation', would retard also the solu- 

 tion of salts, or, what comes to the muk thing, would accelerate 

 their crystallization when they were dissolved s and in fact a satu- 



P 2 



