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XV. — On the combined Action of Heat and Pressure on Water, 

 Sulphuric Mther, and rectijied Oil of Petroleum. By the 

 Baron Cagniard de la Tour*. 



I 



T is well known that the temperature of liquids may be raised 



much above their boihng points by heating them in a Papin's 

 Digester ; and it miglit be expected that llie compression 

 within, increasing with the temperature, would be an obstacle 

 to the total conversion of the liquid into vapour, especially when 

 the space left above the liquid is only of a limited extent. 



It appears that the expansion -j- of a volatile liquid has a limit, 

 beyond which, notwithstanding its compression, the whole 

 ought to be converted into vapoui", provided the capacity of 

 the vessel in which it is heated is sufficient to suffer it to di- 

 late beyond its maximum of expansion. 



In order to ascertain this fact, a piece of strong iron gun 

 barrel was filled about two-thirds full of alcohol. A small ball 

 of silex was also introduced, and the noise occasioned by its 

 rolling backward and forward was observed while the whole 

 was in a cold state. 



When this apparatus was heated to a certain point over 

 charcoal, the ball appeared to strike the inside of the gun-bar- 

 rel as if no liquid was contained in it, which was rendered more 

 perceptible by applying to the ear a small handle attached to 

 the apparatus. On suffering the apparatus to cool, this effect 

 ceased, but took place again on restoring the temperature. 



The same experiment was tried with water ; but it did not 

 perfectly succeed, owing to the joints becoming defective from 

 the force of the steam. 



This was not the case with sulphuric aether or rectified 

 oil of petroleum, and they produced the same results as were 

 observed with alcohol. 



These experiments were repeated with the same liquids con- 

 tained in small glass tubes, closed at both ends by the flame 

 of a blow-pipe. 



A tube of this description being filled with alcohol to about 

 two-fifths of its capacity, and then carefully heated, the liquid 

 WaS observed to acquire a greater degree of mobility in pi'o- 



* From the Annales de Clnmie. 



\ By expansion in this case must be iincIcrstooJ tlic mere increase of 

 bulk from heat unattended witli any alteration in the nature of the fluid. 

 M. C.'s opinion appears to be, that this expansion has a fixed limit, and 

 that any addition of heat to a fluid already arrived at this point instantly 

 changes its whole bulk into liiglil}' compressed vapour. 



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