1823.] Effect of Heat and Compression. 291 



nearly double its original volume, disappeared completely, and 

 was converted into so transparent a vapour that the tube seemed 

 suddenly empty ; but on suffering it to cool for a moment, a very 

 thick cloud was formed, after which the fluid reappeared in its 

 original state. A second tube, nearly half full of the same fluid, 

 gave a similar result ; but a third, of which the fluid occupied 

 more than half, was broken. 



Similar experiments made with oil of petroleum, of specific 

 gravity about 0*807, and with ether, presented analogous results, 

 excepting that the ether appeared to require less space than the 

 oil ofpetroleum tube converted into vapour without breaking the 

 tubes, and the latter less than alcohol, which seems to indicate 

 that the more a fluid is naturally dilated, the less volume it takes 

 to attain its maximum of expansion. 



All the tubes in these trials were exhausted of air before they 

 were closed ; the experiments when repeated with tubes in 

 which the air was left, gave similar results ; the progressive 

 expansion of the fluid was even more easily estimated in the 

 latter case, there being no inconvenient ebullition as in the 

 former. 



The last experiment was made with a glass tube about one- 

 third full of water ; this tube lost its transparency, and broke a 

 few seconds afterwards. It appears that at a high temperature 

 water is capable of decomposing glass by combining with its 

 alkali ; this suggests the idea that some other result interesting 

 to chemistry may, perhaps, be obtained by increasing the appli- 

 cations of this process of decomposition. 



By carefully observing the experimental tubes in which the 

 air had been left, it was remarked that those in which the fluid 

 matter had not quite space enough to acquire the dilatation pre- 

 ceding its conversion to vapour, did not always break imme- 

 diately after the fluid appeared to have completely filled this 

 space, and the explosion was slower as the excess of fluid was 

 less apparent. 



Mav it not be concluded that fluids which are usually but 

 slightly compressible at alow temperature, become more so at a 

 higher temperature? and still more strongly in the present case, 

 in which the liquid is ready to become an elastic fluid under a 

 pressure, which, according to theoretical calculations, would 

 appear to be equal to several hundred atmospheres? 



With respect to this, there will probably be some difficulty in 

 admitting, that a small glass tube scarcely three millimetres 

 in diameter, and scarcely one millimetre thick, should resist so 

 considerable an expansive force ; it will, perhaps, be thought 

 preferable to suppose that the molecules of an elastic fluid, and 

 particularly of a fluid vapour, are susceptible at a certain degree 

 of compression and heat, of assuming a change of state similar 

 to senhfusion, and capable of facilitating a greater reduction of 

 volume than that derived from the absolute pressure. 



u2 



