Chemical Science. 145 



from other parts of the flame, while those striking against the 

 ring reservoir are lost for the purpose of illumination. 



II. Chemical Science. 



1. On the Action of Heat and Pressure on certain Fluids. 

 By M. le Baron Cagniard de la Tour. — It is known, that by 

 means of Fapin's digester, the temperature of many fluids may 

 be raised much above their ordinary boiling points ; and one 

 is led to suppose, that the internal pressure augmenting with 

 the temperature, would prove an obstacle to the total evapo- 

 ration of the fluid, especially if the space left above the fluid is 

 not of a certain extent. 



Reflecting on this subject, it occurred to me that there was 

 necessarily a limit to the dilatation of a volatile fluid, beyond 

 which it would become vapour, notwithstanding the pressure, if 

 the capacity of the vessel would permit the liquid matter to 

 extend to its maximum of dilatation. 



To ascertain this point, a certain quantity of alcohol, sp. gr. 

 .837, and a sphere of silcx, were put into a small digester, made 

 out of the thick end of a musket barrel, the liquid occupying the 

 third of the capacity. Having observed the noise produced by 

 the sphere, when rolled in the cold apparatus, it was gradually 

 heated until a point was reached, when the ball seemed to 

 bound from end to end of the digester, as if no liquid had been 

 present. This effect, easily distinguished by holding the end 

 of the handle to the ear, ceased on cooling the apparatus, and 

 was reproduced on re-heating it. 



The same experiment made with water, succeeded only im- 

 perfectly, because of the high temperature required interfering 

 with the tightness of the instrument. But sulphuric ether and 

 naphtha presented the same results as alcohol. 



That the phenomena might be observed with more facility, 

 the liquids were introduced into small tubes of glass, and her- 

 metically sealed. A handle of glass was attached to each tube. 

 A tube was two-fifths filled with alcohol, and then slowly and 

 carefully heated ; as the fluid dilated, its mobility increased, 

 and, when its volume was nearly doubled, it completely disap- 

 peared, and became a vapour so transparent, that the tube ap- 

 peared quite empty. On leaving it to cool for a moment, a 

 very thick cloud formed in its interior, and the liquor returned 

 to its first state. A second tube, nearly half occupied by the 



