Action of Heat and Pressure on IVater^ Sfc. 59 



portion as its temperature was augmented ; and after it had 

 expanded to about double its first bulk it disappeared com- 

 pletely, by being converted into a transparent vapour, so much 

 so that the tube appeared quite empty ; but by permitting it to 

 cool for a moment a thick cloud was formed, and the alcohol 

 appeared again in its original state. 



A second tube filled nearly half full of alcohol produced a 

 similar effect ; but a third tube filled rather more than half fiill 

 was broken on being heated. 



Experiments tried with essential oil of petroleum and with 

 Eether gave analogous results, with the only exception that 

 aether appeared to require less space for its conversion into 

 vapour without breaking the tubes than oil of petroleum, and 

 the latter, less again than alcohol. 



From these facts we may infer that the more a liquid is ex- 

 panded in its natural state, the less additional space it will re- 

 quire to attain its maximum of expansion. 



In all the experiments already described the air was expelled 

 from the tubes before they were closed; but on repeating them 

 without expelling the air they gave similar results, and it be- 

 came more easy to observe the progressive expansion of the 

 liquids in this case, as no ebullition was produced as in the 

 foiTner experiments. 



The last experiment was made with a glass tube filled with 

 water to one-third of its capacity. This tube lost its transpa- 

 rency and was broken in a few moments. 



It appeiu-s that a strong heat enables water to decompose 

 glass by taking up its alkali ; probably this mode of decompo- 

 sition may produce other interesting results in chemistry *. 



On carefiilly observing the tubes employed in tliose experi- 

 ments, when the air had not been previously expelled from 

 them, it was remarked, that those in which the fluid had not 



* Note.— I first observed that glass was acted upon by water, under high 

 degrees of compression, about six years ago.— The glass bulbs of thermome- 

 ters exposed to the continued action of high pressure steam, were found to 

 be first opake like ground glass, and after being immersed for two or three 

 weeks, they became full of minute pores and the mercury escaped without 

 an apparent fracture. 



This action is so very gradual, that I am not inclined to adopt the suppo- 

 sition that the fracture of the tubes in these experiments was owing to the 

 decomposition of the glass, but rather to the elastic force of the inclosed 

 steam.— Neither am I (juite convinced that the alkali is the only part of the 

 glass acted upon; ft)r I have reason to think silex itself is dissolved by water 

 under compression, which may account for tUe quantity of silex deposited 

 by the water of thcCJcyser on any substances exposed to it, as it is cjecteil 

 from this stupendous digester.— P. Tavioh. 



" .'» )■ l>i ,Ji 2 siifficieiit 



