Chemical Science. 147 



ether, submitted to heat and pressure, are converted into 

 vapour, in a space a little more than double that of each liquid. 

 2. That an augmentation of pressure, occasioned by the presence 

 of air, caused no obstacle to the evaporation of the liquid in 

 the same space, but only rendered the dilation of the liquid 

 more regular and observable. 3. That water, though suscepti- 

 ble of being reduced into very compressed vapour, has not yet 

 been submitted to perfect experiments, because of the imperfect 

 closing of the digester at high temperatures, and also because of 

 its action on glass tubes.— ^/iwa/es de Chim. xxi. 127. 



In a supplement to the above Memoire, M. Cagniard de la 

 Tour states the results of experiments made to ascertain the 

 pressure produced in the experiments described. The process 

 adopted was to bend a tube into a syphon, place ether in one 

 leg, and separate it from the other containing air, by mercury ; 

 both legs being sealed, the apparatus was heated, and when the 

 ether became vapour, the diminution in the bulk of the air 

 marked. In the present experiment, 528 parts became 14, a 

 result which was thrice obtained. Ether, therefore, is suscep- 

 tible of being converted into vapour in a space less than twice 

 its original volume, and in this state it exerts a pressure of be 

 tween 37 and 38 atmospheres. 



When alcohol, sp. gr. 837, was used, 476 parts of air be- 

 came 4 ; and from an observation of the volume, it was ascer- 

 tained that alcohol may be reduced into vapour, in a space 

 rather less than thrice its original volume, and that it then 

 exerts a pressure of 119 atmospheres. 



The temperature at which these effects took place was ascer- 

 tained, by repeating the experiments in an oil bath. The ether 

 required a temperature of 320°, F. ; alcohol, that of 405°, F. 

 In the Memoire it was announced, that water heated in tubes 

 of glass altered the transparency, so as to prevent observation 

 of what passed within ; but M. Cagniard de la Tour found that a 

 small quantity of carbonate of soda prevented, in a great measure, 

 this effect. He was enabled therefore, though only with difficulty, 

 from the frequent rupture of the glass tubes, to ascertain, that 

 at a temperature but little removed from that of melting zinc, 

 water could be converted into vapour, in a space nearly four 

 times that of its original volume. — Annales de Chim. xxi. 178. 



2. Berthier on Sulphurets produced from Sulphates. — The 

 experiments made by M. Berthier had for their object the dc- 

 Voj.. XV. L 



