240 



Intelligence and Miscellaneous Articles. 



presents beautiful shades, according to its intensity. It is never 

 rendered turbid by compression. 



The vapour of ether has presented the reverse effect; it becomes 

 turbid by compression and remains transparent by expansion. 



These two results confirm those of M. Hirn, to whom the first 

 observations on this subject are due. 



The following are the new results which were the object of this 

 research: — 



The vapour of chloroform gave a mist when expanded up to 130°. 

 At this temperature it was very feeble and was not easily obtained ; 

 the vapour remained transparent by compression. Above 13G°, 

 compression was accompanied by a very perceptible mist. The 

 higher the temperature the more intense the mist, which was never 

 observed with expansion. Experiments were made from 80° to 150°, 

 and therefore up to nine atmospheres. 



The vapour of benzole behaved like chloroform. There was mist 

 by expansion alone up to 115°, and by compression alone above 130°. 

 Observations between these temperatures were interrupted by an 

 accident. 



It has thus been experimentally proved that for these two liquids 

 there is a temperature of inversion, below which the expansion of 

 dry and saturated vapour, without either addition or subtraction of 

 heat, is accompanied by a partial condensation, while above this tem- 

 perature compression determines condensation. 



There is thus verified a consequence of the formulas of thermody- 

 namics at which several authors have arrived by different methods. 



The temperatures of inversion which I have calculated from these 

 formulae are 520° for water, 113° for ether, 123° for chloroform, 100° 

 for benzole. The first of these numbers was found by Mr. Rankine 

 in 1854; MM. Dupre and Combes have made analogous calcula- 

 tions for other liquids ; and the differences of results are explicable 

 by the choice of data, which are not accurately determined. 



To give an idea of the degree of accuracy which my experiments 

 present, I have calculated from thermodynamic formulae the weights 

 of chloroform vapour precipitated under the circumstances in which 

 I worked :— 



Original 



Original 



Final 



Condensed 



Thermometric 



temperature. 



volume. 



volume. 



vapour. 



effect. 





lit. 



lit, 







100 



5-844 



6-862 



0-174 



-6-8 



110 







0123 



-7-3 



120 







0-070 



-7-6 



130 



6-862 



5-844 



0-518 



+8-5 



140 







0-644 



+ 9-0 



150 







0-815 



+9'6 



The agreement between theory and experiment is as close as could 

 be expected when we consider the want of purity in the liquids, and 

 the uncertainty in regard to some of the data on which the calcula- 

 tions are based. — Comptes Rendus, June 8, 18GS. 





