46 Notices respecting Nerjo Books. 



coetficient ; they are not of equally easy execution, and perhaps are 

 not susceptible of the same degree of exactitude ; nevertheless they 

 lead to the same result, and this is what is required for the determi- 

 nation of numerical elements with some degree of certainty. In 

 these first four series of experiments, the coefficient of dilatation is 

 deduced, by the calculation of the change of elastic force which a 

 given volume of gas undergoes when its temperature varies from 0° 

 to 100°, and the mean of the very closely approximate results gives 



0003665. 



The fifth series furnishes the number 0*003670, which differs notably 

 from those given by the other four ; which depends, as subsequent 

 researches showed, on the fact that in these last experiments the gas 

 dilated freely, preserving the same elastic force. 



After having determined the coefficient of the dilatation of air 

 by different methods, and having thus studied these methods them- 

 selves, and ascertained that when properly executed they conducted 

 to the same result, M. Regnault selected for operation upon the 

 other gases, that which had appeared to him most susceptible of 

 exactitude, and of surest and easiest execution ; this was the method 

 employed in the second series of experiments ; he also occasionally 

 made use of that of the fourth ; finally, he operated with that of the 

 fifth, to obtain comparatively the dilatation under constant pressure 

 and under constant volume. He did not succeed in obtaining re- 

 sults with oxygen, not being able, in spite of every precaution, to 

 prevent the action of this gas upon the mercury. 



The following are the results which demonstrate, that for all the 

 gases, except hydrogen, the coefficient of dilatation, determined by 

 direct observation of the increase of volume, which the same mass 

 of gas undergoes from 0° to 100°, its elastic force remaining con- 

 stant, is greater than that which is deduced by calculation from the 

 observation of the elastic forces presented by an identical volume 

 of gas at 0° and 100°. 



Mean Coefficient of Dilatation between 0° and 100° Centig. 



Under constant Under constant 

 volume. pressure. 



Hydrogen 0*3667 0*3661 



Atmospheric air 0*3665 0*3670 



Nitrogen 0*3668 „ ' 



Carbonic oxide 0*3667 0*3669 



Carbonic acid 0-3688 0*3710 



Protoxide of nitrogen 0*3676 0*3719 



Sulphurous acid 0*3845 0*3903 



Cyanogen 0*3829 0*3877 



This table shows equally that the diff'erent gases present coeffi- 

 cients of dilatation differing very notably from each other, contrary 

 to what has been long believed. No one will overlook the fact that 

 the highest coefficients of dilatation are presented by those which 

 are most easily liquefiable. 



