516 



Drs. Ramsay and Young on 



with accuracy; and we have recently shown in a communica- 

 tion to the Royal Society that the results obtained by Favre 

 and Silbermann, by Regnault, and by Andrews for ethyl 

 alcohol are only approximations to truth. It is probable that 

 the data given for other substances less easy to obtain in a 

 pure state are still less to be relied on. We have also shown 

 in that paper that the density of saturated vapour of alcohol 

 is normal, or nearly so, only at temperatures below 50°. 

 Nevertheless, in calculating by means of the above-mentioned 

 formula the constant for alcohol, it has been assumed that the 

 saturated vapour of alcohol possesses normal density at 78°'4; 

 and from want of knowledge it has similarly been assumed 

 that at their boiling-points the saturated vapours of the other 

 liquids to be considered have also normal density* It must 

 therefore be acknowledged that considerable doubt rests on 



both the expressions in the term and this doubt pre- 



Si — $2 



vented the previous publication of these relations ; but it will 

 be seen in the sequel that the much more trustworthy deter- 

 minations of vapour-pressures amply confirm the law which 

 has been stated. 



The following table exhibits these relations at normal pres- 

 sure : — 



Substance. 



Water , 



Methyl alcohol 



Ethyl alcohol , 



Ethyl oxide , 



Methyl formate, 



Methyl acetate , 



Ethyl acetate 



Ethyl oxalate 



Amy] alcohol (?) 



Acetic acid 



Benzene 



Bromine 



Phosphorus chloride . 

 Carbon disulphide .. 



Methyl iodide 



Ethyl iodide 



Ethyl chloride 



Carbon tetrachloride 



Chloroform 



Mercury 



Nitric peroxide 







L 



S-, — S Q . 



L. 









S l~ S 2 



1695 



537 



0-3166 



865-9 



263-7 



0-3046 



624-7 



202-4 



0*3240 



322-3* 



90-5 



0-2808 



4171 



1171 



0-2808 



362-5 



110-2 



0-3040 



3230 



92-7 



0-2870 



256-2 



72-7 



02835 



375-5 



121-4 



0-3238 



318-0t 



101-9 



0-3204 



370-6 



92-3 



02191 



169-2 



45-6 



0-2695 



209-5 



51-4 



0-2453 



343-3 



86-7 



0-2526 



181-5 



461 



2539 



180-5 



46-9 



0-2598 



3619 



1001 



0-2767 



186-3 



469 



0-2515 



229-1 



612 



02673 



2580 



77-5 



0-3004 



309-6J 



93-48 



0-3019 



* Determined by Horstmann, Annalen, 1868 ; Suppl. vi. 



t Determined by Ramsay and Young. 



J Density taken as 39 (11 = 1) as an approximation. 



.64. 



