Joly — A Method of Determining the Density of a Gas. 541 



From these data the density of dry air at 747-75 mms., and at 

 the temperature 15-70, is found to be 0*0012046. The last figure 

 is doubtful, as being beyond the limit of accuracy with which the 

 volume is known. 



If, for confirmation of this result, reference is made to accepted 

 results from the Tabellen of Sandholt and Bornstein, the density 

 of dry air under the same conditions of pressure and temperature 

 is deduced as 0-0012039. From Biedermann's Chemiker-Kalender 

 (1888) is deduced the number 0'0012052. The mean of these two 

 closely agrees with the experimental result, absolutely indeed to 

 the fourth significant figure, the last reliable one in the determina- 

 tion. 



In conclusion, I may point out that this method leaves the gas 

 finally in a vessel, which, by the addition of a small side way to 

 the connection b, may be made a most convenient one for the 

 subsequent transference of the gas into any apparatus for its 

 analysis. 



The present method may, as in the case of Eegnault's, be by 

 obvious procedures applied to the determination of the variation 

 of the density with change of temperature, or change of pressure. 

 And its application to the determination of vapour densities 

 suggests itself. In this case the temperature of the volumeno- 

 meter would, perhaps, best be adjusted by the use of a vapour in 

 the jacket, and an arrangement for controlling its pressure. 



2S2 



