[ 387 ] 



XLII. 



FORMULA FOE THE EASY DETERMINATION OF GASEOUS 

 VOLUMES AND WEIGHTS. By G. JOHNSTONE STONEY, 

 VICE-PRESIDENT, M.A., D.Sc, F.R.S. 



[Read April 10, 1889.] 



I have used the following approximate formulae for several years 

 and found them convenient. They are proved below. 



Call the barometric pressure of 760 mm. of mercury at Paris 

 and at freezing temperature the standard pressure. [For most 

 laboratory purposes the usual British standard of 30" of mercury, 

 at 62° F., may be used anywhere instead of it.] 



Then, under standard pressure, and at a temperature of 21° C, 



W (the weight of a litre of any gas) = — grammes, 



JL/O 



12 



and V (the volume of a gramme of the gas) = — litres, 



where D is the density of the gas when compared with that of 

 hydrogen as unit. 



At any other temperatures and pressures, not too far removed from 

 the foregoing, 



W = j~ ± a temperature correction, 



± a barometric correction, (1) 



12 



and V = -jr ± Q> temperature correction, 



± a barometric correction, (2) 



where the temperature correction is one per cent, for every 3° C. that 

 the temperature deviates from 21°, and the barometric correction is one 



