362 Prof. J. Dewar. The Specific Volumes of Oxygen 



(H27 c.c., was therefore approximately at the temperature of the room. 

 When the temperature of the flask and its contents became stationary 

 the stopcock was closed, the flask removed, and after heating up to 

 the temperature of the room, weighed against the B flask and any 

 further necessary counterpoise b. The weight of oxygen vapour in 

 the flask at its boiling-point was thus equal to a + b, subject to the 

 corrections which have been indicated. 



To the five sources of error or correction indicated above, there 

 remains to be added that due to additional buoyancy of the air during 

 the weighing of the flask, when filled with oxygen at its boiling-point, 

 for these weighings were made at the temperature of the room, which 

 would cause a rise of pressure in the flask and therefore expansion of 

 its volume. But this error was so small that it could safely be 

 neglected. 



As the intention was not only to ascertain the density of oxygen and 

 nitrogen at their respective boiling-points under atmospheric pressure, 

 but also under diminished pressure, experiments were made with 

 nitrogen at ordinary temperatures and at pressures varying from 

 about one-sixth of an atmosphere to ordinary pressures, in order to 

 find the range of variation in the results with the 316 c.c. flask to be 

 used in the subsequent low-temperature experiments. In the follow- 

 ing table are details of these observations, and the results reduced 

 according to the ordinary gaseous laws. 



Table I. Density of Nitrogen, ordinary Temperature. 



where p\ = barometric pressure at the time of observation, 



T! = temperature of the room at the time of observation, 



p pressure of the nitrogen vapour in the flask during the 



experiment, 



a, b as defined before, 

 V =the volume of the flask corrected for temperature and 



compression, 



d = the calculated density at TI and pressure p, 

 do = the value of d reduced to 0" and 7 80 mm. by the ordinary 

 gaseous laws. 



