1D03.] Measurement of the Pressure Coefficient of Oxygen. 381 



Correcting to a constant volume unity simplifies the calculation. 



The volume of the dead space from a mark on the stem to a mercury 

 meniscus of height O125 cm. in contact with the glass point was 

 0-3904 c.c. 



To obtain the total volume of the dead space it is necessary to apply 

 ?i correction to allow for the fact that the mercury meniscus was not 

 brought exactly into contact with the glass point. This correction 

 amounts to ir? >2 A, where A is the distance between the surface of the 

 mercury and the point and r is the radius of the tube (0'45 cm.). As 

 the height of the mercury meniscus was found to vary considerably in 

 the various experiments, it was necessary to introduce a further 

 correction to allow for the variation of the volume of the dead space 

 from this cause. Assuming the curvature of the meniscus to be 

 constant, the correctioriito be added is Jirr 2 (ti - h) - ITT (A' 3 - A 3 ), where 

 h is the height at which the meniscus stood when the volume of the 

 dead space was measured and k' is the height in the particular 

 experiment. 



6. Method of Observation and Results. The measurements of pressure 

 were taken in the manner adopted by Travers and Jaquerod.* 

 Readings of the ice point and steam point were taken in most instances 

 in alternate pairs, one series of observations being taken by eacji of us 

 for each setting. 



To illustrate the order of accuracy obtained, one series of observations 

 is given in full, in the accompanying table. In the other series only 

 the final corrected values are given. 



Details of Series III. 

 Ice Point. 



* Loc, cit. 



