426 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



the two baths ; P the original pressure ; p the small increase of pressure 

 in the gauge on the reading at higher temperature ; and K the constant 

 value to be subtracted from p due to the greater distance apart of the 

 platinum points in the side tube over the distance apart of those in 

 the bulb. 



Then 



a 



(P + p-K) (V+y)-PV 

 PVt 



It will be seen that it is not necessary to know the numerical value of 

 P very accurately, while/? must be known as precisely as possible. The 

 values V, v, and K are constant, and have already been given as 

 V= 273.73 c.c, v = 32.86 c.c, K— 0.88 mm. The value t° would 

 also be a constant, but for the fact that the sodic sulphate in the bath 

 was not always perfectly pure. A correction for the exposed stem of 

 the thermometer was made in taking this temperature, and the tempera- 

 ture was then reduced to the international hydrogen scale. 



The results of the experiments on hydrogen appear in the following 

 table. The first few determinations are omitted, since the manipulatiou 

 of the apparatus had not at that time become perfected. 



HYDROGEN. 



