(38 DENSITIES OF OX\'«EN AND HYDKOOEN 



lime of the tubes between the three-\\;ty stopcock <, aud tlie stopcocks of the 

 I'lubes, (t (I. But here the volume of the air cliawu from the burette to till the 

 vacuous tuV)es had to be corrected for ditt'eieuce of temperature as well as for de- 

 I'ree of exhaustion ; the determination was made with these tubes covered with ice, 

 just as they were to be covered with ice in the measurement of the pressure of 

 hydrogen in the globes. Afterwards, the three-way stopcock was connected in the 

 same way to tlu' tube leading to the barometer and its capacity determined. The 

 level of the mercury was noted, and deterniinati^>iis of volumes made at different 

 levels. Taking account of the degree of exhaustion and of the differences of tem- 

 perature at the burette and at the barometer, if any, the volumes contained to dif- 

 ferent levels in the barometer were ooniputed, and a table made showing them. 

 The tube leading to the barometer, w hicli had been separated, was now fused in 

 place, and a few determinations made of the united volumes. 



As an example of the process is given the first determination made. 



Blank space, 0.8 cc. 



Connecting tubes which are kept covered with ice; vacniiin, mm., burette, 10.0°. 

 Air drawn in on opening stopcock, 48.1 cc, 48.4 cc, 48.5 cc, 48.5 cc : mean, 48.4 cc ; 

 reduced to 0° and coriected for 6 mm., 45.6 cc, the capacity of the ice-covered ttil»es. 



Fused three-way stopcock to tube leading to barometer; blank space same as 

 before. Air left in vacmini, negligible. 



The details of the computation aie unimportant. The tubes were renewed 

 several times; the table following gives their capacities at different dates : 



( Al>.\( rrv ol' COXNKCTINO TUBES AT DilT-KKENT DATE.s. 



Tubes ke|>t in ice. Barometer and tubes leading to it. 



Mark. May-Oct. Nov. -April 



66.3 cc. 



633 " 

 60.2 " 



57-2 " 

 54-2 " 



5'' 

 48.1 " 



45-0 " 

 42.0 '■ 



38.9 " 

 35-9 " 

 32.8 " 

 29.8 " 

 26.7 " 



