302 A. W. Witkowski on the . 



cent., than the values recorded by the gas-manometer ; this 

 applies as well to the air- as to the nitrogen-manometer. The 

 sign of the difference led me to suspect a leakage of gas in 

 some part of my apparatus. Therefore it was indispensable 

 to submit the apparatus to a severe test, the more so as any 

 leakage in it would vitiate the results, as regards expansion, 

 to an incalculable extent. 



To test the apparatus I charged it (both bulbs at +16°) 

 with compressed air, under a sufficiently high pressure, the 

 value of which was determined simultaneously with the aid of 

 the gas-manometer. The bulbs were then immediately dis- 

 charged into the eudiometers. Next I repeated this same 

 experiment, using the same pressure (as indicated by the gas- 

 manometer), but instead of discharging the bulbs immediately 

 I left them charged for a relatively long time (an hour or 

 two) . I was satisfied to find that the quantity of air collected 

 after long imprisonment was not less than in the first case. 



As an instance of this sort of testing, the following numbers 

 may be given : — 



First experiment. — Nitrogen-manometer— 89'06 atm. 

 The bulbs discharged immediately after charging. 



Bulb. 

 No.l... 

 No. 2... 



Temp, of 

 bulb. s c. mm. a c.mm. A c. mm. 



0=16 901-90 8-7 77723 

 £=16 1919-47 15-0 164903 



P 

 (calc. by 5) 



88-60 



88-49 



Second experiment. — Nitrogen-manometer = 

 Bulbs kept charged 1 hour 15 min. 



89-10. 



Bulb. 



Temp, of 



bulb. s. cr. A. 



P- 



No. 1., 



No. 2 ., 



,. +16 901-90 8-7 77783 

 .. +16 1919-47 15-0 165096 



88-67 

 88-60 



It will be remarked that the pressure indicated by the gas- 

 manometer exceeds in both cases that calculated by (5) by J 

 per cent, nearly. At the same time it is apparent that there 

 was no sensible leakage, since in the long-charge experiment 

 the difference of pressure is even less than in the first. I am 

 not able to give a sufficient explanation of the observed 

 difference, but considering that the constant-volume method 

 employed in the present work deals with larger quantities of 

 gas, and enables us to measure them with greater accuracy, 

 I am inclined to think that the results obtained with my 

 apparatus are at least not less trustworthy than those recorded 

 by an ordinary gas-manometer. 



