386 BABCOCK. 



True Mass of Container filled (in Vacuo) 1434. 6228 grams. 



Volume of Container at 26 . 60 °C. 274 . 1 13 cc. 



Volume of Container at 78 . 0° C. 274 . 054 cc. 



This change in V is within the experimental error and the conclusion 

 is that 5T' is negligible. 



7. E. M. F. of Standard Cell. 



Certified by the U. S. National Bureau of Standards, Oct. 18, 1915. 

 "Unsaturated Weston Standard Cell #1458. 



Electromotive Force at 22.1° C. = 1.01808 international volts. 

 The above value is correct to 0.01 percent." 



8. Resistance of Standard Ohm. 



Certified by the Leeds & Northrup Co. Oct. 11, 1915. 

 " No. 4020 Standard Resistance, Serial $ 27659 

 1 . OOO3 International Ohms at 20° C. 

 Its temperature coefficient between 15° and 30° is 



. 000007 per degree Centigrade. 

 The error in the above comparison is not greater than l/100th%." 



9. Quality of Ammonia Used. 



The ammonia used in these experiments was commercial anhydrous 

 ammonia, NH3, obtained from Armour & Co., Chicago, in February 

 1916, and shipped in a fifty pound drum. 



As to the purity of the ammonia, Mr. J. R. Powell, Chief Chemist, 

 Armour Ammonia Works, may be quoted : 



"As to the impurities that might be expected present, there will 

 probably be traces of water, carbon dioxide, and possibly methyl 

 cyanide, but the total of these impurities should not be over one or 

 two hundredths of one per cent. likewise there may be bare traces 

 of foreign gas dissolved in the ammonia, these gases being principally 

 air. Anhydrous ammonia, as manufactured today is practically a 

 chemically pure product." 



10. Data on Method of Filling Container with Ammonia. 



The ammonia container was connected to the ammonia tank by 

 means of a copper pipe of 5 mm. outside diameter. In this copper 

 pipe was inserted a glass Tee, the branch of which led to a vacuum 

 pump equipped with a gauge. The copper-glass joints were made 

 with Khotinsky cement. 



The ammonia valve was opened slightly, before connecting up, to 

 clear the opening of any foreign matter which might be present in 



