112 Dr. E. P. Perman and Mr. G. A. S. Atkinson. [May 3, 



acid, hut nothing appreciable was condensed. The gas was found to 

 be free from carbon dioxide. A quantity of pure hydrochloric acid 

 was neutralised by passing the gas from the cylinder through it, and 

 the solution was then evaporated to dryness. Chlorine was then esti- 

 mated in the sample by the gravimetric method, and the percentage 

 found was (1) 66'09 ; (2) 66'12; mean, 66'105; theoretical, 66*23. 



Method of Work. The furnace was heated, and when the tempera- 

 ture was sufficiently constant, the filling process was commenced. 

 The globe was exhausted, and ammonia admitted from the cylinder 

 through the drying tube L ; this was repeated from eight to ten 

 times, when the filling .was regarded as complete. Readings of 

 pressure were then made at definite time intervals, and the tempera- 

 ture was also carefully noted, as nearly as possible at the same time, 

 by means of the pyrometer. In one or two of the experiments the 

 temperature was sufficiently high to decompose the ammonia com- 

 pletely in a short time, but in most of them, when a sufficient number 

 of readings had been made, the temperature was raised until 

 (practically) complete decomposition ensued in a few minutes. The 

 volume of the ammonia and decomposition products was kept constant 

 by raising the mercury reservoir F so as to keep the mercury at about 

 the same level in the upper part of the short limb of the pressure 

 gauge. As each time interval was called, the level of the mercury 

 in D was read, and that in the open limb as soon as possible after- 

 wards ; it did not change quickly in the latter, owing to the width 

 of the reservoir. 



Some observations were also made on the effect produced by sudden 

 change of pressure on the rate of decomposition. 



Method of Calculation. The ultimate decomposition of ammonia is 

 customarily represented by the equation 2NH 3 = N 2 4- 3H 2 . Let p 1 be 

 the pressure of the ammonia in the globe at any instant during the 

 decomposition, p^ that of the nitrogen, p 2 ', that of the hydrogen, P, 

 the total pressure at the same instant, Po , the initial pressure of the 

 ammonia at the beginning of the experiment. 



111611 Pi+pi+p*' = P .............................. (1), 



P2 =3 Pl ' ........................... (2), 



Pi'+Pt'-^Po-pi) ..................... (3); 



expressing that (1) the sum of the partial pressures is equal to the 



J pressure ; (2) the pressure of the hydrogen produced is three 



that of the nitrogen; (3) the sum of the pressures of the 



* d Uble ^ Pr6SSUr6 f the ammonia 



sZ ^ f 110WS ^ Substitution ^ Pi = 21* -P, i.e., the 

 the ammonia at any instant is double the initial pressure 



