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



The Decomposition of Ammonia by Heat." By E. P. PERMAN, 

 DSc and G. A. S. ATKINSON, B.Sc. Communicated by 

 Sir WILLIAM RAMSAY, K.C.B., F.RS. Received May 3- 

 Read June 16, 1904. 



This subject has been already dealt with by Ramsay and Young,* 

 who heated ammonia in glass tubes at various temperatures, and 

 found that decomposition began under the most favourable circum- 

 stances at a little below 500, and that the amount decomposed depends 

 on the extent of the heated surface of the solid with which the ammonia 

 is in contact, on the nature of the surface, and on the time of exposure 

 to heat. 



We have thought it desirable to extend our knowledge of the subject 

 still further by investigating the rate of decomposition at various 

 temperatures. The ammonia was contained in porcelain vessels heated 

 in a muffle furnace, and the decomposition was traced by reading the 

 pressure on a mercury manometer, the sum of the volumes of the ammonia 

 and products of decomposition being kept constant. The difficulty of 

 finding the amount of ammonia in the vessel at the beginning of the 

 decomposition was overcome by heating the ammonia at the end of a series 

 of observations until complete decomposition was caused ; the pressure 

 and temperature were then noted, and the original amount of ammonia 

 calculated. We have confirmed the observations of Ramsay and 

 Young that the decomposition is never absolutely complete, but after 

 heating at a temperature of 1100 for a short time the amount of 

 ammonia remaining is so small that it can be neglected for practical 

 purposes. 



Apparatus. The ammonia was heated in a porcelain globe A (fig. 1) 

 of about 2 litres capacity by means of a muffle furnace B ; the capillary 

 stem of the globe was connected with a capillary glass tube by a copper 

 sleeve and some fusible alloy. The pressure gauge D stood 2 metres 

 high, and the level of the mercury was regulated by a movable reser- 

 voir F. The pressure was read on a millimetre scale ; G is a movable 

 piece of mirror glass of rectangular shape, and with a horizontal line 

 drawn across it ; by sliding it along the edge of the millimetre scale 

 and behind the glass tubes of the gauge, the readings were made with 

 great facility. 



H is a U-tube with a stop-cock at the bottom; its object was to cut 

 off the ammonia from the three-way stop-cock k by a column of mercury, 

 and so prevent or indicate leakage. One branch of the stop-cock k led 

 to a water-air pump, and the other to a long tube L containing caustic 

 soda, and thence to a cylinder of ammonia with a safety escape M, con- 

 sisting of a tube dipping into a column of mercury. 



* ' Chem. Soc. Journ.,' vol. 44, p. 88, 1884. 



