COMPOSITION OF AMMONIUM AMALGAM. 175 



ends, about 1*4 centimetre in diameter and having its 

 shorter limb 40 centimetres long. At the bottom of the 

 longer limb, just above the bend, there was an 

 outlet tube, to which was attached a piece of 

 caoutchouc tubing closed by a pinch-cock. 

 Mercury was poured into the tube until it filled 

 about two-thirds of the shorter limb, into which 

 was then introduced the amalgam after the 

 latter had been wiped with filtering-paper. 

 Into the end of the limb containing the amal- ^~^<%> 

 gam, a caoutchouc stopper, perforated with a small open- 

 ing, was immediately thrust so far that its upper surface 

 came a little below the rim of the tube. The decom- 

 position of the amalgam was then allowed to proceed 

 for a few minutes, during which period any moisture ad- 

 hering to the amalgam or present in the tube would 

 become completely saturated with ammonia, and the two 

 gases would begin to escape through the perforation in 

 the stopper in the proportions in which they are really 

 evolved. Mercury was now poured into the open end of 

 the longer limb until the amalgam just made its appearance 

 at the top of the hole in the stopper, which was then closed 

 by pushing in a piece of glass rod. The evolved gases, 

 being thus retained in the tube, pressed up the mercury in 

 the longer limb ; and it was from time to time drawn off 

 by the outlet-tube, to prevent undue pressure on the 

 stopper. When the decomposition was complete, which 

 usually occurred in about if hour (but in one case more 

 than 2f hours were required), the mercury was brought 

 to the same level in both limbs, and the space occupied by 

 the gases was marked on the tube. A little mercury was 

 then let out, so as to make the pressure on the gas some- 

 what less than that of the atmosphere, and the space 

 above the stopper was filled with hydrochloric acid diluted 

 with a little water. The glass rod was now carefully with- 



