formation of Ammonia, 8cc. 21 



mersed in the water, so as to exclude the air from every part, even 

 of the stop-cock. The first jar of gas was thrown away, and only 

 the latter portions used. 



The gas being ready, the experimental tube was attached to the 

 transferring jar by a connecting piece, so that the part of it con- 

 taining the zinc and potash was horizontal, whilst the other portion 

 descended directly downwards. A cup of clean mercury, the 

 metal being about an inch in depth, was then held under the open 

 end of the tube, and by lowering the jar containing the hydrogen 

 in the water of the pneumatic trough, so as to g-ive sufficient 

 pressure, and opening the stop-cock, the hydrogen in the jar was 

 made to pass through the tube, and sweep all the common air 

 before it. When from 100 to 150 cubic inches, or from 200 to 

 300 times the contents of the tube, had passed through, the cup of 

 mercury was raised as high as it could be, so as to prevent the pas- 

 sage of any more gas, the pressure from the jar in the water-trough 

 was partly removed, and the stop-cock closed ; then, by lowering 

 the cup of mercury a little, the surface of the metal in it was made 

 lower than that within the tube, and in this state of things the 

 flame of a spirit lamp applied to the contracted part of the tube, 

 (a, fig. 2.) sealed it hermetically, without the introduction of 

 any air, and separated the apparatus from the jar on the water- 

 trough. 



In this way every precaution was taken that I could devise for 

 th'fe exclusion of nitrogen ; yet, when a lamp was applied to the 

 potash and zinc, the alkali no sooner melted down and mingled with 

 the metal, than ammonia was developed ; which rendered the tur- 

 meric paper brown, the original yellow re-appearing by the appli- 

 cation of heat to the part. 



Still anxious to obtain a potash which should be unexceptionably 

 free from any source of nitrogen, I heated a portion of potash with 

 zinc, endeavouring to exhaust any thing it might contain which 

 could give rise to the formation of ammonia : it was then dis- 

 solved in pure water, allowed to settle, the clear portion poured 

 otf and evaporated in a flask by boiling ; but tlie potash tlms pre- 

 pared gave ammonia, when heated with zinc, in hydrogen gas. 



