Mr. Faraday oH the formation of Ammonia^ &c. 17 



gen were present, it has been supposed that the information ob- 

 tained, though incomplete, might be interesting. 



Having occasion, sometime since, to examine an organic sub- 

 stance with reference to any nitrogen it might contain, I was struck 

 with the difference in the results obtained, when heated alone in a 

 tube, or when heated with hydrate of potassa : in the former case 

 no ammonia was produced; in the latter, abundance. Supposing 

 that the potash acted, by inducing the combination of the nitrogen 

 in the substance with hydrogen, more readily than when no potash 

 was present, and would, therefore, be useful as a delicate test of 

 the presence of nitrogen in bodies, I was induced to examine its 

 accuracy by heating it with substances containing no nitrogen, as 

 lignine, sugar, ^c. ; and was surprised to find that ammonia was 

 still a result of the experiment. This led to trials with dififerent 

 vegetable substances, such as the proximate principles, acids, salts, 

 ^c, all of which yielded ammonia in greater or smaller quantity ; 

 and, ultimately, it was found, that even several metals when treated 

 in the same way gave similar results ; a circumstance which ap- 

 peared considerably to simplify the experiment. 



The experiment may be majie in its simplest form in the follow- 

 ing manner : put a small piece of clean zinc foil into a glass tube 

 closed at one end, and about one-fourth of an inch in diameter ; 

 drop a piece of potash into the tube over the zinc ; introduce a slip 

 of turmeric paper slightly moistened at the extremity with pure 

 water, retaining it in the tube in such a position that the wetted 

 portion may be about two inches from the potash ; then holding the 

 tube in an inclined position, apply the flame of a spirit lamp, so as 

 to melt the potash that it may run down upon the zinc, and heat 

 the two whilst in contact, taking care not to cause such ebullition 

 as to drive up the potash ; in a second or two, the turmeric paper 

 will be reddened at the moistened extremity, provided that part of 

 the tube has not been heated. On removing the turmeric paper 

 and laying the reddened portion upon the hot part of the tube, the 

 original yellow tint will be restored : from which it may be con- 

 cluded that ammonia has been formed ; a result confirmed by other 

 modes of examination to be hereafter mentioned. 

 Vol. XIX. C 



