230 Scientific Notices — Chemistry/, [Sept. 



A paper was also read, entitled " Observations, &c. on a 

 Walk from Exeter to Bridport." Mr. Woods, in this com- 

 munication, describes the nature of the soil in the neigh- 

 bourhood of Exeter, and the strata exhibited in the cliffs 

 and on the sea shore between that city and the east side of 

 Bridport Harbour. 



Article XI. 

 SCIENTIFIC NOTICES. 



Chemistry. 

 1. Formation of Ammonia. 



Mr. Faraday has lately published in the Journal of Science, 

 an account of some experiments on the formation of ammonia 

 by the action of substances apparently containing no azote ; he 

 states his belief, however, that the results depend upon the 

 difficulty of perfectly excluding azote, and the extreme delicacy 

 of the test of its presence afforded by the formation of am- 

 monia. The principal experiments performed by Mr. Faraday, 

 we shall give nearly in his own words : — 



" 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 re- 

 moving 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 concluded that ammonia has 

 been formed ; a result confirmed by other modes of examination." 



The atmospheric being suspected to be the source of the 

 azote, the experiment was repeated on hydrogen gas, but the 

 same results were obtained. It was afterwards imagined that 

 the azote might be furnished by accidentally touching the 

 potash with animal or other substances containing azote ; and 

 as a proof of how necessary it is to avoid fingering the sub- 

 stances experimented upon, Mr. Faraday states the following 

 experiment: — 



