n Mr. Faraday on the 



With regard to the evidence of the nature of the substance 

 produced, it was concluded to be ammonia in the experiments 

 made in hydrogen, from its changing the colour of turmeric paper 

 to reddish brown ; from the disappearance of the reddish brown 

 tint and reproduction of yellow colour by heat ; from its solubility 

 in water, as evinced by the greater depth of colour on moist tur- 

 meric paper than on dry; from its odour; and from its yielding 

 white fumes with the vapour of muriatic acid. When formed in 

 open tubes, its nature was still further tested by its neutralizing 

 acids and restoring the blue colour of reddened bitumus paper ; 

 by its rendering a minute drop of sulphate of copper on a slip of 

 white paper deep blue ; and also, at the suggestion of Dr. Paris, 

 by introducing into it a slip of paper moistened in a mixed solu- 

 tion of nitrate of silver and arsenious acid, the yellow tint of ar- 

 senite of silver being immediately produced. 



These experiments upon the production of ammonia from sub- 

 stances apparently containing no nitrogen, will call to mind that 

 made by Mr. Woodhouse, of Philadelphia, on the action of water 

 on a calcined mixture of charcoal and potash, during which much 

 ammonia was produced* ; and also to the strict investigation of 

 that experiment made by the President of the Royal Society during 

 his inquiries into the nature of elementary bodies t. Sir Hum- 

 phry Davy found that when one part of potash and four of char- 

 coal were ignited in close vessels cooled out of contact of the at- 

 mosphere, pure water admitted to the mixture, and the whole 

 distilled, srflall quantities of ammonia were produced. That when 

 the operation was repeated upon the same mixture ignited a se- 

 cond time, the proportion diminished ; in a third operation it was 

 sensible ; in a fourth barely perceptible. The same mixture, how- 

 ever, by the addition of a new quantity of potash, again gained 

 the power of producing ammonia in two or three successive ope- 

 rations ; and when any mixture had ceased to give ammonia, the 

 power was not restored by cooling it in contact with air. 



Sir Humphry Davy refrains from drawing conclusions from 



* Nicholson's JWma/, xxi.290. t Phil, Trans. 1809, p. 100, 1810, p. 4S. 



