171 



years being the least common multiple of the two cycles, 

 is mentioned by Herodotus as the apocatastatic period used 

 by the Egyptians. 



Professor Kane read a paper ^'on the Theory of Ammo- 

 niacal Compounds." 



In this paper the author first noticed the various hypo- 

 theses which had been from time to time proposed to explain 

 the nature of the combinations formed by ammonia, and 

 adverted particularly to the remarkable fact discovered by 

 Mitscherlich, of the isomorphism of NH3 + ho with k.o, and 

 to the principle deduced by Dumas from the properties of 

 oxamide, that NH3, by losing an equivalent of hydrogen, 

 formed a compound resembling very closely, and capable of 

 replacing in combination, the simple bodies of the chlorine 

 group. 



In the theory proposed by Dr. Kane, it is laid dov^m as 

 the fundamental proposition, that ammonia NPI3 must be 

 represented as a compound of the body NH2and of hydrogen, 

 that is, that ammonia, as gas, is amiduret of hydrogen. The 

 hydrogen of this body, outside the radical, may be replaced 

 by the various metals, or by radicals of organic origin, and 

 hence the amide of potassium, of benzoyl, &c. These 

 amides, resembling remarkably the chlorides, may unite with 

 chlorides or oxides of the same, or of different metals, and' 

 hence the most general proposition, that in the great mass 

 of the various ammoniacal combinations, their real nature 

 assimilates them to complex metallic compounds, an amide of 

 hydrogen, or of a metal, having united with a chloride, 

 oxide, &c. of hydrogen, or of a metal. 



Thus sal ammoniac is considered in this theory as a com- 

 pound of chloride of hydrogen with amide of hydrogen, and 

 the oxide of hydrogen, united with amide of hydrogen, forms 

 *he basic element of the ordinary ammoniacal salts. In like 

 manner, chloride of mercury, united with amide of mercury* 



r2 



