Remarkable Cases of the Formation oj Ammonia. 309 



taiiied in a letter to Mr. Swainson, is expressed in the following 

 words : — 



" This specimen is more analogous to jet than to our Wigan 

 Cannel coal. Its colour is deep brownish black; its lustre 

 resinous ; its cross fracture conchoidal ; its longitudinal frac- 

 turehas aslightly fibrous appearance, as if it had originally been 

 wood. Its hardness is about that of Cannel coal, as is its fran- 

 gibility ; but its lustre is higher. The mean of three careful 

 experiments gave its specific gravity = 1*2248. It becomes 

 considerably electric by friction ; in this character it is ana- 

 logous to jet, and differs from Cannel coal, which scarcely 

 shows any symj^toms of electricity by friction, though I have 

 observed that some pieces of the latter slightly moved an insu- 

 lated cat's hair, which is a veiy delicate electroscope. Kirwan 

 considers the diiference between jet and Cannel in their elec- 

 tric energies, as a diagnostic mark. 



" It burns with a lively flame, and gives out much liquid 

 bituminous matter, or coal tar, so as to cake or become semi- 

 liquid in the fire. It does not decrepitate when heated, like 

 Cannel. When heated before the blowpipe, in a glass tube, 

 its volatile parts are separated ; and it leaves behind about 50 

 per cent ot" a coke which is capable of exciting a pretty strong 

 heat. The volatile portion affords a very pure coal gas. Six 

 grains of it burnt in a platina crucible left behind 0*2 grains 

 of greyish white ash, which is equivalent to 2^ per cent of 

 incombustible matter in it. 



" The smallness of the specimen rendered it impossible to 

 ascertain the relative quantities of carbon, hydrogen, and nitro- 

 gen, which similar substances contain ; but this sort of analysis 

 is rather an object of curiosity than utility." — Quarterly Jour- 

 nal, 



REMARKABLE CASES OF THE FORMATION OF AMMONIA. 



We extract the following remarkable cases of the formation 

 of ammonia from a pa))er on the subject by Mr. Faraday iii 

 the Quarterly .lournal of Science, No. xxxvii. 



Having occasion, some time since, to examine an organic 

 substance 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 po- 

 tassa: in the former case no anmionia was produced; in the 

 latter, abundiince. Sup[)osing that the potash acted, by in- 

 ducing the combination of the nitrogen in the substance with 

 hydrogen, more readily than when no potash was present, 

 and would, thereic)re, be useful as a delicate test of the pre- 

 sence of nitrogen in bodies, I was induced to examine its 

 accuracy by heating it with substances containing no nitrogen, 



as 



