298 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 20, 



of combustion, in which nitrogen, and not oxygen, acts as the sup- 

 porter. After the operation is concluded, a metallic matter, of a 

 copper-red colour, sprinkled with brilliant crystalline laminae, is pro- 

 duced ; and, in proof that this contains nitrogen, it may be suf- 

 ficient to state, that hydrate of potass extricates from it sufficient 

 ammonia to saturate a large amount of muriatic acid. 



It is even not necessary to bring the metal into contact with pure 

 nitrogen ; for if a closed charcoal-crucible containing titanic acid be 

 kept at a high temperature for some hours, sufficient nitrogen pene- 

 trates the porous texture of the vessel to displace the oxygen, and to 

 form with the metal a nitride, capable, as in the preceding instance, 

 of being decomposed by hydrate of potass into ammonia and titanic 

 acid. It is true, that in order to eifect a combination between the 

 metal and the nitrogen, the titanic acid must first be reduced, and con- 

 sequently the presence of carbon in some form or other g would appear 

 to be an essential condition. But if such a reaction be conceived as 

 taking place, not near the surface, but at such depth as that at which 

 the advocates of the Chemical Theory of Volcanos would place the 

 still unoxidized, or but partially oxidized, nucleus of the globe, no 

 reducing agent would then be required to bring about the supposed 

 union*. 



Other experiments are given by Wohler, all tending to establish 

 the same point ; but enough probably has been said to show that, at 

 an elevated temperature, titanium exerts a strong affinity for nitro- 

 gen, and that the compound which it forms evolves ammonia under 

 the agency of the fixed alkalies. Now, that titanium is present 

 in most volcanos, is obvious from the occurrence of titanite in several 

 places in Auvergne, at Kaiserstuhl in Germany, at TenerhTe,in Mexico, 

 and amongst the recent as well as the older products of Vesuvius and 

 its neighbourhood. And, if it be objected that it is found in an oxi- 

 dized and not in a metallic form, the same remark applies equally 

 to all the other bases which are present along with it. 



It may, however, be fairly asked, whether its probable quantity 

 within the mountain be sufficient to account for the large amount of 

 ammonia often disengaged ? 



This, indeed, is a question to which I should be loth to give an 

 affirmative reply ; and therefore, whilst maintaining that the affinity 

 of titanium for nitrogen does furnish us with a vera causa for the 

 presence of ammonia amongst volcanic products, I am more disposed 



* This ammonia would, of course, combine with muriatic acid so soon as ever 

 it came into contact with that body ; but the experiments of Gay-Lussac, which 

 most chemists have repeated, show that, at a high temperature, a chloride in con- 

 tact with silica or alumina has its chlorine set free, whilst its base forms a com- 

 pound with the silicic or other acids present. 



The existence, therefore, even of common salt at the spot where the nitride was 

 formed, would not prevent the alkalies from exerting their proper action upon 

 the nitride, and giving birth to ammonia. 



The only difference in the result would be, that, in this case, the formation of 

 sal-ammoniac would be immediate, whilst otherwise, it might take place during 

 the passage of the gas upwards to the external air. 



