548 Proceedings of the 



analogy and experiment than the former, to the detection of me- 

 tallic bases united to oxygen in the alkaline earths, and to the 

 discovery of the bases of the oilier earths and of boracic acid. 

 These are happy instances of observation, guided by analogy, 

 leading to experiment, and analogy verified by experiment, esta- 

 blishing new scientific truths. The nature of the fixed alkalies 

 having been thus ascertained, and it having been demonstrated that 

 they consisted of metals united to oxygen, analogy, emboldened by 

 previous success, ventured to suggest a similar composition for the 

 volatile alkali or ammonia: this singular body acts upon vegetable 

 colours, and neutralizes the acids in the same way as the other alkalies, 

 but then ammonia had been satisfactorily resolved into hydrogen and 

 nitrogen ; Us nature, therefore, forms more intricate considerations, 

 for, if susceptible of metallisation, its metallic bases must, in all 

 probability, be constituted of those gases or their bases ; and if so, 

 the nature of hydrogen and of nitrogen would be more or less 

 included in the discovery, and perhaps even that of the metals 

 themselves. Such were the analogies that led to the experiment 

 called the metallisation of ammonia, upon which a theory has been 

 founded, under the idea that the singular appearances attendant 

 upon that experiment do really result from the union of metallic 

 matter with the mercury ; but in the first place, the supposed metal 

 has never been separated or insulated ; and in the next, there are 

 strong grounds for believing that the metallisation is a delusion, 

 and that the effects depend upon a mechanical alteration in the 

 arrangement of the particles of the mercury, and not upon its com- 

 bination with an evanescent metal, an opinion strongly corroborated 

 by Mr. Daniell's experiments, of which he has given an account in 

 the first number of this Journal. 



After shewing the supposed metallisation of ammonia by elec- 

 trising mercury in contact with its aqueous solution, and by the 

 action of an alloy of potassium and mercury upon moistened 

 muriate of ammonia, and comparing these appearances with those 

 produced by the action of spongy platinum and mercury upon dilute 

 acetic acid, Mr. Brande made some remarks upon the apparent 

 necessity of the presence of hydrogen in the production of the 

 phenomena, and proceeded to observe that, whatever opinion might 

 be entertained respecting the cause of these appearances, they 

 had opened an avenue to some new speculations upon the discovery 

 of these very singular proximate principles in vegetables, which, 

 under the name of alkalies or alkaloids, constitute a definite series of 

 salifiable compounds : in regard to these the question had arisen, 

 what would be the effect of rendering mercury negatively electrical 

 in contact with them ? The experiments were then shown, of which 

 an account is given in the last number of the present Journal, alter 

 which some observations were offered respecting the ultimate con- 

 stitution of these alkalies, and the analogies which connect them with 

 other vegetable principles bearing many resemblances to them, but 

 not salifiable. The existence of nitrogen in the salifiable bases 

 was especially noticed as a leading 1 peculiarity and connecting link 



