392 Intelligence and Miscellaneous Articles. 



Jan. 20. — " On the Heat disengaged during Metallic Substitu- 

 tions." By Thomas Andrews, M.D., M.R.I. A., Vice-President of 

 Queen's College, Belfast, &c. Communicated bj"- Michael Faraday, 

 Esq.,D.C.L.,F.R.S. &c. 



In a paper which was published in the Philosophical Transactions 

 for 1S44, the author deduced from the experimental inquiry there 

 recorded the general law, that when one base displaces another from 

 any of its neutral combinations with an acid, the heat evolved or 

 abstracted is always the same, whatever that acid element may be, 

 provided the bases are the same. Extending a similar inquiry to 

 salts with metallic bases, he establishes, as the result of the investi- 

 gation of -which an account is given in the present paper, the ge- 

 neral principle that when an equivalent of one and the same metal 

 replaces another in a solution of any of its salts of the same order, 

 the heat developed is, with the same metals, constantlj^ the same, 

 the expression " of a solution of the same order" being understood 

 to mean a solution in which the same precipitate is produced by the 

 addition of an alkali, or, on one view of the composition of such 

 salts, in which the metal exists in the same state of oxidation. The 

 metallic salts, in the precipitation of which by other metals the 

 evolved heat was ascertained, were those of copper precipitated by 

 zinc, iron or lead ; of silver, precipitated by zinc or copper ; and of 

 lead, mercury, and platinum precipitated by zinc : and the acid ele- 

 ments were either the sulphuric, hydrochloric, acetic or formic acids. 

 From the last series of experiments the author deduces, that if three 

 metals A, B, and C, be so related that A is capable of disi)lacing B 

 and C from their combinations, and also B capable of displacing C, 

 then the heat developed in the substitution of A for C will be equal 

 to that developed in the substitution of A for B added to that deve- 

 loped in the substitution of B for C ; and a similar rule may be ap- 

 plied to any number of metals similarly related. 



LI 1 1. Intelligence and Miscellaneous Articles. 



ACTION OF NITRIC ACID ON BRUCIA. BY M. AUG. LAURENT. 



IT is well known to chemists that brucia, when treated with nitric 

 acid, becomes of a very intense red colour. Some time since, 

 M. Gerhardt, on examining this phaenomenon attentively, observed 

 that there was disengaged at common temperatures, a gaseous body 

 slightly soluble in water, which had a very decided smell of apples, and 

 burnt with a yellowish flame, accompanied with nitrous vapours. 

 For want of material M. Gerhardt did not continue his observations ; 

 nevertheless he concluded from them that the gas disengaged from 

 brucia is nitrous aether. 



M. Liebig has repeated this experiment, and expresses himself as 

 follows in the miserable diatribe which he has aimed at us : — " The 

 production of nitrous aether by a body which contains neither alco- 

 hol nor aether appears to me as remarkable as it is important in the 

 history of aethereal combinations, on which account I undertook to 

 repeat the experiments of M. Gerhardt. I condensed a portion of 

 the gas which is disengaged from the brucia, and obtained a liquid 



