1892.] The Formation and Decomposition of Nitrous Acid. 27 



Immiscible metals. 

 Lead and zinc 



Lead and aluminium .... 



Bismuth and zinc 



Bismuth and aluminium. . 



J) 55 



Solvent metal. 

 Tin 

 Silver 

 Tin 

 Silver 

 Tin 

 Silver 

 Tin 

 Silver 



Approximate ratio. 

 PbZn 6 

 Pb 2 Zn 

 Pb 2 Al 7 

 Pb 3 Al 

 BiZn 10 

 BiZn 2 

 BiAl 10 

 Bi 2 Al 



The author has much pleasure in acknowledging the assistance of 

 Mr. Sydney Joyce in carrying out a large proportion of the analytical 

 work requisite for the experiments above described. 



VI. " The Conditions of the -Formation and Decomposition of 

 Nitrous Acid." By V. H. VELEY, M.A., University Museum, 

 Oxford. Communicated by Professor ODLING, F.R.S. Re- 

 ceived April 12, 1892. 



Introductory. 



Throughout the whole science of chemistry there is possibly no 

 reagent so frequently represented as taking part in various trans- 

 formations, but of which so little definite is known, as nitrous acid. 

 In many text-books its properties are cursorily discussed in a few 

 lines, while some writers have gone so far as to deny its existence 

 altogether even in the presence of nitric acid. Among the commoner 

 examples of reactions considered to be effected by nitrous acid, it is 

 necessary only to mention the conversion of the primary paraffinoid 

 amines into the corresponding alcohols, the formation of nitroso- and 

 diazo-derivatives, and the preparation of the fulminates. In a 

 previous paper* it was my endeavour to prove that the solution of 

 certain metals in nitric acid was conditioned by the presence of 

 nitrous acid, and the cause of the chemical change explained on the 

 supposition that the acid is alternately formed and decomposed. 



As a fitting corollary to these investigations, it seemed worthy of 

 interest to examine to some extent the validity of this hypothesis by 

 endeavouring to imitate the reactions supposed to take place on 

 solution of the metal, either when no metal is present, or when the 

 metallic salt is either present or absent. 



The stability of nitrous acid in presence of nitric acid forms also a 

 part of this research, and, conversely, the stability of nitric acid in 

 absence of nitrous acid is discussed. 



In the present, as in my former, investigations, it will be under- 



* ' Phil. Trans.,' 1891, A, pp. 312313. 



