8 P. C. Ray — On Mercnrous Nitrite. [No. 1, 



heating will effect this [decomposition] if the acid be concentrated."* 

 Mercurous nitrite seems to behave exactly like silver nitrite. 



The traces of niti'ous acid, present in the yellow nitric acid, no 

 doubt, start the reaction, but how to account for the continued forma- 

 tion of mercurous nitrite ? For, this small quantity is soon used up 

 according to the equation given above. There must be a parallel 

 reaction going on to keep up the supply of nitrous acid. Acvvorth and 

 Armstrong thus explain the action of copper on nitric acid.f 

 Cu-f 2 HNO3 = 2 H+Cu(N03)2 

 2H + HNO3 = HNO2 + OH2 

 3 HiSr02 = 2 NO + HNO3 + OHg. 



Adopting this view, the mercurous nitrpte would continue to be 

 formed for some time, and being insoluble in the raensti-uum, would be 

 precipated ; wJdlst mercurous nitrate would remain in solution. The 

 strength of the acid also would go on diminishing, till a time arrives 

 when mercurous nitrite is no longer stable in this liquid, the nitrous 

 acid decomposing according to the equation : 



3 HNOg =2 NO + HNO3 + OH2 

 and Marignac's salt begins to be formed. The transformation of the 

 nitrite into nitrate is however very slow, the process extending over 

 weeks. 



During the initial stages of the reaction the reverse change seems to 

 take place ; for, on the surface of the mercury somewhat bi-isk effer- 

 vescence goes on, but proportionally very little nitric oxide escapes. 

 During its upward ascent most part of it is absorbed, thus : — 

 2NO + HN03-fH20 =3HN02. 

 A strong proof in favour of this view seems to be the fact that 

 as *oon as the superincumbent liquid is poured off, torrents of red 

 fumes appear on the surface of mercury. :|: 



* On the Reduction of Nitric Acid, &c., Chem. Soc. Journ., Vol. LI. (1877 ), 

 p. 54 ef .seq. 



t Whether NO is formed through the agency of nascent hydrogen, or by the 

 direct action of the metal on nitric acid must be left at present an open question. 

 Cf. Deville: De I'etat naissant, Cornet. Rend., 1870, liXX., 22, 550. 



X Veley also arrives at this conclusion. " If the conditions are such that 

 " these metals [Copper, Mercury and Bismuth] dissolve, it would appear that the 

 " metallic nitrite is at first formed, together with nitric oxide. The former is de- 

 " composed by the excess of nitric acid to liberate nitrous acid, whilst the latter 

 " reduces the nitric acid to form a further quantity of nitrous acid." 



" Eventually the net result is the product of two reverse chemical changes 

 " represented by the equations - 



(1 ) 2 NO + HNO3 + H.p = 3 HNOo. 



(2) 3 HNO2 = 2 NO + HNO3 + H2O." 



Proc. Royal Soc. (1890), 48. page 458. 



