1871.] Dr. Divers on Salts of Nitrous Oxide. 425 



At Greenwich the egress only will be visible. 



h m s 



Last internal contact, June 5, at 16 44 23 ) Mean times at 

 „ external „ „ 17 2 15 J Greenwich. 



The sun will rise at 15* 46 m . 



II. " On the Existence and Formation of Salts of Nitrous Oxide." 

 By Edward Divers, M.D. Communicated by Professor W. 

 Odling, M.B., F.R.S. Received March 2, 1871. 



1 . Metallic sodium thrown on a solution of an alkali nitrate was found 

 by Schonbein * to reduce it to nitrite. He contented himself, however, with 

 merely detecting the nitrite by the iodide and starch test. By using the 

 sodium in the form of amalgam the complete reduction of the nitrate to nitrite 

 can be readily effected, and silver nitrite freely precipitated from the solu- 

 tion by first neutralizing it with an acid and then adding silver nitrate. 



2. But so soon as nitrite is thus formed by the sodium, it itself begins to 

 suffer reduction, as well as the remaining nitrate, by the action of more 

 sodium. This reduction of the nitrite is rendered evident by the efferves- 

 cence which attends it, the gas given off consisting of pure nitrous oxide. 

 If excess of sodium amalgam be gradually added to the nitrate solution, 

 and its action moderated by keeping the vessel containing the mixture in a 

 stream of cold water, the effervescence only becomes very lively when the 

 sodium added has nearly reached the proportion of two atoms to one of 

 the nitrate used. When four atoms of sodium have been oxidized by the 

 solution, the further addition of it is without effect ; no more effervescence 

 takes place, and the sodium remains unchanged in the mercury. 



3. The very alkaline liquid which is left by the reaction contains a new 

 salt, though in relatively small quantity — the salt of nitrous oxide. The 

 action of sodium on sodium nitrate may therefore be thus formulated 



1st stage : £0, j o + Na 2 =NO } 0+Na 2 0. 



2nd stage: £° }o + Na 2 =*J a } 0+Na 2 0. 



As regards the escape of nitrous oxide during the reduction, this is ex- 

 plained by the reaction on each other of two molecules of the new salt, 

 under the influence of the heat produced by the oxidation of the sodium, 

 thus : — 



L}o + L}o=£}o + ^}o + . 



* Erdmann's Journ. fur prafct. Chemie, vol. Ixxxiv. (1861) p. 202. 



f When ammonium nitrate is employed instead of sodium or potassium nitrate, the 

 action of the sodium is the same ; and it is here interesting to point out that ammo- 

 nium nitrate is an exception to the conclusion at which Gay-Lussac and Thenard arrived 

 (Journ. de Physique, vol. lxix. 1809, p. 463), after they had tried the carbonate, chlo- 



2 Li 2 



