REACTIONS AND IDENTIFICATION 321 dioxide (which is oxidised to sulphuric acid) before passing into lime-water. A mist of condensed water on the upper portion of the tube A indicates the presence of hydrogen. To detect the presence of hydrogen in this way, however, the copper oxide must first be strongly heated in a crucible and then allowed to cool in a good desiccator: otherwise the water normally absorbed by the very hygroscopic copper oxide will always give a mist on the tube A. 2, Nitrogen. The Lassaigne Sodium Test.* This test is general for organic nitrogen compounds. The organic compound is heated with molten sodium, the nitrogen present thus forming sodium cyanide. The latter is extracted with water and then identified by first adding ferrous sulphate and then boiling the alkaline mixture in order to convert the cyanide to ferrocyanide: 6NaCN + Fe(OH) 2 = Na 4 [Fe(CN) 8 ] + 2NaOH Ferric chloride solution is then added to convert the sodium ferrocyanide to the deep blue ferric ferrocyanide (or Prussian Blue), dilute sulphuric acid being
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.