Nitrous acid complexing action

The action is rapid, and the acidity of the electrolyte is unaffected. The error due to nitrous acid is increased by the presence of a large amount of iron iron is reduced by the current to the iron(II) state, whereupon the nitric acid is reduced. This error may be minimised by the proper regulation of the pH and by the addition of ammonium nitrate instead of nitric acid, or, best, by the removal of the iron prior to the electrolysis, or by complexation with phosphate or fluoride. 

The action of nitrous acid on a primary, aliphatic amine is still a complex process, inasmuch as it is necessary to postulate certain steps that are imperfectly understood, but it can nevertheless be considered that the process leads ultimately to a carbonium ion.26,27 The carbonium ion thus formed is termed hot, that is to say, it is non-solvated and chemically activated the nature of the products resulting from its decay is essentially determined by the conformation of the initial state the electronic factors in effect at the time of the transition state exert little influence.27... 

Nitrous acid is also employed as a nitrating agent in organic chemistry. Thus, M. F. Aitken and T. H. Reade studied its action on p-iododimethylaniline, and obtained nitro-derivatives J. Reilly and P. J. Drumm, its action on substituted p-phenylenediamines and F. Bettzieche, and R. H. A. Plimmer, its action on amides and other amino-compounds. Nitrogen trioxide was found by H. Reihlen and A, Hake to form att unstable complex with stannic chloride—possibly 38nCl4.4N02. Nitrogen trioxide reacts with stannic chloride not in the ordinary blue but in the colourless form. A. Klemenc and R. Scholler studied the partition of nitrous acid between ether and water. The poisonous qualities of nitrous acid have been discussed by A. Purcell,3 etc. 

He said that hydroxynitrosylsulphonic acid is produced by the action of sulphur dioxide on nitrous acid in 70 per cent, sulphuric acid as a direct product of the interaction of nitrous and sulphurous acids, and not by the reduction of chamber crystals—nitroxylsulphonic acid—because he supposed that the latter cannot exist in less than 80 per cent, sulphuric acid. This assumption was shown, by W. C. Reynolds and W. H. Taylor, to be unfounded nitroxylsulphonic acid can exist in the presence of even 60 per cent, sulphuric acid. Further, the blue colour produced by the action of sulphurous acid, or other reducing agent, on a nitrite in the presence of a cone, sulphuric acid soln. of a copper salt, was supposed by F. Raschig to be the copper salt of P. Sabatier s acid, whereas, according to W. C. Reynolds and W. H. Taylor, the product is the complex which nitric acid forms with copper sulphate, and studied by W. Manchot, V. Kohlschiitter, etc.— vide supra. The existence of F. Raschig s nitrosylsulphonic acid may therefore be questioned, and the same remark applies to his statement of the identity of P. Sabatier s blue acid with the product of the reaction of nitrous and sulphurous acids in the presence of a copper salt. 

Nitroso Benzene.—The nitroso or nitrous acid derivatives are exactly analogous to the nitro or nitric acid derivatives. As the nitro radical is (AO2), so the nitroso radical is NO) and whenever this radical is present, as we found in the nitroso-amines (p. 61), and as we shall find in some more complex compounds of the dye class, it means nitroso derivative. The simplest representative, viz., nitroso benzene, CeHs—NO, differs from nitro benzene in that it is not formed by the direct action of the acid on the hydrocarbon nor, as shown above, is it able to be isolated as a reduction product of nitro benzene. It is prepared, however, by the oxidation of phenyl hydroxyl amine, either by means of ferric chloride, FeCU, or of chromic acid, CrOa. 

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