The QualitativeTest for Nitrogen in Organic Compounds Using the Oxygen Flask Method In crur firat ).ear lahoratorie~we hd\e wcently c h ~ n g ~irum d thz r r s d ~ r ~ mwdium al f u A n methud forclrmenrnl analysis of organrc nmpoundr tu rhr oxygen !lark method as drwrihed by Hcmltml and Corhrir and .lenkms.' We h a w found this to be a superior test as these authors claim, hut for compounds containing both nitrogen and bromine a negative test for nitrogen & obtained. Boulton indicates that in the comhustion process the organic halogen forms hydrogen halide. If the test is conducted on a sample containing iodine it is immediately obvious that a considerable quantity of free halogen is also formed. This does not interfere in the ease of iodine. but for a samnle containine bromine the oxidation ootential of the elemental bromine produced iz sufficient ra oxidize u, nitrate any n i t k s acid ior&d tram the nitrogcn i n the t q a n i o compuund Thus the subwquent test for n~rnngen,which relic* un the derccrion of nitrous a d , fnh. W e have ncrt expoienccd this prohlem wnth compounds containing chlorine. The difficulty is easily overcome by the presence of a reducing agent in the absorbent solution. Thus, if bromine is found (which we detect using fluorescein) the eomhustion should he repeated, this time using 1ml of 2M NaOH containing 0.1 g of sodium sulfite as the absorbent solution. For compounds that also contain nitrogen, a positive test will now be obtained.
' Boulton, C. H., Educ. in Chem., 10, 231 (1973). Gumrie, R. D. and Jenkins, I.
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D.,J. Chem. Educ., 57,226(1980)
Journal of Chemical Education
Rudolf Thomas University of Tasmenia Hobart. Tasmania. 7005. Australia
