Original scientific paper

Determination of nitrogen dioxide in air

Mirka Fugaš ; Institut za medicinska istraživanja i medicinu rada, Zagreb

Abstract

Three modifications of the Griess-Ilosvay reagent for the nitrite determination were investigated - the one according to the Manual of the ICI practice, the second after Saltzman, and the third after Jacobs and Hochheiser. Saltzman's reagent was found to be better than the ICI's concerning the colour intensity and the concentration range for which the reagent could be applied, and better than Jacobs' and Hochheiser's concerning the time of colour development and colour stability. Sunlight and elevated temperatures have unfavorable effects upon the reagents and their coloured products with NO2. The colour produced by Saltzrnan's reagent, as well as the reagent itself, were very stable at room and refrigerator temperatures. The ICI reagent has one advantage only: a more rapid colour development, 60 that it can be used for quick exposure assessment, on condition that the resulting concentration of NO2 is not higher than 0.5 mg per ml of solution. The colour produced in the reaction of N02 with the ICI reagent was not stable for the concentrations higher than those mentioned above. The consistency of the results obtained with several absorbers of the same type were examined. Out of the six types of absorbers only Pyrex and Sial absorbers with a fritted disk proved satisfactory; the optimal conditions for their use were as follows: air flow 0.1-0.6 l/min: temperature not differing too much from 20° C. As to how much of N02 actually present in the air sample takes part in the production of the azo-dye, the results of Gill (55.58%) are in good agreement with the results of Patty and Petty (57%). Saltzman, however, claims a recovery of 72%. Our results (60%) obtained for the samples taken in evaporated bottles from known mixtures of N02 and the air prepared after Gill confirm the results of Patty-Petty and Gill. Trapping efficiency of Pyrex and Sial absorbers was about 85%, if the efficiency of evacuated bottles was taken as 100%. The overall efficiency of the method using Pyrex or Sial absorbers was practically 50%. Under the given conditions the method is accurate and reliable for a wide concentration range: from a few parts per billion to several thousand parts per million.

Keywords

Hrčak ID:

181754

URI

https://hrcak.srce.hr/181754

Publication date:

25.9.1962.

Article data in other languages: croatian

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