GB1354287A - Detection of nitro and nitrosa compounds - Google Patents

Abstract

1354287 Determination of organic nitro and nitroso compounds; photo-electric measurements NATIONAL RESEARCH DEVELOPMENT CORP 17 May 1971 [21 May 1970] 24596/70 Headings G1A and G1B Organic nitro or nitroso compounds are detected and/or estimated by subjecting vapours from them to a controlled thermal degrading to produce nitrogen dioxide and passing them into or through a test reagent for detecting nitrogen dioxide. The method is particularly suitable for the detection of nitroglycerine but may also be used for the detection of ethylene glycol dinitrate, di-ethyleneglycol dinitrate and nitroisobutyltrinitrate. A suitable reagent is sulphanilamide with N-(1 naphthyl)- ethylene diamine which couple on reaction with nitrogen dioxide to form a red dye. The reagent is preferably absorbed on a substrate of alumina, silica gel or paper. Nitrogen oxide and/or nitrogen dioxide present in the atmosphere may be removed, prior to the thermal degradation step, by scrubbing, preferably with fine chromic acid and powdered sodium hydroxide; or alternatively a comparison test may be carried out simultaneously on a sample of the atmosphere known not to contain organic nitro or nitroso compounds. Tests may be carried out using the semi-portable apparatus shown in Fig. 1, in which the vapours are drawn by an electric pump (not shown) through stainless-steel tube 2, glass scrubbing towers 5, 9, glass tube 13 containing an electrically heated platinum wire 14 for effecting the thermal degradation, tube 19 containing the reagent 20, a moisture trap 23 and a flow-meter 24. The tube 19 may be replaced by an absorbtion cell, Fig. 3, (not shown), filled with a solution of the reagent and fitted with a lamp and a photo-cell. A double cell, Fig. 4b, may be used when a comparison test is to be made. This is made from transparent plastics and each cell chamber 36 has a gas inlet 37, a gas outlet 38, a light source 44 and a photo-cell 39. A filter 41 may be secured by an end cap 40. The outputs of the photo-cells may be measured differentially and the resulting signal may control an alarm.