A method is described for the determination of aromatic isocyanates in air in the presence of primary aromatic amines. Samples of the test atmosphere are drawn simultaneously through two different absorbing solutions a t 1 1 minute-1 for 10 minutes. One sample is collected in a dimethylformamide solution of 1,6-diaminohexane and the other in a dimethylformamidehydrochloric acid solution of 1,6-diarninohexane. The aromatic amine present, or produced, in each absorbing solution is diazotised and coupled with N-( 1-naphthyl) ethylenediamine to form a coloured complex, the optical density of which is measured spectrophotometrically. The difference between the resulting optical densities gives a measure of the isocyanate content of the air. A complete analysis requires about 30 minutes.

A general field method is described for the determination in air of some organic aromatic isocyanates commonly used in industry. Collection of the isocyanate vapour or aerosol, or both, is effected in a mixture of hydrochloric acid and dimethylformamide. The amine produced is diazotised and coupled with N -1-naphthylethylenediamine to form a coloured complex, the intensity of which is compared with a set of permanent colour standards appropriate to the isocyanate being determined. The method enables the determination of up to 0.04 p.p.m. v/v of isocyanate in air to be made. The procedure is simple and the time required for a complete analysis is about 35 minutes.

The development and preparation of a test paper for mercury in air is described, A measured volume of air is drawn through a silica gel-loaded filter-paper coated with a mixture of copper(1) iodide and sodium carboxymethylcellulose, and in the presence of mercury a pink stain is produced. The paper has been validated in the laboratory and a factory for the reliable determination of mercury vapour in air at concentrations up to 100 pg ~n -~.

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A simple field test for primary aromatic amines in air is described in which the sample is drawn through an impregnated paper to form a coloured stain produced by the reaction of aromatic primary amine groups with 4-(dimethyl-amin0)cinnamaldehyde. The test is sensitive to about l o n g of amine and has been found to be applicable to eleven different amines. It does not distinguish individual compounds and can be affected by airborne alkaline or acidic compounds.