Iron chloride hydroxamic acid complexes

The presence of any of these functional types may be established chemically by applying the hydroxamic acid test. These compounds react with hydroxyl-amine in the presence of sodium hydroxide to form the sodium salt of the corresponding hydroxamic acid. On acidification and addition of iron(m) chloride solution the magenta coloured iron(m) complex of the hydroxamic acid is formed. 

Using two cooled bubblers connected in series and charged with ethanol, 0.5-1 L of air was sampled at a flow of 0.3 L/min. The vinyl acetate was converted to N-hydroxyacetamide by the addition of hydroxylamine hydrochloride and sodium hydroxide. After 30 minutes, the hydroxamic acid was complexed with iron by the addition of hydrochloric acid and ferric chloride. The intensity of the color which developed in 10 minutes was compared to the intensities of standards. The lower limit of detection for this method was reported to be 0.3 yg/mL. 

In the next step, the test solution is cooled and acidified with dilute hydrochloric acid R. Add 0.2 ml of ferric chloride solution R1 diluted ten times and a bluish-red or red color is produced. The product responsible for the color is a complex of iron(III) hydroxamates (Figure 3.18.4). 

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