How to identify formaldehyde

The chemical formula of formic aldehyde, SON. Formaldehyde is the first in the homologous series of aldehydes and is a substance having the functional aldehyde group of the – DREAM, which determines the chemical properties of aldehydes, and also gives the opportunity to recognize him among the other substances of other classes. For a more accurate analysis, for example, for the determination of formaldehyde among other aldehydes require more sophisticated reagents and special equipment.

A characteristic reaction of aldehydes is the reaction of silver mirror. In order to do that, it is necessary that the dishes had the perfect sterility, as the slightest impurities on the tube walls can reduce the results of the experiment to zero. Take a test tube and pour into it 2 ml of silver nitrate solution which it is desirable to prepare before commencing work. Dropwise, add diluted ammonia solution. First, there is the sediment, which then dissolves. To the mixture add no more than 1 ml of formaldehyde and put the tube in a water bath. Its walls are covered with a thin layer of silver, which will remind the mirror surface. This is the result of the interaction of ammonia solution of silver oxide with formaldehyde. As a result, formic acid, and recovering silver.

Oxidation of formaldehyde by copper hydroxide (II). Take the tube, pour into it 2 ml of copper sulfate (II), then add potassium hydroxide. The reaction will fall deposits blue. Add to it 1 ml metanola and heat the solution. First fall deposits of yellow color due to the formation of copper hydroxide (I). Continue heating - yellow precipitate change its color to red. This is due to the fact that the hydroxide of copper (I) decomposed to copper oxide (I) and water. Formaldehyde in this reaction is oxidized to formic acid. Loss first yellow and then red precipitate and an indicator of the presence of aldehyde.