Analysis of the Acyl Halogen Compounds

Phosgene may be recognised by its odour. The minimum concentration detectable by odour is 4 mgm. per cu. m. of air, according to Suchier.i 

By the use of chemical methods phosgene can also be detected by one of the usual tests for the hydrochloric acid formed by hydrolysis of the vapour. 

Following are the methods usually adopted for detecting phosgene  

Method using Dimethyl Amino Benzaldehyde—Diphenylamine Paper. Phosgene, even if present in traces in the air, can be detected by means of papers prepared with dimethyl amino benzaldehyde and diphenylamine. 

The test-papers should be kept in a closed container filled with carbon dioxide and protected from light, as it seems that the colour changes merely by the action of sunlight.  

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