Assaying Penta-Treated Wood By Means of Diazo Compounds

Pentachlorophenol is highly toxic to fungi and insects and is widely used as a wood preservative. The light color of the compound, however, makes qualitative assay of the treatment difficult. A hypothesis that an azo-dye, a colored compound, could be produced by coupling pentachlorophenol and a diazotized aromatic amine was tested. Eighteen amines of various molecular configurations and with different substituted groups were tried on treated white pine sections. The experiments showed that diazotized o-chloroaniline gave the best color reaction with pentachlorophenol. Chlorine apparently was displaced from the para position on the pentachlorophenol molecule and the diazo-orthochloroaniline was coupled at this position, the same position open to coupling on the 2, 3, 5, 6-tetrachlorophenol molecule. Also, it was discovered that diazotized o-chloroaniline has promise as a means of distinguishing between heartwood and sapwood. The color tests on toxicant penetration in wood treated with pentachlorophenol through diazonium salt-phenol coupling reaction probably were not distinctly better than other methods currently used to assay preservative penetration.

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