ON THE REACTIVITY OF SAPWOOD AND HEARTWOO D OF DOUGLAS-FIR AS WELL ASTHEIR WATER EXTRACTIVES TOWARDS FORMALDEHYDE

Sap- and heartwood of Douglas fir were fumigated with formaldehyde at 103 degrees C for different time intervals. Thereafter, the extract co ntent and the reactivity of extractives towards formaldehyde, as measu red by the stiasny (Wissing 1955) and UV-method (Roffael 1976), were e valuated. In further investigations, the reactivity of extractives fro m sap- and heartwood of Douglas fir of different ages from different s ites were assessed using the above mentioned methods. The results reve al, that heartwood extractives are much more reactive towards formalde hyde compared with sapwood extractives. The UV-method is more sensitiv e than the stiasny-method in detecting changes in wood extractives due to reactions with formaldehyde. This may be due to the fact, that onl y those reactions leading to precepitation are detectable by the stias ny-method. The results show no pronounced influence of age or site on the reactivity of extractives towards formaldehyde.