Physico-Chemical Methods for Wood Diagnosis

The woods of pond pine and sand pine are not distinguishable on the basis of anatomy, color, odor, taste, weight, or any other known physical property, although they are readily separated by a simple chemical test. When shavings from sapwood of pond pine were placed in one test tube and shavings from sand pine in another, a purple color reaction could be obtained in the former by adding methanol-hydrochloric acid, whereas the same reagent would produce no change of color in the latter. The same reagent can be used to differentiate between black gum end sap gum. Acidified methanol on wood will distinguish virus-infected wood from sound. Fluorescent light has also been used to distinguish between species of wood. Benzidine-sodium nitrite solution can be used to distinguish heartwood from sapwood in the pines. It was first used to distinguish between red and white oak. The reagent is composed of two separate solutions that are mixed in equal amounts before applying to the wood surface. They are: Solution A.–Five grams benzidine dissolved in 23cc. of 25 percent hydrochloric acid and 970 grams of water. Solution B.–A 10 percent solution of sodium nitrite (sodium nitrate will not do). Within 10 minutes after applying the chemical to the oak, a distinctive reddish-orange color appears on the red oak. If the color is a dark greenish-brown, the wood is white oak.

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