Hot- and Cold-Solvent Technique for Creosote Extraction

The room temperature toluene-pyridine method for extracting creosote from wood was compared with the conventional hot-toluene methods. The evaluation also included a comparison of the mechanical shaving of wood with conventional hand splitting. Southern pine sapwood stakes, 3/4 by 3/4 by 30 inches, were impregnated with three different creosote preservatives at nominal retention levels of 5 and 16 pounds per cubic foot, and were tested after weathering for 6 years. For both types of extractives, the amount of creosote retained in the wood was determined by the “weight difference” method as well as by the “weight-of-extract” method. The average extraction calculated by weight difference was about 1 lb./cu.ft. greater than that calculated by the weight of extract. The cold toluene and pyridine method extracted 0.8 lb. more creosote per cubic foot for shaved wood than did the hot toluene method. From shaved samples 8.6 lb./cu.ft. were extracted by the toluene method and 8.8 lb./cu.ft. were extracted by cold solvent methods, while 8.1 and 8.6 lb./cu.ft. of creosote, respectively, were extracted from split samples. The most accurate estimate of the amount of: preservative in wood is obtained therefore by the cold toluene and pyridine method, by shaving the sample to a fine-sized particle, and by calculating the amount extracted by the weight difference method.

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