. Bulletin of the Department of Agriculture. Agriculture; Agriculture. COAL-TAR AISTD WATER-GAS TAR CREOSOTES. 91 Win Support Condanstr 'Cop of fi/rvr pQp«r or ^lundum Wora 'nirar Cup F/aa/i Method.—Weigh 10 grams of dry creosote in 100 cc. beaker. Add about 50 cc. of pure laenzol and transfer at once to'the filter cup. The filter cup or thimble is pre\'iously weighed, and the paper cup shall always be kept in a weighing bottle until ready for use. Wash out the beaker with benzol, passing all washings through the filter cup and place the latter at once in the extraction apparatus. Extract
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. COAL-TAR AISTD WATER-GAS TAR CREOSOTES. 91 Win Support Condanstr 'Cop of fi/rvr pQp«r or ^lundum Wora 'nirar Cup F/aa/i Method.—Weigh 10 grams of dry creosote in 100 cc. beaker. Add about 50 cc. of pure laenzol and transfer at once to'the filter cup. The filter cup or thimble is pre\'iously weighed, and the paper cup shall always be kept in a weighing bottle until ready for use. Wash out the beaker with benzol, passing all washings through the filter cup and place the latter at once in the extraction apparatus. Extractor shall contain a suitable quantity of pure benzol. Sufficient heat to boil the solvent shall be pro\'ided by means of an electric heater or a steam bath. Continue the extraction until the descending solvent is practically colorless and remove the filter cup and dry in steam oven until all solvent is driven off; cool in desiccator and weigh. The balance used for this purpose should be accurate to mg. DAVIS SPOT TEST Worvr /n/er^ ^jfVorer Our/er T. H. Davis {1^6), in 1909, pro- ^^r~l7^ ^°.ir, posed a test, which he called the spot test, for the preliminary testing of creosote oil for free carbon. This test has been used for a long time by distillers, and consists in placing 6 drops of the oil on blotting paper and noting the character of the spots which remain. If free carbon is present it will manifest itself by a ring of free carbon the same size as the spot, but the oil will spread out into a ring 1 to 2 or 2^ inches in diameter. This test is ex- ceedingly delicate and shows the presence of very minute quan- tities of carbon; for this reason it is of small value for deter- mining the amount of free carbon in creosotes. It will, however, show whether the regular free-carbon determinations should be made, and is of value as a preliminary test for this purpose. The test itself has not been given by creosote chemists the attention it deserves. H. Cloukey (47) shows that
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