COAL-TAR AISTD WATER-GAS TAR CREOSOTES. 



91 



Win Support 



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 'nirar Cup 



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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 

 0.5 mg. 



DAVIS SPOT TEST Worvr /n/er^ ^jfVorer Our/er 



T. H. Davis {1^6) , in 1909, pro- ^^r~l7^ ^°<"^ -" s.pporr>.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 the test may be applied for a preliminary 

 examination and will give a good indication to the analyst of what 

 he may expect to find in the creosote under examination. When 

 the color, character, and size of the spot are taken into consideration 

 remarkable approximations may be made, provided a large number 

 of authentic spots are available. Pure coal-tar creosote, pure water- 

 gas-tar creosote, coal tar, water-gas tar, wood tar, wood-tar creosote, 

 and petrol pum oils all give spots that are characteristic of themselves 

 and different from the others. Mixtures of creosote with tars also 

 give characteristic spots. 



Fig. 43.- 



-Type of extractor recommended for 

 carbon" test. 



'free 



