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HIGH temperature tars obtained from coke ovens and gas works are characterised by a high content of aromatic compounds, some of which serve as the main source of phenolic disinfectants, e.g., the phenols and cresols. Producer gas tars are obtained by the gasification of coal at low temperatures and the tar constitutents are believed to be essentially aliphatic.The composition of producer-gas tars does not seem to have been studied in much detail in the past, nor do they seem to have been extensively used as a source of tar acid disinfectants. Sometimes their disposal was difficult, but now they are usually used as industrial fuel. In recent years change in the design of gas producers and the processes of gas cleaning before use have altered the character of the tar.During a recent study into the composition of modern producer-gas tars the opportunity was taken of investigating the germicidal properties of the tar acid constituents. EXPERIMENTAL METHODSPreparation of tar acids from crude tar.The crude tar was obtained from producer-gas plant gasifying bituminous coal. The tar was recovered from the gas by a process of cooling and washing with water, and was distilled in an iron still up to a temperature of 340" C. The distillate oil obtained was washed with caustic soda to remove the tar acids which were subsequently liberated with hydrochloric acid. The mixture of tar acids was re-distilled under partial vacuum and the distillate contained a mixture of refined tar acids. This mixture of acids was then fractionated at 13 mm. pressure in a column, and five separate empirical fractions were obtained at the following temperatures : 110" C. : 110-130" C. ; 130-150" C. ; 150-180" c. ; 180-210" C.Since the tar acids obtained were insoluble in water, suitable emulsions were prepared in castor-oil soap. The Rideal-Walker coefficient was determined on the emulsified soap solutions and the final result obtained by multiplying by the dilution factor introduced. RESULTSThe R.W. coefficients of the five fractions increased progressively for each fraction and varied from approximately 11 for the lowest to 30 for the highest fraction. 24

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