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Water content determination of bioethanol by Karl Fischer Titration
Bioethanol is mixed with gasoline in various ratios in order to reduce both the demand for gasoline and environmental pollution. The gasoline-alcohol mixture is known in the USA as gasohol and in Brazil as Gasolina Tipo C. In the USA the mixtures E10 and E85, which contain 10% and 85% bioethanol respectively, are widespread. In Brazil the bioethanol content of most mixtures lies between 21% and 23%. Coulometric Karl Fischer Titration by Metrohm The 756 and 831 KF Coulometers from Metrohm easily meet all the specifications stipulated in the standard and are outstandingly suitable for this application. In most cases the sample can be injected directly into the reaction solution. In order to improve the solubility of the samples, xylene (dimethylbenzene) is added to the KF reagent. Get rid of side-reactions and contaminations Many biofuels contain additives that could participate in side-reactions during the direct coulometric Karl Fischer titration. In such cases Metrohm recommends that the biodiesel sample is not injected directly into the reaction solution. Instead the water contained in the biodiesel should be driven off in a Karl Fischer oven. The 860 KF Thermoprep oven is suitable for this. The water is driven off at 120 °C and transported to the titration cell of the KF Coulometer in a stream of carrier gas (dry air or inert gas). This process can be completely automated with the 774 Oven Sample Processor. An additional option is reagent exchange using an automated dosing device. The KF vessel does not have to be opened during this procedure. This means that no hazardous reagents have to be handled, which results in increased operator safety. Product information Coulometric KF Titration: KF Oven:
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