Biodiesel density characterization using a pycnometer

Abstract

8 p. : il.This study shows an alternative method to digital density meters to characterize biodiesel density. The possibility of using a pycnometer for biodiesel density measurements was hereby investigated considering biodiesel instability when in contact with air. The choice of method of pycnometer was due to its small measurement uncertainty compared with the requirements of existing regulation in Brazil and ASTM and ISO standards, that consider approved the biodiesel fuel within a range between 850 kg/m³ and 900 kg/m³ at a temperature of 20 ºC. The biofuel is isolated from the atmosphere by covering the pycnometer flask with a plastic foil during the density measurement. Results obtained from samples measured by digital density meters and by this alternative method are compared at several temperatures. The highest difference occurs for 40 ºC being of the order of a few tenths of g/cm³, wich shows significant variation considering the values obtained by national metrology institutes. However, it is still compatible with the Brazilian officiak specifibstion for biodiesel commercial operations