XVIII IMEKO WORLD CONGRESS Metrology for a Sustainable Development September, 17 – 22, 2006, Rio de Janeiro, Brazil CONTRIBUTION TO DETERMINATION OF DENSITY AND ALCOHOLIC CONTENT IN MIXTURES ETHANOL-WATER IN BRAZIL Ricardo Rezende Zucchini 1 ,Juliana de Souza Themudo 2 1 Instituto de Pesquisas Tecnológicas do Estado de São Paulo S.A - IPT, São Paulo, Brazil, zucchini@ipt.br 2 Instituto de Pesquisas Tecnológicas do Estado de São Paulo S.A - IPT, São Paulo, Brazil, jst@ipt.br Abstract: Ethanol is one of the most important Brazilian export goods and its international market is growing strong, mainly because of a number of measures taken by several countries in order to reduce environmental pollution, for example, adding amounts of ethanol into regular gasoline or even using pure ethanol-moved motors. Quality assurance of ethanol is becoming more and more important in order to make Brazil able to achieve larger shares of international market, every day more demanding and competitive. Chemical composition of ethanol-water blends can be determined from their density. In this paper is presented an analysis comparing the density of blends of ethanol with water at 20°C, obtained using Brazilian standard NBR 5992- 80, and by using the model described in the International Recommendation OIML R22. The analysis has identified systematic differences between the results, suggesting that the Brazilian standard should be revised. Keywords: ethanol, density, regulations, standardization 1. INTRODUCTION Since the last decade, growing pressures have been observed for the reduction of the environmental pollution by emissions of CO 2 , as a form of preventing the greenhouse effect. The Kyoto’s Protocol has defined reductions up to 20% of the emissions of CO 2 until 2012. Several developing countries, such like United States, Japan, and Germany among others, started to consider the substitution of part of the fossil sources of energy by new renewable ones, with prominence for the combustible alcohol and the biodiesel. In the study accomplished under the project OPTI [1] , it was verified that the potential of the world market of ethyl alcohol is growing quickly, what makes possible the arising of great new suppliers, futures competitors of Brazil, that is today one of the largest producers of ethyl alcohol, and the largest exporter. In order to achieve larger shares of international market, every day more demanding and competitive, Brazilian producers of ethyl alcohol need to demonstrate the quality of their product. However, the sector demands standardized methods, reference materials widely recognized and up-to-date technical standards. For example, the technical standard NBR 5992-80 [2] presents the reference method for the determination of the density and alcoholic content in mixtures ethanol-water using the hydrometer-method. It also allows to calculate the density of a mixture at 20°C and its alcoholic content, using the measured density of that mixture at an arbitrary temperature between 10°C and 40°C. This is the only Brazilian technical standard that defines the behavior of the densities of mixtures ethanol-water, and that is why used as the reference in analysis and research, being also used as technical foundation for several legal and normative documents, such as the specifications of fuels [ 3] [4] and beverages [5] . Considering its importance and the long validity period without revisions, in this work, was evaluated the accuracy of density of mixtures at standard temperature of 20ºC, in comparison with the Recommendation R22 of the International Organization of Legal Metrology, that presents a international recognized model to densities of mixtures ethanol-water. 2. BEHAVIOR MODELS OF DENSITY OF MIXTURES ETHANOL-WATER 2.1. The Brazilian Model The Brazilian standard, NBR 5992-80, based in governmental decree, is the only Brazilian model for the densities of mixtures ethanol-water in function of temperatures, it also allows to determinate of alcoholic contents, that can be expressed in ºINPM and ºGL. This standard, presents a group of tables from where, using experimental densities in any temperature between 10°C and 40°C, can be obtained the specific gravity at 20°C and the alcoholic content. The standard was established to obtain measurements of densities using the hydrometer–method, with accuracy of 0,0010 g/cm 3 , in function of variabilities of thermometer and hydrometers. However it is necessary, to assure that the model presented in the tables does not have errors, because the accuracy have to defined from the very precise values. Moreover, the model presented in this standard, can be used to convert density values, that can be obtained from the another measurements methods, and for determination of their alcoholic contents.