Determination of absolute salinity via density and refractive index measurements and establishment of speed of dound measurements traceability
Speed of sound measurements have previously been used to derive seawater salinity and density over limited ranges where conductivity measurements have not been reliable. It has been conventional for several decades to derive the salinity of the seawater from measurements of conductivity. These measurements are only affected by the dissolved ionic, electrolytic, solutes in seawater, being the definition of absolute salinity the total mass fraction of all dissolved matter in water. Several studies show the metrological compatibility of salinity results obtained by refractometry and densimetry. The goals of this work are to validate IPQ’s density meter and speed of sound measurement system (Anton Paar, DSA5000M) and to widen the salinity range in which refractometry and densimetry can be used to determine salinity.
João André is currently doing his thesis to obtain a master’s degree in Mechanical Engineering from the NOVA School of Science and Technology-Nova University of Lisbon–Portugal
Andreia Furtado has received a PhD in Materials Science in 2012 from the Faculty of Sciences and Technology – Nova University of Lisbon – Portugal. She is the head of Properties of Liquids Laboratory of Portuguese Institute for Quality (IPQ). where she works as a senior metrology scientist since 2006.
Sara Moura has received a postgraduate degree in Management in Quality and Food Safety in 2004 from the Higher Institute of Health Sciences – South; Egas Moniz C.R.L. – Portugal. She is senior technician in Properties of Liquids Laboratory of Portuguese Institute for Quality (IPQ). where she works since 2021. Her research interests are in the areas of density. viscosity. surface tension and rheology.
Raquel Quendera is a chemist engineer and PhD student in Chemistry. She is the Head of the Electrochemistry Laboratory of IPQ. Her research interests are in the areas of electrochemistry (primary and secondary potentiometric methods for pH and pHT determination in seawater) and environmental analysis (such as metals determination by ICP-MS. ICP-OES. XRF and AAS).
Olivier Pellegrino has received a PhD in Physics in 1995 from the Pierre et Marie Curie University of Paris VI – France. He is the head of Photometry and Radiometry Laboratory of Portuguese Institute for Quality (IPQ). where he has worked as a senior metrology scientist since 2002.
Helena Navas has received a PhD from NOVA School of Science and Technology – Universidade NOVA de Lisboa – Portugal. She is currently Assistant Professor at the Department of Mechanical and Industrial Engineering of the NOVA School of Science and Technology – Portugal and researcher at UNIDEMI. Her research interests are in the areas of innovation, continuous improvement, quality, and process management.
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Density, Refractive index, Salinity, Speed of sound
