Keeping track of evaporating solutions to maintain traceability

Standard solutions are fundamental tools to guarantee traceability in chemical analysis, however, they might suffer solvent evaporation during long storage periods. In this work a measurement model is presented to consider this behaviour and assure the retention of metrological traceability by taking into account solvent evaporation through subsequent weightings at the start and end of the storage period. The proposed iterative formulation is tailored to suit three different experimental setups depending on the available information. Uncertainty budgets based on the proposed models were produced and filled with simulated data to test the contribution of parameters and increment to the combined variance. The results highlighted strengths and drawbacks for each approach but ultimately asserting their suitability within the testing conditions. General considerations were also drawn with recognition of the limitations of the proposed modelisation and the great importance reserved to the knowledge of matrix interactions

Basics of the magnetocaloric effect

This chapter reviews the basic aspects governing magnetocaloric materials from the physics and thermodynamics viewpoint. The thermodynamics of magnetic materials is discussed by introducing the relevant free energy terms together with their microscopic origin and the sources of the magnetic field induced entropy change. Particular attention is devoted to magnetic transitions of the first order type which involves the coupling of different degrees-of-freedom such as: spin, lattice, electronic, magneto-crystalline anisotropy and others. The problem of the irreversibility and hysteresis, present in magnetocaloric materials with transitions of the first order, is discussed in the context of out-of- equilibrium thermodynamics and hysteresis modeling

On the determination of a piston prover dead volume

Dead volume in a piston prover is the part of the internal volume which is never occupied by the piston. It obviously affects measurements performed through the prover, the specific effect depending on the data analysis procedure. In INRIM test rigs, which apply the mass balance method (difference between the estimates of the gas mass at the beginning and at the end of the measurement), the evaluation of the corrections requires knowledge of the initial measurement volume, which depends on the dead volume. Currently, INRIM evaluates the dead volume by geometrical analysis, which involves a large uncertainty. We will propose a method for the dead volume evaluation based on the addition of a well-defined quantity of gas (measured by integration of the output of a calibrated MFC) and by measuring the variation of thermodynamic conditions within the piston. The uncertainty budget of the measurement will be analysed in full detail