ISO 1768-1975 pdf free.Glass hydrometers — Conventional value for the thermalcubic expansion coefficient (for use in the preparation ofmeasurement tables for liquids).
1.SCOPE AND FIELD OF APPLICATION:This International Standard specifies,”for use in thepreparationofmeasurement tables for liquids,aconventional value for the thermalcubic expansion coefficient ofglass hydrometers. ltstates how theindications ofhydrometers having a thermal cubic expansion coefficient differing from the recommendedconventional value may be corrected for use in connection with measurement tables in the construction of which theconventional value has been used.
2.APPLICABILITY oF COEFFICIENT:Measurement tables for liquids provide means for deriving,from the indications of density and/or relative densityhydrometers at various temperatures,the correspondingvalue of the density and/or relative density with respect to water of the liquid at a reference temperature.In principle such measurement tables must take account of the thermalexpansion of the hydrometers.Since hydrometers are made of various glasses,their expansion coefficients differ. Consequently, it is desirable to use ia sngie,ntretioo “ofthermal cubic expansion coefficient in the construction of
measurement tables and toassociate with the tablesinformation on how to adjust appropriately to the tabtesthe indication of a hydrometer having any other thermalcubic expansion coefficient.
3.CONVENTIONAL VALUE OF COEFFICIENT:lt is recommended that when preparing measurement tablesfor liquids the thermal cubic expansion coefficient of glasshydrometers should be taken to be 0,000 0258c.
4.INDICATION OF COEFFICIENT USED
4.1The thermal cubicexpansion coefficient of thehydrometers, namely0,000 025/oC,usedin theconstruction of measurement tables for liquids shall bestated in the tables.
4.2lt shall be indicated in the measurement tables thathydrometer readings may have to be modified preparatoryto using the tables if the thermat cubic expansion coefficient ofthe hydrometers useddiffers from0,000 025/c.
5.USE OF. THE TABLES INASSoCIATION WITHHYDROMETERSHAVINGATHERMALcUBICEXPANSIONcOEFFICIENTDIFFERENT FROM0,000 025/c
5.1 General The relationship between
Assuming that t c is2o°c, the preferred standardtemperature ofdensityhydrometerscomplyingwithISO/R 649，Density hydrometers for general purposes，R’may be modified either by multiplying it by or by adding to it lf t °c is 15 °c or 27°c, the other recommended standardtemperatures, these values shall be substituted for 20°c.ISO 1768 pdf download.