This unit of measurement (also specific density) describes the quotient of two densities as a dimensionless size ratio. In viticulture, the weight ratio between the volume of wine or grape at the same volume of water (density 1,000) at a measuring temperature of 20 ° Celsius. With grape must this is also called Mostgewicht designated. The result is shown with four decimal places with the code "d" (for density) or "d20 / 20" (20/20 refers to calibration of the measuring device and measuring temperature). The value is analyzed in the wine during quality wine tests and is for the award of the Official test number (Germany) and State test number (Austria) mandatory.
This clearly identifies the status of a wine, because if there is a change (manipulation) after the test, this could be clearly determined by a further analysis. The maximum deviation is 10 ten thousandths. With a value of 0.9917, the range 0.9907 to 0.9927 is considered identical - 0.9906 would already be rated as a change. In addition, the relative density is an indication of the total extract and the alcohol content of a wine. The measurement is carried out using pyknometer or according to the bending vibrator principle, with lower requirements, a physical one is sufficient hydrometer out. For more precise measurement methods, see the keyword analytical testing,