. TO AVOID ANY CONFUSION WITH HYDROMETERS GRADUATED AT 15* C AND NORMALLY READ AT THE LIQUID SURFACE , AN INDICATION OF THE GRADUATION IN DENSITY AT 20* C AND OF THE READING AT THE " TOP OF THE MENISCUS " SHALL BE CARRIED EITHER ON THE GRADUATED SCALE OR ON A STRIP OF PAPER ENCLOSED IN THE BULB .
THESE HYDROMETERS SHALL BE CALIBRATED BY A GOVERNMENT DEPARTMENT .
THE RESULT SHALL BE EXPRESSED TO FOUR DECIMAL PLACES TO THE NEAREST THREE UNITS OF THE FOURTH DECIMAL PLACE ( MORE OR LESS 0.0003 ) .
A CALIBRATED THERMOMETER GRADUATED IN MINIMUM STEPS OF 0.5* C SHALL BE USED .
DETERMINATION OF DENSITY - PROCEDURE
POUR 250 ML OF WINE INTO A LEVEL GLASS CYLINDER OF 36 MM INTERNAL DIAMETER AND 320 MM HEIGHT . PLACE A HYDROMETER AND THERMOMETER IN THE CYLINDER .
READ THE OBSERVED TEMPERATURE T* C ONE MINUTE AFTER MIXING THE SAMPLE WELL . REMOVE THE THERMOMETER AND READ THE APPARENT DENSITY FROM THE HYDROMETER AFTER A FURTHER MINUTE .
THE DENSITY AT 20* C IS THEN CALCULATED USING TABLE V , VI OR VII ( 7 ) . ( SEE OJ )
CORRECT THE DENSITY FOR THE EFFECT OF ADDED SULPHUR DIOXIDE AND OTHER PRESERVATIVES IN THE SAME MANNER AS DESCRIBED FOR THE REFERENCE METHOD .
1.5 . SUPPLEMENT TO THE REFERENCE METHOD - MEASUREMENT BY PYCNOMETER ON SINGLE-PAN BALANCE
PRINCIPLE
THE REFERENCE METHOD FOR THE DETERMINATION OF THE DENSITY OF MUSTS AND WINES AND FOR THE DETERMINATION OF THE ALCOHOLIC STRENGTH OF WINES REQUIRES THE USE OF A TWO-PAN BALANCE AND A PYCNOMETER WITH ITS TARE BOTTLE OF THE SAME EXTERNAL VOLUME TO ELIMINATE THE EFFECT OF AIR . THIS SIMPLE TECHNIQUE MAY ALSO BE APPLIED WHEN A SINGLE-PAN BALANCE IS USED SUBJECT TO A SUPPLEMENTARY WEIGHING OF THE TARE BOTTLE TO TAKE ACCOUNT OF THE VARIATIONS OF THE BUOYANCY OF AIR :
- WHEN ESTABLISHING THE PYCNOMETER CONSTANTS : WEIGHT OF THE EMPTY PYCNOMETER , VOLUME AT 20* C , THE WEIGHT T0 OF THE TARE BOTTLE IS DETERMINED ,
- WHEN DETERMINING DENSITY , THE WEIGHT T1 OF THE TARE BOTTLE IS AGAIN DERIVED AND THE WEIGHT OF THE PYCNOMETER FILLED WITH LIQUID IS CORRECTED FOR THE MATHEMATICAL VALUE OF THE DIFFERENCE BETWEEN T0 AND T1 . THE REMAINDER OF THE CALCULATIONS ARE UNCHANGED .
PROCEDURE
1 . STANDARDIZATION OF THE PYCNOMETER
ESTABLISH THE FOLLOWING CONSTANT CHARACTERISTICS OF THE PYCNOMETER :
- ITS WEIGHT EVACUATED , P0 ,
- ITS VOLUME AT 20* C , V20 ,
- AT THE SAME TIME , RECORD ACCURATELY THE WEIGHT OF THE TARE BOTTLE T0 .
THE WEIGHT OF THE TARE BOTTLE T0 IS OBTAINED BY WEIGHING TO THE NEAREST 0.1 MG .
THE WEIGHT OF THE PYCNOMETER EVACUATED , P0 , IS THE WEIGHT P OF THE CLEAN AND DRY PYCNOMETER , FILLED WITH AIR LESS THE MASS M OF THE AIR WHICH IT CONTAINS . OBTAIN THE MASS M OF THE AIR BY