BOTTLE CONTAINING THE SAME QUANTITIES OF THE SAME REAGENTS EXCEPT THAT THE 10 ML OF DISTILLATE HAVE BEEN REPLACED BY 10 ML OF PURE WATER . THE VOLUME OF THE FERROUS SOLUTION USED IS N' .
CALCULATIONS ( SEE OJ )
NOTES :
1 . THE 10 AND 20 ML PIPETTES AND THE BURETTE USED FOR THE MEASUREMENT MUST BE CERTIFIED AND ACCURATE TO AT LEAST ONE PART PER 1 000 .
2 . THE MEASUREMENT OF THE ACETIC ACID FORMED PERMITS CHECKING THE CHROMOMETRIC DETERMINATION OF THE ALCOHOL AND THE IDENTIFICATION OF THAT ALCOHOL . METHANOL , IN PARTICULAR , IS OXIDIZED TO CARBON DIOXIDE AND WATER UNDER THE CONDITIONS WHERE ETHANOL IS CONVERTED TO ACETIC ACID ; THE OXIDATION OF THE FORMER REQUIRES AT LEAST 12 HOURS HOWEVER , WHEREAS THAT OF ETHANOL IS COMPLETE IN 30 MINUTES ( 14 ) .
IT SHOULD BE NOTED THAT 1 ML OF K2CR2O7 OF CONCENTRATION 33.600 G/L OXIDIZES 3.6596 MG OF METHANOL .
TO MEASURE THE ACETIC ACID , STEAM-DISTILL AND COLLECT THE DISTILLATE . THE VOLUME OF THE DISTILLATE SHOULD BE EQUAL TO AT LEAST 10 TIMES THE VOLUME OF THE SOLUTION IN WHICH THE CHROMOMETRIC TITRATION HAS BEEN CARRIED OUT AND TO WHICH A SMALL EXCESS OF FERROUS SULPHATE HAS BEEN ADDED .
1 ML 0.1N NAOH CORRESPONDS TO 4.607 MG OF ETHANOL .
1 ML K2CR2O7 OF CONCENTRATION 33.600 G/L THUS CORRESPONDS TO 1.71 ML OF 0.1N NAOH .
2.4 . USUAL METHODS FOR WINES AND MUSTS
FIRST USUAL METHOD
MEASUREMENT BY A HYDROMETER
APPARATUS
1 . DISTILLATION APPARATUS : THE APPARATUS IS SIMILAR TO THAT DESCRIBED FOR THE REFERENCE METHOD .
AS FOR THE REFERENCE METHOD OTHER TYPES OF EQUIPMENT MAY BE USED . IN PARTICULAR STEAM DISTILLATION MAY BE EMPLOYED FOR THE DISTILLATION OF THE ALCOHOL , WHICH SPEEDS THE OPERATION , PROVIDED THAT THE APPARATUS AND PROCEDURE FULFIL THE CONDITIONS SPECIFIED FOR THE REFERENCE METHOD ( SEE PAGE 16 ) .
2 . HYDROMETER : THE HYDROMETER USED SHALL COMPLY WITH THE SPECIFICATIONS OF COUNCIL DIRECTIVE 76/765/EEC OF 27 JULY 1976 RELATING TO ALCOHOLOMETERS AND ALCOHOL HYDROMETERS .
THIS APPARATUS SHALL BE CALIBRATED BY A GOVERNMENT DEPARTMENT .
A CALIBRATED THERMOMETER GRADUATED IN 1/10TH DEGREES FROM 0 TO 30* C CERTIFIED TO 1/20TH DEGREE SHALL BE USED .
CARRY OUT THE TEST IN AN UPRIGHT CYLINDRICAL TUBE OF 36 MM DIAMETER AND 320 MM HEIGHT . THE INSIDE DIAMETER OF THE CYLINDER MUST EXCEED THE BULB DIAMETER OF THE HYDROMETER BY AT LEAST 6 MM .
PROCEDURE
1 . DISTILLATION : FREE YOUNG OR SPARKLING WINES OF THE BULK OF THEIR CARBON DIOXIDE BY SHAKING 260 ML OF THE WINE IN A 500 ML BOTTLE WHICH HAS PREVIOUSLY BEEN SILICONIZED INTERNALLY .
MEASURE OUT THE WINE TO BE ANALYZED INTO A 250 ML FLASK WITH AN INTERNAL NECK DIAMETER NOT GREATER THAN 12 MM . TRANSFER TO A DISTILLATION FLASK . RINSE THE FLASK FOUR TIMES WITH 5 ML OF WATER . ADD 10