1 000 ML
PROCEDURE
1 . PRELIMINARY TEST : END-POINT COLOUR DETERMINATION : PLACE 25 ML OF BOILED DISTILLED WATER INTO A CRYSTALLIZING DISH OF 12 CM DIAMETER , ADD 1 ML OF BROMOTHYMOL BLUE ( 4 G / L ) AND 5 ML OF CARBON DIOXIDE FREE WINE . NEUTRALIZE WITH SUFFICIENT 0 * 05N SODIUM HYDROXIDE SO THAT THE COLOUR CHANGES TO GREEN-BLUE . THEN ADD 5 ML OF THE PH 7 BUFFER SOLUTION .
2 . ACTUAL MEASUREMENT : PLACE 30 ML OF BOILED DISTILLED WATER , 1 ML OF BROMOTHYMOL BLUE ( 4 G / L ) , 5 ML OF CARBON DIOXIDE FREE WINE INTO A CRYSTALLIZING DISH OF 12 CM DIAMETER , AND ADD 0 * 05N SODIUM HYDROXIDE TO PRODUCE AN IDENTICAL COLOUR TO THAT IN THE CONTROL .
LET THE TITRATION BE N .
CALCULATIONS
THE TOTAL ACIDITY IS EXPRESSED IN MILLIEQUIVALENTS PER LITRE :
10 N _ 0 * 35 N * _ 0 * 25 N *
OR IN GRAMS OF TARTARIC ACID PER LITRE
0 * 75 ( N _ 0 * 035 N * _ 0 * 025 N * ) .
NOTES :
1 . IN THE CASE OF WHITE , ROSE OR ALMOST COLOURLESS RED WINES THE QUANTITY OF WINE MAY BE DOUBLED . 10 ML OF WINE AND 0 * 1N SODIUM HYDROXIDE ARE THEN USED ; THE FORMULAE FOR THE CALCULATION REMAIN THE SAME .
2 . WHEN SEVERAL WINES OF THE SAME ORIGIN ARE TO BE EXAMINED A SINGLE END-POINT COLOUR MAY BE USED FOR ALL THE MEASUREMENTS . THE ABSENCE OF A CHANGE OF COLOUR ON THE ADDITION OF FURTHER BUFFER WILL VERIFY THAT THE END-POINT HAS BEEN REACHED .
9 . VOLATILE ACIDITY
9.1 . DEFINITION
THE VOLATILE ACIDITY DERIVES FROM THE FATTY ACIDS OF THE ACETIC SERIES PRESENT IN WINE EITHER IN THE FREE STATE OR COMBINED AS A SALT .
9.2 . PRINCIPLE OF THE METHOD
SINGLE REFEREE AND ROUTINE METHOD . SEPARATION OF THE VOLATILE ACIDS IS OBTAINED BY STEAM DISTILLATION AND REDISTILLATION OF THE DISTILLATE . THE WINE IS ACIDIFIED WITH TARTARIC ACID ( APPROX . 0 * 5 G FOR EACH 20 ML ) PRIOR TO STEAM DISTILLATION . PRECAUTIONS MUST BE TAKEN TO AVOID THE CARBON DIOXIDE IN THE DISTILLATE . THE INDICATOR USED IS PHENOLPHTHALEIN . THE ACIDITY OF DISTILLED FREE AND COMBINED SULPHUR DIOXIDE IS NOT CALCULATED AS VOLATILE ACIDITY AND SHOULD BE DEDUCTED FROM THE ACIDITY OF THE DISTILLATE AS WELL AS ANY ACIDITY FROM SORBIC ACID .
9.3 . EXPRESSION OF RESULTS
THE VOLATILE ACIDITY IS EXPRESSED IN MILLIEQUIVALENTS PER LITRE AND IS DETERMINED TO THE NEAREST 0 * 5 MILLIEQUIVALENT .
SINGLE REFEREE AND USUAL METHOD
PRINCIPLE OF THE APPARATUS AND ITS CONTROL
THE APPARATUS CONSISTS OF A STEAM GENERATOR , A BUBBLER INTO WHICH THE WINE SAMPLE IS PLACED , ARECTIFYING COLUMN AND A CONDENSER .
IN VIEW OF THE LARGE VARIETY AND TYPE OF EQUIPMENT WHICH HAVE BEEN