PA20 = 1 + 0.987 P , FROM WHICH P CAN BE THEN CALCULATED .
THE QUANTITY OF CARBON DIOXIDE CONTAINED IN A SPARKLING WINE IS GIVEN BY THE FOLLOWING FORMULAE :
- IN LITRES OF CARBON DIOXIDE PER LITRE OF WATER : PA20 ( 0.86 - 0.01 A ) ( 1 - 0.00144 S ) OR ( 1 + 0.987 P ) ( 0.86 - 0.01 A ) ( 1 - 0.00144 S ) ,
- IN GRAMS OF CARBON DIOXIDE PER LITRE OF WINE : 1.977 PA20 ( 0.86 - 0.01 A ) ( 1 - 0.00144 S ) OR 1.977 ( 1 + 0.987 I ) ( 0.86 - 0.01 A ) ( 1 - 0.00144 S ) .
NOTES :
1 . IF THE APHROMETER IS GRADUATED IN ABSOLUTE PRESSURE AND IN ATMOSPHERES , MULTIPLY THE PRESSURE AS MEASURED BY THE COEFFICIENT * GIVEN BY THE TABLE BELOW TO RELATE IT TO 20* C .
2 . IF THE APHROMETER IS GRADUATED IN EXCESS PRESSURE EXPRESSED IN ATMOSPHERES , ADD ONE TO THE MEASURED VALUE BEFORE THE CORRECTION IS MADE .
IN BOTH CASES , HAVING OBTAINED PA20 , ONE CAN CALCULATE P ( THE EXCESS PRESSURE IN BARS AT 20* C ) AND THE QUANTITY OF CARBON DIOXIDE CONTAINED IN THE WINE EITHER IN LITRES OF CARBON DIOXIDE OR IN GRAMS OF CARBON DIOXIDE PER LITRE OF WINE .
RELATION OF THE ABSOLUTE PRESSURE PA20 OF A SPARKLING WINE AT 20* C TO THE ABSOLUTE PRESSURE PAT AT T* C ( SEE OJ )
NOTE :
THE ABOVE EXPRESSIONS ARE SUITABLE FOR ALCOHOL TITRES WITHIN THE RANGE 10 TO 14 % ( V/V ) AND SUGAR CONTENTS TO WITHIN THE RANGE 0 TO 100 G/L . AS WINES DO NOT HAVE A CONSTANT COMPOSITION , THESE EXPRESSIONS ARE ONLY ACCURATE TO WITHIN 2 TO 3 % .
23 . ALLYL ISOTHIOCYANATE
23.1 . PRINCIPLE OF THE SINGLE METHOD
ALLYL ISOTHIOCYANATE PRESENT IN WINE IS COLLECTED BY DISTILLATION AND IDENTIFIED BY GAS CHROMATOGRAPHY .
23.2 . REAGENTS
1 . ETHANOL , ANALYTICAL REAGENT GRADE .
2 . STANDARD SOLUTION : ALCOHOLIC SOLUTION OF ALLYL ISOTHIOCYANATE CONTAINING 15 MG/L .
3 . FREEZING MIXTURE CONSISTING OF ETHANOL AND DRY ICE ( TEMPERATURE - 60* C ) .
23.3 . APPARATUS
1 . DISTILLATION APPARATUS AS SHOWN IN THE FIGURE ON PAGE 86 . A STREAM OF NITROGEN IS PASSED CONTINUOUSLY THROUGH THE APPARATUS .
2 . HEATING MANTLE , THERMOSTATICALLY CONTROLLED .
3 . FLOWMETER .
4 . GAS CHROMATOGRAPH FITTED WITH A FLAME SPECTROPHOTOMETRIC DETECTOR EQUIPPED WITH A SELECTIVE FILTER FOR SULPHUR COMPOUNDS ( = 394 NM ) .
5 . STAINLESS STEEL CHROMATOGRAPHIC COLUMNS WITH INTERNAL DIAMETERS OF 3 MM AND 3 M LONG FILLED WITH CARBOWAX 20 M AT 10 % ON CHROMOSORB WHP 80 TO 100 MESH .
6 . MICROSYRINGES , 10 UL .
23.4 . METHOD
PUT TWO LITRES OF WINE INTO THE DISTILLATION FLASK , INTRODUCE A FEW MILLILITRES OF