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The table of contents is amended as follows:

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In Chapter III the following part is added:

‘III.3.   DETERMINATION OF VOLATILE ACIDITY OF SPIRIT DRINKS

1.   Scope

The method has been validated in an interlaboratory study for rum, brandy, marc and fruit spirits, at levels ranging from 30 mg/l to 641 mg/l.

2.   Normative references

ISO 3696: 1987 Water for analytical use — Specifications and test methods.

3.   Definitions

3.1.   Volatile acidity is calculated by deducting the fixed acidity from the total acidity.

3.2.   Total acidity is the sum of titratable acidities.

3.3.   Fixed acidity is the acidity of the residue left after evaporating the spirit to dryness.

4.   Principle

The total acidity and fixed acidity are determined by titration or by potentiometry.

5.   Reagents and materials

During the analysis, unless otherwise stated, use only reagents of recognised analytical grade and water of at least grade 3 as defined in ISO 3696:1987.

5.1.   0,01 M sodium hydroxide solution (NaOH)

5.2.   Mixed indicator solution:

6.   Apparatus and equipment

Indirect laboratory apparatus, grade A glassware and the following:

7.   Sampling and samples

Samples are stored at room temperature prior to analysis.

8.   Procedure

8.1.   Total acidity

8.1.1.   Preparation of sample

The spirit is irradiated with ultrasonic (ultrasonication) or stirred two minutes under a vacuum to rid it of carbon dioxide if required.

8.1.2.   Titration

Pipette 25 ml of the spirit into a 500 ml Erlenmeyer flask.

Add about 200 ml of cooled boiled distilled water (prepared fresh daily) and 2-6 drops of the mixed indicator solution (5.2).

Titrate with the 0,01 M sodium hydroxide solution (5.1) until the yellow-green colour changes to violet in the case of colourless spirits, the yellow-brown colour to red-brown in the case of brown-coloured spirits respectively.

The titration may also be carried out by potentiometry, to pH 7,5.

Let n1 ml be the volume of the 0,01 M sodium hydroxide solution added.

8.1.3.   Calculation

The total acidity (TA) expressed in milliequivalents per l of spirit is equal to 0,4 × n1.

The total acidity (TA′) expressed in mg of acetic acid per l of spirit is equal to 24 × n1.

8.2.   Fixed acidity

8.2.1.   Preparation of sample

Evaporate 25 ml of the spirit to dryness:

8.2.2.   Titration

Dissolve the residue left after evaporating with cooled boiled distilled water (prepared fresh daily) and make up to a volume to circa 100 ml and add 2-6 drops of the mixed indicator solution (5.2).

Titrate with the 0,01 M sodium hydroxide solution (5.1).

The titration may also be carried out by potentiometry, to pH 7,5.

Let n2 ml be the volume of the 0,01 M sodium hydroxide solution added.

8.2.3.   Calculation

The fixed acidity (FA) expressed in milliequivalents per l of spirit is equal to 0,4 × n2.

The fixed acidity (FA) expressed in mg of acetic acid per l of spirit is equal to 24 × n2.

9.   Calculation of volatile acidity

9.1.   Expression in milliequivalents per l:

Let:

Volatile acidity, VA, in milliequivalents per l is equal to:

TA – FA.

9.2.   Expression in mg of acetic acid per l:

Let:

Volatile acidity, VA, in mg of acetic acid per l is equal to:

TA′ – FA′.

9.3.   Expression in g of acetic acid per hl of pure 100 % vol. alcohol is equal to: