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Ref. No. : NOIR 709-1968 (E)
IS0
I N T E R N AT I O N A L O R G A N IZ AT I O N FOR S TA N DARD 1 ZATl O N
IS0 RECOMMENDATION
R 709
DETERMINATION OF ESTER VALUE
AND CALCULATION OF ESTER CONTENT OF ESSENTIAL OILS
1st EDITION
April 1968
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of IS0 Recommendations and IS0 Standards
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For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 709, Determination of ester value and calculation of ester content
of essenîial oils, was drawn up by Technical Committee ISO/TC 54, Essential oils, the Secretariat of
which is held by the Repartiçao de NormaiizaçZo (IGPAI).
Work on this question by the Technical Committee began in 1953 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In November 1965, this Draft IS0 Recommendation (No. 873) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,
by the following Member Bodies :
Argentina Ireland South Africa,
Australia Israel Rep. of
Belgium Italy Sweden
Brazil Japan Turkey
Canada New Zealand
U.A.R.
Chile Paraguay United Kingdom
France Poland U.S.S.R.
Germany Portugal Yugoslavia
India Romania
One Member Body opposed the approval of the Draft
Netherlands
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council
which decided, in April 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 709-1968 (E)
IS0 Recommendation R 709 April 1968
DETERMINATION OF ESTER VALUE
AND CALCULATION OF ESTER CONTENT OF ESSENTIAL OILS
1. SCOPE
This IS0 Recommendation describes the method to be used in determining the ester value and
calcula&g the ester content of essential oils, expressed as a conventionally accepted ester, with the
exception of certain oils containing lactones and oils containing a substantial proportion of aldehydes,
2. DEFMTION
Ester vatue E. The number of milligrammes of potassium hydroxide required to neutralize the acids
liberated by the hydrolysis of esters present in 1 g of the essential oil.
3. PRINCIPLE OF THE METHOD
Hydrolysis of the esters by standard volumetric solution of alkali and titration of the excess alkali.
4. REAGENTS
4.1 Ethanol, 95 oh (v/v), at 20 OC, freshly neutralized with the alkali solution (4.2) using the
solution (4.4) as indicator, or the solution (4.5) when the essential oil has components that
contain phenol groups.
Potassium hydroxide, 0.5 N solution in ethanol (4.1).
4.2
4.3 Hydrochloric acid, 0.5 N standard volumetric aqueous solution.
Phenolphthalein alcoholic solution, obtained by dissolving 0.2 g of phenolphthalein in ethanol
4.4
(4.1) until a volume of 100 cm3 is obtained.
4.5 Phenol red alcoholic solution, obtained by dissolving 0.04 g of phenol red in 20 (v/v) ethanol
until a volume of 100 cm3 is obtained.
5. APPARATUS
Suitable device for maintaining ebullition
5.1
5.2 Saponification fisk, &&resistant giass flask, with ground-glass neck, of capacity 100 to
200 cm3 to which can be fitted a ground-giass fube at least 1 m in length and about 1 cm
internal diameter, serving as a reflux condenser or, if necessary, a reflux cooler. Equip the
condenser during cooling wi
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