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Ref. No. : ISO/R 754-1968 (E)
IS0
I N T ER N AT I O N A L O R G A N IZAT I O N FOR STAND AR D IZATl ON
IS0 RECOMMEN DATION
R 754
ACETIC ANHYDRIDE FOR INDUSTRIAL USE
METHODS OF TEST
1st EDJTION
June 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore oniy
by the national standards organization of that country, being
a member of ISO.
For each individual country the oniy valid standard is the national standard of that country.
Printed in Switzerland
Ais0 issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 754, Acetic anhydride for industnàl use - Methods of test, was
drawn up by Technical Committee ISO/TC 47, Chemistry, the Secretariat of which is held by the
Ente Nazionale Italian0 di Unificazione (UNI).
Work on this question by the Technical Committee began in 1956 and led, in 1962, to the
adoption of a Draft IS0 Recommendation.
In November 1963, this Draft IS0 Recommendation (No. 653) 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 :
Australia Hungary Romania
Austria India Spain
Belgium Israel
Switzerland
Chile Italy
U.A.R.
Colombia Korea, Rep. of
United Kingdom
Czechoslovakia Netherlands
U.S.A.
France Poland
U.S.S.R.
Germany Portugal
Yugoslavia
Two Member Bodies opposed the approval of the Draft :
Japan
New Zealand
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in June 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 754-1968 (E)
CONTENTS
Page
1. Scope . 7
2. Sample . 7
PART I - METHODS OF TEST FOR GENERAL USE
3. Determination of distillation yield . 7
4. Determination of ash content . 8
5. Limit test for inorganic chlorides . 8
6. Limit test for inorganic sulphates .
9
7. Determination of anhydride content . 10
8. Determination of bromine index . 11
9. Determination of permanganate index . 11
PART II - METHODS OF TEST FOR SPECIAL PURPOSES
1 o. Limit test for heavy metals (including iron) . 13
11. Determination of iron content . . 14
12. Determination of phosphate content . . . 15
13. Determination of arsenic content . . 17
19
14. Determination of water content . .
19
15. Determination of total halogen content* . .
Determination of total sulphur content* . . 19
16.
17. Determination of dichromate index . . . 19
18. Determination of mercury . . 21
19. Sulphuric acid test . . 22
20. Te st re port . . 22
*
Not included in this IS0 Recommendation as these determinations are still under study.
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ISO/R 754-1968 (I
IS0 Recommendation R 754 June 1968
ACETIC ANHYDRIDE FOR INDUSTRIAL USE
METHODS OF TEST
1. SCOPE
This IS0 Recommendation describes methods of test for acetic anhydride for industrial use, and is
divided into two parts, namely :
Part I - Methods of test for general use
Part II - Methods of test for special purposes
2. SAMPLE
Take a volume of sample that is sufficient for all analyses to be carried out so that it is representative
of the bulk.
Place the sample in a clean, dry and air-tight glass stoppered bottle of such a size that it is nearly
filled by the sample.
When it is necessary to seal the container, care should be taken to avoid the risk of contaminating the
sample in any way.
PART I - METHODS OF TEST FOR GENERAL USE
3. DETERMINATION OF DISTILLATION YIELD
Use the method described in IS0 Recommendation R 918, Test method for distillation
3.1
(Distillation yield and distillation range).
3.2
The following details, not given in the above IS0 Recommendation, apply to acetic anhydride :
Thermometer, (see clause 3.2 of IS0 Recommendation R 918) should also comply with the
following requirements :
Values in degrees Celsius
Maximum error in
Thermometer range Graduations Maximum error an interval of
10 degrees Celsius
98 to 152
A correction of 0.050 (JI - 760) degrees Celsius where p is the barometric pressure in standard
millimetres of mercury, is added to the specified distillation temperatures (see clause 5.1 of
IS0 Recommendation R 918). The interval before the first drop of distillate falls from the end
of the condenser should be 12 to 17 minutes (see clause 6.1 of IS0 Recommendation R 918).
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ISO/R 754-1968 (E
4. DETERMINATION OF ASH CONTENT
4.1 Apparatus
Ordinary laboratory apparatus.
4.2 Procedure
4.2.1 Evaporate to dryness a known mass (between 10 and 100 g depending on the ash content
expected) of the sample in a weighed platinum or silica dish of capacity 50 ml, and gently
ignite the residue until all carbonaceous matter has disappeared.
4.22. Cool the dish and its contents to atmospheric temperature in a desiccator containing
anhydrous calcium chloride, and weigh.
4.3 Expression of results
100 X MJ
Ash, 'L (m/m) =
M2
where
is the mass, in grammes, of the residue,
M,
is the mass, in grammes, of the test portion.
M2
5. LIMIT TEST FOR lNORGANIC CHLORIDES
This method is applicable when the chioride content, expressed as C1, is not greater than 0.05 and not
less than 0.0005 'L. If the chloride content lies outside that range, the mass of test portion taken
(5.4.1) should be reduced or increased and an appropriate adjustment made to the expression of
0.05
-ml in clause 5.4.4.
X
5.1 Principle
Comparison of the turbidity, obtained by the addition of silver nitrate to a solution prepared
from the sample in presence-of nitric acid, with that similarly obtained from a chloride solution
of known concentration.
5.2 Reagents
Distilled water or water of equivalent purity should be used in the test. Ali reagents and filter
paper should be chloride free.
5.2.1 Nitric acid, approximately 5 N solution.
5.2.2 Standard chloride solution (0.1 mg Cl/ml). Dilute 28.2 ml of 0.1 N hydrochloric acidsolu-
tion to 1000 ml with water.
5.2.3 Silver nitrate, 50 g/i solution.
5.3 Apparatus
Ordinary laboratory apparatus.
5.4 Procedure
5.4.1 Weigh 50 f 0.5 g of the test sample, dissolve in water, transfer to a 250 ml one-mark volu-
metric flask, dilute to the mark with water and mix.
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ISO/R 754-1968 (
5.4.2 If the solution is not clear, pass it through a filter paper. This should remove turbidity due to
aluminium. If any turbidity remains in the filtrate due to contamination with wax, remove
it by shaking with a suitable solvent, for example, light petroleum.
5.4.3 To prepare the chloride solution of known concentration,add to a 100 ml Nessler cylinder
1.0 mi of the standard chloride solution (5.2.2), dilute to the mark with water, add 2 ml of
nitric acid solution (5.2.1) and mix.
5.4.4 For a sample required to contain not more than x of chloride,expressed as C 1, transfer to
O 05
a 100 ml Nessler cylinder an aliquot, - ml, of the solution prepared from the test sample
X
(5.4.1), dilute to the mark with water, add 2 ml of nitric acid solution (5.2.1), and mix.
5.4.5 Add to each Nessler cylinder 1 ml of silver nitrate solution (5.2.3) and mix. Allow the
cylinders to stand in the dark for 5 minutes then compare the turbidity produced by the test
sample with that produced by the chloride solution of known concentration.
5.5 Expression of results
A sample required to contain not more than x of C 1 does so if the turbidity produced from
its solution (5.4.4) is equal to or less than that produced from the chloride solution of known
concentration (5.4.3).
6. LIMIT TEST FOR INORGANIC SULPHATES
This method is applicable when the sulphate content, expressed as SO4, is not greater than 0.1 and
not less than 0.001 If the sulphate content lies outside that range the mass of test portion taken
o. 1
(6.4.1) should be reduced or increased and an appropriate adjustment made to the expression - ml
X
in clause 6.4.4.
6.1 Principle
Comparison of the turbidity, obtained by the addition of barium chloride to a solution prepared
from the sample in the presence of hydrochloric acid, with that similarly obtained from a
sulphate solution of known concentration.
6.2 Reagents
Distilled water or water of equivalent purity should be used in the test.
c
6.2.1 Sodium carbonate, N solution.
6.2.2 Hydrochloric acid, N solution.
6.2.3 Barium chloride, Bac 1, .2H,O, 100 g/1 solution.
6.2.4 Standard sulphate solution (0.1 mg S04/ml). Dilute 20.8 ml of 0.1 N standard volumetric
solution of sulphuric acid to 1000 ml with water and mix thoroughly.
a
6.3 Apparatus
Ordinary laboratory apparatus.
6.4 Procedure
6.4.1 Weigh 100 * 1 g of the test sample, dissolve it in water, add 0.2 ml of sodium carbonate
solution (6.2.1) and evaporate to dryness in an evaporating basin on a boiling water bath.
Dissolve the residue in water containing 1 ml of hydrochloric acid solution (6.2.2), transfer
to a 250 mi one-mark volumetric flask, dilute to the mark with water, and mix.
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ISO/R 754-1968 (I
6.4.2 If the solution is not clear, pass it through a filter paper. This should remove turbidity due to
aluminium. If any turbidity remains in the filtrate due to contamination with wax, remove
it by shaking with a suitable solvent, for example, light petroleum.
6.4.3 To prepare the sulphate solution of known concentration, add to a 100 ml Nessler cylinder
4.0 mi of the standard sulphate solution (6.2.4), dilute to the mark with water, add 2 ml
of hydrochloric acid solution (6.2.2) and mix.
6.4.4 For a sample required to contain not more than x 'L of SO,, transfer to a 100 ml Nessler
o. 1
cylinder an aliquot, - ml, of the solution prepared from the test sample (6.4. I). Dilute to
X
the mark with water, add 2 ml of hydrochloric acid solution (6.2.2) and mix.
6.4.5 Add to each Nessler cylinder 2 ml of barium chloride solution (6.2.3) and mix, Allow the
cylinders to stand for 5 minutes, mix again, and compare the turbidity produced by the
test sample with that produced by the sulphate solution of known concentration.
6.5 Expression of results
A sample required to contain not more than x 'L of SO, does so if the turbidity produced from
d
its solution (6.4.4) is equal to or less than that produced from the sulphate solution of known
concentration (6.4.3).
7. DETERMINATION OF ANHYDRlDE CONTENT
7.1 Principle
Hydrolysis of a given amount of the sample by means of a standard volumetric solution of
sodium hydroxide, and determination of the alkali consumed, by back titration of the excess
of sodium hydroxide with standard volumetric solution of hydrochloric acid.
Reaction with aniline of an equivalent quantity of sample in accordance with the reaction
(CH,CO),O + C,H,NH,- C,H,NHCOCH, + CH,COOH
and titration of the acetic acid formed using a standard volumetric solution of sodium hydroxide.
Calculation of the acetic anhydride content from the difference between the volumes of sodium
hydroxide solution consumed respectively in the hydrolysis of the sample and in the titration
of the acetic acid formed in its reaction with aniline.
7.2 Reagents
Distilled water or water of equivalent purity should be used in the test.
7.2.1 Sodium hydroxide, N standard volumetric solution.
7.2.2 Hydrochloric acid, N standard volumetric solution.
7.2.3 Benzene, dry, freshly distilled.
7.2.4 Aniline, dry, freshly distilled.
7.2.5 Methanol.
7.2.6 Phenolphthalein. 5 g/l ethanolic solution. Dissolve 0.5 g of phenolphthalein in 100 ml of
95
(v/v) ethanol and make it faintly pink by the addition of dilute sodium hydroxide
solution.
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ISO/R 754 -1968 (
7.3 Apparatus
Ordinary laboratory apparatus, and
7.3.1 Weighingpipette, capacity about 5 ml.
7.3.2 Two flasks, ground glass stoppered, capacity 500 ml.
7.4 Procedure
7.4.1 Dissolve about 2 g of the test sample, accurately weighed by means of the weighing
pipette (7.3.1), in 50.0 ml of the sodium hydroxide solution (7.2.1) contained in a stoppered
flask (7.3.2), and allow to stand for 1 hour. Add 40 ml of benzene (7.2.3), 10 ml of aniline
(7.2.4) and 250 ml of methanol (7.2.5), and titrate the excess of alkali with the hydrochloric
acid solution (7.2.2), using 0.5 ml of the phenolphthalein solution (7.2.6).
7.4.2 Dissolve about 2 g of the test sample, accurately weighed by means of the weighing pipette
(7.3.l),in 20ml of the benzene (7.2.3) in a stoppered flask(7.3.2),cool in ice and add a cold
solution of 10 ml of the anline (7.2.4) in 20 ml of the benzene (7.2.3). Allow the mixture
to stand for 1 hour in ice. Add 250 ml of methanol (7.2.5) and 50.0 ml of the sodium hydro-
xyde solution (7.2.1). Titrate the excess of alkali with the hydrochloric acid solution (7.2.2)
using 0.5 ml of Phenolphthalein solution (7.2.6).
7.5 Expression of results
Acetic anhydride[(CH,CO),C$
where
is the volume, in millilitres, of N hydrochloric acid solution (7.2.2) used in
VI
clause 7.4.1,
is the volume, in millilitres, of N hydrochloric acid solution (7.2.2) used in
V,
clause 7.4.2,
is the mass, in grammes, of the test portion taken in clause 7.4.2,
Ml
is the mass, in grammes, of the test portion taken in clause 7.4.2.
M,
8. DETERMINATiON OF BROMINE INDEX
Use the method described in IS0 Recommendation R 76 1, Method for the determination of bromine
index.
9. DETERMINATION OF PERMANGANATE INDEX
9.1 Definition
The permanganate index is defined as the number of milligrammes of potassium permanganate
reduced by 100 mi of the sample under the conditions of the test.
9.2 Principle
Reaction of the sample under controlled conditions with an excess of potassium permanganate
in the presence of dilute sulphuric acid. Iodometric determination of the quantity of perma-
ganate left unreduced, and subtraction of this quantity from the amount taken.
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ISO/R 754-1968 (E
9.3 Reagents
Distilled water or water of equivalent purity should be used in the test.
9.3.1 Sulphuric acid, 50 g/l solution.
9.3.2 Potassium permanganate, 1 g/l solution.
9.3.3 Sodium thiosulphate, M/30 standard volumetric solution.
9.3.4 Potassium iodide, 100 g/l solution.
9.3.5 Starch, 1 O g/l solution,freshiy prepared.
9.4 Apparatus
Ordinary laboratory apparatus and
9.4.1 Two conicalflasks, ground glass stoppered, capacity 250 ml.
9.4.2 Two microburettes, 10 ml graduated in 0.02 ml divisions.
9.4.3 Water bath, controlled at 20 f 0.5 OC.
9.5 Procedure
9.5.1 To 50 ml of the dilute sulphuric acid solution (9.3.1) contained in one of the stoppered
250mlflasks (9.4.1), add 5.0 ml of the test sample, shaking gently until dissolved (5 to 10
minutes).
9.5.2 Add, at 20 f 0.5 OC, potassium permanganate solution (9.3.2) from a microburette (9.4.2)
until a permanent red colour is established and then add a further 10 ml. Note the total
amount added. Leave in the dark to react for 40 minutes at 20 f 0.5 OC.
9.5.3 Determine the excess of potassium permanganate iodometrically by adding an excess of
potassium iodide solution (9.3.4) and titrating from the second microburette (9.4.2) with
the sodium thiosulphate solution (9.3.3), adding 0.5 ml of starch solution (9.3.5) just before
the end point is reached.
9.5.4 Carry out simultaneously a blank determination, in the second conical flask (9.4.1), using
the above procedure and adding the same total volume of potassium permanganate solution
(9.3.2) as that added in clause 9.5.2.
9.6 Expression of results
Permanganate index = 2 1 ( V2 - V, )
where
is the volume, in millilitres, of M/30 sodium thiosulphate solution used in
V,
clause 9.5.4,
is the volume, in millilitres, of M/30 sodium thiosulphate solution used in
V,
clause 9.5.3.
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ISO/R 754-1968 (E
PART II - METHODS OF TEST FOR SPECIAL PURPOSES
In case where the acetic anhydride is required for special purposes, for example, pharmaceutical,
the following additional test may be required.
10. LIMIT TEST FOR HEAVY METALS (INCLUDING IRON)
10.1 Principle
Conversion of heavy metals, such as lead, copper and iron to their sulphides in ammoniacal
solution, and comparison of the colour produced, with that given by a standard lead solution
treated with sodium sulphide in the same way.
NOTE. - The method detects only the heavy metals present in noncomplex form and is not specific
for any one heavy metal.
10.2 Reagents
i
Distilled water or water of equivalent purity should be used in the test.
10.2.1 Aqueous ammonia, d = 0.88.
10.2.2 Sodium sulphide, 100 g/l solution
10.2.3 Standard lead solution (10 pg Pb/ml), freshly prepared. Dissolve 0.0160 g of lead nitrate
in water and make up to 1000 mi.
10.3 Apparatus
Ordinary laboratory apparatus.
10.4 Procedure
10.4.1 Pipette 25 ml of the test sample into a 250 ml one-mark volumetric flask, add 150 ml
of water, shake over a period of 10 minutes (until the sample is completely dissolved)
and then dilute to the mark with water. Mix well.
L
10.4.2 Transfer a 10 ml aliquot to a Nessler cylinder. Add the aqueous ammonia (10.2.1)
until the solution is alkaline to litmus paper, and dilute to 50 ml with water. Add 0.1 ml
(two drops) of sodium sulphide solution (10.2.2) and mix well.
10.4.3 Preparation of agreed standard matching solution. To 40 ml of water contained in a
second Nessler cylinder, add the agreed quantity of the standard lead solution (10.2.3)
and 1 ml of the aqueous ammonia (10.2.1). Dilute to 50 ml with water and mix well. Add
0.1 mi (two drops) of sodium sulphide solution (10.2.2) and again mix well.
10.4.4 Compare the darkening of the test solution (10.4.2) with that of the agreed standard
matching solution (1 0.4.3).
10.5 Expression of results
Report the darkening of the test solution as greater than, equal to, or less than that of the
agreed standard matching solution, mentioning the lead content of the latter.
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ISO/R 754-1968 (E
11. DETERMINATION OF IRON CONTENT
1 1.1 Principle
Conversion of any iron present in the sample into the sulphate b! evaporation to dryness in
: iron using 2,2 'bipyridyl.
the presence of sulphuric acid, and colorimetric determination off
NOTE. - Although this method specifies the use of spectrophotometre or photometer, it is permissible to
employ as an alternative procedure a visual method comparing the test solution with a series of standard
solutions (see clause 11.5.5).
matching
1 1.2 Reagents
Distilled water or water of equivalent purity should be used in the test.
11.2.1 Sulphuricacid, d = 1.84, diluted 1 + 6 by volume.
11.2.2 Nitric acid, d = 1.4, diluted 1 + 3 by volume.
11.2.3 Urea solution. Dissolve 100 g of urea in 100 ml of water.
11.2.4
Hydroxylammonium chloride, 100 g/i solution.
4'
Ammonium acetale 500 g/1 solution.
11.2.5
11.2.6 2,2 Lbipyridyl, 5 g/i hydrochloric acid solution. Dissolve 0.5 g of 2,2 'bipyridyl in 100 ml
of N hydrochloric acid.
11.2.7 Standard iron solution (10 pg Fe/ml). Dissolve 0.7022 g of pure iron (II) - ammonium
. (NH4)2S04 . 6H20] in 50 ml of the sulphuric acid
sulphate hexahydrate [FeS04
solution (11.2.1) and dilute to 1000 ml with water. Dilute 100 ml solution thus obtained
to 1000 ml with water.
11.3 Apparatus
Ordinary laboratory apparatus, and
11.3.1 Spectrophotometer or photometer.
11.4 Calibration charts
11.4.1 Place in 100 ml one-mark volumetric flasks the following quantities of standard iron
solution (1 1.2.7)
O - 2.0 - 4.0 - 7.0 - 10.0 - 15.0 - 20.0 ml
To each add 20 ml of the nitric acid solution (1 1.2.2), 2 ml of the urea solution (1 1.2.3)
and 2 mi of the hydroxylammonium chloride solution (I 1.2.4). Mix and ailow to stand
for 2 minutes. Then add 30 ml of the ammonium acetate solution (1 1.2.5) and 5 mi of
the 2,2%ipyridyl solution (1 1.2.6) and dilute to the mark with water.
11.4.2 Measure the optical densities of the solutions in the spectrophotometer or photometer
(11.3.1), determining the optical density at a wave length between 510 and 520 nm.
11.4.3 Draw a graph plotting optical densities as a function of the quantities of iron (in
microgrammes) in 100 ml of the solution.
11.5 Procedure
11.5.1 Weigh lOOg of the test sample in a platinum basin of capacity about 150ml and evaporate
to dryness on a water bath under a hood having a good draught. Allow to cool and add
10 mi of sulphuric acid solution (I 1.2.1)
...