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UDC 661.185 : 543
IS0
INTERN AT I ON A L ORGANIZATION FOR STAND AR D IZATl ON
IS0 RECOMMENDATION
R 895
SURFACE ACTIVE AGENTS
TECHNICAL SODIUM SECONDARY ALKYLSULPHATES
METHODS OF ANALYSIS
1st EDITION
December 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 only
of that country, being
by the national standards organization
a member of ISO.
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 895, Surface active agents - Technical sodium secondary alkylsulphates -
Methods ofanalpis, was drawn up by Technical Committee ISO/TC 91, Surface active agents, the Secretariat of
which is held by the Association Française de Normalisation (AFNOR).
Detailed work on this question by the Technical Committee led, in 1963, to the adoption of a Draft IS0
Recommendation.
-
In March 1967, this Draft IS0 Recommendation (No. 1036) 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 Iran South Africa, Rep. of
Belgium Ireland Spain
Brazil Israel Switzerland
Canada Italy Turkey
Czechoslovakia Japan U.A.R.
France Netherlands United Kingdom
Germany New Zealand Yugoslavia
Greece Portugal
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council, which decided,
in December 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 895 -1968 (E)
CONTENTS
Page
......................... 5
Introduction . .
General .
Part 1
1. Scope .
2. Field of application .
3. Preparation of sample .
4. General principle .
Determination of water content . 8
Part il
Measurement of pH .
Part II1 10
Part IV Determination of free alkalinity or free acidity .
10
Part V Determination of total alkalinity . 11
Part VI Determination of matter extractable by hexane . 12
.... 15
Part VI1 Determination of the sodium secondary alkylsulphates content
Part VI11 Determination of the organic sulphur content arising from
the sulphate group (Wurzschmitt method) . 18
20
Part 1X Determination of sodium sulphate content .
Part X Determination of sodium chloride content . 22
Part XI Report of the analysis . 23
General scheme of analysis . 25
Appendix Y
Appendix Z Determination of organic sulphur arising from the sulphate group of
sodium alkylsulphates (isolated in accordance with
Part VI1 of this IS0 Recommendation) (Grote-Krekeler method) . 26
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I
ISO/R 895 -1 968 (h)
IS0 Recommendation R 895 Decem ber 1968
SURFACE ACTIVE AGENTS
TECHNICAL SODIUM SECONDARY ALKYLSULPHATES
METHODS OF ANALYSIS
INTRODUCTION
The word “secondary”, preceding the generic name for the products in the title, is intended to distinguish products
from those which, in accordance with current scientific usage, could be designated as technical sodium primary
alkylsulphates. As shown in the general formula given below, the former may be considered as derived from
secondary alcohols, whereas the latter are derived from primary alcohols.
It is therefore the former which are the subjects of this IS0 Recommendation. They are commonly known today
as techriical sulphates of secondary fatty alcohols.
In order to simplify the test of this IS0 Recommendation and avoid unnecessary repetition, the word “secondary”
has been omitted from the term “sodium alkylsulphates”, but it should be understood that only “sodium secondary
alkylsulphates” are covered.
The general formula of the products which are the subject of this 1SO Recommendation is
R\
CH - O -- SO3 Na
R
where R and R ‘are aliphatic radicals.
,,
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ISO/R 895-1968 (E)
PART 1
GENERAL
1. SCOPE
This 1SO Recommendation describes the methods of analysis of technical sodium secondary alkylsulphates. It
covers the following determinations :
Determination of water content.
Measurement of pH.
Determination of free alkalinity or free acidity.
Determination of total alkalinity.
Determination of matter extractable by hexane.
Determination of the content of sodium secondary alkylsulphates.
Determination of the organic sulphur content arising from the sulphate group (Wurzschmitt method).
Determination of sodium sulphate content.
Determination of sodium chloride content.
It also describes in Appendices
a general scheme of analysis;
( i )
a method for the determination of the content of organic sulphur arising from the sulphate group of technical
(2)
sodium alkylsulphates. (isolated in accordance with Part VI1 of this IS0 Recommendation) (the Grote-Krekeler
method).
2. FIELD OF APPLICATION
This IS0 Recommendation is applicable only to technical sodium secondary alkylsulphates in liquid form,
free from other products extraneous to their manufacture.
It is not at present applicable to powders or pastes.
3. PREPARATION OF SAMPLE
As the material for analysis is a liquid (see section 3) and is thus homogeneous at a temperature of 20 OC,
it is not necessary to carry out the procedure for the preparation of a representative sample.
Storage
Liquid products should be kept in wide-necked flasks with ground-glass stoppers and not in metallic containers.
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ISO/R 895 -1 968 (E)
4. GENERAL PRiNCIPLE'
Preparation of an aqueous alcoholic solution of a test portion of the raw material, from which are isolated the
products extractable by hexane.
Separation of the sodium alkylsulphates from an aliquot portion of the residual aqueous alcoholic liquid, after
repeated evaporation to dryness in the presence of propan-2-01 and final extraction of the anhydrous residue by
means of propan-2-01.
Determination of the organic sulphur content, after complete evaporation of the solvent.
On separate test portions of the raw material
- determination of water content,
- measurement of pH,
- determination of free alkalinity or free acidity,
-. determination of total alkalinity,
- determination of sodium sulphate content,
- determination of sodium chloride content.
*
See Appendix Y for general scheme of the method.
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ISO/R 895-1968 (E)
PART II
DETERMINATION OF WATER CONTENT
1. PRINCIPLE
Entrainment of the water in the vapour state, by boiling xylene.
2. REAGENT
Xylene, commercial quality (any isomers or mixture of isomers in any proportion) saturated with water.
3. APPARATUS
3.1 Apparatus comprising the following :
a short-necked round-bottomed flask not less than 500 ml, connected to the tube, shown below,
a)
by means of a ground-glass joint;
a graduated cylindrical tube, shown diagrammatically below, with or without discharge tap;
b)
a straight reflux condenser, connected to the tube by means of a ground-glass joint;
c)
3.2 Analytical balance.
-Ground-glass joint
Discharge
- Before use, clean the graduated tube and the interior of the reflux condenser of all trace of fatty mattcr, for
NOTE.
example, by washing them successively in chromic/sulphuric acid mixture, then with distilled water, and finally with acetone.
Dry them. Perfect cleanliness of the apparatus is essential for the success of the test.
1
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ISO/R 895-1968 (E)
4. PROCEDURE
4.1 Test portion
Weigh, to the nearest 0.01 g, about 5 g of the raw material, into the round-bottomed flask.
4.2 Determination
Add to the test portion, 250 ml of xylene and a dry boiling aid, for example a few fragments of pumice
stone.
Attach the flask to the rest of the apparatus.
Heat gradually to boiling point (2 to 3 drops per second) and maintain at this temperature until the distilled
xylene becomes clear and water no longer separates from it.
If drops of water adhere to the sides of the tube, remove them by warming the tube carefully, using a small
flame.
If foaming is troublesome during the determination, it can be eliminated by adding, for example, dry paraffin
wax or dry oleic acid to the flask.
Leave to settle until the water has completely separated without an emulsified layer.
Read the volume of the water in the graduated tube, at the standard reference temperature of 20 OC.
5. EXPRESSION OF RESULTS
Method of calculation and formula
5.1
The percentage of water in the sample is equal to
1 O0
vx-
M
where
M is the mass, in grammes, of the test portion;
V is the volume, in millilitres, of the aqueous layer.
5.2 Reproducibility
The difference between results obtained on the same sample, in two different laboratories, should not exceed
1 g of water for 100 g of sample.
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ISO/R 895-1968 (E)
PART 111
MEASUREMENT OF pH
PROCEDURE
(m/m) of the raw material.
Using distilled or deionized water of pH between 6.5 and 7, prepare a solution of 5
Measure the pH to the nearest O. 1 unit, by means of a pH meter suitable for this purpose.
Read the meter as rapidly as possible, i.e. between 30 seconds and 1 minute after immersion of the electrodes.
PART IV
DETERMINATION OF FREE ALKALINITY OF FREE ACIDITY
1. DEFINITION
By ‘‘free alkalinity” or “free acidity” is understood alkalinity or acidity determined using phenolphthalein as
indicator under specified conditions. It is expressed as the alkali value or the acid value as the case may be.
2. PROCEDURE
Dilute 10 g of the raw material in 100 ml of propan-2-01, 50 %(V/V), previously neutralized in the
presence of phenolphthalein, and determine either the acidity or the alkalinity, by titration with a standard
volumetric solution of strength 0.1 N (0.1 N potassium hydroxide or 0.1 N hydrochloric or sulphuric acid).
3. EXPRESSION OF RESULTS
Express the results as acid value or alkali value, whichever is appropriate, i.e. in milligrammes of potassium hydroxide
required to neutralize 1 g of raw material.
The acid value (or the alkali value) is equal to
VX 5.61
M
where
M is the mass, in grammes, of the test portion;
V is the volume, in millilitres, of the standard volumetric solution used,
NOTES
1. If the standard volumetric solution used is not exactly of strength 0.1 N, a suitable correction factor should be used in calculating
the results.
2. When the value found is less than 0.3, express the result as follows :
Acid value or alkali value (as appropriate) <0.3.
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ISO/R 895-1968 (E) I
PART V
DETERMINATION OF TOTAL ALKALINITY
1. INTRODUCïION
It may happen that on measuring the pH in accordance with Part III of this IS0 Recommendation, a pH which is
significantly greater that 7 is observed, and that on determing the alkalinity in accordance with Part IV, an alkali
value significantly greater than 0.3 is obtained. In such a case, it is advisable to carry out the determination of the
total alkalinity as below.
2. DEFINITION
By “total alkalinity” is understood the alkalinity determined using methyl orange (or bromophenol blue) as
indicator under specified conditions. It is expressed as alkali value.
3. PROCEDURE
Weigh, to the nearest 0.001 g, about 5 g of the raw material into a 100 ml beaker. Transfer the product quantita-
tively with 100 ml of distilled water into a 250 ml conical flask, heating if necessary.
Add 5 drops of methyl orange (or bromophenol blue) and titrate at room temperature with a solution of 0.1 N
sulphuric acid until a colour change to a brownish red (or to yellow depending on the indicator) is observed.
4. EXPRESSION OF RESULTS
Express the results as the alkali value as defied in Part IV of this IS0 Recommendation.
The total alkalinity. expressed as alkali value, is equal to
VX 5.61
M
where
M is the mass, in grammes, of the test portion;
V is the volume, in millilitres, of the standard volumetric solution used.
NOTE. - If thc standard volumetric solution used is not exactly of strength 0.1 N, a suitable correction factor should be used in
calculating the results.
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ISO/R 195-1961 (E)
PART VI
DETERMINATION OF MATTER EXTRACTABLE BY HEXANE
1. INTRODUCTION
Matter extractable by hexane consists of sulphur-free products as well as products containing sulphur which,
when present, are non-ionizable in aqueous solution.
I
2. PRINCIPLE
Extraction, by means of hexane, of the products specified in section I in the aqueous alcoholic solution of the test
portion, taking into consideration the volatility of the products in question.
3. REAGENTS
3.1 Propan-2-01, 98 (v/v) solution.
3.2
Hexane, not less tlm 95 'Io.*
3.3 Sodium hydroxide, approximately 0.1 N solution in distilled water.
3.4 Sodiurn sulphate, neutral and anhydrous, analytical reagent grade.
3.5 Phendphthalein, 0.3 'Io solution in ethanol.
4. APPARATUS
Ordinaty laboratoty apparams not otherwise specified, and the following items
round-bottomed distillation flask, 250 ml, with ground-glass neck;
fractionating column, 20 cm long and inside diameter approximately 8 mm. with a ground-glass cone at its
lower end to fit into the neck of the distillation flask;
three separating funnels, 500 mi, with ground-glass stoppers;
vertical condenser, 80 cm long;
beakers, 1 O0 ml and 400 ml;
volumetric flask, 500 ml;
conical flask, 300 mi;
hotplate or water bath;
analytical balance.
*
If hexane is not available, use freshly distilled light petroleum spirit, of boiling range 30 to 60 OC. In reporting the results
it should be stated which of the two solvents has been used.
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ISO/R 895 -1 968 (E)
5. PROCEDURE
5.1 Test portion
Weigh, to the nearest 0.01 g, a quantity of the raw material containing approximately 4 g of sodium secondary
alkylsulphates, into the 100 ml beaker.
Let Mo be the mass weighed.
5.2 Determination
lntroduce the test portion into one of the 500 ml separating funnels (A) and wash the beaker with distilled
water so as to obtain a final volume of approximately 125 ml; add 50 ml of propan-2-01 (3.1).
Check that liquid is faintly alkaline to phenolphthalein, and if necessary make it so with sodium hydroxide
solution (3.3) until a pale pink colour is obtained with the indicator (3.5).
Shake to render the mixture homogeneous.
Add 50 ml of hexane (3.2).
Shake vigorously for 30 seconds and allow to separate. Add the minimum quantity of propan-2-01 (3.1)
necessary to break any emulsion that may be formed.
Transfer the lower layer into a second separating funnel (B).
Extract with another 25 ml portion of hexane (3.2).
Collect the lower layer in the third separating funnel (C) and transfer the upper layer to the first separating
funnel (A).
Extract the aqueous alcoholic phase three more times, each time using 15 ml of hexane (3.2).
Combine the hydrocarbon extracts in the separating funnel (A) and transfer the aqueous alcoholic layer to
the 400 ml beaker after the last extraction.
Wash both the separating funnels (B) and (C) three times, each time using 20 ml of distilled water. Alternatively.
a 5 to 10 solution of propan-2-01 in distilled water may be used.
Add the washings to the aqueous alcoholic phase in the beaker.
Wash the hydrocarbon extract with successive portions of 15 ml of distilled water until the washings are no
longer alkaline; add the washings to the aqueous alcoholic phase.
Heat the aqueous alcoholic phase on a boiling water bath for 10 to 15 minutes to evaporate the hexane and
allow to cool.
Ensure that the solution is still alkaline to phenolphthalein, and if necessary render alkaline with sodium
hydroxide solution (3.3).
Transfer the solution to the 500 ml volumetric flask, rinsing the beaker with water and adding the washings
to the volumetric flask. Dilute to the mark.
This solution, LI, will be used for the determination of the content of sodium aikylsulphates.
Transfer the hydrocarbon layer quantitatively into a 300 ml conical flask, containing sodium sulphate (3.4).
Shake the liquid and allow it to stand for 30 minutes. Then filter through filter paper into the distillation
flask, previously tared, containing a few glass beads. Wash the conical flask, the sodium sulphate and the
filter five times, each time using 10 ml of hexane (3.2). Pay particular atteiition to the edges of the filter
paper, which should not show greasy marks.
bit the fractionating column to the distillation flask, place the assembly on the hotplate or in the water btth
and distil until nearly all the solvent has passed over. Remove the fractionating column, cool to about 30 C
and eliminate the last traces of solvent by a gentle current of air.
To do this, maintain the current of air and rotate the distillation flask by hand, in an inclined position, out of
the hotplate or water bath. In this way, the liquid in the flask will spread over the interior in a thin film and
so assist in the removal of the last traces of solvent.
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ISO/R 895 -1 968 (E)
To avoid loss, care is necessary in evaporating the solvent, particularly while passing the current of air.
For this purpose, first weigh the flask, cooled to room temperature and carefully dried, while there is still a
detectable odour of solvent. Note the mass, then reheat the flask to approximately 30 "C so as to liquefy the
contents and pass a current of air over them for a further minute. After cooling and drying the flask, weigh
it again and note the mass.
By repeating these operations and plotting successive weighings on a graph on millimetre squared paper, it
will be noted that, after a rapid fall, the curve reaches a practically horizontal lower level. The second weighing
on the horizontal part is regarded as the end of the operation and the mass noted is recorded as that of the final
dry residue.
Any difference between the two last weighings should be apparent only in the third significant figure
6. EXPRESSION OF RESULTS
Method of calculation and formula
6.1
The percentage of matter, extractable by hexane, in the raw material, is equal to
1 O0
MI X -
Mo
where
is the niasse. in grammes, of the test portion;
Mo
is the mass, in grammes, of the residue obtained.
Ml
6.2 Reproducibility
The difference between results obtained on the same sample. in two different laboratories, should not exceed
1 g of matter extractable by hexane for 100 g of sample.
I
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ISO/R 895-1968 (E) m
PART VI1
DETERMINATION OF THE SODIUM SECONDARY ALKYLSULPHATES CONTENT
1. PRINCIPLE
Evaporation of an aliquot portion of the aqueous alcoholic liquid, LI, from the previous determination to
one fifth of its volume, addition of propan-2-01, then evaporation to dryness. Further addition of propan-2-01
and evaporation to dryness (these successive evaporations are made to remove completely the water in the
aqueous alcoholic solution). Extraction of the sodium secondary alkylsulphates by means of hot propan-2-01,
from the dry residue thus obtained.
Isolation of the sodium secondary alkylsulphates by evaporation of the solvent. The residue may include
part of the sodium chloride and sodium carbonate present, the masses of which are determined and subtracted
from the total mass of the residue of the extract.
NOTE. -~ It is very important that thc solution remain alkaline throughout this determination.
2. REAGENTS
2.1 Propan-2-ol, 98 solution rendered just alkaline to phenolphthalein by sodium hydroxide 0.1 N
solution.
Sodium hydroxide solution, approximately 0.1 N in distilled water.
2.2
2.3 Sulphuric acid, 0.1 N standard volumetric solution in distilled water.
2.4 Phenolphthalein, 0.7 "Io solution in ethanol.
2.5 Acetone, analytical reagent grade. The residue on evaporation of the acetone must be less than 5 rng
per 100 ml.
3. APPARATUS
Ordinary laboratory apparatus not otherwise specified, and the following items :
pipette, 100 ml;
water bath;
glass beads;
oven regulated at 85 to 90 OC;
vacuum desiccator,
two beakers, 750 rnl;
twu ruund-bottomed Basks, 250 ml;
analytical balance.
4. PROCEDURE
4.1 Test portion
Using the aqueous alcoholic solution, LI, remaining from the determination of matter extractable by
hexane (see Part VI of this IS0 Recommendation), and corresponding to the test portion, Mo, introduce by
means of the 100 ml pipette an aliquot of 100 ml of the test portion into each of the two 250 ml beakers.
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ISO/R 895-1968 (Et
4.2 Determination
Treat the contents of each beaker as indicated below.
Reduce the volume to about I O 1111 by evaporation on the water-bath using a current of air. Add 20 ml of
propan-2-01 (2.1) and evaporate again to dryness. Then add 50 mi of propan-2-01 (2.1), break up the residue
thoroughly with a glass stirrer and bring to the boil on the water bath. Allow to boil for 3 minutes and stir
from time to time.
Allow the matter insoluble in the alcohol to settle and decant the hot supernatant liquor, filtering it through
a filter paper into one of the 250 mi flasks, which has been previously tared, containing a few glass beads.
l'lace the flask on the boiling water bath so that the filtrate may evaporate while the solvent vapour is drawn
off through a tube inserted into the neck of the flask.
Add 35 ml of propan-2-01 (2.1) to the beaker, bring to the boil and allow to boil gently for 2 mi
...