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Ref. No.: ISO/R 275 - 1962 (E)
IS0
1 NTERN AT1 O N A L ORGAN IZATl O N FO R STA N DA RD IZATl ON
I SO R ECO M M EN DATI O N
R 275
1st EDITION
November 1962
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
by the national standards organization of that country, being
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
t
The IS0 Recommendation R 275, Zinc Ox de for Paints, was drawn up by Technical Com-
mittee ISO/TC 35, Raw Materials for Paints, V d rnishes and Similar Products, the Secretariat of
which is held by the Nederlands Normalisatie-Instituut ("1).
Work on this question by the Technical Committee began in 1953 and led in 1958 to the
adoption of a Draft IS0 Recommendation.
In December 1958, this Draft IS0 Recommendation (No. 266) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to some modifications of an editorial
nature, by the following Member Bodies :
India Poland
Israel Romania
Italy Spain
Japan United Kingdom
Netherlands U.S.S.R.
Six Member Bodies opposed the approval of the Draft:
Austria Germany
Belgium New Zealand
Sweden
France
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in November 1962, to accept it as an IS0 RECOMMENDATION.
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ISO/R 275 - 1962 (E)
R 275 November 1962
I SO Recommendation
ZINC OX E FOR PAINTS
B
1. SCOPE
This IS0 Recommendation defines the important requirements for zinc oxide for paints and the
methods of test for these requirements. *
2. DEFINITION
Zinc oxide for paints is a white pigment which consists mainly of zinc oxide (ZnO).
3. REQUIRED CHARACTERISTICS AND THEIR TOLERANCES
Zinc oxide for paints should have the following characteristics :
Clause
descnbin
Property TypeIII TypeIV
Type V
test
method
I
Zinc oxide (ZnO)
12.0 to 68.C 5.1
min. 99.0 4.0 to 99.( 7.0 to 94.0168.0 to 87.C
content %
~~ ~~~~~ -.
Lead content (lead
compounds,
0.3 to 3.0 3.0 to 8.0 ~ 8.0 to 22.0 i2.0 to 27.C 5.2
max. 0.3
expressed as lead,
!
Pb) %
Residue on sieve,
0.3 1 0.3 O. 3 5.3
o. 1
%
max.
~~
Matter volatile at
0.3 0.3 ~ 0.3 0.3 5.4
105 OC, max. %
Loss on ignition at
1.0 i 1.0 5.5
O. 5
5OO0C, max. %
1
Matter soluble in
O. 5 1.5 1 1.5 5.6
water, max. %
____
Neutrality of the
Neutral to methyl red 5.7
aqueous extract
To match that of the agreed sample 5.8
Colour
5.9
Lightening power
To be agreed between purchaser and vendor
Oil absorption 5.10
Hiding power 5.11
* For painting building interiors Convention No. 13 of the International Labour Organization limits the use of zinc oxides
for paints to pigments containing less than 2 % of lead.
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IÇO/R 275 - 1962 (E)
4. SAMPLING
See IS0 Recommendation R *, Saiupliiig Raw Materialsfor Paints and Varnishes.
5. TEST METHODS
All reagents should be of analytical grade. Water should be distilled water or water of at least
equal purity.
5.1 Zinc oxide content
5.1.1 Reagents
5.1.1.1 Aqueous ammonia, concentrated (d - 0.9).
5.1.1.2 Aqueous ammonia 4N.
5.1.1.3 Hydrochloric acid, concentrated (d = 1.19).
5.1.1.4 Hydrochloric acid 4N.
5.1.1.5 Hydrogen peroxide solution, 3 %.
5.1.1.6 Hydrogen sulphide, saturated aqueous solution.
5.1.1.7 Potassium hexacyanoferrate (II) * *, standard solution, approximately 0.05 molar.
Dissolve 21 .O g of potassium hexacyanoferrate (II), 300 mg of potassium hexacyano-
ferrate (III) *** and 2 g of anhydrous sodium carbonate (to stabilize the solution)
in water, and dilute with water to 1000 ml.
5.1.1.8 Zinc chloride, standard solution, containing 5 g of zinc per litre.
Weigh accurately 5.0 g of chemically pure zinc, dissolve in 300 ml of hydrochloric
acid 4N, and dilute with water to 1000 ml in a volumetric flask.
Alternatively, it may be more convenient to weigh accurately a quantity of zinc
which is not exactly 5.0 g, in which case appropriate adjustment should be made in
the calculations to take account of the fact that the zinc chloride solution does not
contain exactly 5 g of zinc per litre.
5.1.1.9 Diphenylamine solution in ethanol, 5 g per 100 ml.
5.1.1.10
Congo paper.
5.1.1.11 Lead acetate paper.
5.1.2 Standardization of the potassiuni hexacyanoferrate (II) solution
Pipette 25.0 ml of the zinc chloride solution into a flask and add ammonia 4N until
a piece of Congo paper placed in contact with the solution just turns to a pure red colour.
Then carefully neutralize the solution by adding the hydrochloric acid 4N from a dropp-
ing bottle and add a few drops in excess until the Congo paper turns to a permanent
blueish-red or reddish-blue colour (pH 3.0 to 1.5).
Make up to 150 ml with water, heat the solution to boiling, and add 10 drops of the
diphenylamine solution.
* At present Draft IS0 Recommendation No. 731.
* * International Union of Pure and Applied Chemistry (IUPAC) name for potassium ferrocyanide, K,Fe(CN)s.
* * * International Union of Pure and Applied Chemistry (IUPAC) name for potassium ferricyanide, K,Fe(CN),.
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ISO/R 275 - 1962 (E)
Immediately titrate the solution with the potassium cyanoferrate solution until the
colour turns to a permanent yellow or yellowish-green (Vl ml being used).
Then backtitrate the solution with the zinc chloride solution until the colour just turns
to blue again (V, ml being used).
The standardization factor F of the potassium cyanoferrate solution expressed in
grammes of zinc per ml, is given by the following formula:
0.005 (25 + V,) *
F = -
Vl
5.1.3 Procedure
Accurately weigh about 1.0 g of the zinc oxide (dried at 105 3~ 2 OC) (rn grammes).
Mix with 15 ml of the concentrated hydro
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