ISO 56-2:1979

INTERNATIONAL STANDARD
INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONWWE~YHAPO~HAR OPrAHM3Al&lR fl0 CTAH~APTM3A~MbWORGANISATION INTERNATIONALE DE NORMALISATION
Shellac - Specification - Part II : Machine-made shellac
Gomme laque en feuies - Sphcification - Partie lf : Gomme laque en feuies de fabrication mhcanique
First edition - 1979-04-01
w
-
UDC 668.447.31 Ref. No. ISO 56/11-1979 (E)
Descriptors : shellac, materials specifications, Chemical analysis, tests,$ sampling,
T
Price based on 35 pages
FOREWORD
ISO (the International Organization for Standardization) is a worldwide federation
of national Standards institutes (ISO member bodies). The work of developing
International Standards is carried out through ISO technical committees. Every
member body interested in a subject for which a technical committee has been set
up has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work.
Qraft International Standards adopted by the technical committees are circulated
to the member bodies for approval before their acceptance as International
Standards by the ISO Council.
International Standard ISO 56/ll was developed by Technical Committee
lSO/TC 50, Lac, and was circulated to the member bodies in November 1976.
lt has been approved by the member bodies of the following countries :
Austral ia Korea, Rep. of Sweden
Austria Mexico Turkey
Czechoslovakia Netherlands Yugoslavia
India Romania
The member body o f the following country expressed d
isapproval of the document
on technical grounds
Canada
This International Standard cancels and replaces ISO Recommendation R 56-1957
of which it constitutes a technical revision.
GI International Organkation for Standardkation, 1979 l
Printed in Switzerland
Acknowledgement is due for the assistance that has been derived from the specifi-
cations and publications of the American Society for Testing and Materials, the
American Bleached Shellac Manufacturers’ Association, the United States Shellac
Importers’ Association, the British Standards Institution, the Agricultural
Marketing Adviser to the Government of India, Messrs. Angelo Brothers Ltd.,
Calcutta, and the lndian Lac Research Institute. Considerable assitance has been
derived also from A Handbook of Shellac Analysis, by M. Rangaswami and H. K.
Sen, issued by the India Lac Research Institute.

Page
CONTENTS
..........................................
0 lntroduction 1
...............................
1 Scope and field of application 1
........................................... 2
2 Definitions.
..................................... 2
3 Form and condition.
....................................... 2
4 Types and grades.
5 Mandatory requirements. . 2
....................................
6 Optional requirements 2
7 Sampling . 3
Annexes
A Determination of matter insoluble in hot alcohol . 4
...................... 9
B Detection of rosin (Halphen-Hicks method)
................................... 10
C Detection of orpiment.
............................ 11
D Determination of arsenic content.
................ 16
E Determination of volatile matter (moisture) content
.............................. 17
F Determination of colour index
.................................... 18
G Determination of wax
.................................... 21
W Determination of ash.
J Determination of matter soluble in water
and test for neutrality of aqueous exact . 22
K Flowtest . 23
.................................. 26
L Heat polymerization test
................................ 28
M Determination of acid value
N Determination of load content . 29
..............................
P Determination of grit content. 31
..............................
Q Determination of iodine value. 33
................................
R Test for clarity of solution. 34
S Sampling . . ._. 35
iV
INTERNATIONAL STANDARD ISO 56/ll-1979 (E)
Part II : Machine-made shellac
Shellac - Specification -
0 INTRODUCTION f) wax,
0.1 ISO/R 56, published in 1957, covered shellac, hand- 9) asb
made as well as machine-made. lt has been revised into two
h) matter soluble in water,
Parts, one for each kind.
j) flow test,
0.2 The types and grades of machine-made shellac have
k) heat polymerization test,
been found to require modification in Order that the
characteristics of a given consignment of this material may
m) acid value,
be clearly defined. Machine-made shellac has now been
n) lead content,
divided into four main types, on the basis of the method of
manufacture, and then into grades, within each type, on the
pl grit,
basis of colour. Requirements for matter insoluble in hot
.alcohol, colour index and ash have now been prescribed
q) iodine value, and
based on the new System of types and grades.
r) clarity of Solution,
0.3 Whereas in lSO/R 56 the limit for wax was left subject
are optional.
to agreement between the purchaser and the supplier,
definite values have now been included. New requirements
0.6 The sizes of sieves given in the text of this Inter-
have been laid down for grit, iodine value, clarity of
national Standard have been indicated in terms of aperture
Solution, and alkalinity of the aqueous extract.
dimensions, in accordance with ISO 565, Test sieves -
Woven metal wire cloth and perforated plate - Nominal
0.4 The requirement for non-volatile matter soluble in
sizes of apertures.
cold alcohol has not been retained as the requirement is
applied in practice to waste products of lac only. The
0.7 For the purpose of deciding whether a particular re-
methods for quantitative determination of rosin have also
quirement of this International Standard is complied with,
been dropped since this type of adulteration is no longer
the final value, observed or calculated, expressing the result
in evidente. In ISO/R 56, an alternative method (the
of a test or an analysis, shall be rounded off to the same
Westinghouse method) was given for determination of
number of places as the specified value, it being always
flow. In this International Standard it has been dropped.
understood that the analyst will carry out the determi-
nation to at least one place more than in the specified value.
0.5 Three of the requirements for machine-made shellac,
namely those for
1 SCOPE AND FIELD OF APPLICATION
a) matter insoluble in hot alcohol,
1.1
This International Standard specifies requirements and
b) absence of rosin, and
corresponding methods of test for machine-made shellac.
c) absence of orpiment,
1.2 This International Standard is intended chiefly to
are included in this International Standard as essential
cover the technical provisions for guidance in the purchase
clauses.
of the material, but does not include all the necessary
The remaining requirements, namely those for provisions of a contract.
d) volatile matter (moisture),
1.3 The limits prescribed in this International Standard
are limits for rejection.
e) colour index,
ISO 56/11-1979 (E)
5.2 Rosin
2 DEFINITIONS
Machine-made shellac shall not contain any rosin, when
For the purpose of this International Standard, the
tested by the method specified in annex B.
following definitions apply.
5.3 Orpiment
2.1 sticklac : The natura1 product of lac insects.
5.3.1 Machine-made shellac shall not contain any
2.2 seedlac : The product obtained by washing crushed
orpiment, when tested by the method specified in annex C,
sticklac.
except when a specified percentage is agreed to between the
purchaser and the supplier, in which case the determination
2.3 shellac : The product obtained by refining seedlac by
shall be carried out as specified in annex D, method 1.
heat process or by solvent process or by both heat and
solvent procecses.
5.3.2 When the material is required for food or drug
preparations, the determination of traces of arsenic, too
2.4 approved Sample : The Sample aggreed upon between
small for titration by method l in annex D, shall be carried
the purchaser and the supplier as the Standard for colour
out by method II in annex D.
and appearance.
6 OPTIONAL REQUIREMENTS
The optional requirements given below shall be subject to
3 FORM AND CONDITION
agreement between the purchaser and the supplier.
Machine-made shellac shall be in the form of flakes, sheets,
buttoms, or any other from agreed between the purchaser
6.1 Volatile matter (moisture)
and the supplier.
Machine-made shellac shall not contain more than 2,0 %
(m/m) volatile matter (moisture) as determined by the
method specified in annex E.
4 TYPES AND GRADES
4.1 Four types of machine-made shellac are specified, 6.2 Colour index or colour and appearance
namely
6.2.1 The colour index of machine-made shellac, as
- produced by heat process. determined by the method specified in annex F, shall not
Type 1
exceed the limits given in table 2.
Type II - produced by hot solvent process.
TABLE 2
Type Ill - de-waxed.
Type IV - decolorized and de-waxed.
4.2 Five grades in each of types I and II, namely grades 1,
32 22 35 50
1, II 8
in each of types I II
2, 3, 4 and 5 are specified. Four grades
and IV, namely grades 1, 2, 3, and 4 are specified.
9 20 35 50 -
Ill
IV 03 2s 3,5 5,0 -
b
5 MANDATORY REQUIREMENTS
6.2.2 Alternatively, the appareance and colour of the
5.1 Matter insoluble in hot alcohol
shellac shall be not inferior to those of an approved Sample
Machine-made shellac shall not contain matter insoluble in
when judged by visual examination.
hot alcohol, determined by either of the methods specified
in annex A, as agreed between the purchaser and the
6.3 Wax
supplier, in excess of the Iimits given in table 1.
Machine-made shellac of type I and type II shall not
contain more than 5,5 % (mlm) of wax, and that of
TABLE 1
type Ill and type IV not more than 0,2 % (mlm) of wax,
when tested in accordance with method I and method II
Maximum
Type
respectively, specified in annex G.
% (mh)
I I I
6.4 Ash
Machine-made shellac shall yield not more than 0,3 %
(m/m) of ash, as determined by the method specified in
annex H.
ISO 56/ll-1979 (E)
6.9 Lead content
6.5 Matter soluble in water
The maximum limit for lead content shall be subject to
Machine-made shellac shall not contain more than 0,5 %
agreement between the purchaser and the supplier and the
(m/m) of matter soluble in water and the aqueous extract
lead content shall be determined by the method specified
shall not be acidic to methyl red or alkaline to bromo-
in annex N.
thymol blue. Matter soluble in water shall be determined
by the method specified in annex J.
6.10 Grit content
The maximum limit for grit content shall be as agreed to
6.6 Flow test
between the purchaser and the supplier. When required, it
Machine-made shellac shall have a flow within the range
shall be determined by the method specified in annex P.
agreed to between the purchaser and the supplier, when
tested by the method specified in annex K.
6.11 lodine value
The maximum limit for the iodine value shall be as agreed
6.7 Heat polymerization test to between the purchaser and the supplier. When required,
it shall be determined by either of the two methods
Machine-made shellac shall have a heat polymerization time
specified in annex 0.
within the range agreed to between the purchaser and the
supplier, when tested by the method specified in annex L.
6.12 Clarity of Solution
Unless otherwise agreed, the temperature of test shall be
150 Oc.
This requirement is applicable to type 111 and type IV
shellac and shall be subject to agreement between the
purchaser and the supplier. The shellac shall show no
6.8 Acid value
turbidity when tested by the method specified in annex R.
The acid value of the machine-made shellac shall be fixed, if
desired, by agreement between the purchaser and the
7 SAMPLING
supplier. lt shall be determined by the method specified
in annex M. Samples shall be taken in the manner specified in annex S.

%SO 56/ll-1979 (E)
ANNEX A
(See 5.1)
DETERMINATION OF MATTER INSOLUBLE IN HOT ALCOHOL
having a width of approximately 100 mm and other
Al PRINCIPLE
dimensions as given in figure 2.
Extraction of a test Portion with 95 % (V/V) ethanol and
weighing of the undissolved residue. The cover has a flanged hole of diameter 57 + 1 mm, for
a 200 ml beaker, and also a hole of diameter 35 + 1 mm
through which the top of the filter tube (A.2.2.1.4)
projects. Directly below this hole, in the bottom of the
A.2 METHOD I
bath, is a flanged hole, of diameter 25 + 1 mm, to hold the
rubber stopper, through which the stem of the filter tube
A.2.1 Reagent
extends, to discharge into the flask (A.2.2.1.3). The hot
water bath is mounted on a low tripod or stand.
Alcohol, 95 % (WV) ethanol or 95 % (V/V) denatured
spirit.
A.2.2.5 Gas burner, low form, adjustable, Bunsen type,
carrying a draught shield, or any other suitable heating
A.2.2 Apparatus
device.
Ordinary laboratory apparatus and
A.2.2.6 Electric oven, capable of being maintained at
100 + 2 “c.
Extraction apparatus, comprising
A.2.2.7 Desiccator, containing sulphuric acid (e i ,84 g/mI).
A.2.2.1.1 Condenser, all glass, of the type and dimensions
shown in figure 1, the tip of which is tut at an angle of
45 ‘. The condenser has two holes in its tip through which A.2.2.8 Balance, accurate to 0,002 g.
Passes the wire holding the Siphon tube (A.2.2.1.2).
A.2.2.9 Stop-watch or good two-minute sand-glass.
A.2.2.1.2 Siphon tube, of glass, of the type and
dimensions shown in figure 1. The Siphon tube has two
A.2.3 Preparation of extraction cartridge
holes near the top for a wire to be fastened to the
condenser tip, leaving about 6 mm space between the top
A.2.3.1 Place 125 ml of the alcohol (A.2.1) in the conical
sf the tube and the condenser tip.
flask (A.2.2.1.3) and a new extraction cartridge (A.2.2.2) in
the Siphon tube (A.2.2.1.2). Introduce the Siphon tube into
A.2.2.1.3 Conical flask, heat resistant, wide mouthed,
the flask and connect it to the condenser (A.2.2.1 .l),
conical, preferably of borosilicate glass of height
making Sure that there is an ample flow of cold water
approximately 175 mm and approximately 50 mm inside
through the condenser. Adjust the rate of heating so as to
diameter at the top. The flask has a tight-fitting cork of
give a cycle of fiiling and emptying in the Siphon tube every
depth 25 mm, bored to fit the stem of the condenser. The
2 min and extract for 30 min. Dry the cartridge in the oven
bottom of the cork is just above the holes for the wire (A.2.2.6), maintained at 100 + 2 “C. After 2 h, weigh it in
in the condenser. To support the flask, a suitable ring
the tared weighing bottle (A.2.2.3), which has been kept in
support with iron clamp and nickel-chromium or iron gauze
the desiccator (A.2.2.7), Iifting the stopper of the bottle
SS used. The gauze has no asbestos covering.
momentarily before weighing. Repeat the operations of
drying, for periods of 1 h, and weighing, until the loss in
mass between two successive weighings does not exceed
IJ.2.2.1.4 Carbon filter tube, of the type and dimensions
shown in figure 1, having a light spiral spring at the bottom 0,002 g.
to hold up the extraction cartridge (A.2.2.2). The stem of
the filter tube is fitted with a rubber stopper and firmly
A.2.3.2 Use only new cartridges. A number of cartridges
held in the hot water bath (A.2.2.4).
may be extracted, dried, weighed and kept in weighing
bottles in the desiccator until needed for use.
A.2.2.2 Extraction cartridges, of fat-free Paper, of
diameter approximately 25 mm and height approximately
A.2.4 Test Portion
60 mm.
Before analysis, thoroughly mix the “test Sample”
As2.2.3 Weighing bottle, glass-stoppered, of height
(see S.3.1 of annex S) by rolling on Paper, at least ten
approximately 80 mm and diameter approximately 40 mm.
times, to ensure uniformity of the test Sample. Weigh,
directly from the Paper, 4,5 to 5,5 g of the Sample, to an
accuracy of 0,Ol g.
A.2.2.4 Hot water bath, made of topper or stainless steel,
ISO 56/ll-1979 (E)
Dimensions in millimetres
All dimensions are approximate
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Condenser Filter tube
FIGURE 1 - Extraction apparatus for determination of matter insoluble in hot alcohol (method 1)
Dimensions in m il I imetres
All dimensions are approximate
-
Qext.32+ I
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FIGURE 2 - Hot water bath for determination of matter insoluble in hot alcohol (method 1)
ISO 56/ll-1979 (E)
1 h, and weighing until the loss in mass, between two
A.2.5 Determination
successive weighings does not exceed 0,002 g.
Place the test Portion (A.2.4) in a 200 ml tall, lipped
From the mass of the residue and the mass of the Sample,
beaker, add 125 ml of the alcohol (A.2.1) cover with a
calculate the percentage of insoluble matter. Use the
watch-glass and place on the hot water bath (A.2.2.4)
(see figure 2). Boil the Solution vigorously for 30 min to lowest mass in calculation.
ensure complete Solution of the shellac and dispersion of
wax. Keep the volume of alcohol constant by adding from
A.2.6 Expression of results
a wash-bottle, washing down the sides of the beaker.
The matter ins01 uble i n hot alcohol is given, expressed
Meanwhile, place an extracted and weighed cartridge
as a percentage by mass, by the formula
(A.2.2.2) in the filter tube (A.2.2.1.4). Maintain the hot
water around the tube at a temperature of not less than
!Ldoo
90 “C. Wet the cartridge with hot alcohol and decant the
mO
boiling Solution into the heated cartridge until the beaker
is nearly empty.
Wash the remaining Solution and the insoluble matter
is the mass, in grams, of the test Portion
mO
into the cartridge, using a “policeman ”, if necessary, with (A.2.4);
successive portions of hot alcohol contained in a wash-
is the mass, in grams, of the residue.
ml
bottle kept hot on the water bath. Finally, wash the
cartridge from the top downwards with a fine stream of
hot alcohol. A complete washing and transfer from the
original beaker will require at least 75 ml of hot alcohol.
A.3 METHOD II
Transfer the cartridge containing the insoluble matter to
the Siphon tube (A.2.2.1.2), place 125 ml of the alcohol
A.3.1 Reagent
in the conical flask (A.2.2.1.3) and connect up the
Alcohol, 95 % (WV) ethanol or 95 % (WV) denatured
apparatus. Start the water flowing through the condenser
spirit.
(A.2.2.1.1), making Sure that there is an adequate supply
for efficient condensation. Light the burner (A.2.2.5) and
time the extraction from the first emptying of the Siphon,
A.3.2 Apparatus
running the extraction for exactly 1 h. Immediately adjust
Ordinary laboratory apparatus and
the rate of heating so that a complete filling and emptying
of the Siphon tube takes place every 2 min, as determined
Extraction apparatus’ ), consisting of Siphon tube,
by the stop-watch or preferably by the two-minute sand- A.3.2.1
glass (A.2.2.9), one for each extraction apparatus. adaptor, condenser and flask, assembled with the aid of
corks or ground glass joints so that the solvent tan be kept
In this way exactly 30 cycles per hour are accomplished.
boiling in the flask and its vapour tan pass upwards by way
lf this cycle rate is not meticulously maintained, neither
of the adaptor to the condenser. The refluxing solvent runs
check results on duplicate samples in the Same laboratory,
from the condenser into the cup of the Siphon tube.
nor concordant figures from one Iaboratory to another tan
be obtained, even when working on the Same Standard
A.3.2.1.1 Siphon tube, of glass, of the type shown in
Sample. lt is also necessary to protect the apparatus from
figure 3, having approximate internal height of 52 mm and
draughts while in Operation, otherwise the proper cycle
a minimum internal diameter of 32 mm, resting in an
rate cannot be maintained.
adaptor tube in such a way that the Siphon tube is
Occasionally, shellacs are encountered which do not surrounded by the ascending vapours of the boiling solvent
(See figure 3).
yield the required number of 30 siphonings per hour,
due to slow filtration. In these cases, continue the
extraction until 30 siphonings have been accomplished or
A.3.2.1.2 Condenser, of any convenient design.
repeat the test with a 2 g test Portion and report the
Sample as abnormal or slow filtering.
A.3.2.1.3 Flask, of any convenient size.
Remove the cartridge, drain in an upright position on filter
A.3.2.2 Filter Paper, of diameter 125 mm, medium grade.
Paper and dry in the oven (A.2.2.6), maintained at
100 t 2 “C. Aft d
er rying for 2 h, place the cartridge in the
weighing bottle (A.2.2.3), cool in the desiccator (A.2.2.7)
and weigh, removing the stopper momentarily just before
weighing. Repeat the operations of drying, for periods of
The type of extraction apparatus used is not critical, provided that it is of such a design as to ensure a continuous series of extractions at
1)
approximately the boiling temperature of the solvent. If preferred, the apparatus specified in method l (see clause A.2), consisting of Siphon
tube, condenser and flask, could be satisfactorily used.
ISO 56/11-1979 (E)
Dimensions in m il I imetres
All dimensions are approximate
Fitted th rough cork
to reflux condenser
Tube
flask
FIGURE 3 - Siphon tube and adaptor
A.3.2.4 Gas burner, low form, adjustable, Bunsen type, oven (A.3.2.5), maintained at 100 + 2 “C for 30 min.
carrying a draught shield, or any other suitable heating Rapidly transfer to separate weighing bottles (A.3.2.3)
device. which have been kept in the desiccator (A.3.2.6). Place
each bottle and its contents back in the desiccator for
20 min, then weigh by counterbalance, preferably using
A.3.2.5 Electric oven, capable of being maintained
a rapid-weighing balance of the aperiodic type.
at 100?2 ”C.
Place the test Portion (A-3-3) in the filter Paper envelope S;
A.3.2.6 Desiccator, containing sulphuric acid (p 1,84 g/mI).
fold in the original folds, taking care not to leave any
channel through which finely divided material might
A.3.2.7 Balance, accurate to 0,002 g.
escape. Again enclose in Paper C and secure with thread.
Place the resulting envelope in a 100 ml beaker and cover it
with the alcohol (A.3.1). Allow to stand overnight at room
A.3.3 Test Portion ’
temperature. Place the envelope in the cup of the Siphon
Weigh 4,5 to 5,5 g of the “test Sample” of shellac (See S.3.1
tube (A.3.2.1.1) and extract continuously with hot alcohol
of annex S) to an accuracy of 0,Ol g.
for 4 h. Keep the envelope wholly below the surface of the
alcohol, when the cup is full. Maintain a rapid rate of
A.3.4 Determination extraction throughout, though the extract time taken for
the cycle of filling and emptying the cup of the Siphon tube
Fold the filter Paper (A.3.2.2) so that it forms a completely
is not critical.
closed envelope (see figure 4). Mark this Paper S (for
Sample); wrap it closely in a second filter Paper marked C At the end of the specified time, remove the Paper
(for counterpoise). Separate the filter Papers and dry in the envelope, allow to drain, separate the two Papers, dry each
lSQ 56/11-1979 (E)
on a glass plate in air for 15 min and then for 2 h in the
operations of drying and weighing until the differente
oven, maintained at 100 + 2 “C. Place the Papers rapidly
between two successive weighings is less than 0,002 g. Use
in their respective weighing bottles, allow to stand in the
the lowest mass in the calculation.
desiccator for 20 min and again weigh by counterbalance,
after momentarily removing and replacing the Stoppers in
the usual manner. Dry the Papers for a further period of
A.3.5 Expression of results
1 h at a temperature of 100 -t 2 “C and weigh again. If
there is a loss in mass in excess of 0,002 g, repeat the
As for method I (see A.2.6).
@@
S
@
S
e
FIGURE 4 - Folding of filter Paper
ISO 56/1 I-l979 (E)
ANNEX B
(See 5.2)
DETECTION OF ROSIN (HALPHEN-HICKS METHOD)
B.l REAGENTS B.2.7 Watch-glass.
B.l.l Ethanol, absolute.
B.3 PROCEDURE
B.1.2 Acetic acid, glacial.
8.3.1 Place about 2 g of the “test Sample” (see S.3.1 of
annex S) in the 250 ml conical flask (B.2.1) add 10 ml of
B.l.3 Petroleum ether, boiling Point below 80 “C.
the ethanol (B.l.l) or of the glacial acetic acid (B.1.2) and
Shake until dissolution of the resinous materials is
B.1.4 Solution A, comprising 1 part by volume of Phenol
complete. Then add slowly and with continuous agitation
dissoived in 2 Parts by volume of carbon tetrachloride.
50 ml of the Petroleum ether (B.1.3). After the addition
of the Petroleum ether, add 50 ml of water in exactly the
B.1.5 Solution B, comprising 1 part by volume of bromine same manner, transfer to the small separating funnel (B.2.2)
dissolved in 4 Parts by volume of carbon tetrachloride. and allow it to stand until the Petroleum ether separates.
Draw off the water layer, wash the Petroleum ether layer
once with water and then filter the Petroleum ether extract
through a dry filter Paper (B.2.3) into the evaporating dish
(B.2.4). Evaporate to dryness on the steam bath (B.2.5).
B.2 APPARATUS
B.3.2 Add 1 to 2 ml of Solution A (B.1.4) to the residue
B.2.1 Conical flask, of capacity 250 ml.
left after evaporation of the Solution in Petroleum ether
and pour this mixture into the cavity of the porcelain
B.2.2 Separating funnel.
colour-reaction plate (8.2.6) until it just fills the
depression. Immediately fill an adjacent cavity with
B.2.3 Filter Paper.
Solution B (B.1.5). Cover the plate with the inverted watch-
glass (B.2.7) and note the colour, if any, produced in
B.2.4 Evaporating dish, round bottomed.
solution A by the action of the bromine vapour from
Solution B.
B.2.5 Steam bath.
B.3.3 A decided purple or deep indigo blue colour is an
B.2.6 Porcelain colour-reaction plate. indication of the presence of rosin.
ISO 56/11-1979 (E)
ANNEX C
(See 5.3.1)
DETECTION OF ORPIMENT
C.l PRINCIPLE C.3 PROCEDURE
The presence of 0,5 % (m/m) or more of orpiment in C.3.1 Prepare in a small conical flask a 200 g/l Solution of
shellac gives the shellac flake a yellow, opaque appearance. the shellac in the alcohol (C.2.1) or borax Solution (C.2.2).
Even a trace of orpiment tan be detected from a Solution Allow the Solution to-stand, to allow any orpiment present
in ethanol or in aqueous borax if the shellac is free from to settle in a layer at the bottom. Examine from below.
dirt.
C.3.2 Yellow particles of orpiment will be visible if it is
present; 0,3 % (mlm) orpiment gives a continuous layer.
C.2 REAGENTS
C.3.2.1 This method is most sensitive when the alcohol is
C.2.1 Alcohol, 95 % (VW) ethanol or 95 % (VlV) de-
cooled to 0 “C before preparing the solution. The same
natured spirit.
effect is not obtained by dissolving at room temperature
and then cooling because, under these conditions, the
C.2.2 Borax, 50 g/l Solution of sodium tetraborate deca- agglomerates of wax are liable to hold the orpiment
hydrate (Na,B,O,4OH,O) in distilled water. particles in Suspension.
ISO 56/11-1979 (E)
ANNEX D
(See 5.3.1 and 5.3.2)
DETERMINATION OF ARSENIC CONTENT
D.2.3 Apparatus
D.l SCOPE
Ordinary laboratory apparatus and
This annex specifies two methods for the determination of
arsenic content, one for an appreciable amount of arsenic
and the other for traces of arsenic.
D.2.3.1 Kjeldahl flask, made of heat-resistant glass or
silica, of capacity 100 or 200 ml.
D.2 METHOD I (Appreciable amount of arsenic)
D.2.3.2 Kjeldahl distillation apparatus, as shown in
figure 5.
D.2.1 Principle
Digestion of the shellac with nitric acid and sulphuric acid,
treatment of the Solution with a chloride-hydrazine-
0.2.4 Test Portion
bromide mixture, distillation, and titration of the arsenic
compound obtained by a suitable method. Weigh 4,5 to 5,5 g of the “test Sample” (see S.3.1 of
annex S) to an accuracy of 0,Ol g.
D.2.2 Reagents
During the analysis, use only reagents of recognized analy-
0.2.5 Determination
tical grade and only distilled water or water of equivalent
purity .
D.2.5.1 Place the test Portion (0.2.4) in the Kjeldahl
flask (D.2.3.1), add 10 ml of the dilute nitric acid solution
D.2.2.1 Sodium hydrogen carbonate.
(D.2.2.5) and heat the mixture until any initial vigorous
reaction subsides and ceases. Cool and add gradually IO ml
D.2.2.2 Nitrit acid, p 1,42 g/ml.
of the sulphuric acid (0.2.2.3) at such a rate as to prevent
excessive frothing or heating (10 min are usually required)
D.2.2.3 Sulphuric acid, p 1,84 g/ml. and continue heating. Add to the hot Solution 5 ml of the
nitric acid (0.2.2.2) in small portions, and boil until colour-
less. If necessary, add the nitric acid in further small
D.2.2.4 Hydrochlorit acid, p 1,16 g/m 1.
portions at a time. Note for the purpose of the blank test
the total volume of nitric acid added. (The digestion usually
D.2.2.5 Nitrit acid, dilute (3 + 7) solution.
takes about 30 min.) Cool, dilute with 50 ml of water and
transfer to the flask of the distillation apparatus (0.2.3.2).
D.2.2.6 Sodium hydroxide, approximately 2 N Solution.
Boil the Solution, without inserting the condensing arm, till
the bulk is reduced to about 10 ml or until white fumes
D.2.2.7 Chloride-hydrazine-bromide mixture.
appear. Cool, dilute and again boil down to 10 ml; cool and
add 7 ml of water. Cool the liquid weil, add 5 g of the
Mix 5 g of sodium chloride, 0,5 g of hydrazine sulphate and
chloride-hydrazine-bromide mixture (D.2.2.7), followed
0,02 g of potassium bromide and store in a tightly
rapidly by 10 ml of the hydrochloric acid (0.2.2.4).
stoppered bottle.
0.2.5.2 Fit the condenser quickly and distil the liquid
D.2.2.8 Potassium bromate, 0,Ol N Standard volumetric
into 20 ml of water, the exit tube dipping below the surface
Solution.
of the liquid; cool in ice until about 5 min after the
condenser is full of steam. Dilute the distillate to 100 ml,
D.2.2.9 lodine, 0,Ol N Standard volumetric Solution.
add a few drops of the methyl orange indicator Solution
(D.2.2.10), heat the Solution to 80 ‘C, and titrate with the
D.2.2.10 Methyl orange indicator, 0,4 g/l Solution in 20 %
Standard volumetric potassium bromate Solution (0.2.2.8)
(WV) ethanol.-
or, alternatively, nearly neutralize the distillate with the
sodium hydroxide Solution (D.2.2.6), then add 3 g excess
D.2.2.11 Starch Solution.
of the sodium hydrogen carbonate (0.2.2.1) and titrate the
Solution with the Standard volumetric iodine Solution
Make a Paste of 0,2 g of soluble starch in cold water and
(D.2.2.9), using the starch Solution (D.2.2.11) as indicator.
pour into 100 ml of boiling water. Boil for 5 min, cool and
bottle.
D.2.5.3 Make sure that no solid material Comes in contact
Prepare a fresh Solution every 2 or 3 days. with the ground-in Portion of the flask.
60 56/11-1979 (E)
Dimensions in millimetres
25 ml
Y
25 ml
\ 100 or 200 ml
FIGURE 5 - Kjeldahl distillation apparatus for use in the determination of arsenic content (method 1)
D.2.6 Blank test Standard volumetric iodine Solution (0.2.2.9) used for
the determination (D.2.5), after applying correction for
Carry out a blank test at the Same time as the
the blank test;
determination, following the same procedure and using
the Same reagents, but omitting the test Portion. T is the normality of the Standard volumetric
potassium bromate Solution (0.2.2.8) or of the Standard
volumetric iodine Solution (0.2.2.9);
D.2.7 Expression of results
m is the mass, in grams, of the test Portion (D.2.4).
The arsenic (As) content is given, expressed as a percentage
by mass of arsenic(lll) sulphide (As&), by the formula
D.3 METHOD II (Traces of arsenic)
6,15 V T
m
D.3.1 Reagents
where
During the analysis,
use only reagents of recognized
V is the volume, in millilitres, of the Standard volu- analytical grade and only distilled water or water of
metric potassium bromate Solution (D.2.2.8) or of the equivalent purity. All the reagents, with the exception of
ISO 56/ll-1979 (E)
(0.3.1.1 1) and (D.3.1.12), shall be free from traces of 0.3.1.13 Mercury(lI) chloride Paper, consisting of smooth
arsenic. white filter Paper of width not less than 25 mm, soaked in a
saturated Solution of mercury(ll) chloride in water, pressed
to remove superfluous Solution, and dried at 60 “C in the
D.3.1.1 Potassium iodide, crystals or in the ferm of
dark. The grade of the filter Paper shall be such that the
powder.
grammage is between 65 and 120 g/m2 ; the thickness, in
millimetres, of 400 Papers shall be approximately equal,
D.3.1.2 Zinc, granulated, complying with the following
numerically, to the grammage, in grams per Square metre.
test :
Mercury(I 1) chloride Paper should be sotred in a stoppered
Take 50 ml of water, 10 ml of the stannated hydrochloric
bottle in the dark. Papers which have been exposed to
acid Solution (0.3.1.8) and 0,l ml of the dilute Solution of
sunlight or to ammonia gas should not be used as they give
arsenic (0.3.1.12) in the wide-mouth bottle (0.3.2.1). Add
a lighter coloured stain or no stain at all when employed
1 g of the potassium iodide (0.3.1.1) and 10 g of zinc.
in the quantitative test for arsenic.
Quickly place the prepared glass tube (0.3.2.2) in Position.
Allow the reaction to continue for 1 h. A faint but distinct
0.3.1.14 Methyl orange indicator, 0,4 g/l Solution in 20 %
yellow stain shall be produced on the mercury(ll) chloride
(WV) ethanol.
Paper (0.3.1.13).
D.3.2 Apparatus
0.3.1.3 Nitrit acid, p 1,42 g/mI.
The follow ing apparatus assembled as shown in figure 6 is
requ ired.
0.3.1.4 Sulphuric acid, p 1,84 g/mI.
D.3.2.1 Wide-mouth bottle, of capacity 120 ml.
D.3.1.5 Hydrochlorit acid, p 1,16 g/m 1.
D.3.2.2 Glass tube, made from ordinary glass tubing, and
D.3.1.6 Nitrit acid, dilute ( 3 + 7) solution.
having a total length of 200 mm, an internal diameter of
exactly 6,5 mm and an external diameter of about 8 mm.
D.3.1.7 Tin(ll) chloride Solution.
lt shall be drawn out at one end to a diameter of about
Dilute 60 ml of concentrated hydrochloric acid with 20 ml
1 mm and a hole not less than 2 mm in diameter shall be
of water, add to it 20 g of tin, heat gently until gas ceases
blown in the side of the tube, near the constricted part.
to be evolved, and add sufficient water to produce 100 ml,
The upper end of the tube shall be tut off Square and shall
allowing the undissolved tin to remain in the Solution.
be either rounded off slightly or ground smooth.
Decant the clear Solution, add an equal volume of
concentrated hydrochloric acid, boil down to the original
D.3.2.3 Rubber bungs, three
volume and filter through a finegrained filter Paper.
Cne shall fit exactly into the mouth of the wide-mouth
bottle and shall have a hole bored centrally to take the tube
D.3.1.8 Stannated hydrochloric acid solution.
from its constricted end. Esch of the other two rubber
Mix together 1 ml of the tin(ll) chloride Solution (0.3.1.7)
bungs (about 25 mm x 25 mm) shall have a hole of
and 100 ml sf the hydrochloric acid (0.3.1.5).
diameter 6,5 mm, bored centrally, and shall be fitted with
a rubber band or spring Clip for holding them tightly
D.3.1.9 Lead acetate, 100 g/l Solution in distilled water, together.
recently boiled.
0.3.2.4 Preparation of the glass tube.
D.3.1 .lO Chloride-hydrazine-bromide mixture.
Meisten a small quantity of cotton wool with the lead
acetate (D.3.1.9) and then dry it in a dust-free atmosphere.
Lightly pack the glass tube (0.3.2.2) with this cotton wool,
SO that the upper surface of the cotton wool is not less than
25 mm below the top of the tube. Insert the upper end of
the tube into the narrow end of the one of the pair of
D.3.1 .11 Arsenic, concentrated Solution.
rubber bungs (D.3.2.3), either to a depth of about 10 mm
Dissolve 0,132 g of arsenic trioxide in 50 ml of the hydro-
when the tube has a rounded-off end, or so that the ground
’
chloric acid (0.3.1.5) and add sufficient water to produce
end of the tube is flush with the larger end of the bung.
100 ml.
Place a piece of the mercury(lI) chloride Paper (D.3.1.11)
flat on the top of the bung. Place the other bung over this
D.3.1.12 Arsenic, dilute Solution. with its larger end in contact with the piece of mercury(II)
chloride Paper. Fasten the two bungs by means of the
Dilute 1 ml of the concentrated Solution of arsenic
rubber band or the spring Clip, in such a manner that the
(0.3.1 .ll) with sufficient water to produce 100 ml.
bores of the two bungs (or the upper bung and the glass
1 ml of this Solution contain 0,Ol mg of arsenic (or tube) form a continuous tube of diameter 6,5 mm
0,0132 mg of As,O,). interrupted by a diagram of mercury(lI) chloride paper-
ISO 56/11-1979 (E)
oride a water bath and evaporate the residue twice to dryness
Any other method of attaching the mercury( 11) ch
with 5 ml of water to remove any nitric acid. Dissolve the
Paper may be used, provided that
final residue by warming in 3 ml of the sulphuric acid
I the
a) the whole of the evolved gas Passes throug
(D.3.1.4), cool and dilute with water. Transfer the whole
Paper;
of the Solution to the wide-mouth bottle (D.3.2.1), add
15 ml of the stannated hydrochloric acid Solution (0.3.1.8)
b) the Portion of the Paper in contact with the gas is
and 1 g of the potassium iodide (0.3.1.1). Then add 10 g
a circle of diameter 6,5 mm;
of the zinc (D.3.1.2). Quickly place the prepared glass
c) the Paper is protected from sunlight during the test. tube (0.3.2.2) in Position. Allow the reaction to
continue for 40 min. Remove the piece of mercury(I 1)
chloride Paper at the end of this period. If arsenic is present
0.3.3 Procedure
in the material, compare the yellow stain produced on the
D.3.3.1 Treat 5 g of the “test Sample” exactly in the
mercuric chloride Paper, by daylight, with the Standard
manner prescribed in D.2.5.1 and then proceed as follows.
stains prepared as described under D.3.3.4. If the stain
in this test exceeds that equivalent to 0,02 mg of arsenic
D.3.3.2 Fit the condenser quickly and distil the liquid trioxide (As,O& make up the Solution to a known volume
into a mixture of 10 ml of water and 2 ml of the nitric with dilute sulphuric acid (1 : 8) and take an aliquot
acid (0.3.1.3). Then evaporate the distillate to dryness on Portion to produce a stain suitable for matthing.
Dimensions in millimetres
Mercury (1 I ) chloride
Paper
Spring cl ips
Cotton wool
with lead acetate
.@ 2 min.
Wide-mou th bottle
of capacity 120 ml
Granulated zinc
FIGURE 6 - Apparatus for the determination of arsenic content (method II )
ISO 56/11-1979 (E)
The reaction may be accelerated by placing the apparatus sol utions as described under 0.3.3.2 to prepare the
on a warm surface, care being taken that the mercury( II) sta ndard stains.
chloride Paper remains quite dry throughout the test. The
Make Sure that no solid material
Comes in contact with
most suitable temperature for carrying out the test is
the ground -in Portion of the bottle.
generally about 40 ‘C, but because the rate of evolution of
the gas varies somewhat with different batches of zinc, the
temperature may be adjusted to obtain a regular, but not
D.3.4 Blank test
too violent, evolution of gas. The tube should be washed
Carry out a blank test in parallel with the determination,
with concentrated hydrochloric acid. rinsed with water, and
following the Same procedure and using the same quantities
dried between successive tests.
of all the reagents, but omitting the test Portion. No visible
stain should be produced on the mercury(ll) chloride
D.3.3.3 Compare th e stains with freshl y prepare d Standard
Paper.
stains immediately at the completion of the test.
0.3.3.4 Prepare the Standard stains as follows :
D.3.5 Expression of results
Mix together 50 ml of water, 10 ml of the stannated Express the arsenic content of the shellac Sample as Parts of
hydrochloric acid Solution and appropriate volumes of the
arsenic (As) or arsenic trioxide Oxide (As,OJ per million
dilute Solution of arsenic (D.3.1.12). Treat the resulting Parts of shellac.
ISO 56/ll-1979 (E)
ANNEX E
(See 6.1)
DETERMINATION OF VOLATILE MATTER (MOISTURE) CONTENT
E.1 PRINCIPLE E.3.2 Keep the dish with the test Portion, without
covering it, in the oven (E.2.2) maintained at 40 2 2 “C for
Heating of a weighed test Portion of the “Sample as
4 h. At the end of this period, transfer the dish and cover
received” at 40 It: 2 “C f or 4 h followed by storage over
to a vacuum desiccator (E.2.3). Immediately evacuate the
concentrated sulphuric acid in vacuo for 18 h.
desiccator and keep the Sample uncovered in vacuo for
18 h. Remove the dish, cover it with the ground glass cover
and immediately weigh.
E.2 APPARATUS
E.2.1 Flat-bottomed dish, of 75 mm diameter, provided
with a ground glass cover.
E.2.2 Oven, well ventilated capable of being controlled at
40 + 2 “c.
E.4 EXPRESSION OF RESULTS
The volatile matte r (moisture) tonten t is given, expressed as
E.2.3 Vacuum desiccator, containing sulphuric acid
a percentage by m ass, by the f ormula
(p 1,84 g/mI) as desiccant.
“0 -ml
x 100
E.3 PROCEDURE mO
E.3.1 Use the “Sample as received” ground to specified
size (see S.3.2 of annex S) for this test. Weigh the clean,
m. is the mass, in grams, of the test Portion before
dry, flat-bottomed dish with ground glass cover (E.2.1).
drying;
Transfer approximately 2 g of the powdered Sample of the
dish, cover it with the ground glass cover and weigh it is the mass, in grams, of the test portion after
ml
again. The differente gives the mass of the test Portion. drying.
ISO 56/ll-1979 (E)
ANNEX F
(See 6.2.1)
DETERMINATION OF COLOUR INDEX
F.l PRINCIPLE F.4.2 Pipette 5 ml of the filtered shellac Solution into a
thin-walled test tube (F.3.2). Take 5 ml of the appropriate
Comparison of the colour of a Standard Solution of iodine
Standard iodine Solution, (F.2.2) or (F.2.3), in another test
with a Solution of the shellac in ethanol, by diluting either
tube (F.3.2) for matthing. Compare the colour of the two
Solution progressively until a close match is obtained.
solutions, holding the test tubes against the light with a
piece of moistened filter Paper or opal glass interposed
in between the light Source and the test tubes. Add the
F.2 REAGENTS
alcohol from a burette to the shellac Solution with shaking
During the analysis, use only reagents of recognized until the colour is the same as that of the Standard iodine
analytical grade and only distilled water of equivalent Solution. Note the volume of alcohol added. Alternatively,
purity. in the case of type IV shellac, if the lac Solution is lighter,
dilute the Standard Solution (F.2.3) with water contained in
a second burette until a match is obtained and note the
F.2.1 Alcohol, 95 % (V/V) rectified spirit; or 95 % (V/V)
volume of water added.
denatured spirit, provided that it is colourless.
...