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I N TERN AT1 O NA L O RG A N I ZATl ON FOR STA N DA RD I ZATl O N
IS0 RECOMMENDATION
R 57
SPECIFICATION FOR BLEACHED LAC
1st EDITION
December 1957
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
Copies to be obtained through the national standards organizations.
Also issued in French and Russian.
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BRIEF HISTORY
The IS0 Recommendation R 57, Specification for Bleached Lac, was drawn
up by Technical Committee ISO/TC 50, Lac, the Secretariat of which is held
by the Indian Standards Institution (ISI).
This Technical Committee decided to place on its program of work the
question of Bleached Lac and the ISO/TC 50 Secretariat submitted a first
draft proposal based on the studies made previously by the Indian Member Body.
This draft proposal was discussed at the first meeting of Technical Com-
mittee ISO/TC 50, held in New Delhi, in January 1950. A second draft
proposal, which took into account the resolutions adopted at this meeting, was
then circulated to the members of the Technical Committee and discussed at
O
the second meeting of Technical Cornmittee ISO/TC 50, held in New York, in
June 1952. A major change was made at this meeting; the title of the subject
was changed to “Bleached Lac”, and a working document submitted by the
United Kingdom was taken into consideration, A revised third draft proposal
for Bleached Lac was then formulated. Some changes were made in this
document at the third meeting of the Technical Committee, held in London, in
October 1954 and the Technical Committee adopted the document thus revised,
as a Draft IS0 Recommendation.
On 12 September 1956, the Draft IS0 Recommendation (No. 100) was
distributed to all IS0 Member Bodies and was approved, subject to modifica-
tions, by the following 21 (out of a total of 37) Member Bodies:
*Australia Hungary Spain
Austria *Ireland *Sweden
*Bulgaria Netherlands Turkey
*Canada Pakistan Union of South Africa
*Denmark Poland United Kingdom
O
Portugal U.S.A.
France
*Greece Romania *U.S.S.R.
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 1957, to accept it as an
IS0 RECOMMENDATION,
These Member Bodies stated that they had no objection to the Draft being approved.
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CONTENTS
Foreword . 5
1 . Scope . 7
2 . Terminology . 7
3 . Sampling . 7
4 . Form . 7
5 . Conditions and types . 8
6 . Volatile matter (moisture) . 8
7 . Matter insoluble in hot alcohol . 8
8 . Colour . 8
9 . Wax . 9
10 . Ash . 9
11 . Rosin and copals . 9
12 . Matter soluble in water . 9
13 . Chlorine content . 9
14 . Acid value and mineral acid . 9
15 . Non-volatile matter soluble in cold alcohol . 10
16 . Character of requirements . 10
17 . Tests . 10
Table 1 - Requirements for bleached lac . 10
Appendix A - Sampling of bleached lac . 11
Table 2 - National sieve designations and mesh apertures corre-
............. 13
sponding to specified sizes
Appendix B - Determination of volatile matter (moisture) . 14
Appendix C - Determination of matter insoluble in hot alcohol . 16
Appendix D - Comparison of colour . 23
Appendix E - Determination of wax . 25
Appendix F - Determination of ash . 28
Appendix G - Detection of rosin (Halphen-Hicks method) . 29
Appendix H - Detection of copals . 30
31
Appendix J - Determination of matter soluble in water .
Appendix K - Determination of chlorine . 32
Appendix L - Determination of acid value . 33
Appendix M - Determination of mineral acid . 34
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FOREWORD
1. This IS0 Recommendation is based on the decisions arrived at in the flrst three
meetings of the Technical Committee on Lac of the International Organization for Stan-
dardization (ISO/TC 50) which were held in New Delhi, India, on January 16, 17, IS and
19,1950; in New York, U.S.A., on June 23,24 and 25,1952; and in London, United Kingdom,
on October 11, 12 and 13, 1954, respectively.
II. Hitherto the material dealt with in this IS0 Recommendation has been called
bleached shellac. The name is due to the fact that it was manufactured formerly by
bleaching shellac, which alone was the common article exported from
India. Now,
however, bleached lac is manufactured generally by bleaching seedlac or sometimes
shellac and the old name is, therefore, incorrect and misleading. The new name intro-
duced in this IS0 Recommendation, “Bleached Lac”, is therefore not a misnomer and
it will, at the same time, avoid confusion between the ordinary shellac and the bleached
product.
This IS0 Recommendation covers bone-dry bleached lac, an intermediate surface-
dry (air-dry) bleached lac, and wet bleached lac, the three differing in their requirements
in the moisture content. No distinction is sought to be introduced between bone-dry,
kiln-dry or vac-dry bleached lac or between the various designations of the intermediate
type covering dried, crushed hanks, or flats in granules or flakes, or between wet bleached
lac in hank, bar or any other form. Only three conditions, i.e. bone-dry, surface-dry
(air-dry) and wet, and two types in each condition, namely (a) regular bleached lac (cloudy
or waxy), and (b) refined bleached lac (transparent or wax-free), more briefly indicated
as “regular” and “refined”, are recognized.
111. Notwithstanding the extensive activities of the Indian Lac Cess Committee con-
o
cerning the rationalization of production and marketing of lac products in India and
abroad, through the Indian Lac Research Institute, Namkum, Bihar, India, and the London
Shellac ResearchBureau, and in spite of the interest taken in this matter by the United States
Shellac Importers’ Association, the American Bleached SheUac Manufacturers’ Association,
and the American Society for Testing Materials, considerable confusion and disagreement
still exist in the various specifications on seedlac and shellac that have been evolved and
are in use in different countries by different agencies. Bleached lac, on the other hand,
does not present the same difficulties. There is a considerable degree of uniformity and
unanimity of opinion on the requirements for bleached lac, and international acceptance
of agreed standards should not, therefore, present any difficulty.
IV. At the second and third meetings of ISO/TC 50, it was decided that the position
regarding limits of variation of certain requirements should be indicated in the Foreword
for the guidance of the contracting parties. These decisions are given below.
Normally
V. No limit has been prescribed for the chlorine content of bleached lac.
the chlorine content of bleached Iac varies between 1.5 and 4.5 per cent on moisture free
material, but ISO/TC 50 has decided to place it on record that it is desirable to maintain
it at a low value (say at 3 per cent, maximum).
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VI. Likewise, no limit has been prescribed for the acid value of bleached lac.
This
depends on the technique of bleaching. The acid value of a good bleached lac is normally
between 65 and 100 on the moisture-free material. ISO/TC 50 considers it desirable to
retain the acid value at as low a value as possible below 105.
VIL Similarly the mineral acid content of bleached lac should also be as low as possible,
requiring for neutralization under the conditions specified in Appendix M not more than
82 ml of 0.1 N sodium hydroxide per I00 g of the moisture-free material which is equivalent
to 0.4 per cent of mineral acid calculated as sulphuric acid (H,SO,).
VIII. The question of requirements and methods of test for non-volatile matter soluble
in cold alcohol is under consideration by ISO/TC 50, for which separate IS0 Recom-
mendations may be issued in due course. Pending this, the limits and methods of test
have been made subject to agreement between the purchaser and the vendor. The two
methods for cold alcohol solubles under study by the Committee are contained in the
following documents:
(1) ISO/TC 50 (Secretariat-50) 83,
Q
(2) ISO/TC 50 (Secretariat-51) 84.
IX. The maximum limit for the volatile matter (moisture) in the bone-dry material has
been specified as a mandatory requirement, i.e. a maximum of 6 per cent (see Section 6.)
In so far as surface-dry (air-dry) and wet bleached lacs are concerned, the actual limits
have been made the subject of agreement between purchaser and vendor.
The normal
moisture content of the surface-dry (air-dry) material does not exceed 12 per cent, that
of wet bleached lac does not exceed 30 per cent.
X. In pursuance of the resolution passed at the second and third meetings, the mesh
sizes of sieves given in the text of this IS0 Recommendation have been indicated in terms
of aperture dimensions, and a note, giving number designations of approximately equiva-
lent sieves of U.S.A., United Kingdom, France, India and other countries has been added
for the sak of convenience.
XI. Acknowledgement is due for the assistance that has been derived from the speci-
fications and publications of the United States Shellac Importers’ Association, the American
Bleached Shellac Manufacturers’ Association, the British Standards Institution, and the
0
Indian Lac Research Institute, more particularly from “A Handbook of Shellac Analysis”
by M. Rangaswami and H.K. Sen, issued by the Indian Lac Research Institute, which
gives a critical review of the characteristics and methods of tests of lac and lac products
and which was designed by the authors to serve as an approach to international agreement
on standardization in this field. The comments received from the American Standards
Association, the British Standards Institution, Association Française de Normalisation,
and the Indian Standards Institution, which were forwarded for the consideration of
ISO/TC 50, are also acknowledged.
XII. For the purpose of deciding whether a particular requirement of this IS0 Recom-
mendation is complied with, the final value observed or calculated, expressing the result
of test or analysis shall be rounded off to the same number of places as that in the specified
value; it being always understood that the analyst will carry out his determination to
at least one place more than in the specified value.
XIII. In order to facilitate cross references to clauses of the different appendices in this
IS0 Recommendation, the clauses in each appendix bear, besides the serial number, a
Thus reference to
letter prefix corresponding to the letter number of the appendix.
A-2 or B-3 means that clause 2 of Appendix A or clause 3 of Appendix B is under reference.
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ISO/R !XI - 1957 (E)
I EO Recommendation R 57 Decem ber 1957
SPECIFICATION FOR BLEACHED LAC
t. SCOPE
1.1 This IS0 Recommendation prescribes the requirements and methods of
test for Bleached Lac in any form that may be agreed upon between the
purchaser and the vendor.
1.2 This IS0 Recommendation is intended chiefly to cover the technical
provisions for guiding the purchase of the material, but does not include all
the necessary provisions of a contract.
1.3 The limits prescribed in this IS0 Recommendation are limits for rejection.
2. TERMINOLOGY
2.1 For the purposes of this IS0 Recommendation, the following definitions
apply :
(a) Sticklac is the natural product of lac insects.
(b) Seedlac is the product obtained by washing crushed sticklac.
(c) Shellac is the product obtained by refining seedlac by heat processes or by
both heat and solvent processes.
(d) Bleached lac is the product obtained by subjecting seedlac or shellac in
solution to a process of bleaching and then recovering the product in a solid
form.
(e) Regular (cloudy or waxy) bleached lac is the ordinary type of bleached lac
from which wax has not been removed.
(f) Refined (transparent or wax-free) bleached lac is the type of bleached lac
from which wax has been removed during the process of manufacture.
(9) Approved sample is the sample agreed upon between the purchaser and the
vendor as the standard for colour.
3. SAMPLING
3.1 Samples are taken in the manner prescribed in Appendix A.
4. FORM
4.1 The form of bleached lac is subject to agreement between the purchaser
and the vendor.
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ISO/R 57 - 1857 (E)
5. CONDITIONS AND TYPES
5.1 There shall be three conditions of bleached lac, namely:
(a) bone-dry,
(b) surface-dry (air-dry) and
(c) wet.
5.2 There shall be two types under each of these conditions, namely:
(a) regular (cloudy or waxy), and
(b) refined (transparent or wax-free).
6. VOLATILE MATTER (moisture)
6.1 Bone-dry bleached lac shall contain not more than 6 per cent of volatile
matter (moisture), as determined by the method prescribed in Appendix B.
O
6.2 The percentage of volatile matter (moisture) present in surface-dry (air-dry)
bleached lac is subject to agreement between the purchaser and the vendor
and is determined by the method prescribed in Appendix B (see Foreword,
clause IX).
6.3 The percentage of volatile matter (moisture) in wet bleached lac is subject
to agreement between the purchaser and the vendor and is determined by the
method prescribed in Appendix B (see Foreword, clause IX).
7. MATTER INSOLUBLE IN HOT ALCOHOL
7.1 Bleached lac shall not contain matter insoluble in hot alcohol, computed
on the basis of moisture-free material, in excess of the limits given below:
regular: 1.1 per cent
refined: 0.2 per cent
O
7.1.1 Matter insoluble in hot alcohol is determined by either of the methods
prescribed in Appendix C, as agreed between the purchaser and the vendor.
8. COLOUR
8.1 The appearance and colour of bleached lac shall not be inferior to that
of the approved sample when judged by visual examination. Alternatively
the colour in solution may be tested by either of the methods prescribed in
Appendix D, as agreed between the purchaser and the vendor.
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ISO/R 57 - 1057 (E)
O. WAX
9.1 Bleached lac shall not contain wax, as determined by the appropriate method
prescribed in Appendix E and computed on the basis of moisture-free material,
in excess of the limits given below:
regular: 5.5 per cent
refined: 0.2 per cent
IO. ASH
10.1 Bleached lac shall not leave ash, as determined by the method described
in Appendix F and computed on the basis of moisture-free material, in excess
of the limits given below:
regular: 1.0 per cent
refined: 0.5 per cent
O
11. ROSIN AND COPALS
11.1 Bleached lac shall contain no rosin, as tested by the method described in
Appendix G.
11.2 Bleached lac shall contain no copals, as tested by the method described
in Appendix H.
12. MATTER SOLUBLE IN WATER
12.1 Bleached lac shall not contain matter soluble in water, as determined by
the method prescribed in Appendix J and computed on the basis of mois-
ture-free material, in excess of the limits given below:
regular: 1.0 per cent
refined: 0.3 per cent
8
13. CHLORINE CONTENT
13.1 The chlorine content of bleached lac is subject to agreement between
the purchaser and the vendor and, when specified, it shall be determined by
the method prescribed in Appendix K (see Foreword, clause V).
14. ACID VALUE AND MINERAL ACID
14.1 The acid value of bleached lac is subject to agreement between the pur-
chaser and the vendor and, when specified, it is determined by the method
prescribed in Appendix L (see Foreword, clause VI).
14.2 The mineral acid content of bleached lac is subject to agreement between
the purchaser and the vendor and, when specified, it is determined by the method
prescribed in Appendix M (see Foreword, clause VII).
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ISO/R 57 1957 (E)
15.
NON-VOLATILE MATTER SOLUBLE IN COLD ALCOHOL
15.1 The limits and methods of test for non-volatile matter soluble in cold
alcohol are subject to agreement between the purchaser and the vendor (see
Foreword, clause VIII).
16. CHARACTER OF REQUIREMENTS
16.1 The character of requirements for bleached lac is given in table 1, below.
16.1.1 The optional requirements are subject to agreement between the
purchaser and the vendor.
17. TESTS
17.1 Except where otherwise indicated, calculations regarding bleached lac
in any form or condition shall be made in terms of the moisture-free materials.
17.2 All analytical work on bleached lac except the determination of volatile
matter (moisture) content is carried out on the “prepared sample” obtained as
described under clause A-3.1 (Appendix A).
17.2.1 The volatile matter (moisture) content of the “prepared sample” is
determined by the method described in Appendix B and this figure is used to
correct the analytical results, other than for volatile matter (moisture), to
O
terms of moisture-free material.
TABLE 1
Requirements for Bleached Lac
~
Maximum Limits for Type
Method of Test11
Clause Character
Charaeteristie Reference
Referenee of Requirement
to Appendix
Regular Rellned
I
6 Essential Volatile mat-
ter (moisture)
B
per cent
Bone-dry
6.0 I 6.0
Other condi- As agreed between purchase]
and vendor
tions
7 Essential Matter insolu-
ble in hot alco-
hol, per cent* 1.1 1 0.2 C
8 Close visual match to the
Essential Colour
D
approved sample
O
E
9 Essential Wax,percent* 5.5 0.2
F
10 Ash, per cent *
Essential 1.0 0.5
G
11.1 Essential Rosin Nil Nil
H
Copals Nil Nil
11.2 Essential
12 Essential Matter soluble
in water, per
J
cent* 1.0 0.3
K
4s agreed between purchaser
13 Optional Zhlorine con-
tent* and vendor
(see Foreword, clause V)
L
Acid value* 4s agreed between purchaser
14.1 Optional
and vendor
(see Foreword, clause VI)
M
14.2 Optional Mineral acid* 1s agreed between purchaser
and vendor
(see Foreword, clause VII)
1s agreed between purchaser
15 Optional Von-volatile
and vendor
natter soluble
ncoldalcohol* (see Foreword, clause VIII)
I
* To be calculated on a moisture-free basis.
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ISO/R 5‘1 - 1957 (E)
Appendix A
(Section 3)
SAMPLING OF BLEACHED LAC
Note. - It is essential that the operations described for the drawing, reduction
and preparation of analysis samples are carried out as expeditiously as possible
in order to minimize loss of moisture.
A-I. DRAWING OF SAMPLES
A-1.1 Only original, unopened packages of bleached lac are sampled.
A-1.2 Not less than ten per cent of the packages, selected at random from each
lot, are sampled.
A-1.3 For this purpose a lot does not exceed 200 packages.
A-1.4 Unused portions of samples are sent to the purchaser on request.
A-1.5 FREE-FLOWING BLEACHED LAC. Samples are taken from different places
in each package by means of a suitable tryer so as to yield a total of 5 kg (or
10 lb) of material consisting of approximately equal portions from each package
sampled. The material is then thoroughly mixed and heaped and quartered
along two diameters which intersect at right angles, and two opposite quarters
are mixed. One half of the material may, if necessary, be further subdivided
by the normal process of quartering to form a number of samples which serve
separately as “original observation samples” and “samples for the determina-
tion of volatile matter (moisture)”. These samples are placed in air-tight
containers, sealed and labelled accordingly. The samples labelled “for the
determination of volatile matter (moisture)” are treated as prescribed in
clause A-3.2. The other half of the material is treated as described under
A-2.1 to form the “analysis sample”.
clause
A-1.6 BLOCKY OR MATTED BLEACHED LAC. Samples are taken from different
places in each package, by chipping or other suitable means, so as to yield a
total of 5 kg (or 10 Ib) of material consisting of approximately equal portions
from each package sampled. The material is then thoroughly mixed and heaped
and quartered along two diameters which intersect at right angles, and two
opposite quarters are mixed. One half of the material may, if necessary, be
further subdivided by the normal process of quartering to form a number of
samples which serve separately as “original observation samples” and as
“samples for the determination of volatile matter (moisture)”. These samples
The samples
are placed in air-tight containers, sealed and labelled accordingly.
labelled “For the determination of volatile matter (moisture)” are treated as
prescribed in clause A-3.2. The other half of the material is roughly ground
so as to pass a sieve having a nominal aperture of 6.3 mm (see clause A-4.1)
and is then treated as prescribed under clause A-2.1 to form the “analysis
sample”.
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ISO/R 57 - 1957 (E)
A-1.7 BLEACHED LAC IN HANKS, BARS OR FLATS. Two hanks, bars or flats
are drawn from different places in each package and a large piece is broken
from each, by suitable means, so as to yield a total of 5 kg (or 10 lb) of material,
or flat.
consisting of approximately equal proportions from each hank, bar
The composite sample is quickly crushed to lumps of about 25 mm3 (or 1 ins).
The material is then thoroughly mixed and heaped and quartered along two
diameters which intersect at right angles, and two opposite quarters are mixed.
One half of the material may, if necessary, be subdivided by the normal process
of quartering (without crushing) to form a number of samples to serve separately
as “original observation samples” and “samples for the determination of volatile
matter (moisture)”. These samples are placed in air-tight containers, sealed
and labelled accordingly. The samples labelled “for the determination of
volatile matter (moisture)” are treated as prescribed in clause A-3.2. The
remaining half of the material is roughly ground so as to pass a sieve having
a nominal aperture of 6.3 mm (see clause A-4.1) and is then treated as
described under clause A-2.1 to form the “analysis sample”.
A-2. REDUCTION OF SAMPLES
Note. - If the material at any time during the following operations shows
signs of surface moisture, it shall be air dried at room temperature before
further mixing and grinding.
A-2.1 The material for the analysis sample, as obtained under clause
A-1.5, A-1.6 or A-1.7 is mixed thoroughly, heaped and quartered along
Two opposite quarters are
two diameters which intersect at right angles.
mixed and ground to pass entirely through a sieve having a nominal aperture
of about 2 mm (see clause A-4.1). The material is then thoroughly mixed
so as to yield four samples of approximately 250 g (or 0.5 lb)
and quartered
each. These four samples are placed in air-tight containers, sealed labelled
“sample for analysis” and sent to the interested parties.
A-2.2 The date of sampling, the number of packages sampled, the condition of
the packages and contents, and the name and code number of the vendor are
given on a label attached to each sample.
A-3. PREPARATION OF ANALYSIS SAMPLES FOR TESTING
A-3.1 The samples for analysis are ground to pass entirely through a sieve whose
nominal aperture does not exceed 0.425 mm (see clause A-4.1). This finely
ground material is mixed thoroughly and placed in an air-tight container and
labelled “ unconditioned sample for analysis ”. Before this material is used for
any analytical work, it is brought to less than 6 per cent volatile matter (moisture)
content by exposing it to the atmosphere for at least 24 hours at room tem-
perature and then desiccating overnight over fused calcium chloride. The
material is then known as the “prepared sample”.
A-3.2 The sample or samples labelled “for the determination of volatile matter
(moisture)” (see clauses A-1.5, A-1.6 and A-1.7) are treated according to the
method described in Appendix B.
A-4. NOTE ON SIEVE SIZES
A-4.1 Table 2 (page 13) gives some of the national sieve designations and mesh
apertures corresponding approximately to the sizes specified in the preceding
clauses and in Appendices B and J.
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ISO/R 57 - 1957 (E)
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ISO/R 57 - 1957 (E)
Appendix B
(Section 6)
DETERMINATION OF VOLATILE MATTER (MOISTURE)
B-I. OUTLINE OF METHOD
B-1.1 The volatile matter (moisture) content of bleached lac is determined in
two stages, the first stage being by drying a weighed specimen of the original
observation sample marked "for the determination of volatile matter (moisture)
content" by keeping it over a concentrated sulphuric acid in vacuo for 12 to
24 hours. In the case of bone-dry bleached lacs, this first stage may be omitted.
B-1.2 For the second stage, grind the partially dried material thus obtained
to the specified size and further dry a portion by heating it in a well-ventilated
oven maintained at a temperature of 41 "C f 1 "C for 18 hours.
8-2. PROCEDURE
B-2.1 Use a portion of the original observation sample and crush, if necessary,
into granules using a heavy pestle and mortar, keeping the latter covered as
far as possible during the process. Weigh a clean, dry, flat-bottomed dish of
about 100 mm diameter, provided with a glass cover. Transfer approximately
10 g of the ground sample to the dish as rapidly as possible, cover it with the
glass cover and reweigh. The difference gives the weight of sample taken.
B-2.2 Transfer the dish and contents to a vacuum desiccator containing
concentrated sulphuric acid and remove the cover of the dish. Immediately
evacuate the desiccator and keep the sample, uncovered, in vacuo for not
less than 12 hours and not more than 24 hours. Remove the dish, replace
The difference between this weight and the weight of
the cover and weigh.
Grind the partially dried
the dish is the weight of the partially dried sample.
sample thus obtained until it passes a sieve having a nominal aperture of
0.425 mm (see A-4.1).
8-2.3 Weigh approximately 2 g of the ground material, to an accuracy of 1 mg,
into a covered tared dish of the type described in B-2.1 and transfer to a well-
ventilated oven maintained at a temperature of 41 "C f 1 "C for 18 hours, the
cover of the dish being removed during the drying process. At the conclusion
of the heating period, replace the cover and transfer the covered dish to a
desiccator; weigh when cool. This weight minus the weight of the dish is
the weight of the completely dried ground sample.
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ISO/R 57 - 1057 (E)
8-3. CALCULATION
8-3.1 The percentage of volatile matter (moisture) in the original sample is
given by the following formula:
w4 w* )
Volatile matter (moisture), per cent = 100 (1 -
w3 w,
where W, = weight of crushed wet sample taken for stage
of drying in vacuo,
Wa = weight of partially dried sample,
W3 = weight of partially dried, ground sample taken
for final oven drying and
W4 = weight of completely dried, ground sample.
B-3.2 If the first drying stage (see B-2.2) is omitted, the percentage of volatile
matter (moisture) in the original sample is given by the formula:
w,
Volatile matter (moisture), per cent = 100 (1 - --)
Wl
where W, = weight of sample taken for oven drying and
Wa = weight of completely dried, ground sample.
I
I
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ISO/R 57 - 1957 (E)
Appendix C
(Section 7)
DETERMINATION OF MATTER INSOLUBLE IN HOT ALCOHOL
C-I. GENERAL
C-1.1 The matter insoluble in hot alcohol is determined by extracting a known
weight of bleached lac with 95 per cent (by volume) ethanol and determining
the percentage of the undissolved residue by either of the two methods de-
scribed below, as may be agreed.
O
C/l METHOD I
C/l-l. APPARATUS
C/I-I.I The apparatus consists of the following:
C/~-l.l.l Condenser - all glass, of the type and dimensions shown in figure 1,
page 17, with the tip cut at an angle of 45 degrees.
c/1-1.1.2 Siphon tube - of glass, of the type and dimensions shown in figure 1.
The siphon tube has 2 holes near the top for a wire to be fastened to a condenser
tip, leaving about 6 mm space between the top of the tube and the condenser tip.
C/I-1.1.3 Flask - heat resistant, wide-mouth, conical, preferably of boro-
silicate glass, 176 mm f 3 mm in height and 48 mm & 2 mm in inside
diameter at the top. The flask has a tight-fitting cork 25 mm in depth and
bored to fit the stem of the condenser. The
...