Crude petroleum and liquid or solid petroleum products - Determination of density or relative density - Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods (ISO 3838:1983)

Migrated from Progress Sheet (TC Comment) (2000-07-10): Decision of BT to submit this ISO document to UAP procedure.

Rohöl und flüssige oder feste Mineralölerzeugnisse - Bestimmung der Dichte oder der relativen Dichte - Verfahren mittels Pyknometer mit Kapillarstopfen und Bikapillar-Pyknometer mit Skale (ISO 3838:1983)

Pétrole brut et produits pétroliers liquides ou solides - Détermination de la masse volumique ou de la densité relative - Méthodes du pycnomètre à bouchon capillaire et du pycnomètre bicapillaire gradué (ISO 3838:1983)

Surova nafta in tekoči ali trdni naftni proizvodi - Določanje gostote ali relativne gostote - Metoda s piknometrom s kapilarnim zamaškom in metoda z graduiranim bikapilarnim piknometrom (ISO 3838:1983)

General Information

Status
Withdrawn
Publication Date
03-Oct-1995
Withdrawal Date
30-Apr-2004
Current Stage
9960 - Withdrawal effective - Withdrawal
Due Date
01-May-2004
Completion Date
01-May-2004

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SLOVENSKI STANDARD
SIST EN ISO 3838:1998
01-maj-1998

6XURYDQDIWDLQWHNRþLDOLWUGQLQDIWQLSURL]YRGL'RORþDQMHJRVWRWHDOLUHODWLYQH

JRVWRWH0HWRGDVSLNQRPHWURPVNDSLODUQLP]DPDãNRPLQPHWRGD]JUDGXLUDQLP
ELNDSLODUQLPSLNQRPHWURP ,62

Crude petroleum and liquid or solid petroleum products - Determination of density or

relative density - Capillary-stoppered pyknometer and graduated bicapillary pyknometer

methods (ISO 3838:1983)

Rohöl und flüssige oder feste Mineralölerzeugnisse - Bestimmung der Dichte oder der

relativen Dichte - Verfahren mittels Pyknometer mit Kapillarstopfen und Bikapillar-

Pyknometer mit Skale (ISO 3838:1983)

Pétrole brut et produits pétroliers liquides ou solides - Détermination de la masse

volumique ou de la densité relative - Méthodes du pycnometre a bouchon capillaire et du

pycnometre bicapillaire gradué (ISO 3838:1983)
Ta slovenski standard je istoveten z: EN ISO 3838:1995
ICS:
75.040 Surova nafta Crude petroleum
75.080 Naftni proizvodi na splošno Petroleum products in
general
SIST EN ISO 3838:1998 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 3838:1998
---------------------- Page: 2 ----------------------
SIST EN ISO 3838:1998
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SIST EN ISO 3838:1998
---------------------- Page: 4 ----------------------
SIST EN ISO 3838:1998
International Standard 3838

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION@ME)KAYHAPO~HAR OPrAHH3Al#lR fl0 CTAHJJAPTH3A~WWORGANlSATlON INTERNATIONALE DE NORMALISATION

Crude petroleum and liquid or solid petroleum products -
Determination of density or relative density - Capillary-
stoppered pyknometer and graduated bicapillary
pyknometer methods

P&role brut et produits p&roliem liquides ou solides - D&ermination de la masse volumique ou de la densitt! relative -

M&hodes du pycnom&tre 8 bouchon capillaire et du pycnom&tre bicapillaire grad&
First edition - 1983-06-01
UDC 665.6/.7 : 531.756.4
Ref. No. ISO3838-1983 (E)

Descriptors : petroleum products, crude oil, liquids, solids, pyknometric analysis, density (mass/volume), density measurement, testing

conditions, test equipment, calibrating.
Price based on 11 pages
---------------------- Page: 5 ----------------------
SIST EN ISO 3838:1998
Foreword

IS0 (the International Organization for Standardization) is a worldwide federation of

national standards bodies (IS0 member bodies). The work of developing International

Standards is carried out through IS0 technical committees. Every member body

interested in a subject for which a technical committee has been authorized 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.

Draft International Standards adopted by the technical committees are circulated to

the member bodies for approval before their acceptance as International Standards by

the IS0 Council.
International Standard IS0 3838 was developed by Technical Committee ISO/TC 28,
Petroleum products and lubricants, and incorporates draft International Standard
ISO/DIS 3658. Both documents were circulated to the member bodies in July 1981.
They have been approved by the member bodies of the following countries :
Australia
India Romania
Austria
Iraq South Africa, Rep. of
Belgium Israel Spain
Brazil
Italy Sweden
Canada Japan Switzerland
China
Netherlands United Kingdom
France Norway USA
Germany, F. R. Peru * USSR
Hungary Poland
No member body expressed disapproval of the documents.
Peru approved DIS 3838 only.
0 International Organization for Standardization, 1983
Printed in Switzerland
---------------------- Page: 6 ----------------------
SIST EN ISO 3838:1998
INTERNATIONAL STANDARD IS0 38384983 (E)
Crude petroleum and liquid or solid petroleum products -
Determination of density or relative density - Capillary-
stoppered pyknometer and graduated bicapillary
pyknometer methods
1 Scope and field of application 3 Definitions
For the purpose of this International Standard, the following
1.1 This International Standard specifies methods for the
definitions shall apply.
determination of the density or relative density of crude
petroleum and of petroleum products handled as liquids.
3.1 density : The mass of the substance divided by its
1.2 The capillary-stoppered pyknometer method is also for
volume.
use with solids and this method may also be used for coal tar
products, including road tars, creosote and tar pitches, or for
When reporting the density, the unit of density used, together
mixtures of these with petroleum products. This method is not
with the temperature, shall be explicitly stated, for example
suitable for the determination of the density or relative density
kilograms per cubic metre, or grams per millilitre, at t OC.
of highly volatile liquids having Reid vapour pressures greater
than 56 kPa (0,5 bar) according to IS0 3007 or having an initial
boiling point below 40 OC.
3.2 apparent mass in air : The value obtained by weighing
in air against standard masses without making correction for
1.3 The graduated bicapillary pyknometer method is recom-
the effect of air buoyancy on either the standard masses or the
mended for the accurate determination of the density or relative
object weighed .
density of all except the more visco.us products, and is par-
ticularly useful when only small amounts of samples are
available. The method is restricted to liquids having Reid
3.3 observed density : The value required in order to enter
vapour pressures of 130 kPa (1,3 bar) or less according to
tables 53A and 53B referred to in IS0 91/l or given in table A in
IS0 3007 and having kinematic viscosities less than 50 cSt
ISO/R 91 Addendum 1, determined with soda-lime glass ap-
(50 mm%) at the test temperature. ’
paratus at a test temperature which differs from the calibration
temperature of the apparatus, no correction having been made
Special precautions are specified for the determination of the
for the thermal expansion or contraction of the glass.
density or relative density of highly volatile liquids.
relative density : The ratio of the mass of a volume of a
3.4
2 References
substance at a temperature tI to the mass of an equal volume of
another substance at a temperature t2. The temperatures tl and
IS0 91, Petroleum measurement tables. 1)
t2 may be equal. For the purpose of this International Standard,
the other substance is water, i.e. the relative density is the ratio
IS0 653, Long solid-stem thermometers for precision use.
t, to the den-
of the density of the substance at a temperature
sity of water at a temperature t2.
IS0 3007, Petroleum products - Determination of vapour
pressure - Reid method.
When reporting the relative density, the temperatures t, and t2
must be explicitly stated. IS0 91 refers only to tables for the
IS0 3567, Pyknometers.
reduction of relative density to 60/60 OF. If results are required
referred to another reference temperature, the determination
IS0 5024, Petroleum liquids and gases - Measurement -
should be carried out at that temperature.
Standard reference conditions.

1) IS0 91/l has been published, but the revision of ISO/R 91 Addendum 1 is at present at the stage of draft.

---------------------- Page: 7 ----------------------
SIST EN ISO 3838:1998
Is0 38384983 (El
The pyknometers shall conform to the relevant requirements of
4 Principle
IS0 3507.
41 Capillary-stoppered pyknometer
NOTE - The “warden” form [see a) in figure 11 is recommended for
all except viscous or solid products and should always be used for
The masses of equal volumes of the sample and of water are
volatile products. The ground glass cap, or “warden ”, greatly reduces
compared. Equal volumes are ensured by the pyknometer being
expansion and evaporation losses and this form of pyknometer may be
filled so as to overflow when placed in a bath at the test
used when the test temperature is lower than that of the laboratory.
temperature until equilibrium is reached. The calculation
(clause 10) includes corrections for thermal expansion of glass
The form of pyknometer shown in b) in figure 1, known
5.1.1
and for buoyancy.
as the Gay-Lussac type, is suitable for non-volatile liquids ex-
cept those of high viscosity.
4.2 Graduated bicapillary pyknometer
5.1.2 The wide-mouth (Hubbard) form of pyknometer [see c)
The graduated arms of the pyknometer are calibrated, using
in figure 11 is used for very viscous liquids and solids.
water, in terms of the apparent mass in air of water contained
in the pyknometer, and a graph prepared. The liquid sample is
5.1.3 As the forms of pyknometer shown in b) and c) in
drawn into the dried pyknometer and, after it has reached

equilibrium at the test temperature, the liquid levels are noted figure 1 have no “warden” or expansion chamber, they cannot

be used when the temperature of the test is so far below that of
and the pyknometer weighed. The apparent mass in air of an
the laboratory as to cause loss of sample by expansion through
equal volume of water is read from the graph and the density or

relative density of the sample is calculated, with corrections the capillary during weighing.

being made as in 4.1.
5.2 Graduated bicapillary pyknometer, capacity 1 to
10 ml, conforming to the dimensions given in figure 2, con-
5 Apparatus
structed of borosilicate glass or soda-lime glass, annealed after
manufacture, and having a total mass not exceeding 30 g. Any
pyknometer conforming with the requirements of the Lipkin
5.1 Capillary-stoppered pyknometer, one of the three
pyknometer given in IS0 3507 may be used.
types shown in figure 1 (see 8.1 .l).
b) Capillary-stoppered
a) Warden c) Wide-mouth capillary-
pyknometer stoppered pyknometer
pyknometer
(Hubbard type)
Capillary-stoppered pyknometers
Figure 1 -
---------------------- Page: 8 ----------------------
SIST EN ISO 3838:1998
IS0 38384983 (El
Table 1 - Characteristics of the graduated bicapillary
pyknometer
Nominal capacity, ml
1 2 5 10
Difference between actual capacity
and nominal capacity, max., ml
l?I 0,2 f 0,3 f 0,5 f 1
Maximum mass, g
30 30 30 30
Overall height, A, mm
175 f 5
Height above scale, B,
.min., mm
Height from bulb to scale, C,
min., mm
Distance between centres of vertical
limbs, D, mm
28 f 2
External diameter of tubing, F, mm
Internal diameter of tubing, G, mm
1 fO,l
Length from bottom of bulb to
zero graduation line, H, mm
External diameter of bulb, J, mm
11 14 20 25
x IO ml
Figure 2 -
Graduated bicapillary pyknometer
(Lipkin type)
---------------------- Page: 9 ----------------------
SIST EN ISO 3838:1998
For the determinations of relative density 60/60 OF a Fahrenheit
Dirnensions in millimetres
thermometer of suitable range graduated at 0.2 OF intervals
may be used or the specified Celsius thermometer may be used
at 15,56 OC.
5.5 Pyknometer holder (optional), to hold the pyknometer
Sheet metal (brass)
vertically and at the correct depth in the constant temperature
bath. It shall be constructed of any suitable metal which will not
A-A
corrode in the water bath.
A suitable design of holder for the graduated bicapillary
. 1 Wing nut
pyknometers is shown in figure 3.
Several pyknometers holders may be conveniently supported in
A I Washer the water bath by the use of a non-corrodible rectangular metal
bar of sufficient length to lie across the rim of the bath. A series
Solder
of holes of sufficient diameter to accommodate the 6,5 mm rod
\ Hexagon nut
of the pyknometer holder is drilled in the bar at about 45 mm
apart. Each rod is secured in its hole by locking the bar between
the hexagon nut, and the winged nut and washer.
5.6 Balance, capable of weighing to the nearest 0,l mg.
6 Preparation of pyknometer
Thoroughly clean the pyknometer and stopper with surfactant
cleaning fluid, rinse well with distilled water, then with a water-
soluble volatile solvent such as acetone, and dry. Ensure that all
traces of moisture are removed, using a current of filtered air if
necessary. Cleaning should be carried out in this manner
whenever the pyknometer is to be calibrated or whenever liquid
’ B
fails to drain cleanly from the internal walls of the pyknometer
p 1 .-
or the capillary of the stopper. Normally the pyknometer may
Sheet metal
be cleaned between determinations by washing with a suitable
tray (brass)
light petroleum spirit such as 40/60 OC petroleum spirit, fol-
sheet thickness
0,315 lowed by vacuum drying.
Solder J
NOTE - If surfactant cleaning fluids do not give adequate cleaning,
chromic acid cleaning solution may be used. Chromic acid is a strong
acid and powerful oxidizing agent and great care must be taken when
using it.
7 Calibration of pyknometer
L 3 holes @ 3
B-B
7.1 Conditioning
A suitable design of holder for graduated
Figure 3 - After drying, allow the pyknometer to reach room temperature.
bicapillary pyknometer
Dissipate any static charge which may have formed on it and
then weigh to the nearest 0,l mg.
NOTES
5.3 Constant-temperature water bath, having a depth
1 If the balance case is not fitted with a static eliminator, static
greater than that of the pyknometer, capable of being main-
charges may be dissipated by breathing on the pyknometer, but ensure
tained within 0,05 OC (0.1 OF) of the desired temperature.
that the pyknometer has regained constant mass before recording the
mass.
5.4 Bath thermometer, conforming to the specification
IS0 653/STL/O, l/ - 5/ + 25. Other total immersion thermo-
2 For greatest accuracy, all the weighings should be made at

meters of suitable range and equal or greater accuracy may also temperatures within a 5 OC range so as to limit differences in air den-

be used. sity.
---------------------- Page: 10 ----------------------
SIST EN ISO 3838:1998
the sums of the scale readings on the two arms against the cor-
7.2 Capillary-stoppered pyknometer
responding masses. The points should lie on a straight line
which gives the mass of water contained by the pyknometer for
7.2.1 Fill the pyknometer with freshly boiled distilled water,
any combination of scale readings. If the points show a scatter
cooled to slightly below the selected reference temperature,
of more than two small scale divisions on either side of a
and firmly insert the stopper, taking care to avoid the inclusion
straight line drawn through the array of points and subsequent
of any air bubbles. Immerse the pyknometer to the neck in the
tests do not correct this, discard the pyknometer as imperfect.
constant-temperature bath and maintain it at 15 + 0,05 OC,
20 + 0,05 OC or 60 * 0.1 OF as appropriate, for not less
7.4
than 1 h. Other reference temperatures
If it is desired to determine the relative density referred to water
7.2.2 When the pyknometer and its contents have reached
at some temperature other than 60 OF or to determine density
the bath temperature, wipe the top of the stopper so that it is
at a temperature other than 15 OC or 20 OC, calibrate the
dry and the meniscus of the water in the capillary is flush with
pyknometer at the desired temperature.
the top of the stopper. Care is necessary during this operation,
since capillary action of the cloth can draw material out of the
stopper. Place the “warden” firmly on the stopper (if the 7.5 Recalibration
pyknometer is of this type).
Recalibrate pyknometers at intervals as dictated by experience.
7.2.3 Remove the pyknometer from the bath. If not of the
NOTE - It is recommended that new pyknometers should be
“warden” form, cool the pyknometer and its contents to a
recalibrated after one year, and thereafter at intervals dependent upon

temperature slightly below the temperature of the bath. the magnitude of any changes found.

7.2.4 Dry the exterior surface of the pyknometer by wiping
8 Procedure for capillary-stoppered
with a clean, lint-free cloth, dissipate any static charge and
pyknometers
weigh to the nearest 0,l mg.
8.1 Procedure for liquids
7.2.5 The difference between the apparent masses in air of
the filled and empty pyknometer gives the water equivalent at
8.1.1 Choose an appropriate form and size of pyknometer for
the selected reference temperature.
the sample to be tested. The 25 ml and 50 ml sizes are normally
the most suitable.
7.3 Graduated bicapillary pyknometer
8.1.2 Weigh the clean, dry calibrated pyknometer, if neces-
7.3.1 Fill the pyknometer with sufficient freshly boiled,
sary dispersing any static charge (see notes following 7.1).
cooled, distilled water to obtain readings near the top of the
Pyknometers of 25 ml or greater capacity should be weighed to
graduated capillaries. Filling is readily achieved by placing the
the nearest 0,5 mg, and those of smaller capacity to the nearest
hooked tip in the liquid while keeping the pyknometer upright,
0,l mg.
thus allowing the liquid to be drawn over the bend in the
capillary by capillary attraction. The pyknometer then fills by
8.1.3 Fill the pyknometer with the test sample, if necessary
siphoning. Place the pyknometer in the constant-temperature
warming both sample and pyknometer to assist filling and
bath so that the whole of the liquid in the pyknometer is below
separation of air bubbles. Bring the pyknometer and its con-
the level of the bath liquid. Maintain the temperature of the
tents to the test temperature ft (see 10.1) by immersing the
bath at 15 + 0,05 OC, 20 + 0,05 OC or 60 + 0.1 OF, as re-
pyknometer up to its neck in the constant-temperature bath
quired. Keep the pyknometer in the bath for 20 min then read
(see note and 10.2.3). Immerse the pyknometer in the bath for
the scale to the nearest small division at the liquid level in each
20 min in order to stabilize the temperature and to permit air
arm.
bubbles to rise to the surface. If after this time the liquid level is
still changing, keep the pyknometer in the bath until the liquid
7.3.2 Remove the pyknometer from the bath, allow the water
level becomes stable.
on the exterior to drain off. The pyknometer may be dipped into
NOTE - For mixtures of products, it is essential to ensure that the test
acetone in a beaker to assist drying and wiped with a clean,
temperature is the same as the final reporting temperature unless an
dry, lint-free cloth. Allow it to come to room temperature,
approximate value is acceptable and the volumetric composition of the
dissipate any static charge, and weigh to the nearest 0,l mg.
mixture is known together with the correction coefficients of the com-
ponents in the mixture.
7.3.3 The difference between the apparent masses in air of
the filled and empty pyknometer gives the mass of water con-
8.1.4 When the temperature is constant, firmly insert the
tained at the test temperature, corresponding to the sum of the
capillary stopper, which has also been brought to the test
two scale readings. By removing successive quantities of
temperature, taking care to avoid trapping air bubbles below
water, repeat the determination so as to obtain a series of at
the stopper.
least three pairs of readings, together with the corresponding
apparent masses in air, with the water level at different scale
NOTE - It is essential to ensure that no air bubbles are left trapped in
points on the graduated arms. One pair of readings shall be at
the liquid and adequate time must be allowed for air bubbles to rise to

the upper end of the scale and another at the lower end. Plot the surface before inserting the stopper.

---------------------- Page: 11 ----------------------
SIST EN ISO 3838:1998
IS0 38384983 (El
9 Procedure for graduated bicapillary
Wipe excess liquid from the top of the stopper so that the
meniscus of the liquid in the capillary is flush with the top of the
pyknometers
stopper. Place the “warden” over the stopper (if the
pyknometer is of this type).
9.1 Weigh the clean, dry, calibrated pyknometer to the
nearest 0,l mg, dissipating any static charge if necessary. (See
notes in 7.1.)
8.1.5 Remove the pyknometer from the bath and, if not of the
“warden” type, cool to a temperature slightly below ft. Cool
the pyknometer and contents to room temperature if the test
9.2 Fill the pyknometer with the sample at approximately the
temperature is above ambient.
test temperature by the method specified in 7.3.1, so that the
liquid levels are in the graduated portions of the capillaries (see
note). If the test temperature is lower than the laboratory
Remove all traces of sample and water from the exterior
8.1.6
temperature, low scale readings should be aimed at in order to
surface of the pyknometer by wiping with a clean, lint-free
minimize any losses due to evaporation during weighing. Bring
cloth, disperse any static charge and weigh to the precision
the pyknometer and contents to the test temperature ft
given in 8.1.2.
(see 10.1) by immersion for 20 min in the constant-temperature
bath as specified in 7.3.1 and obtain readings of the liquid level
in the two graduated arms. In the case of more viscous
8.2 Procedure for solid or semi-solid samples
samples, no readings shall be taken until ample time for drain-
ing has been allowed after any disturbance of the pyknometer.
8.2.1 Weigh the clean, dry calibrated pyknometer, which
The 20 min immersion time is normally sufficient, provided that
should be of the wide-mouth type [see c) in figure 11, to the
the pyknometer has not been disturbed during this period.
nearest 0,5 mg. For bituminous materials, only the wide-mouth
type shall be used.
NOTE - For mixtures of petroleum products and non-petroleum prod-
ucts it is essential to ensure that the test temperature is the same as the
final reporting temperature, unless an approximate value is acceptable
8.2.2 Introduce a suitable amount of the sample in the form of
and the volumetric composition of the mixture is known together with
small pieces, which should be as regular as possible in order to
the correction coefficients of the components in the mixture.
reduce the possibility of trapping air bubbles. Alternatively,
pour the molten sample into the warmed pyknometer, taking

care to avoid the inclusion of air bubbles. 9.3 Remove the pyknometer from the bath, allow the water

on the exterior to drain off. The pyknometer may be dipped into
acetone in a beaker to assist drying and wiped with a clean,
its contents to room
8.2.3 Bring the pyknomete r and
dry, lint-free cloth. Allow to come to room temperature,
and weigh to the nearest
temperature a5
ma dissipate any static charge, and weigh to the nearest 0,l mg.
8.2.4 Fill the pyknometer with freshly boiled, cooled, distilled
9.4 When carrying out the determination on highly volatile
water, removing all air bubbles. A fine wire may be used to
samples containing appreciable amounts of material boiling
facilitate the removal of bubbles.
below 20 OC, or on any sample where there is uncertainty con-
cerning loss which might result from evaporation during the
Bring the pyknometer and its contents to the test temperature
determination, cool the sample and pyknometer to a temperature
ft by immersing the pyknometer up to its neck in the constant-
of 0 to 5 OC before filling. If the dew point is sufficiently high to
temperature bath. Immerse the pyknometer in the bath for
cause condensation of moisture in the pyknometer during the
20 min in order to stabilize the temperature and to permit
cooling operation, attach a drying tube to the arm of the
bubbles to rise to the surface. If after this time the liquid level is
pyknometer in order to avoid this. With samples of this type it is
still changing, keep the pyknometer in the bath until the liquid
essential to restrict the filling of the pyknometer to obtain a low
level becomes stable.
scale reading, thus minimizing losses due to evaporation. If the
total length of unfilled capillary is over 10 cm, the rate of diffu-
sion is so low that even with highly volatile compounds such as
8.2.5 When the temperature is constant, firmly insert the
vapour losses during the determination are
isopentane,
capillary stopper, which has also been brought to the test
negligibly low.
temperature, taking care to avoid trapping air bubbles below
the stopper. Wipe excess water from the top of the stopper so
that the meniscus of the water in the capillary is flush with the
10 Calculation
top of the stopper.
10.1 Symbols
8.2.6 Remove the pyknometer from the bath and cool to a
temperature slightly below tt. Cool the pyknometer and con-
The following symbols are used in the calculations :
tents to room temperature if the test temperature is above am-
bient.
fr is any reference temperature, e.g. 15 OC, IS0 5024
(see 10.2.1);
8.2.7 Dry the exterior surface of the pyknometer by wiping
is the temperature at which the pyknometer is calibrated
with a clean, lint-free cloth, disperse any static charge and
by water filling, (see 10.2.2);
weigh to the nearest 0,5 mg.
---------------------- Page: 12 ----------------------
SIST EN ISO 3838:1998
IS0 38384983 (El

ft is the temperature at which the pyknometer is filled with 10.2 Reference, calibration and test

the liquid under test, (see 10.23);
temperatures
m, is the apparent mass in air, in grams, of the empty
10.2.1 The standard reference temperature for international
pyknometer;
trade in petroleum and its products is 15 OC (IS0 50241, but
other reference temperatures may be required for legal
is the apparent mass in air, in grams, of the pyknometer
metrology or other special purposes.
filled with water at the calibration temperature t l
10.2.2

mt is the apparent mass in air, in grams, of the pyknometer The pyknometer may be calibrated at any convenient

temperature and this may correspond with the reference, or
filled with the liquid under test at the temperature tt;
test temperatures (see 7.1, note 2).
is the apparent mass in air, in grams, of the pyknometer
plus solid or semi-solid sample;
10.2.3 For qualitative purposes, the test temperature is
usually chosen to correspond with the required reference
is the apparent mass in air, in grams, of the pyknometer
temperature, but for quantitative purposes involving the
plus sample, filled with water at the temperature tt;
calculation of the mass or of the apparent mass in air of a given
quantity of oil, the density or relative density should be deter-
C is the correction for air buoyancy, in kilograms per cubic
mined within 3 OC of the temperature at which the volume of
metre (see table 2) (see 7.1, note 2);
oil is measured by the selected dynamic or static method.
However, to minimize the loss of light fractions from very
is the density of water, in kilograms per cubic metre, at
volatile samples, carry out the test at a temperature of 15 OC or
the temperature of calibration
tc (see table 3);
below if the Reid vapour pressure exceeds the following :
is the coefficient of cubical expansion of borosilicate
a) for capillary-stoppered pyknometer - 10 kPa (0,l bar),
glass (see 10.3.2);
b) for bicapillary pyknometer - 50 kPa (0,5 bar).
a2 is the coefficient of cubical expansion of soda-lime
glass (see 10.3.3);
1.0.3 Correction for the thermal expansion of the
the density of the sample, in kilograms cubic
I& is Per
pyknometer
metre, at the test temperature tt;
10.3.1 General
the density of the sample, in kilograms per
cubic
e, is
metre, at any reference temperature t,;
The calculation of density or of relative density from measure-
ments made at a temperature tt which differs from the
the density of the sample, in kilograms cubic
e15 is
Per
temperature tc at which the pyknometer was calibrated, in-
metre, at the reference
temperature of 15 OC;
volves a correction for cubical expansion of the glass from
which the pyknometer is made.
the density of the sample, in kilograms per cubic
@a is
metre, at the reference temperature of 20 OC;
If the calculation is based on the density or relative density cor-
rection tables referred to, or given, in IS0 91, a similar correc-
Q: is the observed density in kilograms per cubic metre at
tion may also be required (see 10.3.4).
the test temperature tt as determined in soda-lime glass ap-
paratus calibrated at the reference temperature t, = 15 OC
or 20 OC, i.e. the observed density uncorrected for glass ex-
10.3.2 Pyknometers made of borosilicate glass
pansion required for entering the tables referred to in
IS0 91.
10.3.2.1 The coefficients of cubical expansion of borosilicate

NOTE - These calculations have been based on density in glasses are known to depend on the source of the glass and to

kilograms per cubic metre but if it is desired to use density in grams fall into three main categories having coefficients of cubical ex-

per millilitre the result should be divided by 1 000 (see clause 12).
pansion of 10 x 10m6, 14 x 10D6, and 19 x 1O-6 OC-’
respectively.
is the relative density at the test temperature tt;
NOTE - In current production, pyknometers made of borosilicate
glass usually have a coefficient of cubical expansion of
is the relative density at the reference temperature t,;
10 x 10-60c- ‘.
dm is the relative density at the reference temperature
of 60 OF;
10.3.2.2 For determination of the highest accuracy when
borosilicate pyknometers are used therefore, either
d: is the observed relative density at the test temperature tt
as determined in soda-lime glass apparatus calibrat
...

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