Crude petroleum and liquid or solid petroleum products - Determination of density or relative density - Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods (ISO 3838:2004)

ISO 3838:2004 specifies methods for the determination of the density or relative density of crude petroleum and of petroleum products handled as liquids.
The capillary-stoppered pyknometer method is also for use with solids and this method may also be used for coal tar products, including road tars, creosote and tar pitches, or for mixtures of these with petroleum products. This method is not suitable for the determination of the density or relative density of highly volatile liquids having Reid vapour pressures greater than 50 kPa according to ISO 3007 or having an initial boiling point below 40 degrees Celsius.
The graduated bicapillary pyknometer method is recommended for the accurate determination of the density or relative density of all except the more viscous products, and is particularly useful when only small amounts of samples are available. The method is restricted to liquids having Reid vapour pressures of 130 kPa or less according to ISO 3007 and having kinematic viscosities less than 50 mm2/s (50 centistokes (cSt)) at the test temperature.
Special precautions are specified for the determination of the density or relative density of highly volatile liquids.

Rohöl und flüssige oder feste Mineralölerzeugnisse - Bestimmung der Dichte oder der relativen Dichte - Verfahren mittels Pyknometer mit Kapillarstopfen und Bikapillar-Pyknometer mit Skale (ISO 3838:2004)

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 3838:2004)

L'ISO 3838:2004 spécifie des méthodes de détermination de la masse volumique ou de la densité du pétrole brut et des produits pétroliers manipulés sous forme liquide.
La méthode qui utilise le pycnomètre à bouchon capillaire s'applique aussi aux produits sous forme solide et cette méthode peut aussi être appliquée aux goudrons de houille, y compris les goudrons pour revêtement routier, les créosotes et les brais, ou à des mélanges de ces goudrons avec des produits pétroliers. Cette méthode ne convient pas à la détermination de la masse volumique ou de la densité de liquides très volatils dont les pressions de vapeur Reid déterminées selon l'ISO 3007 sont supérieures à 50 kPa ou dont le point d'ébullition initial est inférieur à 40 °C.
La méthode utilisant le pycnomètre bicapillaire gradué est recommandée pour la détermination précise de la masse volumique ou de la densité de tous les produits, à l'exception des plus visqueux; elle est particulièrement utile lorsque de faibles quantités d'échantillon sont disponibles. L'application de la méthode est limitée aux liquides dont la pression de vapeur Reid déterminée selon l'ISO 3007 est inférieure ou égale à 130 kPa (1,3 bar) et dont la viscosité cinématique est inférieure à 50 mm2/s [50 centistokes (cSt)] à la température de l'essai.
Des précautions spéciales sont spécifiées dans le cas de la détermination de la masse volumique ou de la densité des liquides très volatils.

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 3838:2004)

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Published
Publication Date
30-Apr-2004
Current Stage
9093 - Decision to confirm - Review Enquiry
Due Date
20-Mar-2013
Completion Date
20-Mar-2013

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.JUDGXLUDQLPRohöl und flüssige oder feste Mineralölerzeugnisse - Bestimmung der Dichte oder der relativen Dichte - Verfahren mittels Pyknometer mit Kapillarstopfen und Bikapillar-Pyknometer mit Skale (ISO 3838:2004)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 3838:2004)Crude petroleum and liquid or solid petroleum products - Determination of density or relative density - Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods (ISO 3838:2004)75.080Naftni proizvodi na splošnoPetroleum products in general75.040Surova naftaCrude petroleumICS:Ta slovenski standard je istoveten z:EN ISO 3838:2004SIST EN ISO 3838:2004en01-september-2004SIST EN ISO 3838:2004SLOVENSKI

STANDARDSIST EN ISO 3838:19981DGRPHãþD
SIST EN ISO 3838:2004
SIST EN ISO 3838:2004
SIST EN ISO 3838:2004
Reference numberISO 3838:2004(E)© ISO 2004

INTERNATIONAL STANDARD ISO3838Second edition2004-05-01Crude petroleum and liquid or solid petroleum products — Determination of density or relative density — Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods Pétrole brut et produits pétroliers liquides ou solides — Détermination de la masse volumique ou de la densité — Méthodes du pycnomètre à bouchon capillaire et du pycnomètre bicapillaire gradué

SIST EN ISO 3838:2004

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ii © ISO 2004 – All rights reserved
SIST EN ISO 3838:2004

ISO 3838:2004(E) © ISO 2004 – All rights reserved iii Contents Page Foreword............................................................................................................................................................iv 1 Scope......................................................................................................................................................1 2 Normative references...........................................................................................................................1 3 Terms and definitions...........................................................................................................................2 4 Principle.................................................................................................................................................2 4.1 Capillary-stoppered pyknometer.........................................................................................................2 4.2 Graduated bicapillary pyknometer......................................................................................................2 5 Apparatus...............................................................................................................................................2 6 Preparation of pyknometer..................................................................................................................6 7 Calibration of pyknometer....................................................................................................................6 7.1 Conditioning..........................................................................................................................................6 7.2 Capillary-stoppered pyknometer.........................................................................................................8 7.3 Graduated bicapillary pyknometer......................................................................................................8 7.4 Other reference temperatures.............................................................................................................8 7.5 Recalibration.........................................................................................................................................8 8 Procedure for capillary-stoppered pyknometers...............................................................................9 8.1 Procedure for liquids............................................................................................................................9 8.2 Procedure for solid or semi-solid samples........................................................................................9 9 Procedure for graduated bicapillary pyknometers..........................................................................10 10 Calculations.........................................................................................................................................10 10.1 Symbols...............................................................................................................................................10 10.2 Reference, calibration and test temperatures..................................................................................11 10.3 Correction for the thermal expansion of the pyknometer..............................................................12 10.4 Calculation of density of a liquid.......................................................................................................14 10.5 Calculation of relative density of a liquid.........................................................................................15 10.6 Calculation of density or relative density of a solid or semi-solid................................................16 11 Precision..............................................................................................................................................16 11.1 Capillary-stoppered pyknometer method.........................................................................................16 11.2 Graduated bicapillary pyknometer method......................................................................................17 12 Test report............................................................................................................................................17

SIST EN ISO 3838:2004

ISO 3838:2004(E) iv © ISO 2004 – All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established 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. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 3838 was prepared by Technical Committee ISO/TC 28, Petroleum products and lubricants, Subcommittee SC 3, Static petroleum measurement. This second edition cancels and replaces the first edition (ISO 3838:1983), which has been technically revised.

SIST EN ISO 3838:2004

INTERNATIONAL STANDARD ISO 3838:2004(E) © ISO 2004 – All rights reserved 1 Crude petroleum and liquid or solid petroleum products — Determination of density or relative density — Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods 1 Scope 1.1 This International Standard specifies methods for the determination of the density or relative density of crude petroleum and of petroleum products handled as liquids. 1.2 The capillary-stoppered pyknometer method is also for use with solids and this method may also be used for coal tar products, including road tars, creosote and tar pitches, or for mixtures of these with petroleum products. This method is not suitable for the determination of the density or relative density of highly volatile liquids having Reid vapour pressures greater than 50 kPa according to ISO 3007 or having an initial boiling point below 40 °C. 1.3 The graduated bicapillary pyknometer method is recommended for the accurate determination of the density or relative density of all except the more viscous products, and is particularly useful when only small amounts of samples are available. The method is restricted to liquids having Reid vapour pressures of 130 kPa or less according to ISO 3007 and having kinematic viscosities less than 50 mm2/s [50 centistokes (cSt)] at the test temperature. Special precautions are specified for the determination of the density or relative density of highly volatile liquids. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 91-1:1992, Petroleum measurement tables — Part 1: Tables based on reference temperatures of 15 °C and 60 °F ISO 91-2:1991, Petroleum measurement tables — Part 2: Tables based on a reference temperature of 20 °C ISO 653:1980, Long solid-stem thermometers for precision use ISO 3007:1999, Petroleum products and crude petroleum — Determination of vapour pressure — Reid method ISO 3507:1999, Laboratory glassware — Pyknometers ISO 5024:1999, Petroleum liquids and liquefied petroleum gases — Measurement — Standard reference conditions SIST EN ISO 3838:2004

ISO 3838:2004(E) 2 © ISO 2004 – All rights reserved 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 density mass of the substance divided by its volume NOTE When reporting the density, it is necessary for the unit of density used, together with the temperature, to be explicitly stated, for example kilograms per cubic metre, or grams per millilitre, at t °C. 3.2 apparent mass in air value obtained by weighing in air against standard masses without making correction for the effect of air buoyancy on either the standard masses or the object weighed 3.3 observed density value required in order to enter Tables 53A, 53B and 53D, or 59A, 59B and 59D, referred to in ISO 91, determined with soda-lime glass apparatus at a test temperature which differs from the calibration temperature of the apparatus, no correction having been made for the thermal expansion or contraction of the glass 3.4 relative density ratio of the mass of a volume of a substance at a temperature t1 to the mass of an equal volume of another substance at a temperature t2. The temperatures t1 and t2 may be equal. For the purpose of this International Standard, the other substance is water, i.e. the relative density is the ratio of the density of the substance at a temperature t1 to the density of water at a temperature t2. NOTE When reporting the relative density, it is necessary for the temperatures t1 and t2 be explicitly stated. ISO 91-1 refers to tables for the reduction of relative density to 60/60 °F. If results are required referred to another reference temperature, the determination should be carried out at that temperature. 4 Principle 4.1 Capillary-stoppered pyknometer The masses of equal volumes of the sample and of water are compared. Equal volumes are ensured by the pyknometer being filled so as to overflow when placed in a bath at the test temperature until equilibrium is reached. The calculation (Clause 10) includes corrections for thermal expansion of glass and for buoyancy. 4.2 Graduated bicapillary pyknometer The graduated arms of the pyknometer are calibrated, using water, in terms of the apparent mass in air of water contained in the pyknometer, and a graph is prepared. The liquid sample is drawn into the dried pyknometer and, after it has reached equilibrium at the test temperature, the liquid levels are noted and the pyknometer weighed. The apparent mass in air of an equal volume of water is read from the graph and the density or relative density of the sample is calculated, with corrections being made as in 4.1. 5 Apparatus 5.1 Capillary-stoppered pyknometer, one of the three types shown in Figure 1 (see 8.1.1). 5.1.1 The pyknometers shall conform to the relevant requirements of ISO 3507. SIST EN ISO 3838:2004

ISO 3838:2004(E) © ISO 2004 – All rights reserved 3 The “warden” form [see a) in Figure 1] is recommended for all except viscous or solid products and should always be used for volatile products. The ground glass cap, or “warden”, greatly reduces expansion and evaporation losses and this form of pyknometer may be used when the test temperature is lower than that of the laboratory. 5.1.2 The form of pyknometer shown in b) in Figure 1, known as the Gay-Lussac type, is suitable for non-volatile liquids except those of high viscosity. 5.1.3 The wide-mouth (Hubbard) form of pyknometer [see c) in Figure 1] is used for very viscous liquids and solids. 5.1.4 As the forms of pyknometer shown in b) and c) in Figure 1 have no “warden” or expansion chamber, they cannot be used when the temperature of the test is so far below that of the laboratory as to cause loss of sample by expansion through the capillary during weighing.

a) b) c) Figure 1 — Capillary-stoppered pyknometers

5.2 Graduated bicapillary pyknometer, capacity 1 ml to 10 ml, conforming to the dimensions given in Figure 2 and the characteristics given in Table 1, constructed 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 pyknometer given in ISO 3507 may be used. SIST EN ISO 3838:2004

ISO 3838:2004(E) 4 © ISO 2004 – All rights reserved Table 1 — Characteristics of the graduated bicapillary pyknometer Nominal capacity, ml 1 2 5 10 Difference between actual capacity and nominal capacity, max, ml ± 0,2 ± 0,3 ± 0,5 ± 1 Maximum mass, g 30 Overall height, A, mm 175 ± 5 Height above scale, B, min., mm 40 Height from bulb to scale, C, min., mm 5 Distance between centres of vertical limbs, D, mm 28 ± 2 External diameter of tubing, F, mm 6 Internal diameter of tubing, G, mm 1 ± 0,1 Length from bottom of bulb to zero graduation line, H, mm 40 External diameter of bulb, J, mm 11 14 20 25

SIST EN ISO 3838:2004
ISO 3838:2004(E) © ISO 2004 – All rights reserved 5 Dimensions in millimetres

The explanations of symbols A to J are given in Table 1. Figure 2 — Graduated bicapillary pyknometer (Lipkin type) SIST EN ISO 3838:2004

ISO 3838:2004(E) 6 © ISO 2004 – All rights reserved 5.3 Constant-temperature water bath, having a depth greater than that of the pyknometer, capable of being maintained within 0,05 °C (0,1 °F) of the desired temperature. 5.4 Bath thermometer, conforming to the specification ISO 653/STL/0,1/−5/+25. Other total immersion thermometers of suitable range and equal or greater accuracy may also be used. NOTE For the determinations of relative density 60/60 °F, a Fahrenheit thermometer of suitable range graduated at 0,2 °F intervals may be used or the specified Celsius thermometer may be used at 15,56 °C. 5.5 Pyknometer holder (optional), to hold the pyknometer vertically and at the correct depth in the constant temperature bath. It shall be constructed of any suitable metal that will not corrode in the water bath. A suitable design of holder for the graduated bicapillary pyknometers is shown in Figure 3. Several pyknometer holders may be conveniently supported in 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 of holes of sufficient diameter to accommodate the 6,5 mm rod 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 0,1 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 fails to drain cleanly from the internal walls of the pyknometer or the capillary of the stopper. Normally, the pyknometer may be cleaned between determinations by washing with a suitable light petroleum spirit such as 40/60 °C petroleum spirit, followed by vacuum drying. NOTE If surfactant cleaning fluids do not give adequate cleaning, chromosulfuric acid cleaning solution may be used. CAUTION — Chromosulfuric acid is a health hazard. It is toxic, a recognized carcinogen as it contains Cr (VI) compounds, highly corrosive and potentially hazardous in contact with organic materials. When using chromosulfuric acid cleaning solution, eye protection and protective clothing are essential. Never pipette the cleaning solution by mouth. After use, do not pour cleaning solution down the drain, but neutralize it with great care owing to the concentrated sulfuric acid present, and dispose of it in accordance with standard procedure for toxic laboratory waste (chromium is highly dangerous to the environment). 7 Calibration of pyknometer 7.1 Conditioning After drying, allow the pyknometer to reach room temperature. Dissipate any static charge which may have formed on it and then weigh to the nearest 0,1 mg. If the balance case is not fitted with an electrostatic eliminator, electrostatic charges may be dissipated by breathing on the pyknometer, but ensure that the pyknometer has regained constant mass before recording the mass. For the greatest accuracy, all the weighings should be made at temperatures within a 5 °C range so as to limit differences in air density. SIST EN ISO 3838:2004

ISO 3838:2004(E) © ISO 2004 – All rights reserved 7 Dimensions in millimetres
Key 1 solder 4 washer 2 spring clip 0,32 mm 5 hexagon nut

sheet metal (brass) 6 sheet metal tray (brass), sheet thickness 0,315 mm 3 wing nut 7 3 holes, ∅ 3 mm Figure 3 — A suitable design of holder for graduated bicapillary pyknometer SIST EN ISO 3838:2004

ISO 3838:2004(E) 8 © ISO 2004 – All rights reserved 7.2 Capillary-stoppered pyknometer 7.2.1 Fill the pyknometer with freshly boiled distilled water, cooled to slightly below the selected reference temperature, and firmly insert the stopper, taking care to avoid the inclusion of any air bubbles. Immerse the pyknometer to the neck in the constant-temperature bath and maintain it at (15,00 ± 0,05) °C, (20,00 ± 0,05) °C or (60,0 ± 0,1) °F as appropriate, for not less than 1 h. 7.2.2 When the pyknometer and its contents have reached the bath temperature, wipe the top of the stopper so that it is dry and the meniscus of the water in the capillary is flush with 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 pyknometer is of this type). 7.2.3 Remove the pyknometer from the bath. If not of the “warden” form, cool the pyknometer and its contents to a temperature slightly below the temperature of the bath. 7.2.4 Dry the exterior surface of the pyknometer by wiping with a clean, lint-free cloth, dissipate any static charge and weigh to the nearest 0,1 mg. 7.2.5 The difference between the apparent masses in air of the filled and empty pyknometer gives the water equivalent at the selected reference temperature. 7.3 Graduated bicapillary pyknometer 7.3.1 Fill the pyknometer with sufficient freshly boiled, cooled, distilled water to obtain readings near the top of the graduated capillaries. Filling is readily achieved by placing the hooked tip in the liquid while keeping the pyknometer upright, thus allowing the liquid to be drawn over the bend in the capillary by capillary attraction. The pyknometer then fills by siphoning. Place the pyknometer in the constant-temperature bath so that the whole of the liquid in the pyknometer is below the level of the bath liquid. Maintain the temperature of the bath at (15,00 ± 0,05) °C, (20,00 ± 0,05) °C or (60,0 ± 0,1) °F, as required. Keep the pyknometer in the bath for 20 min then read the scale to the nearest small division at the liquid level in each arm. 7.3.2 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, dry, lint-free cloth. Allow it to come to room temperature, dissipate any static charge, and weigh to the nearest 0,1 mg. 7.3.3 The difference between the apparent masses in air of the filled and empty pyknometer gives the mass of water contained at the test temperature, corresponding to the sum of the two scale readings. By removing successive quantities of water, repeat the determination so as to obtain a series of at least three pairs of readings, together with the corresponding apparent masses in air, with the water level at different scale points on the graduated arms. One pair of readings shall be at the upper end of the scale and another at the lower end. Plot the sums of the scale readings on the two arms against the corresponding masses. The points should lie on a straight line that gives the mass of water contained by the pyknometer for any combination of scale readings. If the points show a scatter of more than two small scale divisions on either side of a straight line drawn through the array of points and subsequent tests do not correct this, discard the pyknometer as imperfect. 7.4 Other reference temperatures If it is desired to determine the relative density referred to water at some temperature other than 60 °F or to determine density at a temperature other than 15 °C or 20 °C, calibrate the pyknometer at the desired temperature. 7.5 Recalibration Recalibrate pyknometers at intervals as dictated by experience. It is recommended that new pyknometers should be recalibrated after one year, and thereafter at intervals dependent upon the magnitude of any changes found. SIST EN ISO 3838:2004

ISO 3838:2004(E) © ISO 2004 – All rights reserved 9 8 Procedure for capillary-stoppered pyknometers 8.1 Procedure for liquids 8.1.1 Choose an appropriate form and size of pyknometer for the sample to be tested. The 25 ml and 50 ml sizes are normally the most suitable. 8.1.2 Weigh the clean, dry calibrated pyknometer, if necessary dispersing any electrostatic charge (see 2nd and 3rd paragraphs of 7.1). Pyknometers of 25 ml or greater capacity should be weighed to the nearest 0,5 mg, and those of smaller capacity to the nearest 0,1 mg. 8.1.3 Fill the pyknometer with the test sample, if necessary warming both sample and pyknometer to assist filling and separation of air bubbles. Bring the pyknometer and its contents to the test temperature tt (see 10.1) by immersing the pyknometer up to its neck in the constant-temperature bath (see note and 10.2.3). Immerse the pyknometer in the bath for 20 min in order to stabilize the temperature and to permit air 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 level becomes stable. NOTE For mixtures of products, it is essential to ensure that the test temperature is the same as the final reporting temperature, unless an approximate value is acceptable and the volumetric composition of the mixture is known together with the correction coefficients of the components in the mixture. 8.1.4 When the temperature is constant, firmly insert the capillary stopper, which has also been brought to the test temperature, taking care to avoid trapping air bubbles below the stopper. It is essential to ensure that no air bubbles are left trapped in the liquid, and adequate time shall be allowed for air bubbles to rise to the surface before inserting the stopper. 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 stopper. Place the “warden” over the stopper (if the pyknometer is of this type). 8.1.5 Remove the pyknometer from the bath and, if it is not of the “warden” type, cool to a temperature slightly below tt. Cool the pyknometer and contents to room temperature if the test temperature is above ambient. 8.1.6 Remove all traces of sample and water from the exterior surface of the pyknometer by wiping with a clean, lint-free cloth, disperse any electrostatic charge and weigh to the precision given in 8.1.2. 8.2 Procedure for solid or semi-solid samples 8.2.1 Weigh the clean, dry calibrated pyknometer, which should be of the wide-mouth type [see c) in Figure 1], to the nearest 0,5 mg. For bituminous materials, only the wide-mouth type shall be used. 8.2.2 Introduce a suitable amount of the sample in the form of small pieces, which should be as regular as possible in order to 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. 8.2.3 Bring the pyknometer and its contents to room temperature and weigh to the nearest 0,5 mg. 8.2.4 Fill the pyknometer with freshly boiled, cooled, distilled water, removing all air bubbles. A fine wire may be used to facilitate the removal of bubbles. Bring the pyknometer and its contents to the test temperature tt by immersing the pyknometer up to its neck in the constant-temperature bath. Immerse the pyknometer in the bath for 20 min in order to stabilize the temperature and to permit 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 level becomes stable. SIST EN ISO 3838:2004

ISO 3838:2004(E) 10 © ISO 2004 – All rights reserved 8.2.5 When the temperature is constant, firmly insert the capillary stopper, which has also been brought to the test 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 top of the stopper. 8.2.6 Remove the pyknometer from the bath and cool to a temperature slightly below tt. Cool the pyknometer and contents to room temperature if the test temperature is above ambient. 8.2.7 Dry the exterior surface of the pyknometer by wiping with a clean, lint-free cloth, disperse any electrostatic charge and weigh to the nearest 0,5 mg. 9 Procedure for graduated bicapillary pyknometers 9.1 Weigh the clean, dry, calibrated pyknometer to the nearest 0,1 mg, dissipating any electrostatic charge if necessary. (See 2nd and 3rd paragraphs in 7.1.) 9.2 Fill the pyknometer with the sample at approximately the 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 temperature, low scale readings should be aimed at in order to minimize any losses due to evaporation during weighing. Bring the pyknometer and contents to the test temperature tt (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 samples, no readings shall be taken until ample time for draining has been allowed after any disturbance of the pyknometer. The 20 min immersion time is normally sufficient, provided that the pyknometer has not been disturbed during this period. NOTE For mixtures of petroleum products and non-petroleum products, it is essential to ensure that the test temperature is the same as the final reporting temperature, unless an approximate value is acceptable and the volumetric composition of the mixture is known, together with the correction coefficients of the components in the mixture. 9.3 Remove the pyknometer from the bath and allow the water on the exterior to drain off. The pyknometer

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