GB/T 13377-1992 Crude petroleum and liquid or solid petroleum products — Determination of density or relative density — Pycnometer method

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

GB/T 13377-1992 specifies the pycnometer method for determining the density or relative density of crude petroleum and of liquid or solid petroleum products; this page is a historical study note on the withdrawn 1992 edition, covering its two method routes, apparatus, calibration, calculation and precision.

Evidence note: original historical study material based on the original of the 1992 edition; the official record shows withdrawal on 2011-05-01 and wholesale replacement by the 2010 edition. It is not the full text of the standard or a controlled operating procedure, and technical review is pending. Discrepancies in the original units and in the role of temperature are retained, and method precision is not the uncertainty of a product batch.

Historical identity: Original physical page 1 of the 1992 edition. The 13 physical pages of the original of the same edition are GB/T 13377—92, approved 1992-01-30 and implemented 1992-12-01; the number follows the 1992 edition. The official detailed record for 1992 gives withdrawal on 2011-05-01, and the detailed record for 2010 lists wholesale replacement of the 1992 edition, implemented on the same day; the content is presented as historical study material. Institutional metadata of this kind is not independent technical acceptance, and the original statement "adopted with reference to ISO 3838-1983" does not imply current equivalence.

Scope of the two method routes: Original physical page 1 of the 1992 edition. The capillary-stopper method is used for solids and for specified petroleum products, for liquids with a Reid vapour pressure not greater than 50 kPa and an initial boiling point not lower than 40 °C; the graduated double-capillary method excludes the more viscous products and solids and is limited to a Reid vapour pressure not greater than 130 kPa and a kinematic viscosity at the test temperature below 50 mm²/s. The 50/130 of the two routes are not product parameter promises and must not be conflated into a single limit.

Density, relative density and temperature: Original physical pages 1 and 5 of the 1992 edition. Density is mass per unit volume and must be stated with temperature and units; the density at 20 °C is the standard density of this edition. Relative density is the ratio of the density of the sample at a specified temperature to the density of water at the standard temperature and carries no density unit. The apparent mass in air has not been corrected for buoyancy and cannot be equated directly with mass in vacuum.

The two measurement principles: Original physical page 2 of the 1992 edition. The capillary-stopper method compares the masses of equal volumes of sample and water, and the calculation includes the glass-expansion and buoyancy corrections. The double-capillary method first establishes a calibration line from the sum of the two arm readings and the apparent mass of water, then obtains the mass of water of equal volume. A mass ratio that has not been verified through the temperature/buoyancy branches cannot be taken as the final density.

Apparatus and dimensional limits: Original physical pages 2 and 3. The guard-cap type, the Gay-Lussac type and the wide-mouth type are to be selected according to the sample conditions of original clause 5; the solid/asphalt/wax route may not be switched to another bottle at will. The double capillary has a capacity of 1–10 mL and a total mass not exceeding 30 g; the water bath is more than 150 mm deep with temperature control of ± 0.05 °C; the balance has a sensitivity of 0.0001 g, and the bath thermometer is fully immersed with a division of 0.1 °C. Complete manufacturing drawings/supports and all cross-page dimensions have not been reconstructed, and the study figures are not to be used for purchasing acceptance.

Cleaning and sample handling: Original physical pages 3 and 4. The clause 7 cleaning involves a chromic acid warning as a strong acid and strong oxidiser; an extract cannot replace occupational protection and waste-disposal procedures. Water and mechanical impurities are to be pre-treated by the original route, crude petroleum citing GB 2538, with light samples mentioning filtration through anhydrous sodium sulfate; solids are cut up or melted. The requirements of the original edition do not automatically become authorisation for handling all samples today.

Capillary-stopper calibration: Original physical pages 3 and 4. The reference calibration of this edition is usually at 20 °C: freshly boiled water cooled to about 18 °C is filled into the bottle and held in a 20 ± 0.05 °C bath for at least 1 h. The water value is determined at least five times with a range not greater than 0.0005 g, and the mean is taken. Weighing is to 0.0001 g, and the ambient temperature during weighing should be kept within a 5 °C range. The 0.0005 g is the range of the water value and must not be taken as the precision of a liquid result.

Double-capillary calibration and interval: Original physical page 4. The double capillary is held in a 20 ± 0.05 °C bath for 20 min and the two arm scales are read; at least three different water values (upper, middle and lower) are taken and a straight line is drawn of scale against water value. If a point lies more than two minimum divisions from the line and re-measurement does not change it, the measurement is to be rejected under the original clause. Clause 7.2.4 states explicitly that the pycnometer is calibrated once every two years; this interval cannot be taken directly as a current requirement, and the original gives no uniform daily QC frequency.

Calibration roles: Capillary-stopper water value | at least 5 determinations, range ≤ 0.0005 g | not the repeatability of sample results Double-capillary water value | at least 3 points (upper, middle, lower); rejected if more than 2 minimum divisions from the line and unchanged on re-measurement | not a promise that any instrument is acceptable Calibration interval | once every two years | original clause of this historical edition only

Weighing liquids and solids: Original physical pages 4 and 5. Liquids are usually in 25 mL or 50 mL bottles: 25 mL and above are weighed to 0.0005 g, small capacities to 0.0001 g; the conditions of a stable liquid level and no bubbles cannot be replaced by a fixed 20 min. Solids or semi-solids use a wide-mouth bottle, weighing the empty bottle, the bottle with sample, and the bottle with sample and water; the role of the solid mass must not be changed to a filled mass. The corresponding weighing accuracies, 0.0005 g and 0.0001 g for the double capillary, are listed separately.

Test temperature and highly volatile samples: Original physical pages 5 and 6. When used for quantity metering, the test temperature should be within 3 °C of the selected metering temperature. Clause 9.2 requires highly volatile samples — Reid vapour pressure above 10 kPa for the capillary-stopper method and above 50 kPa for the double capillary — to be tested at 15 °C or below; temperature requirements of different editions must not be mixed. For the double capillary, cooling to 0–5 °C before filling a highly volatile sample is sample handling within the method, not storage of an arbitrary product; a note that an arm is not filled over a length of more than 10 cm does not replace verification of volatilisation loss.

Formula symbols and original unit discrepancies: Original physical pages 5, 6, 7 and 8. In the original, t_r is the reference temperature, t_c the calibration temperature and t_t the test temperature; m_0 the empty bottle, m_c the bottle with water, m_t the bottle with liquid, m_1 the bottle with solid and m_2 the bottle with solid and water, all apparent masses in air in g. Clause 9.1 lists ρ_c/ρ_t in g/cm³ while C is in kg/m³; clause 9.3 marks results in kg/m³ in several places, while 9.3.2.5 and 9.5 again print kg/cm³. Note 1 to Table 1 specifies that C is divided by 1000 when density is in g/cm³. The original's unit linkage is doubtful: the original values are retained pending technical review, and no calculator or unilateral unit harmonisation is offered.

Calculation and rounding: Original physical pages 6, 7 and 8. Let the original mass ratio be (m_t − m_0)/(m_c − m_0); equation 2 in the original is [mass ratio × ρ_c + C]/[1 − α(t_c − t_t)] in full, with α taken as borosilicate or soda-lime according to the bottle material, and the unit linkage must be checked together with Note 1 to Table 1. Equations 9/10 divide ρ_t or ρ_20 by 0.99820 for relative density respectively, and the density units must be the same; for solids 9.5 replaces the liquid mass ratio with (m_1 − m_0)/[(m_c − m_0) − (m_2 − m_1)], which is not an independent density. Intermediate values below 1.00000 g/cm³ or 1000.00 kg/m³ take five significant figures, otherwise six; relative density is calculated to five decimal places. Equations 4, 6 and 7 involve the whole-term corrections 25×10⁻⁶(t_r − t_t), (α₂ − α₁)(t_r − t_t) and α₂(t_r − t_c) respectively. The temperature-subscript linkage in the original figure for equation 8 still awaits technical review and is not rewritten from common sense; all conditional branches and table look-ups have not been reconstructed, and no calculator is published.

Precision by route: Original physical page 10. The original 95 % Tables 3/4: for samples not readily volatile and not very viscous, the capillary-stopper method gives r/R both 0.0006 g/cm³, i.e. 0.6 kg/m³, and both 0.0006 for relative density; for wide-mouth asphalt samples r 0.003/R 0.005 g/cm³, i.e. 3/5 kg/m³, and 0.003/0.005 for relative density. The double capillary covers density 0.7770–0.8920 g/cm³, i.e. 777.0–892.0 kg/m³, with r 0.0007/R 0.0010 g/cm³, i.e. 0.7/1.0 kg/m³, and 0.0007/0.0010 for relative density. These cannot be extrapolated to the whole scope of the method or taken as the uncertainty of a product batch. Route and sample boundary | Repeatability r | Reproducibility R | Relative density r/R Capillary-stopper: not readily volatile, not very viscous | 0.6 kg/m³ | 0.6 kg/m³ | 0.0006 / 0.0006 Wide-mouth: asphalt samples | 3 kg/m³ | 5 kg/m³ | 0.003 / 0.005 Double capillary: 777.0–892.0 kg/m³ | 0.7 kg/m³ | 1.0 kg/m³ | 0.0007 / 0.0010

Reporting and unverified boundaries: Original physical pages 10, 11, 12 and 13. Clause 11 takes the arithmetic mean of two duplicate results; density is reported to 0.0001 g/cm³ or 0.1 kg/m³ with the temperature and units stated, and relative density to 0.0001. The original clause 11 prints the temperatures to be stated as t_c and t_t, whereas 9.1 defines t_c as the calibration temperature and 9.4 defines relative density by the reference water density; the linkage of the temperature roles in reporting is left for technical review and is not harmonised to t_r on the author's behalf. Annexes A/B were "supplementary" in the original and are not renamed informative. Every cell of the dense water-density tables, the manufacturing dimension drawings, the software and the complete controlled safety procedures and independent technical acceptance still await review; the positioning of the 13 pages does not amount to full technical approval.

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