GB/T 2540-1981 Determination of density of petroleum products (pycnometer method)
Some standard content:
National Standard of the People's Republic of China
Determination of density of petroleum products
(Pyknometer method)
Petroleum products--Determination of density-Pyknometer method GB2540-81
(Confirmed in 19th century)
This method is applicable to the determination of the density of liquid or solid petroleum products, but is not suitable for the determination of the density of highly volatile liquids (such as liquefied petroleum gas, etc.).
1 Summary of the method
Density is the mass per unit volume at temperature: 1.5°C. It is expressed in g/m2 and kg/m2. When reporting density, the temperature must be specified. The density at 20°C is called the standard density and is expressed in P:. 2 Instruments and materials
2.1 Instruments
2.1.1 Pyknometer, which must be marked with a line or a capillary ground stopper and have a volume of 25 ml. As shown in the figure, there are three types: a ground-mouth plug type b capillary plug type c wide-mouth type 2.1.1.1 Ground-mouth plug type, with a ground-mouth plug on the top and a capillary in the middle. It is applicable to all kinds of samples except viscous products, and is usually used for volatile products such as gasoline, etc. It can prevent the volatilization of the sample. It has an expansion chamber and can be used when the room temperature is higher than the measurement temperature. 2.1.1.2 Capillary plug type: The top is a conical plug with a capillary. It is suitable for liquids that are not easy to volatilize, such as lubricating oil, but not suitable for samples with too high viscosity. GB254081 2.1.1.3 Wide-mouth type: The top is a ground-mouth plug with a capillary. It is suitable for measuring high viscosity (such as heavy oil, etc.) or solid products. 2.1.2 Thermostatic bath depth is greater than the height of the pycnometer, and the water bath temperature can be kept within ±0.1C. 2.1.3 Thermometer: 0~50℃ or 50~100℃, graduation is 0.1C. 2.1.4 Pycnometer stand: It can support the pycnometer and make it perpendicular to the constant temperature bath. It can be made of metal or other materials. 2.2 Materials
2.2.1 Chromic acid cleaning solution.
2.2.2 Washing with light gasoline or other solvents, used to wash the oil stains on the pycnometer. 3 Preparation
3.1 First remove the oil stains on the pycnometer and the stopper, thoroughly clean them with chromic acid cleaning solution, clean them with water, and then rinse them with distilled water and dry them. If necessary, use a filtered dry air stream to remove the decaying water. The pycnometer should be cleaned until there are no water drops on the inner and outer walls of the bottle, and the water can flow out completely from the inner wall of the pycnometer or the capillary plug. 3.2 Determination of water value of pycnometer at 20℃
Weigh the pycnometer that has been carefully washed, dried and cooled to room temperature to 0.0002 grams, and sieve the empty pycnometer to measure m. Use a syringe to fill the top of the pycnometer with distilled water that has been freshly boiled and cooled to 18-20℃. Add a stopper and then put it in a constant temperature water bath at 20±0.1-℃, but do not immerse the pycnometer or the upper end of the capillary. Keep the above pycnometer filled with distilled water in the constant temperature water bath for at least 10 minutes. When the temperature reaches equilibrium, there are no bubbles, and the liquid level no longer changes, absorb the excess water with filter paper. For the ground-mouth stopper pycnometer, wipe off the sample above the mark and cover it with a ground-mouth stopper. Take out the pycnometer. Carefully wipe the outside of the pycnometer dry with a silk cloth and weigh it to 0.0002 grams. The mass of the pycnometer filled with water m1 is obtained. The water value m2a of the pycnometer at 20°C is calculated according to formula (1):
Where: m1—water value of the pycnometer at 20°C, g; t2a—mass of the pycnometer filled with 20°C water, g; mass of the empty pycnometer, g.
The water value of the pycnometer should be measured 3 to 5 times and the arithmetic mean value is taken as the water value of the pycnometer. t
a.3 If it is necessary to measure the density at 1°C, the water value m of the pycnometer can be measured at the required temperature t°C. The operation method is the same as 3.2. The water value m of the pycnometer at ?°C should be measured 3 to 5 times and the arithmetic mean value is taken as the water value of the pycnometer. 3.4 According to frequent use, the water value of the pycnometer should be re-measured after a certain period of time. 8.5 For samples that obviously contain water and mechanical impurities, water and mechanical impurities should be removed. Solid petroleum products need to be crushed or small pieces. 4 Test steps:
.1 Select a specific gravity bottle of appropriate type according to the sample. Adjust the thermostat to the required temperature. 4.2 Weigh the clean and dry specific gravity bottle to 0.0002 grams. 4.8 Carefully put the sample into the specific gravity bottle with a determined water value using a syringe, add cold water, and immerse the specific gravity bottle in the constant temperature bath until the top. Be careful not to cover the specific gravity bottle stopper or the upper end of the capillary. The constant temperature time in the bath shall not be less than 20 minutes. When the temperature reaches equilibrium, there are no bubbles, and the sample surface no longer changes, use filter paper (or syringe) to absorb the excess sample at the top of the capillary (or in the capillary), cover the ground-mouth stopper type specific gravity bottle with a ground-mouth stopper, take out the specific gravity bottle, carefully wipe its outside and weigh it to 0.0002 grams, and get the mass m1 of the specific gravity bottle containing the sample. .4.4 For solid or semi-solid samples, it is best to use a wide-mouthed pycnometer, add half of the sample, and do not contaminate the bottle wall. If the sample is a brittle solid (such as asphalt), crush or melt it before loading, then use heating, evacuation, etc. to remove bubbles, and cool it to nearly 20°C. Weigh the above pycnometer to 0.0002 grams, and get the mass of the pycnometer filled with half a bottle of sample m3. Fill the pycnometer with distilled water. Place it in a constant temperature water bath at 20°C for no less than 20 minutes. When the temperature reaches equilibrium, there are no bubbles, and the liquid level no longer changes, use filter paper to absorb the excess water at the top of the capillary and take out the pycnometer. Carefully wipe the outside and weigh it to 0.0002 grams, and get the mass of the pycnometer filled with half a bottle of sample and water m1.
5 Calculation
GB254081
The density P0 of the liquid sample at 20℃ is calculated according to formula (2): e
Formula m,bzxz.net
(m; -m1) (0.998 20 - 0.001 2)m20
Mass of the specific gravity bottle loaded with the sample at 20℃, gMass of the empty specific gravity bottle, g,
-Water value in the specific gravity bottle at 20℃, g, m+
-Density of water at 20℃, g/cm",
0. 998 20 -
0.0012——Density of air at 20℃ and atmospheric pressure of 760 mmHg, g/cm*. 5.2 Density of solid or semi-solid sample at 20℃10, calculated according to formula (3): Phn
Where: m
(m, - front,) (0.99820-0:0012)mzo-(m, -m)
Mass of the specific gravity bottle with half a bottle of sample at 20℃, g empty Mass of pycnometer, g,
- Water value of pycnometer at 20°C, g, - Mass of pycnometer with half a bottle of sample and water at 20°C, g: -0.0012
- Density of water at 20°C, g/cm
.0.0012- Density of air at 20°C and atmospheric pressure of 760 mmHg, g/cm. 5.8 Density of liquid sample at 7°C, calculated according to formula (4): p
(m, -m1) (8 - 0.0012)
Formula, m, -— Mass of pycnometer with sample at 1°C, g; m_
+ 0.0012-
Mass of empty pycnometer, g,
Water value of pycnometer at ! ℃ (mass of pycnometer filled with water at ! ℃ minus mass of empty pycnometer) g: --density of water at 20℃, g/cm2*See Appendix A, 0.0012--density of air at 20℃ and atmospheric pressure of 760 mmHg, g/cm2. Precision
The difference between two repeated determination results shall not exceed the following values: Sample
Liquid petroleum products
Solid or semi-solid petroleum products
Allowable difference, g/cm2!
Note: In this case, the density regulations apply to 20℃, and the precision at 7℃ is not specified. ? Report
Take the arithmetic mean of the two repeated determination results as the determination result. (2)
g/cm2:
0. 999 84
0.999 941
0. 999 86
0.998 9-1
GB 2540-81
Appendix A
Density of water
(Supplement)
g/cm
0.997 77
g/cm!
0.988 04
GB2640-81
Appendix B
Method for conversion to 20℃ density
(Supplement)
Some samples (such as crude oil, heavy oil, etc.) are solidified or very viscous at 20℃, but the density measurement result at 20℃ is required. In this case, the density at 1℃ can be measured without measuring the water value at ℃. The water value at 20℃ is used to calculate the following formula! Apparent density at ℃ p: t =
(m, ~ m,) (0.998 20 -0:001 2)+0.0012
Where: p.—apparent density at r℃, g/cm", m,—density bottle with sample at t℃, g, m———mass of empty density bottle, g;
m20——water value at 20℃ in density bottle, g
0.99820——density of water at 20℃, g/cm 0.0012-~20℃, air density at atmospheric pressure of 760 mmHg, g/cm. Then the calculated pi value is checked from the apparent density conversion table in Table I of the petroleum conversion table (GB1885) to obtain the density value at 20℃. Additional remarks:
This standard is proposed by the Ministry of Petroleum Industry of the People's Republic of China. This standard is drafted by the Petrochemical Science Research Institute. From the date of implementation of this standard, the density bottle method in the former Ministry of Petrochemical Industry Standard SY2206-76 "Determination of Density of Petroleum Products" shall be invalid.
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