Objective: to consolidate theoretical knowledge and gain practical skills in determining the density of fuels and lubricants.
Objectives: During the work it is necessary to determine the density of several petroleum products and fuels that are in glass cylinders.
Utensils: cylinders, glass
Equipment: hydrometer
Methods of laboratory work
Using a hydrometer, the density of oil and oil products having a viscosity at 50 ° C of not more than 200 mm / s is determined. Hydrometers are selected in such a way that when immersed in the analyzed oils and petroleum products, they do not sink and do not float above the part where the calibration density scale is applied. Determination of density by hydrometer is based on Archimedes’ law. Before determining the density of the analyzed sample of oil or petroleum product is kept at ambient temperature in order for the sample to take this temperature.
To determine the density of the gasoline fraction with a hydrometer, it is selected with a scale from 0.690 to 0.760.
In the case where the diesel fraction is obtained from gas condensate or light oil, its density may be in the range of 0.790-0.820 g / cm3. The diesel fraction obtained from heavy oil can have a density of 0.850–0.880 g / cm3. Therefore, to determine the density of the diesel fraction, it is necessary to have a set of hydrometers with different scales: 0.750-0.820 and 0.820-0.880 g / cm3.
In a clean dry glass (or metal) cylinder with a diameter of at least 5 cm, mounted on a solid stand, carefully pour oil on the wall or on a glass rod in such a way that when immersing the hydrometer, the analyzed sample does not spill over the edges of the cylinder. Then a clean and dry hydrometer is slowly and carefully immersed in oil or petroleum product, holding it by the upper end.
After the hydrometer is installed and its oscillations stop, the density value is counted along the upper edge of the meniscus. The eyes of the researcher should be at the level of the meniscus – the level of “a-b”.
At the same time determine the temperature of oil or petroleum product on a hydrometer thermometer or an additional thermometer (hydrometers come with a thermometer and without a thermometer).
Counting on the scale of the hydrometer gives the density of oil or petroleum product at the temperature of the analysis. To bring the found density to the density ρ4 at normal temperature use the formula
ρ = 2ρ1- ρ2,
Depending on the type of hydrometer, the difference between the parallel density determinations should not exceed 0.001–0.002.
To determine the density of high-viscosity oils and petroleum products with a viscosity at 50 ° C greater than 200 mm2 / s, they must first be diluted with kerosene. Grizzly oil is diluted with an equal volume
m of kerosene with a known density.

Fig. 1. Determination of oil density and oil product

If the density of kerosene is unknown, it can be determined by the same hydrometer. The density of the analyzed viscous oil is calculated by the formula:
ρ = 2 ρ 1– ρ 2,
where ρ1 is the density of the mixture;
ρ2 is the density of kerosene.
Depending on the type of hydrometer, the difference between the parallel determinations of the density of viscous oils should not exceed 0.004-0.008.
Video density determination
Processing of the obtained results
The protocol of laboratory work should include: basic definitions and general provisions on the density of fuels and lubricants; description of the laboratory installation; results of laboratory research – measurements and calculations, densities of substances that were used in laboratory work.
Control questions
For what purpose is it necessary to know the density of an oil product?
What are the methods of determining the density of petroleum products and what is their essence?
How to bring the density to standard conditions?
What are the features of determining the density of viscous petroleum products?