The weight ratio of the substance to its volume or mass per unit volume it is called density.It all substances varies and depends on the nature and composition.For example, for fresh water, it is equal to approximately 1.003 g / cm3, and marine - 1.025 g / cm3.Also, the physical quantity is subject to the rule of additivity.That is, the density of the multi-component mixture (which is, for example, gasoline) will be equal to the sum of the products of the characteristics of each component by its weight fraction: ρsmesi = Σρi • ci.Calculation method can be used for a known composition, as well as in those cases where there is required to determine the density of the fuel with high precision.Another disadvantage of the method calculation - the complexity and high costs for determination of each component.It requires expensive chromatographic equipment and highly qualified staff, as each brand oil is characterized by a wide variability of sets of a large number of individual, preferably organic compounds (hydrocarbons).
Qualitative and quantitative composition, causes the density of gasoline varies and depends on the feedstock and the technological method of processing.Get different brands through direct oil distillation, reforming, isomerization, alkylation, catalytic cracking.Gasoline consists predominantly of a mixture of paraffins, naphthenes and olefins.At present, many countries have introduced restrictions on the content of aromatic hydrocarbons and olefins.This situation is caused by the environmental requirements, and the need to reduce carbon formation, which occurs due to the presence in the fuel benzene compounds and the ethylene series, they often contain petrol.The density of the product octane number is increased by the aromatics is generally higher than that of fuel with a low content of benzene and its homologues.
In addition, the final product may contain special additives.They also affect the density of the gasoline.For example, oxygenates, such as ethanol, allow to increase the combustion efficiency and reduce the concentration of carbon monoxide in the exhaust gases.Regulations and technological regulations of the enterprise determines the components that can be added to the fuel.Currently in our country there are a few documents, normalizing the quality of motor fuels for vehicles with petrol engines.
Interstate standard GOST 2184-77 reissued in February 2003, with amendments 1-6 on the 1981, 1983, 1984, 1990, 1997 and 2002. As well as two amendments from 2000 and 2001. He is recognized by 10 states -the former Soviet republics.In the Russian Federation, its requirements apply only to unleaded product A-76.The density of gasoline at 20 ° C on the guests are not regulated, but its definition is certainly to the shipment to the consumer.For this purpose areometrichesky pycnometric and test methods described GOST 3900-85.
State standard of our country GOST 51105-97 (to him were published in 1999 and 2000. Change number 1 and number 2) is applied to the 01.01.1999 and applies to unleaded motor gasoline, which, depending on the value of the octane number fallto mark: Super 98 Premium 95 Regular 92 Regular 91, 80. The normal density of gasoline and other products 92 RON 91 to 98 is standardized at 15 ° C and in the range from 725 to 780 kg / m3.For product grade Normal 80 it can vary from 700 to 750 kg / m3.Determine this feature by using the hydrometer on the test method according to GOST 51069-97.
other national standard - GOST R 51886-2002 - put into effect in the Russian Federation, 01.07.2002, 01.07.2008 and with him came the change № 1. The document corresponds to the normal Europeans EN 228-2004, it spreadsunleaded gasoline brands Super Euro 98 and Euro 95 Premium.They are characterized by an octane rating of 98 and 95, respectively.The density of both gasoline grades at 15 ° C in the range of 720-750 kg / m3 and is determined according to GOST 51069-97 areometricheskim method.
What caused the need to determine the density of motor fuel?Firstly, this value indirectly characterizes the composition of the product and helps identify it.For example, if the measured density is 0.980 kg / m3 or 0.650 kg / m3, then it's safe to say that it's not gasoline, and some other product.Also, the density of the gasoline are widely used in practice: knowing the volume of product in a large tank, which can not be weighed, its weight is calculated by multiplying the density by volume.This is called indirect, it contains requirements of GOST R 8.595-2004.Measure the temperature and the level of product in the reservoir and its volume was calculated.Withdraw single samples in accordance with the requirements of GOST 2517-85, unite them and determine the density of the GOST 51069-97 or by GOST 3900-85.The measurement results lead to the standard conditions (temperature 15 to 20 ° C), but then these values are used to calculate the mass of product in the reservoir.
