Methods for determining the specific surface of rocks. Determination of the specific surface Installation for the determination of the specific surface by the bed method

GOST 23401-90
(ST SEV 6746-89)

Group B59

STATE STANDARD OF THE UNION OF THE SSR

METAL POWDERS

Catalysts and supports. Determination of specific surface area

metal powders. Catalysts and carriers.
Determination of specific area

Introduction date 1992-01-01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Academy of Sciences of the Ukrainian SSR

DEVELOPERS

V.N.Klimenko, V.V.Skorokhod, A.E.Kushchevsky, I.V.Uvarova, L.D.Bernatskaya, T.F.Mozol

2. APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Product Quality Management and Standards dated December 27, 1990 N 3376

3. Periodicity of inspection 5 years

4. The standard fully complies with ST SEV 6746-89

5. REPLACE GOST 23401-78

6. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS

This International Standard specifies a method for determining the specific surface area of ​​metal powders, catalysts and carriers from 0.05 to 1000 m/g by thermal desorption of a gas (nitrogen or argon).

The essence of the method is to determine the volume of gas first adsorbed on the surface of the analyzed sample from the flow of the working gas mixture (nitrogen-helium or argon-helium) at liquid nitrogen temperature, then desorbed from it with increasing temperature and subsequent calculation of the specific surface area of ​​the sample.

1. SAMPLING METHOD

1. SAMPLING METHOD

1.1. The sample is taken according to GOST 23148*.
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GOST 23148-98

1.2. The mass of the sample for the determination test according to the table.

Before measurement, the sample is dried in an oven to constant weight.

2. EQUIPMENT

Installations (Fig. 1, 2) for determining the specific surface area consist of 1 - cylinders with helium; 2 - pressure gauges - according to GOST 2405* (2 pcs.); 3 - porous pre-filters (2 pcs.); 4 - gas mixing unit; 5 - exemplary pressure gauge for a pressure of 0.1 MPa according to GOST 6521; 6 - Dewar vessel according to NTD with liquid nitrogen according to GOST 9293; 7 - traps with silica gel-indicator according to GOST 8984; 8 - comparative and measuring cells of the detector by thermal conductivity; 9 - KSP-4 potentiometer with measurement limits of 0-10 mV and time for the indicator to pass through the entire scale no more than 1 s according to GOST 7164; 10 - integrator; 11 - stopcock (2 pcs.); 12 - flow meters designed to register the gas flow rate from 0 to 55 cm/min (2 pcs.); 13 - dosing valve; 14 - adsorbers 6 (Fig. 1) and 12 (Fig. 2) pieces; 15 - thermostat providing temperature up to 400 °C; 16 - a cylinder with nitrogen or argon brand A in accordance with GOST 10157; 17 - eight-way valve.
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* On the territory of the Russian Federation, GOST 2405-88 applies. - Database manufacturer's note.

Damn.1. with a parallel flow of the gas mixture through the detector cells

Installation diagram for determining the specific surface area of ​​samples
with a parallel flow of the gas mixture through the detector cells

Damn.2. Scheme of the installation for determining the specific surface area of ​​samples during the sequential passage of the gas mixture flow through the detector cells

Installation diagram for determining the specific surface area of ​​samples
during the sequential passage of the gas mixture flow through the detector cells

Adsorbers with samples are combined into blocks A and B (Fig. 2). In each block, depending on the required capacity of the plant, there can be from one to six adsorbers.

The sensitivity of the detector should be from 0.7·10 to 0.8·10 mV.

Laboratory scales, providing a weighing error of not more than 0.0002 g.

Thermometer 3-A3 according to GOST 8624.

Stopwatch according to GOST 5072.

The drying case providing temperature (200±20) °C.

Aneroid barometer.

Syringe medical injection with a capacity of 1 cm.

High purity helium according to normative and technical documentation.

3. PREPARATION FOR CONTROL

3.1. Checking the installation for leaks

At the outlet of the gas from the installation, the stopcock 11 is closed, creating an excess pressure of 4 10 Pa in the system, measured by a pressure gauge 5. If the pressure drop does not exceed 100 Pa within 20 minutes, the installation is considered tight.

3.2. Composition of the working gas mixture

3.2.1. An argon-helium or nitrogen-helium mixture with a given adsorbate gas concentration is used as a working gas mixture. It is allowed to use dried hydrogen as a carrier gas.

3.2.2. The concentration of the adsorbate in the gas mixture is controlled by the ratio of the flows of carrier gas and adsorbate gas. From the ratio of the velocities of these streams, the partial pressure of the adsorbate gas is calculated.

This method of compiling a gas mixture makes it possible to calculate the total adsorption and desorption isotherms of the adsorbate gas and determine the specific surface area from the total adsorption and desorption isotherms (the method of S. Brunauer, P.X. Emmett and the BET method of E. Teller).

3.2.3. Preliminary preparation of gas mixtures in cylinders in volume fractions is allowed:

adsorbate from 5 to 10%;

carrier gas from 90 to 95%.

The mixture is prepared on a block consisting of two cylinders with a carrier gas and an adsorbate, connected by a copper or brass tube with union nuts with Teflon gaskets, and a reference manometer for a pressure of 16 MPa.

The cylinder with the working gas mixture must be aged for 10 days before putting it into operation.

When re-preparing the mixture, the existing cylinders with a residual pressure of the working gas mixture of 0.5-0.7 MPa should be used.

This method of composing the working gas mixture will allow the determination of the specific surface area at a single point.

3.3. Choosing the optimal current strength

To find the optimal current strength of the detector, control experiments are carried out by connecting empty adsorbers 14. The speed of blowing the installation with the working mixture is set to (50±5) cm/min. 5 minutes after purge, voltage is applied to the detector by setting the current to 50 mA using the ammeter.

The temperature and output of the detector signal by thermal conductivity are stabilized within 30-40 minutes after the device is connected to the network and gas is passed through the cells of the katharometer. The stabilization process is monitored by a potentiometer.

After the zero line is established on the potentiometer's chart tape, the adsorbers are immersed sequentially in Dewar vessels with liquid nitrogen and the oscillations of the zero line are recorded. Upon returning the pen of the recorder to its original position in the last adsorber, the Dewar vessel is replaced by a container with water at a temperature of (20 ± 5) ° C to accelerate desorption. This operation is repeated for each adsorber.

The deviation from the zero line when the adsorbers are immersed in liquid nitrogen and water is recorded every 10-20 mA, changing the detector strength from 50 to 100 mA.

The maximum value of the current strength, at which the zero line fluctuations are no more than 30% of the potentiometer scale, is optimal.

The sensitivity of the detector is provided by a supply voltage of 5 V, which must be constant during its operation.

3.4. Metering tap calibration

The installation must have a set of metering valves with a capacity of 0.1; 0.5 and 2.5 cm.

Calibration of metering valves is allowed by any known methods at least once a year. The method of certification of dosed capacities of volumes by the adsorption-weight method is predominant.

The simplest, but less accurate, is the chromatographic pulse method using a medical syringe. The flow rate of the working gas mixture or carrier when checking dosing valves should be (50 ± 1) cm / min. After heating and establishing a zero line on the potentiometer tape, a volume of gas-adsorbate is injected into the gas flow with a medical syringe, corresponding to the calibrated volumes of the dosing tap. Developing peaks are recorded on the potentiometer and integrator. The operation of introducing the sample is repeated 10 times.

Next, a sample of gas-adsorbate is introduced with a calibrated capacity of the dosing valve. To do this, with the flows of the working gas mixture and adsorbate gas turned on, the metering valve is turned so that the volume of adsorbate gas in the metering valve is captured by the working gas mixture and fed to the detector. The readings are recorded by a potentiometer and an integrator. The operation of introducing the sample with a dosing crane is repeated 10 times.

Permissible discrepancies of parallel measurements should not exceed 3%.

Calibrated capacities of metering valves () in cubic centimeters, reduced to normal conditions, are calculated by the formula

where is the volume of the adsorbate gas sample injected with a syringe, cm;

The average area of ​​the developing peak, recorded by the integrator during the introduction of a gas-adsorbate sample by a dosing tap, cm;

- barometric pressure, Pa;

- the average area of ​​the developing peak, recorded with the introduction of a sample of adsorbate gas with a syringe, cm;

- air temperature in the room, °С;

- normal pressure,

3.5. Determination of the concentration of adsorbate gas (nitrogen or argon) in the working gas mixture

In the absence of a gas mixing unit, the concentration of adsorbate gas in cylinders with a working gas mixture is checked either according to the readings of a pre-calibrated katharometer using the frontal method. In this case, it should be possible to independently connect cylinders with a carrier gas and a gas mixture using a three-way valve to the thermal conductivity detector cells.

To carry out the analysis, a carrier gas flow is passed through the measuring and comparative cells of the thermal conductivity detector until the detector readings stabilize. After establishing the zero line, the carrier gas flow in the measuring cell of the potentiometer is replaced by the flow of the working gas mixture. In this case, the pen of the recorder will deviate from the zero position by a distance and write out a line parallel to the zero one.

The volume fraction of adsorbate gas () as a percentage is calculated by the formula

where is the calibration coefficient of the detector, cm, calculated by the formula

Distance between the front and zero lines on the chart recorder strip, cm;

- speed of the chart tape, cm/min;

- volumetric velocity of the working gas mixture, cm/min;

- calibrated volume of the dosing valve, cm;

- the average area of ​​the developing peak recorded by the integrator during the introduction of a gas-adsorbate sample by a dosing tap, cm

3.6. Preparation of adsorbers

The adsorbers are thoroughly washed and dried in an oven at a temperature of (200 ± 20) °C. Then it is weighed with an error of not more than 0.0002 g, the sample is loaded and re-weighed to determine the mass of the sample. Adsorbers are chosen in such a capacity that a minimum free space remains above the sample for the passage of the gas mixture. When determining specific surfaces up to 1 m/g, it is recommended to pass the gas mixture in adsorbers through a layer of powder granules. To avoid entrainment of the powder, cotton swabs are provided.

3.7. Preparing the detector for measurements and degassing the sample

3.7.1. The operations of preparing the detector and degassing the sample are carried out simultaneously.

To prepare the detector, the working gas mixture from the gas mixing unit is passed at a speed of (50 ± 1) cm/min through the trap 7 (Fig. 1, 2), cooled with liquid nitrogen, six adsorbers into the comparative and measuring cells of the detector 8.

5 minutes after the start of the purge, voltage is applied to the detector, setting the optimal current or voltage. The detector is heated in the working gas mixture for 30 min. 15 minutes before the end of the warm-up, the potentiometer and integrator are turned on.

The readiness of the detector for operation is checked by the stability of the zero line, which is recorded with the pen of the potentiometer recorder on a chart tape.

3.7.2. Degassing of samples is carried out by purging adsorbers 14 with a working gas mixture for 40-50 minutes. The flow rate is controlled by a flow meter 12. A thermostat 15 is placed under the adsorbers and the temperature is set taking into account the thermal stability of the powder, but not higher than 400 °C. At the end of degassing, the pen of the recorder goes to the zero line and the samples are cooled to a temperature of (20 ± 5) °C.

4. MEASUREMENTS

4.1. Adsorbers alternately, starting with the first gas in the direction, are immersed in Dewar vessels with liquid nitrogen. In order to avoid air leakage through the gas outlet line, in the absence of an automatic device for lifting the adsorbers, they should be immersed in liquid nitrogen at such a speed that the film in the flow meter 12 moves only upwards. When adsorbed, the pen of the potentiometer recorder deviates from the zero line. The adsorbers are kept in liquid nitrogen until the pen of the potentiometer recorder returns to the zero line, i.e. until adsorption equilibrium is established (15-30 min, depending on the adsorbent gas).

4.2. The last adsorber along the gas flow is removed from the Dewar vessel with liquid nitrogen and immersed in a vessel with water. The temperature of the water in the vessel must be (20 ± 5) °C.

During desorption, the pen of the recorder writes out the desorption peak on the potentiometer's chart tape, and the integrator displays figures proportional to the area of ​​this peak.

Desorption measurements are carried out sequentially for all remaining samples.

4.3. A sample of gas-adsorbate is introduced into the system by a dosing valve. At the same time, numbers are recorded on the potentiometer's chart tape and appear on the integrator, corresponding to the area of ​​the developing peak, depending on the calibrated capacity of the metering valve (). When calculating the specific surface, the calibrated capacity is taken into account, the area of ​​which is closer to the area recorded during the desorption of adsorbate gas from the surface of the measured powder samples.

4.4. To determine the specific surface of a substance by the BET method, the measurement according to paragraphs 4.1 and 4.2 should be repeated at three to five different concentrations of the adsorbate gas in the working gas mixture within: 3-5; 5-7; 7-10; 10-17; 17-25%. The concentration of the adsorbate gas in the working gas mixture is controlled by the mixing unit according to the ratio of the volumetric flow rates of the adsorbate gas and the carrier gas.

The specific surface is expressed as the ratio of the total surface of a porous or dispersed body in a given medium to its volume or mass. The specific surface is proportional to the dispersity or, which is the same, inversely proportional to the particle size of the dispersed phase.

Specific surface value

The absorption capacity of adsorbents, the efficiency of solid catalysts, and the properties of filter materials depend on the specific surface area. The specific surface area of ​​activated carbons is 500-1500, silica gels - up to 800, macroporous ion-exchange resins - no more than 70, and diatomite carriers for gas-liquid chromatography - less than 10 m 2 /g. The specific surface characterizes the dispersion of powdered materials: mineral binders, fillers, pigments, pulverized fuel, etc. The value of their specific surface usually ranges from tenths to several tens of m 2 /g. The measured value of the specific surface depends on the size of the sorbed molecules. The same substance during the sorption of large molecules has a smaller specific surface area, while during the sorption of small molecules it has a larger specific surface area. For large molecules, the surface of small pores, measured by the sorption of small molecules, does not seem to exist. Therefore, in addition to the specific surface area, an important characteristic of porous bodies is the distribution of the pore surface over the pore radii (the distribution of pores over the radii).

Determination of specific surface area

The specific surface is most often determined by the amount of inert gas adsorbed by the material and by the air permeability of the layer of powder or porous material. Adsorption methods provide the most reliable data.

The most widely used methods for determining the specific surface area of ​​powdered materials are based on an assessment of their air permeability or adsorption capacity with respect to various gases.

Air permeability method is based on the effect of filtering air through a layer of powder of a certain thickness at atmospheric pressure. To determine the specific surface area using this method, devices of various designs are used, for example, PSH-2. Schematic diagram of the PSKh-2 device is shown in fig. 5. Located in a ditch 1 the perforated partition is covered with a circle of filter paper and the cuvette is filled with a sample of the powder to be tested, weighed on a technical balance with an accuracy of 0.01 g. The powder is covered with a second circle of filter paper and compacted with a plunger 2. The thickness of the compacted powder layer is measured using a vernier bar mounted on the protruding cylindrical part of the plunger and a millimeter scale applied to the outer surface of the cuvette. The plunger is removed, tap 4 is opened and, using a rubber bulb, 5 a vacuum is created under the layer of the material under test, sufficient to lift the colored water filling the pressure gauge 3, into the upper extended part of the manometer. Then close the faucet 4 and using a stopwatch, determine the time for the passage of the meniscus of the liquid between the control risks 1-2 or 3-4 on the manometer tube. At least three parallel measurements are carried out, and for subsequent calculations, the average value of the passage time for the liquid meniscus between the corresponding pair of marks: “upper” (1–2) or “lower” (3–4) is used.

When testing fine-grained materials, the meniscus of the liquid descends very slowly in the manometer tube, and the upper pair of notches is used to shorten the measurement time. When testing coarse-grained materials, the liquid in the gauge initially descends so rapidly that it is difficult to accurately measure the time it takes for its meniscus to pass between the upper marks; in this case, use the bottom pair of notches.

A weighed portion of the powder to be tested g, g, determined by the formula

where ρ is the density of the tested material, g/cm 3 .

Specific surface S, cm 2 /g, calculated by the formula

where K– instrument constant (K values ​​for the lower and upper pairs of notches are given in the instrument certificate); M - coefficient depending on the thickness of the test material layer L and air temperature during measurement (values M reference data); τ - the time during which the meniscus of the liquid falls between the corresponding risks; g- sample of the tested powder, g.

The advantage of the air permeability method is the simplicity of the instruments used and the short duration of the test, which makes it especially convenient, for example, for on-line control of the fine grinding process. However, the values ​​of the specific surface area measured by this method depend significantly on the degree of compaction of the tested powders, which practically excludes the possibility of using it to determine the specific surface area of ​​highly dispersed powders, which are often hygroscopic and very prone to particle aggregation. In practice, the air permeability method is usually used to study powdered materials, the specific surface area of ​​which does not exceed 5000–7000 cm 2 /g (0.5–0.7 m 2 /g).

adsorption methods used to study highly dispersed powders with a specific surface area from 0.5 to 1000 m 2 /g. If a solid body, such as coal, is placed in a closed space filled with gas or vapor at a certain pressure, the solid body begins to adsorb the gas and its mass increases, while the pressure of the gas decreases. After some time, the pressure becomes constant, and the body weight stops increasing. Based on the laws of ideal gases, if the volumes of the vessel and the solid are known, it is possible, based on the decrease in pressure, to calculate the amount of gas (or steam) necessary for the formation of a saturated adsorption monomolecular layer on the surface of the particles of the material A m. By size A m and from the area occupied in such a layer by one adsorption gas molecule, one can calculate the specific surface area of ​​the material under study.

the value A m in moles is calculated according to the adsorption isotherm equation of S. Brunauer, P. X. Emmett and E. Teller (BET equation), which has a linear form

where A m is the amount of gas adsorbed at equilibrium pressure R, moths; Ps is the pressure of saturated gas vapors at the temperature of the experiment; FROM - energy constant.

The BET equation is valid in the range of values P/Ps from 0.05 to 0.35.

In coordinates "P / A (P s -P) - P / P s" the adsorption isotherm according to the above formula is depicted by a straight line, the slope of which is equal to ( C–1)/(A m ∙C), and the segment cut off on the y-axis is equal to 1/(A m ∙ C). Having defined the value A m at different values P, obtain the data necessary for constructing the adsorption isotherm and, accordingly, for determining the value A m.

Measurements are carried out using instruments that most often use nitrogen adsorption at its boiling point (78 K). The weight of the sample is taken depending on the expected specific surface and varies from 0.03 to 0.15 g. The larger the surface, the smaller the weight. Before measuring the adsorption isotherm, all previously physically adsorbed substances are removed from the surface of the adsorbent. This is best achieved by pumping under high vacuum. For the complete removal of physically adsorbed substances from the narrowest pores (microporous adsorbents), it is necessary to pump out at temperatures of 350–400 o C.

Measurements of the specific surface are carried out with the supply of gaseous nitrogen at the temperature of liquid nitrogen. The specific surface of the sample is calculated based on the mass of the sample, the volume of the measuring cell with and without the sample, and the amount of gas adsorbed by the sample.

The results obtained by the adsorption method give the most complete picture of the true value of the specific surface area of ​​the materials under study, since they (unlike the results obtained, for example, by the air permeability method) fix not only the "external" surface of the particles, but also the surface formed by the internal porosity of the particles. . Obviously, the comparison of the values ​​of the specific surface area of ​​materials can be carried out only when they are measured by the same method.

There are direct and indirect methods for determining the shape of particles. Direct methods include: optical microscopy (Figure 1) and electron microscopy (Figure 2).

Picture 1– Images obtained from an optical microscope

Figure 2– Images obtained from an electron microscope

Indirect methods include: light scattering methods and rheological measurements.

Light scattering method used to evaluate the shape and size of particles of monodisperse powders. For polydisperse systems, preliminary fractionation is necessary. The determination of the shape of particles by the method of light scattering is carried out by the intensity of scattered light of a given wavelength, by estimating the spectrum of scattered light, or by the polarizability of scattered light at a given wavelength. The shape of colloidal particles can be determined by light scattering methods using an ultramicroscope. If the particles are asymmetric, then they have a variable brightness. Spherical particles have a constant brightness.

Rheological method determination of particle shape is based on the fact that dilute aggregate-stable disperse systems do not form a structure, and therefore their rheological properties are close or similar to those of a dispersion medium. The dependence of the viscosity of these systems on the concentration of the dispersed phase is linear and is described by the Einstein equation:



(1)

where η 0 is the viscosity of the dispersion medium; φ f is the volume fraction of the dispersed phase; α is the particle shape factor.

Dependencies η =f(φ f ) determine the value of the coefficient α and draw a conclusion about the shape of the particles (Figure 3) .

Figure 3– To determine the shape of particles according to Einstein's equation of viscosity

Table 1 presents the main parameters of the particle shape.

Table 1– Basic particle shape parameters

To determine the specific surface, adsorption and kinetic methods are used. adsorption methods are based on determining the volume or mass of a substance adsorbed on the surface and forming a monomolecular layer. Gases, liquids and solids are used as adsorbates. The gas-adsorption method and the method of adsorption of surfactants from solutions are most widely used. Test data are processed according to BET theory.

Kinetic methods are based on measuring the resistance to filtration of air or gases through a layer of powder. Filtration is carried out at atmospheric pressure or under vacuum.

– Egorova, E.V. Surface phenomena and disperse systems: textbook. allowance / E.V. Egorova, Yu.V. Polenov // Ivan. state chemical-technological un-t. - Ivanovo, 2008. - 84 p.

– Mikheeva, E.V. Surface phenomena and dispersed systems. colloidal chemistry. Collection of examples and tasks / E.V. Mikheeva, N.P. Pikula, S.N. Karbainova // textbook for students of XTF, FTF, EEF, IGND and IDO. - Tomsk: TPU Publishing House, 2008. - 116 p.

"Belov, V.V. Computer implementation of solving scientific, technical and educational problems: a textbook / V.V. Belov, I.V. Obraztsov, V.K. Ivanov, E.N. Konoplev // Tver: TvGTU, 2015 . 108 p."

In addition to the above methods for determining the specific surface of rocks (by their granulometric composition, by porosity and permeability), there are the following methods for estimating this parameter: filtration, based on measuring the resistance to flow through a porous body of rarefied air; adsorption, as well as the method of labeled atoms.

Methods for determining the specific surface of porous media based on the use of the Poiseuille mode of air flow through the object of study [i.e. based on the use of formulas like (1.35)] are applicable only for an approximate estimate of the surface of coarse-grained homogeneous media, the width of the pores in which is much greater than the mean free path of air molecules. In this case, it is not necessary to take into account the sliding of the gas along the walls of the pores. The movement of gas in a finely dispersed porous medium is greatly facilitated by the sliding of molecules along the walls of the pores, and the resistance of a medium with a high specific surface area to the passage of gases through it is sometimes significantly less than those calculated by formulas like (1.35), which do not take into account the sliding of gas along the walls. Therefore, in this case, it is possible to use a method based on measuring the resistance to flow through a porous body of rarefied air in the Knudsen regime, which is more of a diffusion character. The Knudsen regime sets in when the maximum pore gaps become less than the mean free path of gas molecules. In this case, the collisions of molecules with each other become rare (compared to impacts on the pore walls). The dependence of the molar gas flow rate on the specific surface area and other parameters is expressed by the equality;

where SUD is the specific surface of the sample, m2/m3; Q is the number of kilomoles of air flowing through 1 m2 of the cross section of a porous medium with a thickness? x (in m) for 1 s at a pressure drop? p (in Pa); M is the relative molecular weight; air, kg/kmol; R - universal gas constant, J / (kmol - degree); T is the temperature of the experiment, °C.

Special devices have been designed to determine the specific surface of porous bodies from the results of measurements of the Knudsen filtration regime.

The rocks that make up the reservoir are filled with a liquid medium - water and oil. The specific surface (for example, clays and some other rocks) under the influence of the aquatic environment can change, and "dry" methods of its measurement do not always correspond to the actual conditions of the occurrence of rocks in natural conditions.

The specific surface area of ​​porous media in an aqueous medium is usually determined by the adsorption of dyes or by surface measurement using radioactive tracers. In this case, the surface area of ​​minerals Syd is calculated from the number of radioactive tracer molecules absorbed by the porous medium and from the area per atom of this radioactive substance on the crystal surface:

where bm is the number of moles (atoms) of the substance associated with 1 g of the solid phase; u is the area per atom of a given substance on the surface of a crystal (its value is known for many substances); N is Avogadro's number.

The amount of a radioactive ion absorbed by a substance when it is immersed in a solution is determined by the decrease in the activity of the solution filtrate due to the absorption of the labeled atom by the solid phase.

The adsorption method occupies a special place in accuracy due to the fact that the surface of a porous medium is measured by such small objects as the molecules of the adsorbed substance, lining them

Pov. porous environment. The specific surface area of ​​the porous medium is calculated from the amount of the adsorbed substance (i.e., from the number of its molecules) and the area per atom of the given substance.

Adsorption methods for studying the specific surface area of ​​porous media require complex equipment and highly skilled performers. Therefore, in the lab. physics of the oil reservoir, this rock surface is usually estimated by filtration methods.

According to the results of measurements by F.I. Kotyakhova specific pov. cores varies from 38,000 to 113,000 m2/m3.