Method of determining volatility and heat of vaporisation of mixture liquid substances

FIELD: physics.

SUBSTANCE: method of determining volatility and heat of vaporisation of a mixture of liquid substances from the rate of evaporation from a flat surface involves establishing a correlation relationship between volatility values, calculated using known reference data, for individual liquid substances selected as calibration liquids, and the rate of evaporation thereof, determined based on data from thermogravimetric analysis carried out in isothermic conditions when an equilibrium state is achieved. The rate of evaporation of the analysed mixture is determined and the volatility value is found from the correlation relationship. The heat of vaporisation of the mixture of liquid substances in the analysed temperature range is determined using the relationship between the found volatility values and temperature. The value of the heat of vaporisation is determined from the value of the slope of a linear graph, the abscissa of which is the value of the inverse absolute temperature and the ordinate is the logarithm of the product of the experimentally determined volatility value and the absolute temperature value.

EFFECT: high reliability and objectivity of estimating volatility of not only individual liquids, but also mixtures thereof at different temperatures, broader functional capabilities of the method of determining volatility.

2 cl, 6 dwg

The invention relates to the field of research or analysis of non-biological materials by determining their chemical or physical properties, specifically studies of phase changes by removing any component, for example, evaporation, and weighing the residue.

Volatility is a property of liquid and solids to pass into the gaseous state. The measure of volatility is the concentration of the vapor of this substance at this temperature. Volatility is expressed in mg/m3or in mg/l is calculated according to expression (1):

$C=P⋅M/R⋅T,(1)$ where C is the concentration of saturated steam;

P is the gas pressure;

M - molecular mass of the gas;

R - universal gas constant;

T is the absolute temperature.

The expression (1) is a consequence of the equation of state for ideal gases (equation Clapeyron-periodic):

$P⋅V=n⋅R⋅T,(2)$ where V is the volume of gas at temperature T;

n is the number of moles of the research the constituent gas.

Given that n=m/M where m is the mass of gas, and after mathematical transformation of equation (2), we obtain the expression for calculating volatility (1).

With increasing temperature increases the vapour pressure of the substance, the expression (2), resulting in increases and volatility /Chemical encyclopedic dictionary [Text] / M.: Soviet encyclopedia, 1983. - 792./.

Known direct and indirect methods of determining the volatility of individual substances. To determine the saturated vapor pressure and volatility direct methods are necessary to achieve saturation of the air in pairs analyte. Saturation of air with vapors of a substance can only be in static conditions enclosed volume /Hal E. the Equilibrium between liquid and vapour [Text] / Ahala, Ipik, Vpred [and others]. - M: IL, 1962. - 438 S.; Reid, P. the properties of gases and liquids [Text]: Per. s angl. / Red, Cepnet, Sherwood. - Leningrad: Khimiya, 1982. - 591 S./.

Indirect methods for the determination of the vapour pressure and volatility based on the use of ratios chromatographic retention parameters of the investigated substances and substances comparison to known reference data on volatility /Smut GV determination of the volatility of herbicides derivatives of 2,4-D by gas chromatography [Text] / Gavin, Vghenemisel, Man [and other] // Chemistry in agriculture. 1974. No. 4. - p. 67-71; Turkeltaub GN. The definition of elasticity pair in serial chromatographic device [Text] / Hunterkiller, Bmosquea // Zavodskaya laboratoriya. - 1969. No. 10. - s; A.S. 800868 USSR MKI3G01N 31/08. The method for determining the vapour pressure legalandgeneral non-condensable impurities in the gas mixture [Text] / Wegscheider, SEO, Ahitophel (USSR). - 1976/.

Despite the diversity of the known methods of determining the maximum concentration of vapor in the air, they all relate to individual compounds, but not their mixtures. Possible a direct determination of the vapour pressure of the mixture of organic compounds in a confined space, however, for the calculation of the maximum concentration of vapor in the expression (1) necessary information about the molecular weight of the mixture, the calculation of which for a mixture of complex and sometimes uncertain composition is problematic.

In this regard, research on the development of a method for determining the volatility of mixtures of liquid organic substances can be recognized as relevant.

It is known that the volatility determines the rate of evaporation of the analyte with a flat surface /Kuznetsov V.V. Physical and colloid chemistry [Text] / VV Kuznetsov. - 2nd ed. - M.: Higher school, 1968. - 390 S.; Franke, H. Chemistry of toxic substances [Text]: 2 tons / France. - M.: Chemistry, 1973. 1. - 365 S./.

On came the communication speed of evaporation from a flat surface and volatility based known method of determining the relative volatility of the solvents ethyl ether /GOST 18188-72, 3.4. Solvents brands 645, 646, 647, 648 for paints and varnishes. Technical specifications [Text]. - M: the Institute Publishing house of standards, 1972./. In this method, the volatile solvent is relative volatility of ethyl ether, characterized by full evaporation spots of liquid deposited on a flat surface ashless filter, i.e. by evaporation.

This method is the closest of the analogues. With the undeniable advantages of this method, it has several drawbacks:

- does not determine the absolute values of volatility;

- not possible to assess the dependence of the volatility of the investigated liquid temperature;

the subjectivity of the assessment of completeness of evaporation caused stains liquid does not imply a high precision determination of the relative volatility.

The present invention is to develop a method for determining the absolute values of volatility at different temperatures and heat of vaporization of a mixture of liquid substances.

The solution of this problem involves the technical result consists in increasing the accuracy and objectivity of the evaluation of volatility not only the individual liquids and their mixtures at different temperatures, extending the functionality of the method of determination of volatility due to the possibility of the use of the Finance obtained experimental data to determine the heat of vaporization.

The inventive method can be used at the stage of development of new mixed liquid paint systems, fuels and lubricants in the evaluation of their physicochemical properties, parameters of explosion and fire risk, and optimization of composition.

The problem is solved in that in the method for determining the volatility and the heat of vaporization of a mixture of liquid substances on the rate of evaporation from a flat surface according to the proposed solution set correlation values of volatility, calculated according to known reference data for individual liquid substances selected as the calibration fluid, the speed of evaporation, determined on the basis of experimental data of thermogravimetric analysis carried out in isothermal mode when reaching the equilibrium state; for the studied mixtures determine the evaporation rate and the correlation found is volatility; then, using the dependence of the found values of the volatility of the temperature, determine the heat of vaporization of a mixture of liquid substances in the investigated temperature range.

The magnitude of the heat of vaporization of the mixture is determined by the value of the tangent of the slope, graph the linear dependence, the abscissa is the reciprocal of the absolute temperature, and PR is intoi - logarithm works experimentally found values of volatility on the value of the absolute temperature.

The invention is illustrated by drawings shown in figures 1-6. In the first phase of research to develop a method to determine the volatility and the heat of vaporization of a mixture of liquid substances was the choice of compounds suitable for the construction of correlation (calibration) depends upon the assessment of the volatility of the investigated mixtures of liquid substances.

When solving the problem of justification of the choice of compounds suitable for the construction of calibration dependence when estimating the volatility of the investigated mixtures of liquid substances, have been calculated values of pressure and saturated vapor concentration at 20°C for members of a homologous series of saturates, aromatics, alcohols.

We used reference data table according to the temperature and pressure of saturated vapors /Stall D.R. Table vapour pressure of individual substances [Text]: a Handbook / Dremel. - M, Foreign literature, 1949. - 72 S./. To calculate the pressure and concentration of saturated steam at a given temperature used simplified equation Clapeyron (3) /Comely I. Chemical thermodynamics [Text] / Pregain, Rdea - Novosibirsk.: Nauka, 1966. - 550 C. and the expression (4) to calculate the concentration at sennoga pair as a consequence of the expression (1):

$lnP=A-B/T,(3)$ where P is the vapour pressure;

T is the absolute temperature of the liquid-vapor system;

A, B - coefficients.

$C=15,9⋅P⋅M/T,(4)$ where C is the volatility (the concentration of the saturated steam), mg/l;

15,9 - coefficient taking into account the value of the universal gas constant R and the ratio of units /Vigdergauz MS Calculations in gas chromatography [Text] / Mshvildisrit. - M.: Chemistry, 1978. - 248 S./;

P is the saturated vapor pressure, mm Hg;

M - molecular mass, g/mol;

T - temperature, K.

Equation (3) is a mathematical expression of the linear dependence of ln P against 1/T, and the coefficient B (the slope of a straight line) is connected with the heat of vaporization: B= ∆ H/R, which implies that:

$ΔH=B⋅R,(5)$ where B is the coefficient of equation (3),

ΔH is the molar ental the Oia of vaporization (evaporation heat), cal/mol;

R is the universal gas constant, equal to 1.98 cal/mol·K.

Despite the fact that, in accordance with the expression (4) concentration of saturated steam is directly proportional to molecular weight and pressure, volatility decreases with increasing molecular weight, as reduced and saturated vapor pressure. Maximum volatility have the first members of a homologous series, and the dependence of the heat of vaporization from the number of carbon atoms in the molecule homologues has a linear character.

On this basis, we were selected as the connection with the maximum volatility pentane or diethyl ether. As compounds with intermediate values of volatility when constructing a calibration based on what you choose liquid, representatives of various classes of organic compounds: water, benzene, acetone, methyl alcohol. However, the list of selected compounds requires clarification of the methodology for determining the evaporation rate.

Determination of the evaporation rate of the liquid based on measuring the mass loss of the evaporated substance for a known interval of time. To do this, use the gravimetric method. With the undeniable advantages and versatility of this method real the feasibility of it depends primarily on the accuracy of weighing the image is a; in addition, the accuracy of the measurement time interval and the accuracy of temperature control when determining the rate of evaporation.

The combination of high precision weighing and temperature control during the experiment to determine the rate of evaporation can be achieved by using a thermogravimetric method.

Experimental and theoretical research aimed at the development of methodologies for the determination of the evaporation rate of the individual components and of the investigated mixtures of liquid substances, their volatility using thermogravimetric analysis method, extend the functionality of the method.

The difficulty of the solution is the development of methods to determine the rate of evaporation is related to the fact that the standard equipment for thermogravimetric studies (empirical DTG-60, Shimadzu, Japan) does not allow to carry out research in isothermal mode. Therefore, the sample was subjected to intermittent heating in open platinum cells in an atmosphere of air at a speed of 2...10°/min up to the equilibrium temperature in the range of 20...60°C. the accuracy of the weight measurement is 1%, the sensitivity of 0.005 mg the temperature measurement Accuracy of 0.1°C.

When the evaporation from the surface of the liquid fly the fastest molecules, the kinetic energy which is revised the kinetic energy of their relationship with the rest of the liquid molecules. This leads to the reduction of the average kinetic energy of the remaining molecules, that is, to the cooling fluid. In the processes of heating and evaporation of the sample is set to the state of equilibrium, with changes in temperature would not exceed 0.1°. The temperature corresponding to this state, was recorded as the temperature determine the rate of evaporation. The figure 1 shows the state of the overlay thermograms for determining the rate of evaporation of water.

Curves of temperature stabilization (1, 2, 3) in figure 1 reflect the temperature of the establishment of the equilibrium state: 17,8; 43,9 and 47.4°C. For each of these temperatures on the figure 1 presents curves thermogravimetric analysis (TGA) (4, 6, 8) and differential thermal analysis (DTA) (5, 7, 9) is water.

Range temperature stabilization with an accuracy of 0.1°C helps to allocate TGA curve a straight line segment, a corresponding decrease of the mass by evaporation of the liquid, which should be used when determining the rate of evaporation.

At the initial stage of the experimental studies it was found that previously justified the list of fluids to build the calibration dependence of volatility on the rate of evaporation should be corrected. So, determine the rate of evaporation of glycerol is possible at temperatures over 60°C, because p and lower temperatures there is no loss of sample mass, and its growth: the process of absorption of moisture air prevails over the process of evaporation of low volatile liquids.

The use of pentane or diethyl ether as samples with a maximum volatility limited definition high speeds evaporation, because it requires tahaliyani samples. So as connections to build the calibration dependences were the following compounds: water, methyl alcohol, benzene, and acetone.

However, experimental data, in particular for water, allow to determine the evaporation rate at a particular temperature equilibrium state (17,8; 43,9 and 47.4°C). When determining the evaporation rate for any desired temperature, the necessary dependence of the rate of evaporation temperature. To establish this dependency, you can use mathematical tools to investigate the kinetics of chemical processes.

Calculations of kinetic parameters on the curve of the TGA is based on formal kinetic equation:

$V=-dm/dt=K⋅mn,(6)$ where V is the reaction rate;

m is the mass of neproreagirovavshikh the substance at time τ;

n is the reaction order;

K is the reaction rate constant.

Investigated the evaporation process is not a chemical process, therefore, using the kinetic equation, it makes sense to talk about the change in mass of the substance by turning to steam, but without chemical transformations in another connection.

In the case when the dependence of a change in mass with time is linear as in the study of the evaporation process, and the tangent of an angle is a constant that does not depend on mass, the reaction order is zero. For the reaction is zero order reaction rate numerically equal to the rate constant:

$dm/dt=-K.(7)$ For a narrow temperature range just the Arrhenius equation, reflecting the dependence of the rate constant on temperature:

$K=Ko⋅e-E/RT,(8)$ where K is the reaction rate constant at temperature T;

Ko- constant temperature coefficient is based;

E - the activation energy of the reaction;

R is the universal gas constant.

Taking into account expressions (7) the dependence of the rate of evaporation from temperature has the same character. In the logarithmic form of the dependence of evaporation rate on temperature is:

$lnVandwith ap=A1-B1⋅1/T,(9)$ where VCOIthe rate of evaporation at the temperature t, °C;

T is the absolute temperature, (t+273)K;

A1B1- coefficients, and B1=E/R, where

$E=B1⋅R.(10)$ The figure 2 shows the dependence of the logarithm of the experimentally found values of the evaporation rate of the investigated liquids on the value of the inverse absolute temperature.

As can be seen in figure 2, the dependences are linear with correlation coefficient, r2not less than 0,98 that is proof that the evaporation process is described by a kinetic equation zero poradek is. This allows them to be used in the calculation of the evaporation rate for any temperature in the range of the research 10...40°C.

Table 1 shows the results of calculation of the evaporation rate of the investigated liquids experimentally found dependencies, figure 2, for selected temperatures: 10, 20, 30, 40°C. In the same table shows the values of saturated vapor pressure and volatility, calculated using the expressions (3, 4) for temperatures: 10, 20, 30, 40°C.

Confirmation of the correlation values of volatility and evaporation rate dependence is presented in figure 3 based on the data of table 1 for the temperature range 10...40°C.

Because the maximum concentration of saturated vapor are calculated values, and the values of the evaporation rate was determined experimentally, the presence of linear dependencies for all four compounds with correlation coefficient, r2not less than 0,99 confirms the objectivity of assumptions about the valuation of volatility in the rate of evaporation.

Using the data in table 1, we can construct graphs of correlation (calibration) dependency of volatility on the rate of evaporation for water, methanol, benzene and acetone as the substances selected as calibration compounds, at temperatures of 10, 20, 30 and 40°C. figure 4 shows to the relational (calibration) the dependence of volatility on the rate of evaporation for a temperature of 20°C.

 Table 1 The results of calculating the rate of evaporation, the vapour pressure and volatility of the investigated liquids Connection name Defined feature Values defined characteristics at temperature, °C 10 20 30 40 Water The evaporation rate, VCOI(mg/min 0,18 0,31 0,53 0,91 The activation energy Eexpkcal/mol 9,6 The saturated vapor pressure, P, mm Hg 9,0 18,0 34,1 64,1 Volatility, Cmaxmg/l 9,1 17,6 32,2 53,6 Methanol The evaporation rate, VCOI(mg/min 0,30 0,61 1,17 2,24 The activation energy Eexpkcal/mol 11,7 The saturated vapor pressure, P, mm Hg 54,1 94,8 159,2 266,1 Volatility, Cmaxmg/l 97,2 164,3 267,3 430,9 Benzene The evaporation rate, VCOI(mg/min 1,48 2,22 3,22 with 4.64 The activation energy Eexpkcal/mol 6.7 The saturated vapor pressure, P, mm Hg 37,0 65,1 108,9 of 182.2 Volatility, Csub> maxmg/l 162,0 273,9 445,5 722,1 Acetone The evaporation rate, VCOI(mg/min 2,10 3,72 6,30 10,59 The activation energy Eexpkcal/mol 9.5 The saturated vapor pressure, P, mm Hg 110,0 177,3 275,9 428,4 Volatility, Cmaxmg/l 358,3 559,2 840,0 1262,2

As can be seen in figure 4, the correlation is linear with correlation coefficient, r2equal to 0.94, and allows to calculate the volatility of the mixture on experimental data evaporation rate at 20°C. According to other temperatures also have a linear or close to linear, therefore, can be used as calibration curves when evaluating the volatility of mixtures of p and different temperatures.

The next phase of research was devoted to the determination of the heat of vaporization for mixtures of liquids on experimental values of volatility.

For individual substances and artificial mixtures of known composition can be calculated molecular mass of the mixture and to determine the saturated vapor pressure at different temperatures, and, with the dependence of the saturated vapor pressure on temperature, to estimate the heat of vaporization of the mixture, using the expression (5).

However, for real mixtures of complex composition determination of the molecular mass of the mixture can be difficult and unproductive work, as it requires you to spend a qualitative and quantitative analysis of a mixture of all components. Without the value of the molecular weight of the mixture it is impossible to calculate the saturated vapor pressure, and hence to determine the heat of vaporization.

Simple mathematical transformations of the expressions (3, 4) it can be shown that the dependence of the logarithm of the product of the volatility on the absolute temperature on the magnitude of the inverse absolute temperature is expressed by the equation of the straight line as the dependence of the logarithm of the pressure, the expression (3). Moreover, the value of the second coefficient In the equation of the straight line associated with the magnitude of the heat of vaporization is the same in both cases: where C is a volatile liquid at absolute temperature T;

M - molecular mass;

A, B - coefficients of linear equations.

This expression allows to determine the heat of vaporization for the mixtures according to the experimental values of volatility. The figure 5 shows the graphs of the dependencies (3) and (11) for artificial mixtures of methanol with water in a volume ratio of 1:1.

As can be seen in figure 5, direct parallel, i.e. have the same tangent angle, the same coefficient B of equation of a straight line, and hence the same value of heat of vaporization.

The equation shown in figure 5, are of the form:

lnP=22,04-5418 precision mechanical·1/T, r2=0,99;

ln(C·T)=28,01-5445·1/T, r2=0,99.

Values of the coefficient B of equation differ by not more than 0.5%.

Consequently, it is possible for an experimentally-determined values of volatility to estimate the heat of vaporization of the mixture of liquids, without the data on molecular weight and vapour pressure.

An example of the method

When checking the possibility of using correlation (graduierten the x) relationships to estimate the volatility of the mixture were prepared binary mixture of methanol with water with a volume ratio of methanol to water is 1:1, 2:1 and 1:2. The choice of the components of the mixture due to the fact that the availability of data on the saturated vapor pressure and volatility of the original mixture components will allow you to check the correct assessment of the volatility of the mixture, using the results of calculations on the basis of the law Raul /Chemical encyclopedic dictionary [Text] Moscow: Soviet encyclopedia, 1983. - 792/:

$P=Po⋅X,(12)$ where P is the saturated vapor pressure of the solvent above the solution;

Pois the saturated vapor pressure of pure solvent at the given temperature;

X is the mole fraction of the solvent in the solution.

A particular case of the application of the law of Raul for a mixture of mutually miscible liquids is the expression:

$P=∑(Pio⋅μi),(13)$ where P is the saturated vapor pressure of the mixture;

$Pio$ is the saturated vapor pressure of the individual i-th component of the mixture is ri given temperature;

µiis the mole fraction of the i-th component of the mixture in the liquid state.

The figure 6 shows the dependence of the logarithm of the experimental values of the evaporation rate of the studied two-component mixtures of methanol with water from the values of the inverse absolute temperature.

Table 2 shows the results of calculation of the evaporation rate for mixtures of methanol with water on an experimentally-determined dependencies, figure 6, for selected temperatures: 10, 20, 30, 40°C. In the same table shows the values of the molecular mass of the mixture, calculated by expression (14), and experimental values of the activation energy for the evaporation process, is found by expression (10)using the tangent of the angle of direct (figure 5), in comparison with the calculated values of activation energy, the expression (15).

Analysis of the data given in figure 6, allows to conclude that for the mixtures according to the logarithm of the rate of evaporation from the values of the inverse absolute temperature are linear with correlation coefficient, r2not less than 0.97, which confirms that the evaporation process is described by a kinetic equation of zero order. Ego has allowed us to use them to calculate the evaporation rate for any temperature in the range of the research 10...40°C (table 2). When this energy values of the asset is the AI for the mixture, found experimentally, close to the calculated values.

 Table 2 The results of the calculation of molecular weight, evaporation rate and activation energy of the evaporation process for mixtures of methanol with water Surroundthe ratio of methanol and water The mole fraction of methanolin the mixture, µ1 The molecular mass, M, g/mol The evaporation rate, VCOI(mg/min, at a temperature, t, °C The activation energy Eexpkcal/mol The activation energy Ecalckcal/mol 10 20 30 40 1:1 0,31 22,34 0,11 0,21 0,38 0,67 10,33 of 10.25 2:1 0,47 24,58 0,17 0,30 0,54 0,94 to 10.62 or 10.60 1:2 0,18 to 20.52 0,09 0,17 0,31 0,54 10,38 9.98 Note: $M=M1⋅μ1+M2⋅μ2,(14)$ where M is the molecular weight of the mixture, g/mol; M1, M2- the molecular weight of methanol and water, respectively, g/mol; µ1, µ2is the mole fraction respectively of methanol and water. $Epandwith ah=E1⋅μ 1+E2⋅μ2,(15)$ where Ecalcis the calculated value of activation energy of the mixture, kcal/mol; E1E2values of activation energy, respectively, of methanol and water (table 1), kcal/mol; µ1, µ2is the mole fraction respectively of methanol and water.

Using the calibration dependence of volatility on the rate of evaporation at temperatures of 10, 20, 30 and 40°C (figure 4) and found values for the rate of evaporation of mixtures for these temperatures (table 3), it is possible to determine the values of volatility for mixtures.

The use of artificial mixtures of known composition allows to calculate the molecular weight of the mixture and to determine the saturated vapor pressure of the mixture using the expression (4). This allows you to evaluate the correctness of the volatility of the mixture, using the results of calculations of the pressure of the mixture on the basis of the law of Raul. The results of the calculations are given in table 3.

 Table 3 The volume ratio of methanol and water Defined feature Values defined characteristics at temperature, °C 10 20 30 40 1:1 Volatility, Cmaxmg/l 22,7 42,0 of 83.4 125,2 The saturated vapor pressure, P, mm Hg 18,1 34,6 71,1 110,3 The calculated value of the pressure according to the law of Raul, Pcalc, mm Hg 23,1 41,8 72,9 a 126.7 2:1 Volatility, Cmaxmg/l 31.0 54,4 104,1 73,3 The saturated vapor pressure, P, mm Hg 22,4 40,8 80,7 138,8 The calculated value of the pressure according to the law of Raul, Pcalcmm RT. Art. 30,2 54,1 92,9 159,0 1:2 Volatility, Cmaxmg/l 19,5 36,6 74,1 99,7 The saturated vapor pressure, P, mm Hg 15,9 31,1 68,0 95,6 The calculated value of the pressure according to the law of Raul, Pcalcmm RT. Art. 17,1 of 31.8 56,6 to 100.4

Analysis of the data given in table 3, allows to make a conclusion about the legality of the determination of volatility, and it and the saturated vapor pressure of the artificial mixtures of methanol with water found on the calibration dependence of volatility on the rate of evaporation. P and maximum deviation values of pressure, calculated based on experimental data from the calculated values according to the law of Raul in all cases does not exceed 26%.

Therefore, the proposed method of determining the volatility of the evaporation rate on the basis of thermogravimetric method can be used to estimate the volatility of mixtures of liquids for any temperature from the temperature range of study.

This allowed us to determine the heat of vaporization for the studied mixtures of methanol with water experimentally found values of volatility, table 4.

From the data presented in table 4, it follows that the experimentally found values of the heat of vaporization for artificial mixtures of methanol with water is close to the calculated values, which confirms the possibility of determining the heat of vaporization values of volatility.

 Table 4 Values of the heat of vaporization for the studied mixtures of methanol with water experimentally found values of volatility The volume ratio of methanol and water mixed The values of heat of vaporization, kcal/mol ΔHthe experts ΔHtheorythe expression is s (16) 1:1 10,84 of 10.25 2:1 10,86 10,59 1:2 10,90 9,98 Note:$ΔHteaboutp=ΔH1⋅μ1+ΔH2⋅μ2,(16)$ where ΔHtheory.the heat of vaporization of the mixture, kcal/mol; ΔH1That ΔN2values of the heat of vaporization of methanol and water, kcal/mol; µ1, µ2is the mole fraction respectively of methanol and water.

Thus, it is shown that, using gravimetric data obtained on a standard thermogravimetric equipment, we can estimate the volatility and the heat of vaporization of the investigated mixtures of liquids.

1. The method for determining the volatility and the heat of vaporization of a mixture of liquid substances the speed of evaporation from a flat surface, wherein the set correlation values of volatility, calculated according to known reference data for individual liquid substances selected as the calibration fluid, the speed of evaporation, determined on the basis of data of thermogravimetric analysis carried out in isothermal mode when reaching the equilibrium state; for the studied mixtures determine the evaporation rate and the correlation found is volatility; then, using the dependence of the found values of the volatility of the temperature, determine the heat of vaporization of a mixture of liquid substances in the investigated temperature range.

2. The method according to claim 1, characterized in that the magnitude of the heat of vaporization of the mixture is determined by the value of the tangent of the slope of a plot of the linear dependence, the abscissa is the reciprocal of the absolute temperature, and the ordinate is the logarithm of the works found values of the volatility of the mixture on the size of the absolute temperature.

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EFFECT: reduced instability of amplitude and frequency of probe mechanical vibrations in analysing constant-viscosity fluids.

6 cl, 6 dwg FIELD: physics.

SUBSTANCE: signal simulator used is in form of at least micro-weighing chemically pure substances inside sealed cavities of a thermoacoustic waveguide rod (TAWR) with acoustic emission (AE) and temperature sensors, where the mass of said substances is determined with maximum accuracy and said substances have reversible anhysteretic temperature and energy of phase transitions (PT) of the first type (crystallisation/melting, evaporation/condensation), from which, in each cycle for heating and (or) cooling a sample in contact with the TAWR, by receiving AE signals of said PT and by simultaneously measuring contact temperature of the TAWR with the sample at PT points, temperature measurement channels and AE (sensors-amplifiers-converters) as a whole are checked and calibrated from temperature and energy characteristics of the PT of the first type of built-in thermodynamic acoustic-emission (TDAE) standards, by changing amplification coefficients or (and) threshold of sensitivity of measurement channels, or (and) amplitude-frequency characteristics (AFC) of temperature, electric and acoustic signal converters or (and) corresponding corrections when converting digital data to physical parameters. Possibility of TDAE standardisation is provided, which enables metrological support for thermal and (or) acoustic-emission analysis installations through dynamic and static inspection of their temperature and acoustic measurement channels.

EFFECT: increased reliability and accuracy of determining temperature and energy characteristics, stages for destruction of materials.

4 cl, 4 dwg FIELD: power industry.

SUBSTANCE: method for determining slagging characteristics of ash for power station coals at flame combustion involves low-temperature ashing of the tested coal, manufacture of test sample from ash for investigation of physical ash properties at heating within temperature of 800°-1300°C with simultaneous fixture of deformation characteristics of the sample by means of measuring tool. Heating of sample in the above temperature interval is performed at constant heating rate of not less than 1.1 deg/sec, during which there determined is dependence of deformation speed of the sample on temperature of its heating; at that, temperature of beginning of ash slagging corresponds to maximum speed of sample deformation, and temperature of load-carrying flue gases at the furnace outlet corresponds to minimum deformation speed. Two to four test samples are subject to tests, and temperatures of the beginning of slagging and load-carrying flue gases at the furnace outlet are determined as arithmetic average of the appropriate values.

EFFECT: improving accuracy of determination of slagging characteristics of ash.

2 cl, 4 dwg

FIELD: nanotechnologies.

SUBSTANCE: nanodiamond is placed into installation for annealing, hydrogen is passed through and maintained at the temperature selected from the range of (900÷1100) °C, cooled down to room temperature. X-ray diffraction pattern is taken. Additionally spectrum of electronic paramagnetic resonance (EPR) is registered at room temperature. Availability of metal phases is identified.

EFFECT: invention makes it possible to increase sensitivity of magnetic admixtures content detection in nanodiamonds of detonation synthesis.

2 cl, 6 ex FIELD: physics, optics.

SUBSTANCE: invention relates to methods of determining physical conditions at which phase transitions in metals and alloys take place. The method is based on joint analysis of the image of fragments of the surface of analysed material and luminance spectra of visible light reflected from the said surface, taken before and after the external physical action causing the phase transition. The analysis results are processed using special computer software.

EFFECT: invention simplifies diagnosis of phase transitions, increases accuracy and degree of automation of processing experimental results.

11 dwg FIELD: investigating or analyzing materials.

SUBSTANCE: thermograph comprises differential thermocouple and aluminum thermal unit provided with two symmetrically arranged cylindrical holes for crucible with specimen and standard. The crucibles are made of cylinders with caps provided with copper pipes for hot junctions of Chromel-cupel thermocouples. The wires of the thermocouples are housed in the two-channel ceramic rods. The thermoelectric heating of the unit is provided with the use of temperature-sensitive resistor made of nichrome wire. The unit is mounted in the steel sealed housing with a lid and provided with a device for locking it inside the housing during cooling and heating.

EFFECT: simplified design and enhanced accuracy of measuring.

1 dwg FIELD: polymorph processes in metals and electro-conducting materials.

SUBSTANCE: method of measuring temperature of polymorph transformation is based upon heating for hardening till temperature providing free sag of rigidly tight sample. The temperature should correspond to α→β polymorph transformation.

EFFECT: improved precision of measurement.

5 dwg FIELD: measurement technology.

SUBSTANCE: device has trier provided with holder and measuring probe provided with thermocouple placed inside the trier. Thermocouple is used which has time constant less than 1,5 sec. Volume of part of thermocouple submerged into salt melt relates to volume of cup of the trier as (5x10-3-10-2):1. Precise value of temperature can be achieved as well as high degree of reproducibility.

EFFECT: improved precision; prolonged service life of thermocouple.

9 cl, 4 dwg FIELD: test equipment.

SUBSTANCE: metal probe of vibration viscosimeter is disposed inside metal dish in tested fluid to make it thermally isolated from outer space. Viscosimeter is excited with preset frequency and with preset force. Temperature of the dish is changed monotonously and continuously to follow specified rule at speed to exceed speed of establishing processes of change in temperature of tested liquid inside the dish. Temperature of the probe is measured within whole preset range of changes in temperature of the dish as well as amplitude and/or phase and/or frequency of oscillations of the probe. Density, viscosity, thermal conductivity, heat capacity and thermal diffusivity of tested fluid are measured depending on fluid's temperature from the relation of heat diffusivity of fluid and from the relation of viscosimeter's probe forced oscillations. The main feature of the device realizing the method has to be the metal probe of viscosimeter made in form of copper ball or silver ball disposed in fluid for thermal insulation onto rod made of thermo-insulating material. Measuring converter of probe's temperature is made in form of thermocouple and built inside probe. Second measuring converter of probe's temperature, also made in form of thermocouple, is placed onto bottom of metal dish thermally insulated from environment.

EFFECT: improved efficiency of test.

10 cl, 5 dwg FIELD: inspection of quality of oil products.

SUBSTANCE: permanent-weight lubricant is subject to heating in thermo-stable glass cup at three temperatures at least, which temperatures exceed that one of beginning of oxidation and then it is subject to mixing by glass mixer at constant speed during 12 hours or less. Samples for photometry are selected in equal time intervals. Factor of absorption of light flux by oxidized oil Ability to evaporation is measured by weighing sample before and after test. Graphical dependences of theses parameters are built relatively temperature of testing. Thermal-oxidative stability of lubricant is determined by critical temperature of service ability, by temperature of beginning of oxidation and by temperature of beginning of oxidation.

EFFECT: improved efficiency of measurement.

2 dwg FIELD: investigating or analyzing materials.

SUBSTANCE: method comprises heating specimens to be analyzed with a rate of 10 deg/min, using standard initial polymineral clays, selecting temperature intervals 20-200°C, 600-800°C, and 20-100° C from the thermo-analytic curves of the standards, determining the reference values in the intervals, determining mass losses, and choosing maximum values of the mass losses in the intervals for the calculation of the fraction ration of clays.

EFFECT: enhanced accuracy of measurements.

6 dwg, 1 tbl, 6 ex FIELD: measurement technology.

SUBSTANCE: method involves carrying out experimental temperature measurements of cooling liquid avalanche dissociation on hot surface under static conditions, without liquid flow being arisen.

EFFECT: simplified cooling liquid quality control process; reduced tested substance quantity in samples under test; personnel safety in carrying out tests.

1 dwg FIELD: measuring technique.

SUBSTANCE: method comprises testing two samples of the lubricant of the same mass, the first sample being tested without catalyzer and the second sample being tested in the presence of catalyzer, determining transparency coefficient by means of photometric measurements, plotting time dependences of the transparency coefficient, and determining oxidation stability of the lubricant from the equation presented.

EFFECT: enhanced precision.

3 dwg, 1 tbl FIELD: measuring technique.

SUBSTANCE: while warming sample up, average value of square of voltage of thermal electrical; fluctuations is measured at terminals of measuring converter. Maximal value, which corresponds to glass transition temperature, is measured, at which temperature the value of dielectric permeability is found and value of hardness coefficient is calculated. Method can be used for measurement of equilibrium hardness coefficient of polymer chains for polymers in unit.

EFFECT: improved precision of measurement.

1 dwg, 6 tbl FIELD: thermometry.

SUBSTANCE: method provides usage of temperature detectors to transform electric signal, and identification of type of phase transition. Electric Signal from temperature detector is corrected for value of electric signal which is generated by phase transition of material. Correcting electric signal is achieved by means of additional probe.

EFFECT: improved precision of measurement.

4 cl, 9 dwg 