CS272461B1 - Method for determining individual members of a mixture of carbonate minerals - Google Patents

Abstract

The solution concerns the possibility of using the manometric method for the determination of carbonates, or rather their isomorphic members. The essence of the solution is that after the completion of the manometric analysis, the amount of insoluble residue in the reaction solution is determined, with which the carbonate content in the sample under investigation is converted to 100% carbonate, the difference between the calculated value of carbon dioxide in the sample under investigation and the calibration value of carbon dioxide, one of the extreme members of the respective carbonate mixture, is determined, then the difference between the calibration values of carbon dioxide for the given extreme members is determined, from the ratio of the calibration difference and the determined difference of carbon dioxide, the percentage representation of one extreme member in the sample in 100% carbonate is determined, after conversion to the actual carbonate content in the sample, the percentage representation of the second extreme member is determined by subtracting the percentage representation of the first extreme member and the insoluble residue from the value 100.

Description

The invention relates to a method for determining the individual members of a mixture of carbonate minerals by a manometric method. '

Carbonates, especially Mg-Fe carbonates, occupy an important position in the Spiš-Gemer Ore Mountains and are among the most widespread minerals. These are mainly carbonates of the isomorphic series magnesite - siderite and dolomite - ferro - dolomite. One of the reasons is that there is no suitable, fast, generally known and sufficiently reliable method for determining the individual members of carbonate mixtures.

One of the methodologies that is suitable for these determinations is the manometric method. The manometric method for carbonate hardening is not sufficiently known. We find modest data about it in the works of -.icK-rh and Canadian researchers from the beginning of the sixties, later in the work of Glagolev - Ilsker (19fi3). In our country he used this method to determine dolomite in magnesite Brežný (1963). The equipment used by these authors was not tempered and could not even be accurate, resp. based on only one quantity - measuring the rate of decomposition of carbonates.

The inaccuracies of the previous methods were eliminated by the manometric method for the quantitative determination of calcite-dolomite carbonates, published by Turan (1965), in which a tempered device is already used. Later, this method (by introducing heating during the analysis) was extended to the quantitative determination of other carbonates (Turan - Vančová 1972) and the device on which the analyzes were performed was the subject of the invention no. 187505 of 1981.

The principle manometric method is the measurement of velocity in evolution of C0 ₂ and a total volume of C0 ₂ · C0 ₂ release rate of a given number of divisions extruded methylene iodide in the time limit of 30 seconds and 30 minutes that were completely decomposed quantitatively carbonate minerals soluble in dilute hydrochloric acid cold (calcite, aragonite, dolomite, ankerite, smitsonite, stroncianite, malachite and azurite). The total volume of CO ₂ is given by the number of parts in the manometer after repeated heating of the sample to boiling and tempering, ie when the carbonate minerals soluble in dilute hydrochloric acid only during boiling (magnesite, siderite, rhodochrosite, cerusite, witherite) are totally decomposed. Based on these two values (C0 ₂ release rate and its total volume), it is possible to identify and quantify individual carbonates or their mixtures even at very low levels in the rocks.

The disadvantage of this method is that the boundary between the individual minerals of carbonate mixtures is not always precisely determined and it is not possible to determine the individual isomorphically members of the carbonate series magnesite - siderite, or dolomite - ferro - dolomite and others.

These disadvantages are substantially eliminated by the process according to the invention, the essence of which is that after the manometric analysis the amount of insoluble residue in the reaction solution is determined, by means of which the carbonate content in the examined sample is converted to 100% carbonate. calculated value of carbon dioxide in the examined sample and calibration value of carbon dioxide, one of the extreme members of the respective carbonate mixture, then the difference between the calibration values of carbon dioxide for the given extreme members is determined, the percentage of carbon dioxide is determined from the percentage of carbon dioxide. member in the sample in 100% carbonate, after conversion to the actual carbonate content of the sample, the percentage of the second extreme member is determined by subtracting the percentage of the first extreme member and the insoluble residue from 100,

However, by means of the manometric method, it is possible to determine not only individual carbonates or their mixtures, but also individual isomorphic members, whether in the isomorphic series magnesite - siderite or dolomite - ferro - dolomite, if we know the% content of insoluble residue. In the study of carbonates, in particular sederite, it was found that in some cases the siderite contained, after deducting an aliquot of CO ₂ bound in dolomite and insoluble residue of the residue, more than CO ₂ than 100% mineral (more than 37.99% CO ₂ ). And precisely this increase in the CO ₂ content, which is proportional to the isomorphic exchange of Fe in the lattice of siderite or ferrodolomite by magnesium, is sufficient for the individual isomorphic members to be determined.

In the magnesite - siderite series, the total C0 ₂ content increases linearly from siderite - 37.99% C0 ₂ to magnesite - 52.18% C0 ₂ , which corresponds to 258 mm, resp. 354 mm C0 ₂ in manometer. In the dolomite-ferrodolomite council, this difference is smaller but sufficient. The C0 ₂ content in dolomite is 47.73%, in ferrodolomite 40.77%, which corresponds to 324 mm, resp. 276 mm C0 ₂ in manometer.

The determination is performed by determining the qualitative composition of carbonates on the basis of the rate of release of C0 ₂ and determining their quantitative representation _{from the total amount of C0 2.} After conversion to 100% carbonate (the insoluble residue is determined gravimetrically from the solution in the reaction vessel after the analysis) from the appropriate diagram, based on the amount of C0 _2, determine the quantitative composition of individual isomorphic members

The method according to the invention can be considered to be sufficiently accurate, reproducible and reliable, which is finally proved by statistical parameters when comparing it with classical chemical analysis. The standard deviation in the repeated determination of CO ₂ in one and the same sample was S = -0.10, for MgO'S = 0.32, for FeO = -0.49. In all cases, the correlation and regression coefficient had values close to 1 / r (correlation coefficient) MgO = = 0.998, r FeO = 0.996, r CaO = 1.001 b (regression coefficient) (MgO = 1.073, b FeO = 0.994, b CaO = 1.037 ). .

Example 1 ·

Pipette 50 ml of dilute HCl (1: 3) into a reaction vessel placed in an air-conditioned vessel. The ultrathermostat is turned on and the whole device is heated to 25 ° C by circulating the medium in the air-conditioning vessel and the air-conditioning cylinders of the U-manometer. Then 0.4 g of the sample is weighed into a special weigher, which after weighing is attached to a rotating spoon of the reaction vessel, which is inserted into the vessel through the side neck. After stabilizing the zero value of the manometer by turning the spoon, the sample is poured into the acid, at the same time the electromagnetic stirrer is started. _{The amount of CO 2} released is then counted on the scale of the U-manometer within the time limits of 15 seconds, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes and 30 minutes.

During the tempering of the apparatus, a dried circular section of filter paper (medium speed filter) is weighed to a constant weight, through which the contents of the reaction vessel are filtered after completion of the reaction. The filter paper is dried to constant weight and weighed again. The amount of insoluble residue is determined from the difference in weight.

Calibration: As this is a calibration method, the apparatus must be calibrated first. This is done using a carbonate mineral with a known CO ₂ content, most often using pure calcite. A sample of carbonate with a known CO ₂ content is analyzed several times under the same conditions as described above by varying the sample weight (0.1-0.2-0.2-0.3-0.4-0.5 g). The measured values during repeated determinations must not exceed the tolerance - 1 mm volume C0 _2> A calibration curve is constructed from the measured C0 _{2 values by plotting the known C0 2} content in% on the x-axis and the measured C0 ₂ values in mm on the y-axis.

The following record was obtained during the calibration of the apparatus:

No. of samples Pressure / temperature Weighing Č.reak.n. Decomposition rate calcite 760/25 ° C 0.4 1 15 - 270 mm 1 '- 279 mm 2 '- 286 mm 3 '- 291 mm 4 '- 295 mm

CS 272461 Bl

No. of samples Pressure / temperature Weighing Č.reak.n. Faster decomposition • 5 ’- 296 mm 10 ’- 296 mm 15 '- 296 mm 30 '- 296 mm

For other carbonates (pure dolomite, magnesite and siderite) whose total C0 ₂ content is known are calculated! corresponding values of C0 ₂ in mm in proportion, for example;

47.73 x 296 dolomite = -------------- = 321.31 mm CO2

43.97

In our case, calcite with a content of 43.97% C0 ₂ corresponded to a measured value of 296 mm, dolomite with a C0 ₂ content of 47.73% would correspond to an ^r value of 321.31 mm, magnesite with a C0 ₂ content of 52.18% would correspond to a value of 351, 27 mm and siderite with a C0 ₂ content of 37.99% will correspond to a value of 255.74 mm.

The following values were taken into account in the analysis of dolomitic limestone; 15210 mm, 1 - 242 mm, 2 '- 258 mm, 3' - 263 mm, 5 '- 277 mm, 10282 mm, 15' - 290 mm, 30290 mm,% NZ = 2.75.

Subtracting the determined amount of insoluble residue (NZ) from 100 to determine the carbonate content of the sample analyzed.

100 - 2.75 = 97.25

Convert the measured (100: 97.25 = x; 290) amount of CO2 to 100% carbonate content according to the proportions

290 x 100 x = -------------- = 298.20 mm

97.25

Calculate the difference between the calculated amount of C0 ₂ for the analyzed sample if it were 100% carbonate and the calibration value for 100% calcite (in our case 296)

298.2 (calculated hours) - 296 (calibration hours) = 2.2 mm.

The difference between the C0 ₂ calibration values measured for 100% calcite (296) and 100% dolomite (321.31) is 25.31 mm. In our case, the difference between the analyzed sample and 100% calcite was 2.2 mm. This difference by proportions (25.31: 2.2 = 100: x) corresponds to the% proportion of dolomite in the sample

2.2 x 100 _x = -------------- = 8.45

25.31

The percentage of calcite in the sample is determined by adding the% dolomite and insoluble residue to 100

100 - (8.45 + 2.75) = 88.80

CS 272461 Bl

The dolomitic limestone sample analyzed contained 88.80% calcite, 8.45% dolomite and 2.75% insoluble residue.

The representation of calcite and dolomite in the analyzed sample of dolomitic limestone can also be calculated directly from the measured CO2 values. This method of calculation is necessary if the sample contains a lot of insoluble residue.

_{The amount of C0 2} released from the analyzed sample over a period of 3 minutes (these correspond to the amount of C0 ₂ corresponding to the calcite) is deducted from the total amount of C0 ₂ released during the decomposition of the analyzed sample. The difference between the total amount of C0 ₂ and the amount released in the time limit of 3 minutes corresponds to the amount of C0 ₂ released by the decomposition of dolomite.

290 - 263 = 27

The percentage of calcite and dolomite is calculated in proportion to their calibration values

263 x 100 calcite (296: 263 = 100: x) x = --------------- = 88.85

296 x 100 dolomite (321.31: 27 = 100: x) x = -------------- = 8.40

321.31

Subtracting the% of calcite and dolomite from 100 gives the non-carbonate content, which ideally corresponds to an insoluble residue.

100 - (88.85 + 8.40) = 2.75

The composition of the analyzed dolomitic limestone sample calculated in this way was equal to 88.85 ¾ calcite, 8.40 ^! Dolomite and 2.75% non-carbonate content.

The mineral composition of the analyzed sample can be converted to MgO, CaO and CO ₂ oxides by means of proportions.

Example 2 (carbonate of the isomorphic series magnesite - siderite)

The analysis is carried out according to the procedure described in Example 1, except that the sample is completely dissolved in hydrochloric acid only at boiling. Therefore, after 30 minutes, the reaction vessel is removed from the air-conditioning vessel, and its contents are repeatedly heated to boiling 2 to 3 times. After completion of the reaction, the reaction vessel is placed back in an air-conditioned vessel, warmed to 25 ° C and the value of the total amount of CO _{2 released is read on a U-manometer.}

The following values were measured during the analysis: 15- 0 mm, 12 mm, 24 mm, 36 mm, 5'- 9 mm, 15'- 24 mm, 30'- 38 mm, - 285,13 mm, NZ = 3,0

According to the initial zero rate of decomposition and the amount of CO ₂ released over a time limit of 30 minutes, it can be said that the sample does not contain other carbonates.

Subtract the determined amount of NZ from 100 to determine the% carbonate content of the sample

100 - 3 = 97.

The measured total amount of CO ₂ per 100% carbonate content is added according to the proportions (100: 97 = X: 205.15).

CS 272461 Bl

285.13 x 100 _x ---- 293.95

From the relevant diagram for minerals of the isomorphic series of magnesium-sideriums by plotting a line from the measured and recalculated amount of C0 ₂ in the analyzed sample (in our case □ d value 293.05) on the curve and running the perpendicular to the individual scales to determine the amount of MgO, C0 ₂ and ( FeO + MnO + CaO). In our case, the analyzed sample contains 19.13 k MgO, 37.21% FeO + MnO + CaO and 43.66% CO ₂ in 100% carbonate, which represents the limit.

The diagram for minerals of the magnesite - siderium isomorphic series has the measured and recalculated CO _{2 contents plotted on the y - axis and the calculated calculated MgO, CO 2} and FeO + MnO + CaO contents on the x - axis. The whole diagram is divided into 6 fields, the boundaries of which are given by the definition of single-faced isomorphic members of this series according to Meixner.

Since the analyzed sample contains only 97% carbonates, it is possible to recalculate the sulphated contents of monovalent oxides in 100% carbonaceous to the appropriate value x 19.13

MgO (100: 97 = 19.13: x) x = ---------------- = 18.56

100 x 37.21

FeO (100: 97 = 37.21: x) x = ----------------- = 36.09

100 x 43.66

C0 ₂ (100: 97 = 43.66: x) X = ---------------- = 42.35

100

This last step is usually not done, as we are interested in the Mg · Fe ratio in the carbon monoxide during the isomorphism study.

Example 3 (carbon of the isomorphic series of dolomites - ferrodolecmit)

The analysis is carried out in the same way as in Example 1.

We also measured values: 15-6 mm, 1'- 43 mm, 2'- 79 mm, 3'- 123 mm, 5'- 180 mm, 15 '- 288 mm, 20' - 293 mm, 25 '- 295 mm, 30'- 295 mm, NZ = 2.5%.

According to the initial faster and the amount of CO ₂ released over a time limit of 30 minutes, it can be said that the sample represents a carbonate of the dolomite group. Its calculation is analogous to the previous one. In this case, only the diagram for the minerals of the dolomite-ferrodolomite isomorphic series is used for the calculation.

The diagram for minerals of the dolomite-ferrodolomite isomorphic series has the measured values of C0 ₂ content in mm plotted on 100-axis and recalculated to 100% carbonate, and the corresponding contents of MgO, CaO, C0 ₂ and FeO + MnO on the x-axis. The whole diagram is divided into 4 fields, the boundaries of which are given by the definition of individual isomorphic members - dolomies, Fe-dolomias, ankerias, ferrodolomas.

In our case, the calculation is as follows:

CS 272461 Bl

100 - 2.5 = 97.5 (100; 97.5 = x: 295), x = 302, 56 mm

From the diagram for the value of 302.56 mm CO ₂ , 44.94% CO ₂ , 28.63% CaO, 13.11% MgO, 13.31 lysed sample lies in the ankerite field.

deducted the following oxide values: FeO. According to the detected values of oxides and

Claims (1)

CS 272461 B1 6 100 - 2.5 = 97.5 (100; 97.5 = x: 295), x = 302, 56 meters The following oxide values were subtracted from the diagram over 302.56 mm CO2: 44.94% CO 2, 28.63% CaO, 13.11 '-s MgO, 13.31 FeO. According to the found values of the oxides, the analyzed sample lies in the ankerite field. OBJECT OF THE INVENTION The method of determining individual members of a carbonate mineral mixture by means of a manometric method by measuring the total amount of carbon dioxide liberated from the carbonate minerals by the action of dilute hydrochloric acid, characterized in that after completion of the manometric analysis the amount of insoluble residue in the reaction solution is determined by converting the carbonate content in the sample to be examined for 100% carbonate, found the difference between the calculated value of carbon dioxide in the sample of interest and the calibration value of carbon dioxide, one of the extreme members of the respective carbonate mixture, then the difference between the carbon dioxide calibration values for the other end members , for the ratio of the calibration difference and the determined carbon dioxide difference, the percentage of one extreme member in the sample in 100% carbonane is determined, after conversion The percentage of the second extreme member is determined by subtracting the percentage of the first extreme member of the insoluble residue from 100 to the actual carbonate content of the sample.