Studies on the Formation of Metal Sulphate:

2-Furoic Acid Complexes (Metal: Mg, Mn, Fe, Ni, Cu, Zn, Cd)

 

Madhushree S N, Sindhu H K, Ramesh T N

Department of Studies and Research in Chemistry,

University College of Science, Tumkur University, Tumkur, India.

*Corresponding Author E-mail: adityaramesh77@yahoo.com

 

 

INTRODUCTION:

A complex compound is made up of a central metal atom or ion and additional ions or molecules (ligand) joined by a coordinate bond.¹ In their aqueous solution, these substances forms a complex ion². Coordination compounds are of three types: i) anionic complexes, ii) cationic and iii) neutral complexes.³ The diversity and versatility of ligands promotes us to explore them to combine with different types of transition metal ions to form different types of structures and interesting applications.⁴

 

Based on the nature of ligands coordinated to the central metal ion, coordination compounds/complexes classified as i) homoleptic complexes in which the central metal ion is coordinated exclusively by one type of ligand, heteroleptic complexes in which the central metal ion is surrounded by two or more different types of ligands.⁷ Several types of metal ligands have been reported. Furoic acid (C₅H₄O₃) is produced by the Cannizzaro reaction and the salts/esters of furoic acids are used in pharmaceuticals and other applications.^8-12 Furoic acid is a versatile compound with applications in various industries.^13-15 Furoic acid has a structure containing a furan ring and a carboxylic acid as functional group.¹⁶ Two different types of furoic acid exists and both are soluble in both cold and hot water.¹⁷ 3-furoic acid forms stable complexes with metal ions and also there are reports on the metal complexes having mixed ligands of which one is 3-furoic acid. 2-Furoic acid (also known as pyromucic acid) contains a furan ring and at the 2-position a carboxylic acid side-group is most widely used  as preservative in food products and as a flavoring agent.^18,19 The optical properties of single crystals of furoic acid have been reported.^20,21 Furoate complexes of transition metal furoate complexes exhibit antibacterial and antimicrobial activity.²¹ Also, Ni(II)/Cu(II)/Zn(II)-2-furoic acid complexes have been reported.²² Electron paramagnetic spectroscopic studies and the biological activity studies have been reported for Cu(II) and Mg(II) with 2-furoic acid complexes.²³ Also magnesium-2 furoic acid and magnesium:3-furoic acid single crystals have been prepared and their crystal structure data has been reported.²⁴

 

It is of general interest to study whether the active oxygen of the furan ring of 2-furoic acid can take part in chelating process like other nitrogen atom containing organic moieties such as pyridine or pyrazine. Alkali earth metal complexes with 2-furoic acid have been prepared, while, 3-furoic acid-based complexes of alkaline earth metals shows preference to act as an acceptor in intermolecular C-H---O hydrogen bond.^25,26 Several complexes containing carboxylic acid as a functional group of alkaline earth metals/transition metals have been reported.²⁷

 

Among the common physical properties, conductance is one of the simplest and easiest to carry out the measurement.²⁸ Molar conductance is a characteristic property of the chemical compound and is also been used for the determination of structure of newly prepared complexes.²⁹ The probable structure formation of coordination compounds can be established using molar conductance studies. The ring size of the ligands and stoichiometry of metal-ligand ratio can be easily predicted using molar conductance and also depending on the nature of the solvent.³⁰

 

In this article, we have explored Job’s/continuous variation, mole ratio and slope ratio methods to predict the formation of metal-2-furoic acid complexes in aqueous solutions for which different metal sulphates (Mg, Mn, Fe, Ni, Cu, Zn, Cd) have been mixed with 2-furoic acid using colorimetry and conductometry.

 

MATERIALS AND METHODS:

Chemicals Used

MgSO₄×7H₂O, MnSO₄×H₂O, NiSO₄×7H₂O, FeSO₄×7H₂O, CuSO₄×5H₂O, ZnSO₄×7H₂O 3CdSO₄×8H₂O, concentrated sulphuric acid, 2-furoic acid (Nice Chemicals India Private Limited, Metal sulphates and acetone were purchased from SD-Fine Chemicals Private Limited, India without purification.

 

Preparation of Metal Sulphate Solution:

0.1 M metal sulphate solutions were prepared by weighing known quantity of the sample and dissolving it with distilled water. For ferrous sulphate solution preparation, 0.5mL of concentrated sulphuric acid was added to the sample prior to addition of distilled water. The details are given in Table 1.

 

Table 1. Weights of the metal sulphate taken to prepare 0.1 M solutions

Metal sulphate solution (0.1 M)	Quantity in g
Magnesium sulphate hexahydrate	2.464
Manganese sulphate hydrate	1.6902
Ferrous sulphate hexahydrate	2.7801
Nickel sulphate hexahydrate	2.806
Copper sulphate pentahydrate	2.496
Zinc sulphate hexahydrate	2.854
Cadmium sulphate dihydrate	2.5651

 

Preparation of 2-Furoic Acid Solution:

1.1208 g of 2-furoic acid was dissolved using distilled water and made up to 100 mL. The colorimetric and conductometric measurements were carried out at 25-28°C.

 

PART-A

Colorimetric Measurements

Job’s method:

l_max for ferrous sulphate-furoic acid, nickel sulphate-furoic acid and copper sulphate-furoic acid solutions were determined by varying the filters of different wavelength and the absorbance values were recorded for the most intense colored solution using Elico 63 colorimeter (510nm for copper sulphate-furoic acid and 670nm for nickel sulphate-furoic acid and copper sulphate-furoic acid). The different concentration of metal sulphate and 2-furoic acid solutions prepared are given in Table 2. Absorbance were recorded for the solution mixtures of different concentrations, 2-furoic acid solution was used a reference (blank) for all the three metal sulphate solutions measurements.

 

Table 2. Different set of solution mixtures containing metal sulphate and 2-furoic acid (for colorimetric measurements)

Sl. No.	Metal sulphate solution (Metal: Fe,Ni,Cu)	2-furoic acid solution
	Volume (mL)
1	2	18
2	4	16
3	6	14
4	8	12
5	10	10
6	12	8
7	14	6
8	16	4
9	18	2

 

Mole Ratio Method:

The different concentrations of metal sulphate solution and 2-furoic acid were prepared as given in Table 3. Absorbance values were recorded for the given solution mixtures.

Table 3. Different solution mixtures containing metal sulphate and 2-furoic acid (for colorimetric measurements)

Sl. No.	Metal sulphate solution (Metal: Fe, Ni, Cu)	2-furoic acid solution	Mole ratio
	Volume (mL)
1	2	1	1:0.5
2	2	2	1:1
3	2	3	1:1.5
4	2	4	1:2
5	2	5	1:2.5
6	2	6	1:3
7	2	7	1:3.5
8	2	8	1:4
9	2	9	1:4.5
10	2	10	1:5

 

Slope Ratio Method:

Metal Sulphate Concentration Constant:

Fixed volume of metal sulphate solution was taken in a beaker (18mL) and to it, 2-furoic acid solution was added at regular intervals (1mL each) and the changes in the absorbance values were recorded (see Table 4).

 

Table 4. Volume of metal sulphate solution is fixed constant and the volume of 2-furoic acid is varied: (for colorimetric measurements)

Sl. No.	Metal sulphate solution (Metal: Fe, Ni, Cu)	2-furoic acid solution	2-furoic acid solution
	Volume (mL)		Concentration (M)
1	18	1	0.0052
2	18	2	0.01
3	18	3	0.014
4	18	4	0.018
5	18	5	0.02
6	18	6	0.025
7	18	7	0.028
8	18	8	0.03
9	18	9	0.033
10	18	10	0.035
11	18	11	0.037
12	18	12	0.04
13	18	13	0.041
14	18	14	0.043
15	18	15	0.045
16	18	16	0.047
17	18	17	0.048
18	18	18	0.05
19	18	19	0.051
20	18	20	0.0526

 

Ligand concentration constant

In second set of experiments, fixed volume of ligand solution was taken in a beaker (18mL) and to it, metal sulphate solution was added at regular intervals (1mL at a time) and the changes in the absorbance values were recorded (see Table 5).

 

Table 5. Volume of 2-furoic acid solution is fixed constant and the volume of metal sulphate solution varied (for colorimetric studies)

Sl. No.	2-furoic acid solution	Metal sulphate solution (Metal: Fe, Ni, Cu)	Metal sulphate solution
	Volume (mL)		Concentration (M)
1	18	1	0.0052
2	18	2	0.01
3	18	3	0.014
4	18	4	0.018
5	18	5	0.02
6	18	6	0.025
7	18	7	0.028
8	18	8	0.03
9	18	9	0.033
10	18	10	0.035
11	18	11	0.037
12	18	12	0.04
13	18	13	0.041
14	18	14	0.043
15	18	15	0.045
16	18	16	0.047
17	18	17	0.048
18	18	18	0.05
19	18	19	0.051
20	18	20	0.0526

 

PART-B:

Conductance Measurements:

Job’s method:

The different concentration of metal sulphate and 2-furoic acid solutions were prepared as given in Table 6. Conductance of the solution mixtures of different concentrations were recorded.

 

Table 6. Different solution mixtures containing metal sulphate and 2-furoic acid (for conductance measurements)

Sl. No.	Metal sulphate solution (Metal: Mg, Mn, Fe, Ni, Cu, Zn, Cd)	2-furoic acid solution
	Volume (mL)
1	2	18
2	4	16
3	6	14
4	8	12
5	10	10
6	12	8
7	14	6
8	16	4
9	18	2

 

Mole Ratio Method:

The different concentrations of metal sulphate solution and 2-furoic acid were prepared as given in Table 7. Conductance values were recorded for the given solution mixtures.

 

Table 7. Different solution mixtures containing metal sulphate and 2-furoic acid (for conductance measurements)

Sl. No.	Metal sulphate solution (Metal: Mg, Mn, Fe, Ni, Cu, Zn, Cd)	2-furoic acid solution	Mole ratio
	Volume (mL)
1	2	1	1:0.5
2	2	2	1:1
3	2	3	1:1.5
4	2	4	1:2
5	2	5	1:2.5
6	2	6	1:3
7	2	7	1:3.5
8	2	8	1:4
9	2	9	1:4.5
10	2	10	1:5
11	2	11	1:5.5
12	2	12	1:6

 

Slope Ratio Method:

Metal Sulphate Concentration Constant:

Fixed volume of metal sulphate solution was taken in a beaker (18mL) and to it, 2-furoic acid solution was added at regular intervals (1mL at a time) and the changes in the conductance values were recorded (see Table 8).

 

Table 8. Volume of metal sulphate solution is fixed constant and the volume of 2-furoic acid is varied (for conductance measurements)

Sl. No.	Metal sulphate solution (Metal: Mg, Mn, Fe, Ni, Cu, Zn, Cd)	2-furoic acid solution	2-furoic acid solution
	volume (mL)		Concentration (M)
1	18	1	0.0052
2	18	2	0.01
3	18	3	0.014
4	18	4	0.018
5	18	5	0.02
6	18	6	0.025
7	18	7	0.028
8	18	8	0.03
9	18	9	0.033
10	18	10	0.035
11	18	11	0.037
12	18	12	0.04
13	18	13	0.041
14	18	14	0.043
15	18	15	0.045
16	18	16	0.047
17	18	17	0.048
18	18	18	0.05
19	18	19	0.051
20	18	20	0.0526

 

Ligand Concentration Constant:

In second set of experiments, fixed volume of ligand solution was taken in a beaker (18mL) and to it, metal sulphate solution was added at regular intervals (1mL at a time) and the changes in the conductance values were recorded (see Table 9).

 

Table 9. Volume of 2-furoic acid solution is fixed constant and the volume of metal sulphate solution varied (for conductance measurements)

Sl. No.	2-furoic acid solution	Metal sulphate solution (Metal: Mg, Mn, Fe, Ni, Cu, Zn, Cd)	Metal sulphate solution
	Volume (mL)		Concentration (M)
1	18	1	0.0052
2	18	2	0.01
3	18	3	0.014
4	18	4	0.018
5	18	5	0.02
6	18	6	0.025
7	18	7	0.028
8	18	8	0.03
9	18	9	0.033
10	18	10	0.035
11	18	11	0.037
12	18	12	0.04
13	18	13	0.041
14	18	14	0.043
15	18	15	0.045
16	18	16	0.047
17	18	17	0.048
18	18	18	0.05
19	18	19	0.051
20	18	20	0.0526

 

PART-C

Preparation of metal sulphate-2-furoic acid complex by solvent evaporation method:

Metal sulphate (1mmol) and 2-furoic acid (1mmol) were taken in separate beakers and dissolved in minimum quantity of water, then both the solutions were mixed thoroughly with constant stirring. The solution mixture was added to a beaker containing 50 to 60mL of acetone. The solution mixture was heated on a hot plate to evaporate the solvent mixture present in it. The residual solid obtained is cooled to room temperature, dried and grind to fine powder. The quantity of reagents used for the preparation of the above are given in the Table 10.

 

Table 10. Details about the quantities of metal sulphate, 2-furoic acid and the conditions at which metal sulphate:2-furoic acid complexes prepared

Reagent	Weight ratio of metal sulphate:2-furoic acid (g:g)					Volume of water (mL)	Volume of acetone (mL)
	1:1	1:2	1:3	1:4	1:6
Magnesium sulphate	0.246:0.11	0.246:0.22	0.246:0.33	0.246:0.44	0.246:0.67	till the solids dissolve completely in separate beakers	60
Manganese sulphate	0.169:0.11	0.169:0.22	0.169:0.33	0.169:0.44	0.169:0.67		60
Ferrous sulphate	0.278:0.11	0.278:0.22	0.278:0.33	0.278:0.44	0.278:0.67		60
Nickel sulphate	0.262:0.11	0.262:0.22	0.262:0.33	0.262:0.44	0.262:0.67		60
Copper sulphate	0.2496:0.11	0.2496:0.22	0.2496:0.33	0.2496:0.44	0.2496:0.67		60
Zinc sulphate	0.2875:0.11	0.2875:0.22	0.2875:0.33	0.2875:0.44	0.2875:0.67		60
Cadmium sulphate	0.7695:0.11	0.7695:0.22	0.7695:0.33	0.7695:0.44	0.7695:0.67		60

 

RESULTS AND DISCUSSION:

PART-A (Colorimetric Measurements)

Job’s method:

It is also called continuous variation method in which variations are made for the solution containing metal ion (M) and ligand (L) with total volume is kept constant.³¹

For reaction,

 

                M+nL --------> ML_n                                           

 

K=    where, K=equilibrium constant

 

The ratio of L/M is satisfied for a maximum concentration of complex in which only species absorbing in the spectral region then the plot of additive property v/s composition of the solution to give a curve with the maximum corresponding to the formulae of the complex. The most commonly utilized solution property for determining Job's plots is absorbance. The ratio of the number of moles of any two reactants involved in the formation of a compound is known as the mole ratio. The mole ratio approach involves mixing different amounts of the metal sulphate and 2-furoic acid to prepare a series of solutions while maintaining the total molar concentration fixed. In Figure 1(b) is shown the plot of absorbance of each solution against the mole ratio of metal sulphate(s)/2-furoic acid. A control experiment was performed in which the metal sulphate solution without 2-furoic acid (water was used to fix the total volume and metal sulphate concentration constant) and their absorbance values can be seen in Figure 1(a). On addition of 2-furoic acid to metal sulphate solution does not change the colour of the solution and no parabolic curve indicates that the metal-2-furoic acid complex do not form. In case of ferrous-sulphate/nickel sulphate:2-furoic acid studies, marginal increase in the absorbance have been observed. 

 

Mole Ratio Method:

Mole ratio method consists of measuring the absorbance of solution of metal and ligand in which the volume of metal solution is fixed constant and ligand concentration are varied and vice versa.³² In this method the amount of 2-furoic acid in each solution is varied while maintaining metal sulphate content constant, resulting in a series of solutions. A plot of absorbance versus mole ratio of metal sulphate to 2-furoic acid gives a straight line indicates the formation of a stable complex, and reaches a point corresponding to the specific mole ratio of metal sulphate: furoic acid. This may form a weak complex and a weak wavy curve is observed, and the formation of these complexes is ambiguous.

 

Slope Ratio Method:

Slope ratio method is used when only one complex is formed at a time for the reaction.

                             mM + nL   ------->   M_mL_n7

 

The concentration of the complex prepared with respect to metal (M) (fixed) and titrated against ligand. Similarly keeping large excess of the ligand, the metal sulphate/metal concentration is varied. If more than one complex is formed at a time, then this method is not applicable and the equilibrium is disturbed. The slope ratio method is used to determine the stoichiometry of metal sulphate-2-furoic acid complexes in solution. The change in absorbance as 2-furoic acid concentration varies; while keeping the metal sulphate concentration constant has been recorded and the data is shown in Figure 3. The slope ratio was analyzed and the details are given in Table 11.  The slope ratios for the nickel sulphate to 2-furoic acid and copper sulphate to 2-furoic acid is approximately 1:1 indicating the formation of 1:1 metal complex. Ferrous sulphate: - 2 -furoic acid data is non-linear, hence could not be analysed.

 

Fig 1. Continuous variation method A: a) ferrous sulphate:2-furoic acid; b) ferrous sulphate: water, B: a) nickel sulphate:2-furoic acid; b) nickel sulphate: water, C: a) copper sulphate:2-furoic acid; b) copper sulphate: water (colorimetry)

 

PART-B:

Conductance Measurements:

Molar conductance values provides information in determining whether the complex exists as a simple, ionized species or as a neutral, non-ionized entity. High molar conductance values indicates the presence of free ions or highly charged complexes, indicating ionic or partially ionic complexes. Conversely, low molar conductance values imply the formation of neutral or less dissociated complexes. By comparing the experimental molar conductance with theoretical values, we can infer the stoichiometry and the extent of ionization of the complex, resulting in the elucidation of its structure and properties. Thus, molar conductance serves as a crucial parameter for predicting the nature of metal-ligand complexes in solution, guiding further structural and thermodynamic studies.

 

Fig 2. Mole ratio method A) ferrous sulphate:2-furoic acid; B) nickel sulphate:2-furoic acid; C) copper sulphate:2-furoic acid (colorimetry)

 

Table 11: Results of slope ratio method for metal sulphate:2 furoic acid

No.	Metal sulphate constant and 2-furoic acid varied	Linear fit (R2)	Slope	2-furoic acid constant and metal sulphate varied	Linear fit (R2)	Slope	Slope ratio
1	Ferrous sulphate	Non linear	5.9283	Ferrous sulphate	Non-linear curve	-	-
2	Nickel sulphate	0.9333	2.1724	Nickel sulphate	0.8857	1.9820	0.91
3	Copper sulphate	0.94998	4.3673	Copper sulphate	0.96613	5.1399	1.17

Fig 3. Slope ratio method: Metal Sulphate Concentration Constant- A) ferrous sulphate:2-furoic acid, B) nickel sulphate:2-furoic acid, C) copper sulphate:2-furoic acid; Furoic Acid Concentrations Constant- D) ferrous sulphate:2-furoic acid; E) nickel sulphate:2-furoic acid; F) copper sulphate:2-furoic acid; b) (colorimetry)

 

Molar conductance data helps to establish if the complex is a non-ionic, neutral or an ionized species. High molar conductivity values point to highly charged complexes or free ions, therefore implying ionic or partially ionic complexes. Low molar conductivity values, in contrast, suggest the formation of neutral or less dissociated complexes. Comparing the experimental molar conductivity to theoretical values allows us to obtain information about the complex stoichiometry, degree of ionization and the electrolytic behavior. Molar conductance is therefore a crucial factor for predicting the features of metal-ligand complexes in solution and guiding towards obtaining thermodynamic and structural studies. Therefore Job’s method, mole ratio method and slope ratio method have been adopted to determine the metal sulphate-2-furoic acid complex formation.

 

Continuous variation (Job’s) Method:

The molar conductance of each metal sulphate: 2-furoic acid measured at each mole fraction is shown in Figure 4. A maximum or minimum point, corresponding to the stoichiometric ratio of the complex was not observed in Figure 4 indicating uncertainty in predicting the formation of a metal sulphate:2 furoic acid complex.

 

Mole Ratio Method:

Figure 5 shows the variation of molar conductance as a function of mole ratio of metal sulphate:2-furoic acid. The molar conductivity drops gradually as the molar ratio of ligand to metal rises from 0.5 to 6. This trend points to the fact that the first high molar conductivity (149.24 at 1:0.5) relates to mostly free ions or fewer complexed species. As more ligand is added, the creation of the metal-ligand complex happens, which generally causes a reduction in free ions or changes in ionization behavior, hence lowering the molar conductance. The steady drop points to the development of a stable complex, maybe with a particular stoichiometry (likely near 1:1 or 1:2), as the conductance plateaus or minimizes at greater ligand ratios.

 

Slope Ratio Method:

The slope ratio method involves comparing the slopes of the conductance at different concentration ranges to identify the number of ions involved in complex formation. Figures 6 and 7 shows the slope ratio method with metal sulphate concentration constant with 2-furoic acid concentration varied and vice versa. The molar conductance increases gradually with concentration from approximately 40.53 to 84.75. The increase suggests ion association or complex formation in solution. 

 

At very low concentrations, molar conductance increases proportionally with concentration, indicating free ions. While at higher concentrations, the slope change (less steep or leveling off) indicates the formation of complex ions or ion pairing.

 

The slope of the initial linear portion of the molar conductance vs. concentration plot, at low concentrations where ions are fully dissociated. At higher concentrations, the conductance approaches a limiting value, indicative of ion pairing or complex formation. The slope ratio of ligand to metal ratio by conductance measurements are given in Table 12. The slope ratio of 2-furoic acid to metal sulphate ratio by molar conductance measurements are given in Table 12.

 

The slope ratio is approximately more than 1:1.14 to 1: 1.86 indicates that magnesium sulphate/manganese sulphate/ferrous sulphate/nickel sulphate and cadmium sulphate likely to form 1:1 complex with 2-furoic acid while copper sulphate forms 1:2 complex.

 

The slope ratio is approximately more than 1:1.14 to 1: 1.86 indicates that magnesium sulphate/manganese sulphate/ferrous sulphate/nickel sulphate and cadmium sulphate likely to form 1:1 complex with 2-furoic acid while copper sulphate forms 1:2 complex.

 

To make sure that the conclusions are appropriate and the molar conductance values for the metal sulphate:2-furoic acid are indeed the metal:2-furoic acid complex, we have compared the molar conductance values of  i) metal sulphate solution, ii) 2-furoic acid solution, iii) addition of metal sulphate and furoic acid molar conductance, iv) subtraction of molar conductance values of iii) from the molar conductance of metal sulphate:2-furoic acid. The measured molar conductance of metal sulphate:2-furoic acid minus the sum of the molar conductances of the metal sulpahate and 2-furoic acid would indirectly provide information about the formation/non-formation of metal-ligand complex in solution. The details for each metal sulphate:2-furoic acid at different concentrations are provided in ST-01-05 (supplementary Information). Figure 8 shows the metal sulphate percentage as a function of difference in the molar conductance to predict the non-additive behavior in the metal sulphate:2-furoic acid at different concentration ratios.

 

The metal sulphate:2-furoic acid complexes prepared by the solvent evaporation method were subjected to powder X-ray diffraction studies. All the metal sulphate:2-furoic acid at (mole ratio of metal sulphate:2-furoic acid ratio-1:1; 1:2:1:3; 1:6) exhibit the two separate compounds i.e. metal sulphate hydrate and 2-furoic acid in their diffraction patterns ruling out the formation of thermodynamically stable compounds in solid phase.

 

CONCLUSION:

The metal sulphate:2-furoic acid complex formation was investigated by using Job’s method, mole ratio method and slope ratio method by colorimetry and conductometry. Colorimetric studies does not provide significant details about the formation of metal-ligand complex. Also, the major limitation is that the solutions should be colored. To overcome this limitation, conductometric studies were carried out to predict the formation of metal-ligand complexes. Job’s method and mole ratio method could not conclusively provide evidence for its formation. To pinpoint the exact ratio, typically reveals the stoichiometry of the complex, slope ratio method was examined and it provides justification for the formation of metal:2-furoic acid complex. Magnesium/manganese, nickel/zinc/cadmium favors 1:1 complex while copper might form 1:2 complex. To rule out the molar conductance contribution is a mere addition of molar conductance of metal sulphate and ligand, the differences between the two with the molar conductance of metal-ligand complex has been calculated. The results indicate that formation of metal sulphate:2-furoic acid in all the metal sulphates used in solution phase while on isolating the same in solid form leads to phase separation to its precursors. 

 

Table 12. Analysis of the molar conductance data using slope ratio method for the metal sulphate:2-furoic acid complex formation.

 

Fig 4. Continuous variation method A-F: a) 2-furoic acid, b) metal sulphate and c) metal sulphate and 2-furoic acid (conductometry)

 

Fig 5. Mole ratio method a) magnesium sulphate:2-furoic acid; b) manganese sulphate:2-furoic acid; c) ferrous sulphate:2-furoic acid d) nickel sulphate:2-furoic acid; e) copper sulphate:2-furoic acid; f) zinc sulphate:2-furoic acid; g) cadmium sulphate: furoic acid (conductometry)

 

Fig 6. Slope ratio method: metal sulfate concentration Constant- a) magnesium sulphate:2-furoic acid; b) manganese sulphate:2-furoic acid; c) ferrous sulphate:2-furoic acid; d) nickel sulphate:2-furoic acid; e) copper sulphate:2-furoic acid; f) zinc sulphate:2-furoic acid; g) cadmium sulphate:2-furoic acid (conductometry)

 

Fig 7. Slope ratio method: furoic acid concentrations constant- a) magnesium sulphate:2-furoic acid; b) manganese sulphate:2-furoic acid; c) ferrous sulphate:2-furoic acid; d) nickel sulphate:2-furoic acid; e) copper sulphate:2-furoic acid; f) zinc sulphate:2-furoic acid; g) cadmium sulphate:2-furoic acid (conductometry)

 

Fig 8. Metal sulphate (%) with difference in the molar conductance (Dm) of a) magnesium sulphate:2-furoic acid; b) manganese sulphate:2-furoic acid; c) ferrous sulphate:2-furoic acid; d) nickel sulphate:2-furoic acid; e) copper sulphate:2-furoic acid; f) zinc sulphate:2-furoic acid; g) cadmium sulphate:2-furoic acid (conductometry)

 

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Received on 26.01.2026      Revised on 27.02.2026 Accepted on 28.03.2026      Published on 27.05.2026 Available online from May 30, 2026 Asian J. Research Chem.2026; 19(3):185-198. DOI: 10.52711/0974-4150.2026.00031 ©A and V Publications All Right Reserved
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