Test method for mixed catalyst solution of cobalt acetate, manganese acetate and hydrobromic acid (2)

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The mass fraction w _{1 of} manganese (Mn ²⁺ ) content , expressed in %, is calculated according to formula (1):

Where:

V— The value of the volume of the standard titration solution (3.

V0—the value of the volume of the standard potassium permanganate titration solution (3.

c— The exact value of the concentration of potassium permanganate standard titration solution, the unit is moles per liter (mol/L);

m ₁ —The value of the mass of the sample, in grams (g);

M—The value of the molar mass of manganese (4/5Mn), in grams per mole (g/mol) (M=43.

The calculation result is expressed to two decimal places

Take the arithmetic average of the two parallel determination results as the determination result, and the absolute difference between the two parallel determination results shall not exceed 0.

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Determine the total amount of cobalt (Co²+) and manganese (Mn) by complexometric titration, subtract the amount of manganese (Mn ² +), and obtain the mass fraction of cobalt (Co ²⁺ ) and the measurement range of this method after conversion The mass fraction of cobalt (Co²+) is 1%～5%
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2 Reagents

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5.
2.
1 Ammonia
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5.
2.
2 Hydroxylamine hydrochloride
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5.
2.
3 Standard titration solution of disodium ethylenediaminetetraacetic acid ; c(EDTA)=0.
02mol/L
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5.
2.
4 Methyl thymol blue-sodium chloride mixed indicator: Weigh (1.
0±0.
1) g methyl thymol blue and (99.
0±0.
1) g sodium chloride respectively , put them in a mortar, mix and grind finely
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5.
3 Analysis steps

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5.
3.
1 Weigh 0.
5g～1.
0g laboratory sample, accurate to 0.
1mg, place it in an Erlenmeyer flask, add 50mL water, add 1.
5g～2.
0g hydroxylamine hydrochloride , add 50mL ammonia water, gently shake to mix it Evenly, add about 5mg of methyl thymol blue-sodium chloride mixed indicator, titrate with the standard titration solution of disodium edetate until the solution turns light blue to light purple and keeps the color unchanged for 30 seconds, which is the end point
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2 At the same time of the measurement, perform a blank test with the same amount of reagent solution without adding the sample according to the same steps as the measurement
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5.
4 Result calculation

The mass fraction w _{2 of the} content of cobalt (Co ²⁺ ) , the value is expressed in %, calculated according to formula (2):

V—The value of the volume of the standard titration solution (3.
5.
2.
3) of disodium ethylenediaminetetraacetic acid consumed by the sample, in milliliters (mL);

V ₀ —The value of the volume of the standard disodium ethylenediaminetetraacetic acid titration solution (3.
5.
2.
3) consumed by the blank, in milliliters (mL);

c— The exact value of the concentration of the standard titration solution of disodium ethylenediaminetetraacetic acid , in moles per liter (mol/L);

m—The value of the mass of the sample, in grams (g);

M ₁ -the value of the molar mass of manganese, in grams per mole (g/mol) (M ₁ =54.
94);

M ₂ ——The value of the molar mass of cobalt, in grams per mole (g/mol) (M ₂ =58.
93);

w ₁ —The mass fraction of manganese (Mn ²⁺ ) measured by 3.
4 , and the value is expressed in %
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The calculation result is expressed to two decimal places
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Take the arithmetic average of the two parallel determination results as the determination result, and the absolute difference between the two parallel determination results shall not exceed 0.
10%
.