Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Ferrous Sulfate Heptahydrate (Iron(II) Sulfate Heptahydrate)
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Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for Ferrous Sulfate Heptahydrate provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), and aqueous solubility. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Insoluble Matter, Chloride, Phosphate, Calcium, Copper, Magnesium, Manganese, Potassium, Sodium, Zinc, and Ferric Ion.
FeSO4 · 7H2O
Formula Wt 278.01
CAS No. 7782-63-0
Note: Due to inherent oxidation, ferric ion (Fe3+) content may increase on storage.
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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green or bluish-green solid quantitative analysis of nitrates melting point, forms monohydrate at 65 °C 48.6 g in 100 mL at 50 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% FeSO4 · 7H2O Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.001% Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 0.001% Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Copper (Cu) . . . . . . . . . . . . . . . . . . . . . . . . 0.005% Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.002%
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4146 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Manganese (Mn) Potassium (K) . . Sodium (Na) . . . Zinc (Zn) . . . . . Ferric ion (Fe3+)
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0.05% 0.002% 0.02% 0.005% 0.1%
TESTS
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Assay (By titration of reductive capacity of FeII). Weigh accurately about 1.0 g, and dissolve in a mixture of 100 mL of water and 3 mL of sulfuric acid that has previously been freed from oxygen by bubbling with an inert gas. Titrate with 0.1 N potassium permanganate volumetric solution to a permanent faint pink end point. One milliliter of 0.1 N potassium permanganate corresponds to 0.02780 g of FeSO4 · 7H2O.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10.0 g dissolved in 100 mL of freshly boiled dilute sulfuric acid (1:99).
Chloride Dissolve 1.0 g in 10 mL of water, and add slowly 2 mL of nitric acid. After the evolution of nitrogen oxides has ceased, dilute with water to 15 mL, filter if necessary through a small chloride-free filter, and add 1 mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.01 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of reagents used in the test. The comparison is best made by the general method for chloride in colored solutions, [Part 2: Colorimetry and Turbidimetry; Chloride].
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 2 (Extracted Molybdenum Blue)]. Dissolve 1.0 g in 10 mL of dilute nitric acid (1:5), and boil to expel the excess gases. Dilute the solution with water to 80 mL, add 5 mL of 10% ammonium molybdate reagent solution, and adjust the pH to 1.8 (using a pH meter) with dilute ammonium hydroxide (1:1). Cautiously heat the solution to boiling but do not boil, and cool to room temperature. If a precipitate forms, it will dissolve in the next operation. Add 10 mL of hydrochloric acid, dilute with water to 100 mL, and continue as described. Prepare a standard containing 0.01 mg of phosphate ion (PO4), the residue from evaporation of the amount of ammonium hydroxide used in adjusting the pH of the sample, and 5 mL of the ammonium molybdate reagent solution in 85 mL of water. Adjust the pH to 1.8 (using a pH meter) with dilute hydrochloric acid (1:9). Cautiously heat the solutions to boiling but do not boil; cool to room temperature. Add 10 mL of hydrochloric acid, and dilute with water to 100 mL. Transfer the solutions to separatory funnels, add 35 mL of diethyl ether to each, shake vigorously, and allow to separate. Draw off and discard the aqueous phase. Wash the diethyl ether phase twice with 100 mL portions of dilute hydrochloric acid (1:9), discarding the washings each time. Add 10 mL of dilute hydrochloric acid (1:9) to which has just been added 0.2 mL of a freshly prepared 2% stannous chloride reagent solution (in hydrochloric acid), shake, and allow to separate. Any blue color in the ether extract from the sample should not exceed that in the ether extract from the standard.
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4146 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Calcium, Copper, Magnesium, Manganese, Potassium, Sodium, and Zinc (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Calcium, Copper, Magnesium, Manganese, Potassium, Sodium, and Zinc
S a m p l e S t o c k S o l u t i o n . Dissolve 20.0 g of sample in 80 mL of water, transfer to a 100 mL volumetric flask, dilute to the mark with water, and mix (1 mL = 0.20 g).
For the Determination of Calcium, Copper, Magnesium, Manganese, Potassium, Sodium, and Zinc
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Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
2.0
0.05; 0.10
N/A
No
Cu
324.7
1.0
0.05; 0.10
A/A
Yes
Mg
285.2
0.50
0.005; 0.01
A/A
Yes
Mn
279.5
0.10
0.025; 0.05
A/A
Yes
K
766.5
2.0
0.02; 0.04
A/A
No
Na
589.0
0.10
0.01; 0.02
A/A
No
Zn
213.9
0.10
0.005; 0.01
A/A
Yes
*A/A is air/acetylene; N/A is nitrous oxide/acetylene.
Ferric Ion Place 0.20 g of the sample and 0.5 g of sodium bicarbonate in a dry 125 mL glass-stoppered conical flask. For the control, place 0.10 g of the sample and 0.5 g of sodium bicarbonate in a similar flask. To each flask, add 94 mL of a freshly boiled and cooled solution of dilute sulfuric acid (1:25), and loosely stopper the flasks until effervescence stops. To the control, add 0.01 mg of ferric ion (Fe3+). Add 6 mL of ammonium thiocyanate reagent solution to each flask. Any red color in the solution of the sample should not exceed that in the control.
© 2017 American Chemical Society
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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.
DOI:10.1021/acsreagents.4146 ACS Reagent Chemicals, Part 4
