Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Magnesium Oxide 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 Magnesium Oxide 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 in Dilute Hydrochloric Acid, Water-Soluble Substances, Loss on Ignition, Chloride, Nitrate, Sulfate, Sulfite, Barium, Calcium, Manganese, Potassium, Sodium, and Strontium, Heavy Metals, and Iron.
MgO
Formula Wt 40.30
CAS No. 1309-48-4
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . absorbant for colorants prior to determination; preparation of Eschka’s reagent Change in state (approximate) . . . . . . . . . . . . melting point, 2800 °C Aqueous solubility . . . . . . . . . . . . . . . . . . . . practically insoluble
SPECIFICATIONS Assay (dried basis). . . . . . . . . . . . . . . . . . . . ≥95.0% MgO Maximum Allowable Insoluble in dilute hydrochloric acid . . . . . . . . 0.02% Water-soluble substances . . . . . . . . . . . . . . . 0.4% Loss on ignition. . . . . . . . . . . . . . . . . . . . . . 2.0% Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.01% Nitrate (NO3) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Sulfate and sulfite (as SO4) . . . . . . . . . . . . . . 0.02% Barium (Ba) . . . . . . . . . . . . . . . . . . . . . . . . 0.005% Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.05% Manganese (Mn) . . . . . . . . . . . . . . . . . . . . . 5 ppm
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4205 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Potassium (K) . . . . . Sodium (Na) . . . . . . Strontium (Sr) . . . . Heavy metals (as Pb) Iron (Fe) . . . . . . . .
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0.005% 0.5% 0.005% 0.003% 0.01%
TESTS Assay (By complexometric titration of Mg). Weigh accurately about 0.5 g of the sample, previously ignited at 600 ± 25 °C. Dissolve cautiously in water and a slight excess of hydrochloric acid, transfer to a 250 mL volumetric flask, dilute to the mark with water, and mix thoroughly. Pipette 50.0 mL of this solution into a 250 mL beaker, add 50 mL of water and 0.10 mL of methyl red indicator solution, and neutralize with 10% sodium hydroxide reagent solution. Add 15 mL of pH 10 ammoniacal buffer solution, about 0.1 g of ascorbic acid, and a few milligrams of Eriochrome Black T indicator mixture. Titrate with 0.1 M EDTA volumetric solution to a blue end point. One milliliter of 0.1 M EDTA corresponds to 0.004030 g of MgO.
Insoluble in Dilute Hydrochloric Acid Dissolve 5.0 g in 125 mL of dilute hydrochloric acid (1:4), heat to boiling, and boil gently for 5 min. Digest the solution in a covered beaker on a hot plate (~100 °C) for 1 h. Filter through a tared, preconditioned filtering crucible, wash thoroughly, and dry at 105 °C.
Water-Soluble Substances Suspend 2.0 g in 50 mL of water, heat to boiling, and filter while hot. Evaporate 25 mL of the clear filtrate to dryness in a tared, preconditioned dish. Moisten the residue with 0.10 mL of sulfuric acid, ignite gently to remove the excess acid, and finally ignite at 600 ± 25 °C for 15 min.
Loss on Ignition Weigh accurately about 0.25 g in a tared, preconditioned covered platinum crucible. Ignite at 600 ± 25 °C for 15 min. Cool, and reweigh.
Chloride [Part 2: Colorimetry and Turbidimetry; Chloride]. Use 0.10 g dissolved in 10 mL of dilute nitric acid (1:9).
Nitrate [Part 2: Colorimetry and Turbidimetry; Nitrate; Procedure for Nitrate, Method 1 (Brucine Sulfate)].
For the Determination of Nitrate
S a m p l e S o l u t i o n A . Suspend 0.20 g in 3 mL of water. Dilute to 50 mL with brucine sulfate reagent solution.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4205 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
C o n t r o l S o l u t i o n B . Suspend 0.20 g in 2 mL of water and 1 mL of nitrate ion (NO3) standard solution. Dilute to 50 mL with brucine sulfate reagent solution. B l a n k S o l u t i o n C . Use 50 mL of brucine sulfate reagent solution.
Heat sample solution A, control solution B, and blank solution C in a preheated (boiling) water bath until the magnesium oxide is dissolved in A and B, then heat for 10 min more. Continue with the procedure as described.
Sulfate and Sulfite Dissolve 0.50 g in (1:1) hydrochloric acid, and evaporate to dryness on a hot plate (~100 °C). Cool, dissolve the residue in 5 mL of water, and evaporate to dryness. Cool, and dissolve the residue in 20 mL of water. Filter through a small, washed filter paper. Add two 3 mL portions of water through the filter paper, and dilute with water to 30 mL. For control, take 0.10 mg of sulfate ion (SO4) in 30 mL of water. To both, add 1 mL of (1:19) hydrochloric acid and 1 mL of 12% barium chloride reagent solution. After 30 min, sample turbidity should not exceed that of the control solution.
Barium, Calcium, Manganese, Potassium, Sodium, and Strontium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Barium, Calcium, Manganese, Potassium, Sodium, and Strontium
S a m p l e S t o c k S o l u t i o n . Cautiously dissolve 10.0 g of sample with dilute nitric acid (1:3), and digest in a covered beaker on a hot plate (~100 °C) for 15 min. Cool, transfer to a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.20 g).
For the Determination of Barium, Calcium, Manganese, Potassium, Sodium, and Strontium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ba
553.6
2.0
0.05; 0.20
N/A
No
Ca
422.7
0.20
0.05; 0.10
N/A
No
Mn
279.5
2.0
0.01; 0.02
A/A
Yes
K
766.5
1.0
0.05; 0.10
A/A
No
Na
589.0
0.002
0.01; 0.02
A/A
No
Sr
460.7
1.0
0.05; 0.10
N/A
No
*A/A is air/acetylene; N/A is nitrous oxide/acetylene.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 5.0 g in 50 mL of dilute hydrochloric acid (1:1), heat if necessary to obtain complete dissolution, and dilute with water to 150 mL. Evaporate 30 mL to dryness on a hot plate (~100 °C), dissolve the residue in 20 mL of water, and dilute with water to 25 mL. For the control, add 0.02 mg of lead to 10 mL of the sample solution, evaporate to dryness on a hot plate (~100 °C), dissolve the residue in 20 mL of water, and dilute with water to 25 mL.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4205 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Add 1.0 g to 50 mL of dilute hydrochloric acid (1:1), and boil gently for 5 min. Cool, dilute with water to 50 mL, and use 5 mL of this solution without further acidification.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4205 ACS Reagent Chemicals, Part 4
