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Potassium Permanganate 0.5 N, 1 Gallon

$135.44
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SKU: ZP1556-128
California prop 65
Description
  • What it is. This potassium permanganate solution is a 0.5 N (0.1 M) volumetric oxidizing titrant, supplied in a 1-gallon size. It is a deep purple solution for permanganometric titrations of iron, hydrogen peroxide, oxalate, and other reducing agents.
  • Normality and molarity. In acid solution, permanganate is reduced from manganese(VII) to manganese(II), gaining five electrons, so its equivalent weight is one-fifth of its formula weight, 31.61. A 0.5 N solution is therefore 0.1 M, containing about 15.80 g of KMnO4 per liter (calculated).
  • Its own indicator. Permanganate is intensely purple, while the manganese(II) product is nearly colorless. At the endpoint, the first excess drop turns the solution faint pink, so no separate indicator is needed.
  • Titrate in sulfuric acid. Permanganate titrations are run in strong sulfuric acid. Hydrochloric and nitric acids can take part in competing redox reactions and reduce accuracy, so sulfuric acid is the standard choice.
  • Standardization. Potassium permanganate is not a primary standard, so its solutions are standardized against sodium oxalate or arsenic trioxide, both available as NIST reference materials. Oxalate titrations are typically warmed to about 55 to 60 °C to speed the reaction.
  • Stability. Permanganate solutions slowly decompose, a process accelerated by light, heat, organic matter, and manganese dioxide. Brown deposits indicate decomposition. Store the solution in the dark and restandardize regularly.
  • What each milliliter titrates. One milliliter of 0.5 N permanganate oxidizes 0.5 milliequivalent of reductant, equal to 27.92 mg of iron(II), 8.505 mg of hydrogen peroxide, or 33.50 mg of sodium oxalate (calculated from equivalent weights).
  • Why 0.5 N. The higher strength suits samples rich in reductant, such as iron ores, concentrated peroxide, and oxalate assays, keeping titration volumes practical. It also serves as a stock for preparing weaker solutions by accurate dilution.
  • Calculating results. Analyte mass equals the titrant volume in milliliters multiplied by the standardized normality and by the analyte's equivalent weight in milligrams per milliequivalent. For iron(II), the equivalent weight is 55.85; for hydrogen peroxide, 17.01.
  • Where it is used. Laboratories use 0.5 N permanganate for iron determination in ores and alloys, hydrogen peroxide assays, oxalate and calcium (as oxalate) determinations, and as a stock for preparing weaker permanganate titrants. The 1 gallon size supports QC labs with high titration volumes.

Technical Specifications

Chemical Name Potassium permanganate, aqueous volumetric solution
CAS Numbers 7722-64-7 (potassium permanganate); 7732-18-5 (water)
EC Number (KMnO4) 231-760-3
Synonyms Permanganate of potash, KMnO4 solution
Formula (active) KMnO4
Formula Weight (active) 158.03 g/mol
Equivalent Weight (acid solution) 31.61 (molar = 5 x normal)
Concentration 0.5 N (0.1 M)
KMnO4 Content About 15.80 g/L (calculated)
Titration Equivalence 1.00 mL = 27.92 mg Fe(II), 8.505 mg H2O2, or 33.50 mg Na2C2O4 (calculated)
Indicator Self-indicating (faint pink endpoint)
Titration Medium Sulfuric acid
Primary Standards Sodium oxalate; arsenic trioxide
Appearance Deep purple liquid
Hazard Profile Oxidizer; stains skin; harmful to aquatic life (confirm on SDS)
Package Size 1 gallon

Applications / Common Uses

  • Iron determination: Titrates iron(II) in ores and alloys.
  • Hydrogen peroxide assay: Measures concentrated peroxide strength.
  • Oxalate and calcium: Determines oxalate and calcium precipitated as oxalate.
  • Stock solution: Dilutes to weaker permanganate titrants.
  • Redox teaching: Demonstrates self-indicating titrations.

Storage, Handling & Shipping

Store tightly closed at room temperature in a dark place, away from reducing agents, organic materials, acids, and combustibles. Light and manganese dioxide deposits speed decomposition, so protect the solution from light and restandardize periodically.

  • Incompatible materials: Reducing agents, organic materials and solvents, combustibles, concentrated acids, and peroxides.
  • Personal protection: Safety glasses and gloves; permanganate stains skin and surfaces brown.
  • Spill response: Absorb with inert, non-combustible material; reduce residues with sodium thiosulfate or bisulfite solution before cleanup.
  • First aid: Eyes: rinse with water for several minutes. Skin: wash thoroughly; brown stains fade over time.

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FAQs

Is 0.5 N potassium permanganate the same as 0.1 M?

Yes, in acid solution. Permanganate gains five electrons when reduced to manganese(II), so its normality is five times its molarity. A 0.5 N solution is therefore 0.1 M, containing about 15.80 g of potassium permanganate per liter. Normality applies to titrations in acid solution, which is how permanganate titrants are almost always used.

Why doesn't a permanganate titration need an indicator?

Permanganate is intensely purple, while its reduced form, manganese(II), is nearly colorless. As long as reductant remains, added permanganate is decolorized. A slight excess turns the solution faint pink, marking the endpoint without any added indicator. Use a white background to judge the faint pink color.

Why must permanganate titrations use sulfuric acid?

Permanganate needs strong acid to fully reduce it to manganese(II). Hydrochloric acid can be oxidized to chlorine, and nitric acid is itself an oxidizer, so both introduce errors. Sulfuric acid provides the acidity without competing redox reactions. Use the acid concentration your method specifies for consistent results.

How is potassium permanganate standardized?

Titrate it against dried sodium oxalate or arsenic trioxide, both available as NIST reference materials. For oxalate, dissolve the standard in dilute sulfuric acid, warm to about 55 to 60 °C, and titrate to the first persistent faint pink. Calculate normality from the standard mass.

Why do permanganate solutions form brown deposits?

Permanganate slowly decomposes to manganese dioxide, a brown solid, especially in light or when it contacts organic matter. Manganese dioxide also speeds further decomposition. Store the solution in the dark and restandardize it regularly, particularly if deposits appear. Filtering out the deposit before restandardizing improves stability.