Primary Standard — Definition, Formula, Properties & Uses | AllChemicals | AllChemicals

Also Known As	Primary titrimetric standard, standard substance, certified reference material (CRM)

What is Primary Standard?

A highly pure, stable substance of known composition used to prepare standard solutions for calibrating titrations. Properties: high purity, stability in air, non-hygroscopic, high molar mass, and reacts according to a simple stoichiometry. Examples include potassium hydrogen phthalate and sodium carbonate.

Properties & Characteristics

A primary standard is a highly pure, stable substance of known composition that can be weighed accurately and dissolved to prepare a solution of exactly known concentration without further standardisation. Requirements: (1) high purity (>99.9%); (2) stable to drying conditions; (3) non-hygroscopic; (4) high molar mass (reduces weighing error); (5) rapid and complete reaction in the intended titration. Examples: potassium hydrogen phthalate (KHP) for NaOH standardisation; Na₂CO₃ for HCl; K₂Cr₂O₇ for sodium thiosulfate.

Uses & Applications

Primary standards are used to standardise (determine exact concentration of) secondary standard solutions (NaOH, HCl, KMnO₄, Na₂S₂O₃). They are also used directly in titrations requiring a primary standard of the titrant. NIST and IUPAC-certified reference materials serve as primary standards in high-accuracy analytical work.

Safety Information

K₂Cr₂O₇ (primary standard for oxidimetry) is a Cr(VI) compound — carcinogenic, mutagenic, and a skin sensitiser. KHP and Na₂CO₃ are of low toxicity. Concentrated solutions of primary standard acids or bases prepared for titrimetry are corrosive. Always follow standard laboratory safety for all titrimetric reagents.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Primary Standard

Index All "P" terms

Synonyms Primary titrimetric standard, standard substance, certified reference material (CRM)

Frequently Asked Questions

What is Primary Standard?

A highly pure, stable substance of known composition used to prepare standard solutions for calibrating titrations. Properties: high purity, stability in air, non-hygroscopic, high molar mass, and reacts according to a simple stoichiometry. Examples include potassium hydrogen phthalate and sodium carbonate.

What is Primary Standard used for?

Is Primary Standard hazardous?

More "P" Terms

P-type Semiconductor Pairing Pairing Energy Palladium Pd Parachor [P] = M(γ)^(1/4) / (ρ_L - ρ_V) Paramagnetic χ_m > 0; unpaired electrons; μ = √(n(n+2)) BM (n = unpaired electrons) Paramagnetism Partial Ionic Character % ionic = (1 - e^(-Δχ²/4)) × 100% Partial Pressure Partial Pressure p_i = x_i × P_total; P_total = Σp_i Particulate Matter Parts Per Million ppm = mg/L (water) or mg/kg; = (mass solute/mass solution) × 10⁶

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