Cream of tartar extra pure

Cream of tartar extra pure is a high-purity grade of potassium bitartrate (potassium hydrogen tartrate, KC₄H₅O₆), appearing as a white crystalline powder or colorless crystals, used as a reagent in analytical chemistry, buffering, and food applications.​

Identity and Composition

Chemical name: Potassium bitartrate; monopotassium L-tartrate.​

Molecular formula: KC₄H₅O₆; molecular weight 188.18 g/mol.​

Grade specifications: Extra pure with assay 99.0–101% (dry basis), loss on drying ≤0.5%, minimal impurities (e.g., chloride ≤0.05%, sulfate ≤0.05%, heavy metals ≤10 ppm).​

Physical Properties

Appearance: White crystalline powder, odorless.​

Density: 1.954 g/mL at 25 °C.​

Melting point: 267 °C (decomposes).​

Solubility: Slightly soluble in water (0.54 g/100 mL at 20 °C, 6.50 g/100 mL at 100 °C); soluble in dilute acids/alkalis; insoluble in alcohol.​

pH: 3.4–3.7 (saturated solution at 20 °C).​

Typical Uses

Extra pure cream of tartar functions as a buffering agent, reducing agent in volumetric analysis, leavening agent in baking, and stabilizer in winemaking to prevent tartrate precipitation.​

Handling and Safety

Hygroscopic; store in airtight containers at room temperature. Non-toxic in food use (E336), but avoid inhalation of dust; incompatible with strong oxidizers.​

For catalog purposes: “Cream of tartar extra pure, KC₄H₅O₆ 99–101%, white crystals, mp 267 °C (dec.), slightly water-soluble, for analysis/baking; hygroscopic.”​