(2S,3S)-D-(-)-tartaric acid stands out as a naturally occurring, chiral organic acid. Known by its molecular formula C4H6O6, this compound appears most commonly in crystalline form, often as clear, colorless crystals or white crystalline powder. Chemistry labs and food producers recognize this acid for its distinct sour taste and strong acidic properties. With its two stereocenters, it features a unique stereochemistry, separating it from the meso and L-enantiomer forms. Many industries understand the difference between these isomers, because the chirality influences reactivity and utility in chemical processes, and flavors in food applications. Its CAS number, product specifications, purity grades, and the presence of water as a hydrate or anhydrous solid, all matter in application settings, especially when tight tolerances for pharmaceutical and fine chemical synthesis are in play.
Physical properties drive selection—knowing density, solubility, melting points, and form makes a real difference between effective formulation and failed results. (2S,3S)-D-(-)-tartaric acid, often labeled with the HS Code 2918.12.00, offers a density of roughly 1.76 g/cm3. Chemists will spot melting points around 168-170 °C. This racemic compound dissolves easily in water, up to about 139 g/L at 20°C, which speeds use in aqueous solution, titration, and formulations that demand controlled pH. Its solubility in alcohols and ethers broadens application, especially when blending raw materials in chemical manufacturing or food processing.
A simple structural formula—HOOC-(CHOH)2-COOH—tells a lot, but experience fills in the picture for those who mix, handle, or analyze the crystals. Each carboxylic acid group gives acidity and reactivity, with two hydroxyl groups positioned for hydrogen bonding, chelating metals, or catalyzing chemical shifts. In real use, (2S,3S)-D-(-)-tartaric acid turns up as irregular flakes, fine powder, larger pearl granules, or solid crystalline blocks. Within the lab, some may prefer crystals for accurate weighing, while others need a solution—2-molar, 4-molar, 10% w/v, and so on—directly in the flask, tank, or reactor.
The choice between powder, flakes, pearls, or ready-made crystalline forms depends on material handling systems, cleanliness, and end-use goals. Reliable supply chains source raw materials mainly by fermentation or extraction from natural sources such as wine lees; synthetic routes exist for research-scale needs or specialized high-purity lots. As a versatile acidulant and chelating agent, (2S,3S)-D-(-)-tartaric acid fills roles in beverage and food processing, where its tart flavor and adjusting pH keep color and flavor bright. Electroplating baths, textile mordants, and photographic developers all benefit from its precise acid strength and chelation.
Users track chemical hazards. This acid ranks as relatively safe compared to strong mineral acids but still requires smart handling. Direct exposure to pure tartaric acid dust or solution can irritate eyes, lungs, and skin. Inhalation of fine powder should be avoided; ASTM or EN standard gloves, eye protection, and dust masks are standard practice. The substance does not support combustion and remains stable under most storage conditions, but it reacts with strong oxidizers or bases. Material Safety Data Sheets emphasize that ingestion in large amounts may cause gastrointestinal discomfort. High-quality suppliers offer packaging that shields against moisture, as these crystals rapidly absorb water vapor from air, potentially clumping or dissolving on shelves. Workers recall stinging hands or red eyes after handling, reinforcing the point that safety is more than formality—it's practical.
Each molecule features a weight of about 150.09 g/mol, with chirality rooted in the (2S,3S) configuration. The acid dissociation constants (pKa values) sit near 2.98 and 4.34, marking it a strong organic acid. Analytical chemists rely on sharp melting points, optical rotation (about [α]D20 = −12° to −13° in water), and high purity (98% and above in most lab-grade and food-grade lots). Industrial specs often demand heavy metals below 10 ppm, low sulfate, and minimal moisture for efficiency. For applications as a chelating agent or resolving racemic bases or amines, the specific stereochemistry and purity drive selectivity and yield in downstream reactions.
Even though food use is considered safe, excessive tartaric acid can cause dental erosion or upset stomach, especially for those unaccustomed to sour foods, or for small children. In factories, improper handling can lead to localized dust clouds, which calls for exhaust ventilation and regular housekeeping. To mitigate harm, staff use closed systems when dispensing fine powder, add the acid slowly to liquids to prevent splashing, and store containers tightly closed, away from incompatible chemicals and humidity sources.
Those who mix chemical solutions from scratch, or scale up food and beverage production, recognize that the added step of verifying identity with IR spectroscopy or titration can prevent costly errors. Going beyond safety, practical experience shows that tartaric acid, though not volatile or subject to rapid degradation, still benefits from cool, dry, well-ventilated storage. Over the years, I've watched new technicians learn that a miscalculation in solution strength, or ignoring the powder's clumping from ambient moisture, slows down entire production lines. Chemically aware teams build redundancy into their work, measuring, recording batch details, and rechecking pH and purity.
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