Sulfuric acid is a cornerstone reagent in biochemical protocols, valued for its strong dehydrating capability and its role in hydrolysis reactions. Due to its high corrosivity and reactivity, handling requires strict adherence to laboratory safety guidelines.

Chemical Properties

Sulfuric acid (H₂SO₄) exhibits a tetrahedral molecular geometry around sulfur, where sulfur is in the +6 oxidation state. The molecule contains two double-bonded oxygen atoms and two hydroxyl groups, conferring strong acidity with approximate pKa values of -3 for the first dissociation and 1.99 for the second dissociation.

It is a dense, oily, colorless liquid with a density of approximately 1.84 g/mL. Sulfuric acid melts at 10.4°C and boils at 337°C, although decomposition may occur at elevated temperatures, releasing sulfur trioxide and water. The compound is highly hygroscopic and releases significant heat upon dilution. Concentrated, anhydrous forms act as powerful dehydrating agents capable of removing water molecules from organic substrates such as sugars and nucleic acids.

Biochemical Applications

In carbohydrate analysis, cold sulfuric acid can hydrolyze polysaccharides into monosaccharides for colorimetric assays such as DNS or phenol-sulfuric acid methods, which quantify glucose production through chromophore formation typically measured at 540 nm.

The reagent also supports lipid chemistry workflows by facilitating activation steps during Folch extraction or enabling phosphate quantification in phospholipids using the Fiske-Subbarow reaction after acid digestion.

In protein biochemistry, diluted sulfuric acid solutions may be used to precipitate casein proteins or assist in histone extraction. In molecular biology applications, it can be employed for controlled hydrolysis of total RNA prior to orcinol-based quantitative assays.