Glycerol and glycerin refer to the exact same chemical compound, a colorless, odorless, and viscous liquid with a sweet taste. The difference lies in context, usage, and purity level. “Glycerol” is the name accepted in scientific and industrial documentation when referring to the pure substance in its fundamental state. Conversely, “glycerin” is the common commercial and pharmaceutical term that typically indicates a standardized, purified product for consumer use.
Glycerol: The Molecule’s True Name and Structure
Glycerol is the systematic chemical name for the compound, formally known as propane-1,2,3-triol. Its molecular formula is C₃H₈O₃, illustrating its structure as a three-carbon chain with a hydroxyl (-OH) group attached to each carbon atom. The presence of three hydroxyl groups classifies it as a polyol and is responsible for its unique physical properties.
The molecule’s structure makes it highly polar and hygroscopic, meaning it readily attracts and binds water. In nature, glycerol forms the backbone of triglycerides, the primary components of animal fats and vegetable oils. When these fats and oils are broken down, the glycerol molecule is released.
Glycerin: The Commercial Context and Purity Standards
The term “Glycerin” is widely used in consumer-facing industries, including cosmetics, food, and pharmaceuticals. This name is a nod to the substance’s characteristic sweetness. The use of “glycerin” often implies that the substance has been refined and standardized for a specific application.
Commercial glycerin is typically a byproduct of saponification (soap-making) or the production of biodiesel. Commercial-grade glycerin is an aqueous solution of glycerol mixed with water and trace impurities. Consumer-grade glycerin is often standardized to be at least 95% pure glycerol.
Pharmaceutical and food-grade glycerin require significantly higher purity levels to meet strict regulatory standards. Food-grade products often require a purity of 99.7% or higher. Pharmaceutical-grade glycerin must meet the stringent requirements of organizations like the European Pharmacopoeia (Ph. Eur.) or the U.S. Pharmacopeia (USP), often aiming for 99.9% purity.
How This Ingredient Is Used
The chemical’s unique properties make it a versatile ingredient across many consumer products. In the cosmetics and skincare industry, its function as a humectant is valued. By drawing moisture from the air and deeper layers of the skin, it helps hydrate the skin and supports the skin barrier.
In the food industry, the substance is designated by the European E-number E422. It functions as a solvent for flavors and colors, a sweetener, and a humectant to prevent foods from drying out. Its thick, viscous nature also allows it to be used as a thickening agent in liquid products.
For pharmaceuticals, the substance acts as a reliable excipient, which is an inactive ingredient that helps deliver the active medicine. It is commonly used as a solvent and stabilizer in liquid formulations, such as cough syrups and elixirs. Due to its mild laxative effect, it is also formulated into suppositories.