Heptane (C7H16) is a colorless, highly volatile liquid hydrocarbon belonging to the alkane family. As a linear chain of seven carbon atoms, it functions as a non-polar solvent, readily dissolving substances like oils and greases while remaining insoluble in water. This property makes it useful for various applications, from analytical chemistry to heavy industry. Selecting the correct grade of heptane is important, as purity directly influences its suitability and performance for a given task.
Common Applications for Heptane
The non-polar nature of heptane makes it an excellent choice for extraction and separation processes in laboratory settings. Chemists frequently use it as a mobile phase solvent in chromatography to selectively separate compounds based on their lack of polarity. It is also effective for extracting non-polar organic compounds, such as fats and oils, from natural materials.
Beyond its solvent capabilities, heptane plays a role in the fuel industry. Pure \(n\)-heptane is assigned the zero point on the octane rating scale, which measures a fuel’s resistance to premature ignition, or “knocking.” A fuel’s octane number is determined by comparing its knock resistance to a mixture of \(n\)-heptane and isooctane. Industrially, it is also used as a degreasing agent and a component in specialized products like adhesives, paints, and rubber cement.
Understanding Purity and Grades
The required application dictates the necessary purity level and the grade of heptane a user should purchase. Technical Grade heptane is the least refined and most cost-effective option, often containing a mixture of isomers and other hydrocarbons. This grade is suitable for general industrial cleaning or degreasing in large-volume applications where minor impurities are acceptable and high precision is not required.
Laboratory Grade heptane usually guarantees a purity of 99% or higher, appropriate for most routine laboratory tasks, general chemical synthesis, and non-critical extractions. For highly sensitive analytical work, such as High-Performance Liquid Chromatography (HPLC) or Spectroscopic analysis, a High-Purity Grade (often exceeding 99.5%) is required. These high-purity solvents are tested for specific contaminants to ensure they do not interfere with detection equipment or compromise reaction accuracy.
Primary Retail and Commercial Sources
For small-scale hobbyists or individuals needing pint to gallon quantities, purchasing heptane requires specialized online chemical suppliers or retailers catering to DIY extraction or solvent needs. These vendors may offer Technical or Lab Grade material and are often the only option for non-institutional buyers seeking pure chemical compounds. Due to its classification as a highly flammable liquid (Class 3, Packing Group II), shipping is regulated, and an additional hazardous material fee may apply to the order.
For users requiring higher grades or bulk quantities, procurement typically shifts to dedicated commercial chemical distributors. Large suppliers like Sigma-Aldrich or Fisher Scientific offer a full spectrum of purity, from Lab Grade to ultra-pure HPLC and Spectroscopic grades. These distributors frequently require a business or institutional account, and purchasing bulk chemicals may necessitate providing documentation for intended use. Pure heptane is rarely found in local hardware or home improvement stores, which instead stock proprietary solvent blends that contain heptane.
Safe Storage and Handling Requirements
Because heptane is a highly flammable liquid with a low flash point (approximately -4°C or 25°F), safety protocols must be followed during storage and handling. Vapors are heavier than air and can travel along the floor to an ignition source, potentially causing a flashback fire hazard. Therefore, it must be stored in tightly closed containers within a cool, dry, and well-ventilated area, safely away from any ignition source, including heat, sparks, and open flames.
When handling heptane, use personal protective equipment, including chemical-resistant gloves (such as nitrile or Viton) and safety goggles to prevent skin and eye contact. To prevent accidental ignition from static electricity, metal containers used for transferring the solvent must be properly grounded and bonded. For disposal, heptane must never be poured down the drain or disposed of with regular trash; it must be collected and managed as a hazardous waste according to local and federal environmental regulations.