Isopropyl alcohol (IPA), commonly known as rubbing alcohol, is a solvent widely used for disinfection and cleaning. Whether this substance conducts electricity depends entirely on its purity. Pure isopropyl alcohol is an electrical insulator, meaning it does not conduct an electric current. This characteristic is tied directly to its molecular structure and the requirements for electrical flow in liquid mediums.
How Electrical Current Flows Through Liquids
For an electric current to move through a liquid, mobile, charged particles must be present to carry that charge. These mobile charge carriers are known as ions, which are atoms or molecules that possess a net positive or negative electrical charge. When voltage is applied, these ions are pulled toward the oppositely charged electrode, creating a flow of electricity.
Substances that produce these ions when dissolved are called electrolytes, and their presence determines a liquid’s conductivity. Without a sufficient concentration of these charged particles, the liquid remains a poor conductor or an insulator. In most liquids, the movement of positive and negative ions is the mechanism for conduction.
Why Isopropyl Alcohol Does Not Conduct Electricity
Pure isopropyl alcohol (IPA) does not conduct electricity because it is an organic molecule held together by covalent bonds. Covalent bonds involve the sharing of electron pairs between atoms, rather than the complete transfer of electrons needed to create ions. Since the atoms in the IPA molecule share electrons, they form a stable, neutral molecule that does not readily dissociate into charged particles.
The lack of free ions means there are virtually no mobile charge carriers available to respond to an applied electric field. IPA’s chemical structure is fundamentally different from ionic compounds, such as table salt, which readily break down into positive and negative ions when dissolved. While a small degree of self-ionization occurs, pure isopropyl alcohol is classified as a non-conductor.
The Critical Role of Water and Impurities
The electrical behavior of commercial isopropyl alcohol differs from its pure form due to water and other impurities. Commercial rubbing alcohol is typically sold as a 70% concentration, meaning the solution contains 30% water. While pure water is a poor conductor, it is an excellent solvent for ionic substances.
Any salts, minerals, or dust particles dissolved in the water component will dissociate and release charged ions. These dissolved ions are the source of conductivity in lower-purity alcohol solutions. Electricity flowing through 70% rubbing alcohol passes through the conductive network created by the water and its dissolved contaminants.
High-purity alcohol, such as 99% IPA, is known as anhydrous because it contains minimal water content, often less than 1%. The lower water content in 99% IPA reduces its ability to dissolve ionic impurities, limiting the number of mobile charge carriers. This is why 99% IPA maintains near-insulating properties, while 70% solutions pose a higher conductivity risk.
Using Non-Conductive Solvents in Electronics
The non-conductive property of high-purity isopropyl alcohol makes it an ideal solvent for cleaning sensitive electronic components. Technicians rely on 99% or higher purity IPA to safely remove contaminants like flux residues, grease, and fingerprints from circuit boards. Using a non-conductive cleaner prevents the risk of short-circuiting delicate electronic traces during cleaning.
The high volatility and rapid evaporation rate of high-purity IPA offer a secondary benefit. Because the alcohol evaporates quickly, it leaves behind virtually no residue, which is an advantage over lower concentrations. Residue from the water component of lower-purity solutions can lead to signal interference or corrosion. The combination of its insulating nature and rapid drying maintains the integrity and performance of high-precision electronics.