Napalm is a highly effective incendiary material created by mixing a thickening agent with a volatile petrochemical, typically gasoline or jet fuel. The resulting jelly-like mixture has distinct properties compared to liquid fuel fires. Developed during World War II, napalm was designed to adhere to surfaces, including vertical ones, and sustain a prolonged, intense burn. The name is a portmanteau from the aluminum salts of naphthenic and palmitic acids, the original gelling agents. The primary purpose of this thickened fuel is to maximize the transfer of heat energy to a target over an extended period.
The Measured Temperature Range of Napalm
The sustained burning temperature of napalm falls within a range of \(800^{\circ}\text{C}\) to \(1,200^{\circ}\text{C}\) (\(1,470^{\circ}\text{F}\) to \(2,190^{\circ}\text{F}\)). This thermal output is significantly higher than many common fires. A typical household wood fire, for example, usually burns between \(600^{\circ}\text{C}\) and \(800^{\circ}\text{C}\), depending on the fuel and airflow. Napalm’s temperature is comparable to the high end of a large bonfire or a specialized industrial furnace.
The specific formulation influences the exact temperature achieved during combustion. Older versions that relied on aluminum soap thickeners tend to burn within the lower end of the range. Modernized versions, often referred to as Napalm-B, utilize a synthetic rubber-like gelling agent, such as polystyrene, blended with gasoline and benzene. This newer mixture can reach the higher end of the temperature spectrum, sometimes exceeding \(1,200^{\circ}\text{C}\).
The duration of the burn is as significant as the temperature reached, with the gelled fuel burning for up to ten minutes on a target. This sustained exposure sets napalm apart from a standard gasoline fire, which burns quickly and spreads as a volatile liquid. The prolonged exposure at this high temperature maximizes thermal damage to structures and organic materials.
Chemical Composition and Sustained Burning
The ability of napalm to reach and maintain a high temperature is primarily due to the gelling agent’s chemical interaction with the fuel. The thickening agent creates a matrix that encapsulates the liquid fuel. This structure prevents the fuel from flowing away and controls the rate at which oxygen reaches the fuel’s surface.
By slowing the rate of combustion, the gel ensures a sustained exothermic reaction rather than a rapid, short-lived flash fire. The sticky nature guarantees that the fuel remains concentrated on the target, maximizing the heat energy released in a localized area. This mechanism ensures the fuel burns completely in place, transferring its thermal potential to the surface it adheres to.
The chemical breakdown of the gelling agent itself also contributes to the sustained heat. For Napalm-B, the polystyrene component breaks down during combustion, releasing additional energy. This controlled and localized burning defines napalm’s effectiveness as an incendiary material.
Immediate Thermal Impact and Heat Transfer
The destructive effect of burning napalm results from multiple heat transfer mechanisms working in concert. The high-temperature gel adheres to a surface, immediately initiating conduction, the direct transfer of heat through physical contact. This causes rapid and deep penetration of thermal energy into materials or tissue.
In addition to direct contact, the large, intensely burning surface area radiates a significant amount of heat energy, known as radiant heat transfer. This heat is felt at a distance and can cause severe burns on exposed skin or ignite secondary fires even without direct contact. Intense thermal radiation can harm people near the fire, leading to hyperthermia or severe burns.
The sustained high temperature of the fire also creates a powerful convection current, where superheated air rises quickly. This intense heat can be conducted through materials not directly in contact with the gel, such as vehicle metal armor. Furthermore, the combustion process rapidly depletes oxygen in the surrounding air while generating high concentrations of toxic carbon monoxide, leading to asphyxiation.