Iodine tungsten lamp has ignition capacity. An iodine tungsten lamp is a kind of tungsten filament lamp filled with iodine vapor for a chemical reaction. It is often used in indoor and outdoor lighting places with high illumination requirements and high installation points. This kind of lamp has a high degree of thermal light source, and there is a risk of burning combustibles on the outer wall of the lamp tube in a short time. Therefore, it is of great significance to understand the ignition ability of iodine tungsten lamp to combustibles for fire prevention and fire investigation.

The standard molar enthalpy of formation of tungsten diiodide is -8.37 kJ/mol. The standard molar enthalpy of formation of tungsten diiodide, Δ_fH_m^θ(WI₂, g, 298 K), is defined as the standard molar enthalpy of formation for the reaction to produce the substance tungsten diiodide (ν_B=+1) from the monomers of the reference state at 298 K. The standard molar enthalpy of formation is -8.37 kJ/mol.

The standard molar enthalpy change for the reaction of tungsten diiodide (WI₂) is -70.61 kJ/mol. it is defined as the thermodynamic energy change between the reactants (i.e., W and I₂) required for the formation of 1 mol of WI₂ and its corresponding reaction product (i.e., the WI₂ gas) under the standard condition. Specifically, the enthalpy of formation of the reaction of tungsten diiodide can be determined by determining the standard molar enthalpy of formation of tungsten, iodine, and tungsten diiodide, a value that can be obtained by experimental measurement.

The type of crystal structure of tungsten diiodide is an orthorhombic crystal system, space group Bbem (No. 64), with lattice parameters a = 1258 pm, b = 1259 pm, and c = 1584 pm, and is a crystal cell with hexahedra. Each hexahedron has a tungsten atom in the center surrounded by six iodine atoms, forming a tungsten-iodine octahedron. The tungsten and iodine atoms are located at positions (0,0,0) and (0.5,0.5,0.5), respectively. The crystal has a layered structure with each layer consisting of tungsten-iodine octahedra, with neighboring layers interacting with each other through weak van der Waals forces.