This standard specifies a method for determining the total chlorine content in several common isocyanates, such as toluene diisocyanate. The core of the method is the "oxygen flask combustion method," which involves high-temperature combustion of the sample in a dedicated oxygen-filled combustion flask to convert organic chlorine into inorganic chloride ions. Subsequently, "potentiometric titration" is used to quantitatively determine the chloride ions in the absorption solution. When conducting tests according to this standard, the required instruments mainly include a dedicated oxygen combustion flask for sample decomposition (typically equipped with a platinum wire catalyst), as well as a potentiometric titrator (or high-precision pH meter) for the final determination, along with specialized electrodes such as silver and calomel electrodes. This method provides critical technical support for evaluating the purity and quality of isocyanate products.