GB/T 20432.13-2007 provides specifications for the determination of the pH value of photographic grade chemicals for photography. The standard clearly applies to all types of photographic grade chemicals, and details the Sample Handling process to ensure test accuracy. Sample pH value is determined by following strict operation procedures through specific instruments, such as acidity meters. The measurement process covers key points such as instrument calibrating, measurement condition control, etc., to ensure reliable results. This standard is essential for controlling the mass of photographic grade chemicals and helps to ensure stable photographic imagery results. It is widely used in photographic chemical production, testing and photography industries.