Reagent A Copper Total 4.5 comes in a 10 g powder form and is designed for accurate copper testing. It reacts with diethyl-p-phenylene diamine (DPD) in a buffered solution allowing for precise measurement using a colorimeter or photometer. For optimal performance, store reagents consistently between 36°F and 85°F (2°C and 29°C), avoid extreme temperature fluctuations, and protect them from prolonged direct sunlight.