What chemicals are primarily used in the hot lime - hot phosphate process?

The hot lime - hot phosphate process is primarily utilized in water treatment, particularly for softening water or removing hardness caused by calcium and magnesium ions. The key chemicals involved in this process are sodium hydroxide and trisodium phosphate.

Sodium hydroxide serves to increase the pH of the water, which helps to precipitate calcium in the form of calcium carbonate. This is essential for the removal of hardness from hard water. Meanwhile, trisodium phosphate acts as a sequestrant that binds to calcium and other hardness-causing minerals, aiding in their removal from water.

The combination of these two chemicals is effective in not just softening the water but also in maintaining the stability of the resulting precipitate, ensuring better removal efficiency during water treatment processes. Therefore, the identification of sodium hydroxide and trisodium phosphate as primary chemicals in the hot lime - hot phosphate process is accurate and reflects their roles in making water suitable for consumption and industrial use.