Tests for: 3 important chemistries in seconds: Potassium Monopersulfate, pH, and Total Alkalinity. Monopersulfate (MPS) is an oxidizing agent used in mineral purification systems such as Spa Frog, Nature2, PoolRx, or SpaRx. Monopersulfate can also be used as an oxidizer for brominated pools and spas. - 12 bottles per case