Hanna Marine Phosphate Reagents HC - HI713-25Includes Reagents for 25x Tests The Hanna Phosphate Low Range Checker bridges the gap between simple chemical test kits and professional instrumentation. Chemical test kits have limited accuracy and resolution since they rely upon the human eye to discern differences in color. Professional instrumentation incorporates a light source such as an LED or tungsten lamp with a filter and a light sensing detector to precisely determine ion concentration.