For determination of nitrate, nitrate ions in a sample are reduced to nitrite ions in the presence of cadmium. The reaction between the nitrite ions and the reagent causes an orange colored complex to form; the greater the concentration, the deeper the color. A color comparator cube is included for an accurate, side-by-side, visual analysis to determine nitrate concentration. These reagents are designed to be used with samples that have an expected nitrate range of 0 to 50 mg/L (ppm) NO₃^--N.