[Usage and dosage] First rinse the test tube with water sample twice, and take water sample to the scale of 3ml. to Drop 10 drops of reagent D in the test tube, 5 minutes later, add a flat scoop of powder 2, a flat scoop Powder 3, shake well and leave for 10 minutes. Compare with the standard colorimetric card, the tone is the same color scale It is the content of urea in water (mg/l). [Storage] Avoid light, must be refrigerated (4-10℃)