Color in the ______ range is determined by a visual comparison of the sample with either a known colored chemical solution or a calibrated color disk.

Color in the ______ range is determined by a visual comparison of the sample with either a known colored chemical solution or a calibrated color disk.

• A. greenish-grey
• B. green to brown
• C. yellow to brown
• D. orange to brown

Answer: (C)

Colorimetric tests read concentration by how the sample’s color matches a standard reference, either a known colored solution or a calibrated color disk. For iron testing in water, the reagent produces a color that deepens as iron concentration increases, typically moving from pale yellow through yellow-brown to brown. That progression is designed so you can visually compare the sample to the reference colors and estimate the iron level. So, the color you’d read falls in the yellow to brown range. The other ranges don’t align with the standard iron color scale used in these tests, where yellow-to-brown reflects increasing iron content.

Colorimetric tests read concentration by how the sample’s color matches a standard reference, either a known colored solution or a calibrated color disk. For iron testing in water, the reagent produces a color that deepens as iron concentration increases, typically moving from pale yellow through yellow-brown to brown. That progression is designed so you can visually compare the sample to the reference colors and estimate the iron level. So, the color you’d read falls in the yellow to brown range. The other ranges don’t align with the standard iron color scale used in these tests, where yellow-to-brown reflects increasing iron content.