How does the formaldehyde test kit FM-1 work?
How the formaldehyde test kit FM-1 works
When using the Formaldehyde Test Kit, Model FM-1 (Product # 2183100), formaldehyde in the sample reacts with sodium sulfite from the Formaldehyde 1 reagent and releases hydroxide ions, which raises the sample pH. Sulfuric acid lowers the pH and changes the thymolphthalein indicator from blue to clear. The number of drops of sulfuric acid needed to bring about the color change is proportional to the amount of formaldehyde in the sample.