Gram’s Iodine Solution is an aqueous solution of iodine and potassium iodide, invented by Lugol in 1829 and named after him. It can be used as an oxidative disinfectant and bactericide for emergency disinfection of drinking water, as well as for starch detection in laboratory settings.
This product adopts a classic formulation with an iodine content of 0.34%. Its main applications include: detecting starch in samples such as leaves and food; cell staining to stain cell nuclei for easier observation; the Schiller test in colposcopy for screening vaginal and cervical lesions — normal tissues stain brown due to high glycogen content, whereas cancerous tissues remain unstained and appear pale; it also acts as an oxidative bactericide. In microbiological experiments, Gram’s Iodine Solution is commonly used as a mordant, combined with crystal violet and safranin for Gram bacterial staining.
For research use only. Not for clinical diagnosis or other applications.
Procedure (For reference only):
1. Stain general Gram‑stain bacterial smears for 1‑2 min. Appropriately prolong the staining time for tissue sections. Operate according to specific requirements for special experiments.
Precautions:
1. Draw circular marks on the reverse side of slides before smearing to locate the target area in subsequent experiments.
2. Proper decolorization is critical for Gram staining, and decolorization time should be determined empirically. Excessive decolorization may result in false‑negative results for Gram‑positive bacteria; insufficient decolorization may produce false‑positive results for Gram‑negative bacteria. 70% ethanol can be used for decolorization.
3. Gram‑positive bacteria may yield false‑negative results if cultured for too long, when dead, or after bacterial lysis.
