Gram’s iodine solution

Specifications

Purity

for microscopy

Appearance

Dark red to brown liquid

Properties

Refractive Index

n20/D 1.334 - 1.336

Density

1.003 - 1.007 g/mL at 20 °C

Documentation

Safety Data Sheet (SDS)

CDX G0065 MSDS.pdf

Shipping

AMBIENT

Short Term Storage

RT

Long Term Storage

RT

Handling Advice

Protect from light and moisture.

Use / Stability

This product should not be used if colour has changed or if there are

Hazard statements

H402

Precautionary statements

P273, P501

Transportation

Not dangerous goods

Description

Gram?s iodine solution acts as a mordant for Gram staining technique. It forms an insoluble crystal violet-iodine complex, which imparts purple color to the cells. The Gram staining allows a fast differentiation of bacteria in Gram-positive and Gram-negative. The mureine structure of the bacteria walls is the basis of the color affinity. Bacteria will be stained with Gram's crystal violet solution - an aniline dye - in the first step. After the treatment with iod solution, a dye-iod complex will form. During the decolorizing step, this complex stays in the multilayer mureine structures of the Gram-positive bacteria and they will appear blue. Gram-negative bacteria have a monolayer mureine structure only, the dye-iod complex does not stay bound to the cellwall, they will be decolorized. Gram-negative bacteria will be counterstained by safranin solution and appear orange.

References

(1) E. Adams, Stain Technol. 50, 227 (1975) , (2) R. Coico, et al., Curr. Protoc. Microbiol. Appendix 3-3C (2005)