Question

welcome back to the lab! what a journey huh? before we move on with the sample analysis, lets do a recap.
what are the four reagents used in the gram stain?
a) crystal blue, safranin, 95% ethyl alcohol, iodine
b) crystal violet, safranin, 90% methyl alcohol, iodine
c) crystal violet, safranin, 95% ethyl alcohol, iodine
d) crystal violet, safranin, 95% ethyl alcohol, hydrogen peroxide

Explanation:

The Gram - stain procedure uses crystal violet as the primary stain, iodine as the mordant, 95% ethyl alcohol as the decolorizing agent, and safranin as the counter - stain.

• Option a: "Crystal blue" is incorrect. The primary stain is crystal violet.
• Option b: 90% methyl alcohol is not the standard decolorizing agent. 95% ethyl alcohol is used.
• Option d: Hydrogen peroxide is not a reagent in the Gram - stain. Iodine is the mordant.

Answer:

C. Crystal violet, safranin, 95% ethyl alcohol, iodine