Preparation of Gram Stain and Normal Saline in Microbiology Laboratory

Preparation of Gram Stain and Normal Saline | M4S Digital Textbook
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Microbiology • Laboratory Reagents

Preparation of Gram Stain and Normal Saline

Preparation of Gram's staining reagents and 0.85% normal saline.

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Preparation of the four reagents used in Gram staining: Crystal Violet, Lugol's Iodine, Acetone-Alcohol Decolourizer and Safranin (Counter Stain).
IngredientQuantity
Crystal Violet20.0 g
Ammonium Oxalate9.0 g
Ethanol or Methanol95 ml
Distilled WaterTo make 1 litre

Preparation

In a clean piece of paper, 20 g of crystal violet is weighed and transferred to a clean brown bottle. Then, 95 ml of ethanol is added and mixed until the dye is completely dissolved. To the mixture, 9 g of ammonium oxalate dissolved in 200 ml of distilled water is added. Finally, the volume is made to 1 litre by adding distilled water.

IngredientQuantity
Potassium Iodide20.0 g
Iodine10.0 g
Distilled Water1000 ml

Preparation

To 250 ml of distilled water, 20 g of potassium iodide is dissolved. Then 10 g of iodine is mixed into it until it is dissolved completely. Finally, the volume is made to 1 litre by adding distilled water.

IngredientQuantity
Acetone500 ml
Ethanol (Absolute)475 ml
Distilled Water25 ml

Preparation

To 25 ml distilled water, 475 ml of absolute alcohol is added, mixed and transferred into a clean bottle. Then immediately, 500 ml acetone is added to the bottle and mixed well.

IngredientQuantity
Safranin10.0 g
Distilled Water1000 ml

Preparation

In a clean piece of paper, 10 g of safranin is weighed and transferred to a clean bottle. Then 1 litre distilled water is added to the bottle and mixed well until safranin is dissolved completely.

IngredientQuantity
Sodium Chloride0.85 g
Distilled Water100 ml

Preparation

The sodium chloride is weighed and transferred to a leak-proof bottle premarked to hold 100 ml. Distilled water is added to the 100 ml mark and mixed until the salt is fully dissolved. The bottle is labelled and stored at room temperature.

ReagentMain ComponentsFinal Volume
Crystal VioletCrystal violet + ammonium oxalate + ethanol/methanol1 litre
Lugol's IodinePotassium iodide + iodine1 litre
Acetone-AlcoholAcetone + absolute ethanol + water1000 ml
SafraninSafranin + distilled water1000 ml
Normal salineSodium chloride + distilled water100 ml
M4S • Microbiology for Students (M4S) • MBLOGSTU
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