Question

Hypo solution is used in histological work for staining. Which of the following is hypo solution ?

• A. Silver Nitrate Solution
• B. Sodium Thiosulfate Solution
• C. Phosphotungstic Acid hematoxylin
• D. Phosphomolybdic Acid Solution

Hint:

Whenever you see a silver-based staining procedure (reticulin stain, fungal silver stains), expect Sodium Thiosulfate (hypo) to be used as the final fixing step to 'clear' the background.

Answer 1

The Correct Option is B

Step 1: Concept:
The question requires the chemical identification of the laboratory reagent commonly referred to as "hypo," frequently utilized in histology and traditional photography.

Step 2: Step-by-step Explanation:

• In traditional darkroom photography and certain silver-based histological staining protocols (like the Grocott's Methenamine Silver stain or Von Kossa stain), a specific chemical is required as a "fixer."

• The purpose of this fixer is to chemically dissolve and wash away any unreduced, unexposed silver halides (like silver bromide or silver nitrate) from the tissue section or photographic film.

• If these unreduced silver salts are not removed, they will eventually react with ambient light over time, turning the entire background of the tissue slide pitch black.

• The chemical exclusively used for this purpose is Sodium Thiosulfate (\(\text{Na}_2\text{S}_2\text{O}_3\)).

• Historically, sodium thiosulfate was originally (and incorrectly) named "hyposulfite of soda." Because of this historical naming, laboratory technicians and photographers universally abbreviated it as "Hypo".

• Silver Nitrate (Option A) is the actual stain that deposits the silver, not the hypo. Options C and D are mordants/stains for muscle and collagen, entirely unrelated to the term hypo.

Step 3: Final Answer:
The term "hypo solution" strictly refers to Sodium Thiosulfate.