The correct answer is (b) Sodium thiosulfate.
Sodium thiosulfate is a chemical compound with the formula Na2S2O3. It is a white, water-soluble solid that is used in a variety of applications, including photography, as an antichlor, and in the textile industry.
In photography, sodium thiosulfate is used to fix the image on photographic film or paper. It does this by converting the unexposed silver halide crystals into silver sulfide, which is a black precipitate that is not soluble in water. This prevents the unexposed silver halide crystals from being developed into an image.
Sodium thiosulfate is also used as an antichlor. Chlorine is used in the textile industry to bleach fabrics. However, the chlorine can also react with the natural oils in the fabric, causing them to become brittle and discolored. Sodium thiosulfate can be used to neutralize the chlorine, preventing these problems.
In addition to its uses in photography and as an antichlor, sodium thiosulfate is also used in a variety of other applications, including:
- As a reducing agent in the production of other chemicals
- As a mordant in the textile industry
- As a fire retardant
- As a food additive
Sodium thiosulfate is a safe and effective chemical that has a wide range of uses. It is important to note, however, that sodium thiosulfate can be toxic if ingested in large quantities.