Sodium Thiosulfate, Pentahydrate, 2.5kg

Sodium thiosulfate appears as white, translucent crystals. It is soluble in water, insoluble in alcohol, absorbed in moist air.

Sodium Thiosulfate is commonly used in…

• Photography — As a fixing agent (hypo) to dissolve unchanged silver salts from exposed negatives.
• Aquaculture — As a chlorine remover from aquariums and ponds (see below).
• Cleaning — A mixture of 1 tsp sodium thiosulfate and ½ cup warm water is a useful recipe for cleaning Betadine or iodine spills on fabric.
• Cyanide poisoning — Sodium thiosulfate reacts with the cyanide to form a less toxic compound, thiocyanate, which can be eliminated from the body.
• Crystal Growing — Sodium thiosulfate readily forms colorless, monoclinic crystals. Read our article, “Growing Large Crystals with Seed Crystals” for more information.

Also used in the following patina formulas…

• No. 7 for Blue Green
• No. 10 for Green
• No. 11 for Green-Blue (Flemish)
• No. 13 for Transparent Blue
• No. 16 for Yellow
• No. 24 for Black – semi-gloss (For Cast Bronze)
• No. 30 for Black (For Cast Brass)

Sodium Thiosulfate as Pond/Aquarium Dechlorinator

Chloramine vs. Chlorine…

The following stock solution of Sodium Thiosulfate does not treat for Chloramine, only Chlorine. Chloramine is a chemical compound composed of chlorine and ammonia and more and more utilities are converting to its use. Check with your municipal water company to learn which chemical they are using. If Chloramine is the disinfectant, please research other knowledgeable sources to learn your best solution for water treatment.

To begin…

Obtain a clean one gallon jug. A photography supply store will likely have good brown jugs. They are used to store darkroom chemicals. Dissolve the 500 grams of Sodium Thiosulfate in a large pitcher of lukewarm tap water. Stir until all the crystals are dissolved. Then transfer the solution with a funnel to the gallon jug. Top off the jug to make a full gallon of stock solution.

• Add two drops of the stock solution per one gallon of the water to be treated.
• One gallon can treat 37,850 gallons or more. Over-dosage is virtually impossible.