Dasteck ChemicalsYantai Dasteck Chemicals Co., Ltd.
Direct answer
Prepare stock solutions with cold water and add the alkali only shortly before use. Solubility in water at 20 °C is about 26.7 g/L; under strongly alkaline conditions up to 100 g/L dissolves, but such alkaline solutions are very unstable and must be prepared and used immediately.
Key points
| Step | Requirement |
|---|---|
| Water | Cold water. Hot water accelerates decomposition |
| Order of addition | Add water first, then the product slowly with stirring, to avoid lumps |
| When to add alkali | Only shortly before use; do not prepare in advance |
| Alkali-free solution | Almost stable for up to 6 hours at room temperature |
| Alkaline solution | Unstable; prepare and use immediately |
Why cold water
Thiourea dioxide is stable at ambient temperature but decomposes slowly when heated, releasing sulphur dioxide. Mixing with hot water consumes reducing power before the bath even starts.
Why alkali must go in first
In weakly acidic solution the product is oxidised to formamidine sulfonic acid and loses its reducing power; it only decomposes to release sulfoxylate under alkaline conditions. The order of addition must therefore be alkali first, then the reducing agent.
Common mistakes on site
Sources
DILUTION INSTRUCTION section of our product technical data sheet.