PRODUCT
PRODUCT
Chlorination with sodium thiosulfate (common name: hypo)
Our Company’s products that are usually used as dechlorinating agents include granular crystalline sodium thiosulfate and sodium thiosulfate solution (32%). For the amount of sodium thiosulfate required to treat various chlorine compounds, please refer to the following table. The above is a theoretical amount, so more may be needed in practice. Eventually, measure the object to be treated and confirm the endpoint. Furthermore, acid is produced after processing. The reference amount to neutralize this acid with caustic soda is also shown in the same table. In practice, check with a pH meter while adding.
Table: Required theoretical amount of sodium thiosulfate (kg) for object to be treated 1 (kg)
| Product name/object to be treated | Crystalline sodium thiosulfate Na2S2O3・5H2O |
Sodium thiosulfate solution Na2S2O3-32% |
NaOH solid equivalent required to neutralize the acid produced after treatment (kg) |
|---|---|---|---|
| Sodium hypochlorite | 0.83 | 1.66 | 0.27 |
| Sodium chlorite | 1.37 | 2.73 | 0.44 |
| Sodium chlorite | 1.75 | 3.48 | 0.56 |
| Chlorine dioxide | 2.30 | 4.57 | 1.33 |
| Chlorine | 0.87 | 1.74 | 1.41 |
| Sodium perchlorate | 2.03 | 4.03 | 0.65 |
| Free residual chlorine (as hypochlorous acid) | 1.19（※） | 2.38 | 1.15 |
The concentration and quantity of the object to be treated are required in order to calculate the theoretical quantity. The theoretical amount of sodium thiosulfate can be obtained by substituting these values into the following equation.
[Target concentration (%)] x [Treatment volume (L)] x [Value in the above table] ÷100 = [Theoretical amount (kg)]
Alternatively, [Object concentration (ppm)] x [Treatment volume (L)] x [Value in the above table] ÷ 1000 = [Theoretical amount (g)]
*Calculation example
For example, to treat 3000L (= 3t = 3m3) of water with 1 ppm of free residual chlorine (as hypochlorous acid) with crystalline sodium thiosulfate, substitute into the above equation
1 × 3000 × 1.19 ÷ 1000 = 3.57
3.57 g is the theoretical amount of crystalline sodium thiosulfate.