Synthesis database: Sodium hypochlorite synthesis

Sodium hypochlorite can be synthesized by leading a stream of chlorine into a solution of sodium hydroxide. The chemicals needed for this synthesis are sodium hydroxide, trichloroisocyanuric acid and hydrochloric acid.

As for the equipment, a simple gas generator is needed, along with an ice bath which has sodium chloride added to it in order to achieve temperatures below 0 °C. It is best to keep the temperature between -5 and 0 °C during this reaction.

When hydrochloric acid comes in contact with trichloroisocyanuric acid, chlorine starts to be generated. This is shown by the following equation:

C₃N₃O₃Cl₃ + 3HCl -> 3Cl₂ + C₃N₃O₃H₃

The generated chlorine reacts with the sodium hydroxide solution. The mentioned reaction is described below:

2NaOH + Cl₂ -> NaClO + NaCl + H₂O

The mass fraction of sodium hydroxide in the solution used in the experiment was equal to 22%. When the mass of such a solution gains one fifth of the initial solution mass, most of the sodium hydroxide reacted with the chlorine gas. The mass fraction of sodium hypochlorite in the obtained solution is approximately 17%. In this experiment, from 12 grams of the initial solution, 14.4 grams of sodium hypochlorite solution (w = 17%) has been obtained.

The result is a clear solution with a slightly greenish color. It has a strong smell typical for aqueous solutions of hypochlorites. Since sodium hypochlorite gradually decomposes, it is best to use this solution as soon as possible. Alternatively, it could be stored in a cold and dark place. On the test tube walls (image above) one can see bubbles which already formed due to the decomposition of sodium hypochlorite in the obtained solution.