Working Hypochlorite Preparation: Introduction, Preparation Requirements, Procedure, and Keynotes

Introduction of Hypochlorite

Sodium hypochlorite (NaOCl) is a compound that is a clear, slightly yellowish solution with a characteristic odor and it can be effectively applied for water purification as well as on a large scale for surface purification, bleaching, odor removal, and water disinfection. In the hospital, it is mostly used for decontamination of blood spillage, floor disinfectant, HIV/AIDS, Hepatitis B, and C positive blood decontamination. Around 1785 the Frenchman Berthollet developed liquid bleaching agents formed on sodium hypochlorite and it has a relative density of is 1,1 (5,5% watery solution). The concentration of a bleaching agent for domestic purposes is 5% sodium hypochlorite (pH~ 11 and irritating). If it is more concentrated, it contains a concentration of 10-15% NaOCl (pH ~13, burning and corrosive).

Working Hypochlorite Preparation Requirements

• Measuring cylinder
• Jar
• The stock of concentrated hypochlorite solution
• Water

Preparation of 0.5% Sodium Hypochlorite (bleach) solution from 5% Sodium Hypochlorite solution

• Measure 1 part (e.g. 100ml) of 5% sodium hypochlorite solution with a measuring cylinder and pour in a jar or gallon.
• Measure 9 parts (e.g. 900 ml to make 1 liter of 0.5% solution) of clean water with a measuring cylinder and pour in the jar containing 1 part of 5% sodium hypochlorite solutions.
• Mix contents in the jar well. This prepared solution can be used for up to 24 hours.

Formulae for Different Concentration (other than 5%)

If sodium hypochlorite solution available in the market has a concentration other than 5% use the
following formula to prepare the 0.5% sodium hypochlorite solution:

Parts of water to be added to 1 part of concentrated sodium hypochlorite solution=(% of Concentration/% of dilution)-1

A simple technique for working hypchlorite preparation

e.g. Concentrated 4%

Diluting 0.5%

According to the formula,

(4/0.5)-1=7

Thus, 7 part water and 1 part stock hypochlorite is needed to prepare 0.5%.

Another formula-

C1 X V1=C2 X V2

Where, C1=Concentration of stock solution

V1=Volume required of the stock solution to be diluted to get a working solution

C2=Concentration of working solution

V2= Required volume of the working solution

For example, I have to prepare 500 ml of working hypochlorite of 1% concentration.

Where the concentration of stock is 4%.

By applying the formula,

4 x V1= 1X500

V1=125 ml

• Add 125 ml stock hypochlorite in a jar with a measuring cylinder.
• And then add 375 ml clean water in a jar to make a final volume of 500 ml.

Keynotes on Hypochlorite

• Sodium hypochlorite is unstable compound.
• Chlorine evaporates at a rate of 0,75-gram active chlorine per day (24 hours) from the solution.
• The contact of sodium hypochlorite with acids, sunlight, certain metals, poisonous and corrosive gasses, heat can disintegrate it, and therefore during transportation transport, storage, and use of sodium hypochlorite precautions must be taken.
• Addition of hypochlorite to water, hypochlorous acid (HOCl) is formed:
  NaOCl + H2O → HOCl + NaOH- Hypochlorous acid is divided into hydrochloric acid (HCl) and oxygen (O). The oxygen atom is a very strong oxidator and thus sodium hypochlorite is effective against bacteria, viruses, and fungi.

Further Reading

1. https://www.sciencedirect.com/topics/chemistry/hypochlorite
2. https://pubmed.ncbi.nlm.nih.gov/17190269/
3. https://www.lenntech.com/processes/disinfection/chemical/disinfectants-sodium-hypochlorite.html
4. https://en.wikipedia.org/wiki/Sodium_hypochlorite
5. https://go.drugbank.com/drugs/DB11123
6. https://www.organic-chemistry.org/chemicals/oxidations/sodiumhypochlorite.shtm