Health Education To Villages




Home Programmes Resources India Partners Site Map About Us Contact Us
 

Centers for Disease Control and Prevention
 CDC Home Search Health Topics A-Z
Foodborne and Diarrheal Diseases BranchLink Online to Foodborne and Diarrheal Diseases BranchCDC MenuSafe Water System Menu

Safe Water System Manual


ANNEX C:


HOW TO TEST CONCENTRATION OF FRESHLY-PRODUCED SODIUM HYPOCHLORITE FOR QUALITY ASSURANCE

 

Materials needed:

· 1 ml pipettes
· pipetter (for drawing up solution into the pipette)
· 2 100-ml graduated cylinders
· distilled water
· colorimetric chlorine comparator (Hach kits, test strips, other colorimeters)

Testing procedure:

· Fill both graduated cylinders with 99 ml of distilled water.
· Draw up 1ml of freshly-prepared sodium hypochlorite and put it in first graduated cylinder, mix well.
· Draw up 1ml of solution from first graduated cylinder and put it in second graduated cylinder, and mix well.
· Measure the solution in the second graduated cylinder in the chlorine comparator-the result will be measured in mg/liter.
· With this method, the units in mg/liter correspond exactly to the concentration of the disinfectant produced. (For example, if the solution from the second graduated cylinder is 0.5 mg/liter, then the sodium hypochlorite solution is 0.5%.)

Basis of this calculation:

First graduated cylinder:
     X mg hypochlorite solution/100ml (99ml H2O + 1ml of hypochlorite solution) = X mg/100ml

Second graduated cylinder:
     Y mg x 1ml of solution from 1st cylinder/100ml (99ml H2O + 1 ml 1st cylinder solution) = Y mg/100ml

Example:

If the sodium hypochlorite solution is 0.5%, this equals 0.5gm/100ml, which equals 500mg/100ml. In 1ml, there are 5mg.

Therefore, in the first cylinder, you have:

5mg/100ml (99ml H2O + 1ml hypochlorite solution)
1ml of this solution has 0.05mg of solution.

In the second cylinder, you have:

0.05 mg/100ml (99ml H2O + 1 ml solution from first cylinder)

The concentration of this solution in mg/liter (which is what is measured in the chlorine comparators) is 0.5 mg/liter. If you get this measurement in the chlorine comparator after doing this procedure, the sodium hypochlorite solution is 0.5 gm/100ml or 0.5%.


Alternative Testing Procedure for Sodium Hypochlorite Concentration (if graduated cylinders are not available)

Materials needed:

· 1ml pipette
· 1 20 liter container
· distilled water
· chlorine comparator

Testing procedure:

· Fill 20 liter container (attempt to fill exactly; variation by a few ml will not appreciably affect results).
· Add 2ml of sodium hypochlorite solution and mix well.
· Measure this solution with chlorine comparator.
· With this method, the units in mg/liter correspond to the concentration of the disinfectant produced. (For example, if the solution is 0.5 mg/liter, then the sodium hypochlorite solution is 0.5%.)

Example:

If the concentration of the sodium hypochlorite solution is 0.5%, or 0.5gm/100ml, or 500mg/100ml, in 1ml of solution there are 5 mg.

In 2ml of solution, there are 10mg.

10mg/20 liters = 0.5mg/liter. If you get this measurement in the chlorine comparator after doing this procedure, the sodium hypochlorite solution is 0.5 gm/100ml or 0.5%.

 

For quality assurance of bleach production, a form should be used to monitor each production run of sodium hypochlorite. The following form is a sample:


Hypochlorite Production Record

DateOperatorTime machine
turned on
Time machine
turned off
Salt
(kg)
Water
(liters)
Sodium
hypochlorite
concentration
pHNo. of
bottles
filled
Comments
          
          
          
          
          
          
          
          
          

 

Home

Centers for Disease Control and Prevention
National Center for Infectious Diseases
Division of Bacterial and Mycotic Diseases
Foodborne and Diarrheal Diseases Branch

 

 The Mother and Child Health and Education Trust Programmes | Resources | India | Partners | Site Map | About Us | Contact Us top of page

Feedback Form