Calculating Chlorine residual?

[Pump2005]

I have a Hach tester that is not designed to read Chlorine levels above 2.20 mg/l. For Iron I can multiply the reading by the number of times I split the sample but I believe the Chlorine residual is calculated a different way when split. Your help would be appreciated.

 

[orenda1168]

Use the same procedure as you do for iron.

Orenda

 

[Jamesliska]

You will also have to take into account the Chlorine demand; you would loose accuracy if you dilute the sample, try to get different reagents for your free chlorine monitor.

James

 

[orenda1168]

Pump2005:

Chlorine demand has no relation to the measurement of free chlorine residual. Sample dilution is OK as long as you compensate for the dilution, for example,with two parts chlorine fee (distilled) water and one part sample, the resultant free chlorine value multiplication factor is 3X.

Orenda

Orenda

 

[Jamesliska]

Distilled water has a chlorine demand, that is a fact, if you dilute the sample some of the free chlorine will be used up by this demand. The total chlorine stays the same, the free chlorine in the sample is reduced, there are ways of controlling this demand by chlorinating the distilled water and allowing the residual to tail off but i have never seen this done successfully.
The errors may be small but they are real.

 

[orenda1168]

Sorry, James, but you are incorrect. There is nothing in distilled water that can create a chlorine demand. If you are finding a "chlorine demand" in distilled water, then there is another issue (read error) in your analysis.

Orenda

Orenda