Simple Chloride Titration
You will need:
A weighing scale that will weigh to at least one tenth of a gram.
Two 1ml diabetic syringes and a 10cc syringe with needles. (or Pipettes).
Small clear glass container that holds approx. 30cc.
Silver Nitrate.
Indicator.
![[picture of some bits and pieces needed]](pmclt.jpg)
Weigh 2.0 grams Silver Nitrate and dissolve in approx. 70cc water and make up to 81.552cc (2.0 grams
Silver Nitrate dissolved in 81cc (81 grams) water is accurate enough). Store in a stoppered bottle. This
quantity of reagent will do many tests, at least 80.
Indicator is Sodium or Potassium Chromate. About 4 grams Chromate dissolved in 25cc water is OK. If you do
not have any Chromate you can use Dichromate. About 4 grams Dichromate dissolved in 20cc water mixed with
1 gram Na (or K) Hydroxide dissolved in 5cc water. 25cc total of indicator. About 6 drops of this is used
per titration.
Take a 1cc sample of solution to be measured for Chloride concentration using a diabetic syringe.
Add this 1cc sample to the quantity of water shown in the table. You will have an idea of what the
approximate concentration of Chloride is in the solution before you start. If not then use the
0 to 350 value and titrate again if more accuracy is required should the actual concentration turn out
to be much lower.
Estimated
concentration
of Na Chloride
in grams per liter | Add to
|
| 0 to 350 | 349cc |
| 0 to 200 | 199cc |
| 0 to 100 | 99cc |
| 0 to 50 | 49cc |
Mix well and take 10 cc of the now diluted sample and place into a clear glass container
that gives a clear view of it's contents and hold approximately 30cc. Add another 10cc water to the
10cc already in the 30cc container.
Add 6 drops of the indicator solution. The Chloride sample solution to be titrated will be a yellow colour.
Take 1cc of the Silver Nitrate solution using a diabetic syringe.
Drop the Silver Nitrate into the sample solution stirring all the time. Insoluble Silver Chloride is formed and
the solution will have a cloudy but still yellow colour.
A slight permanent red colour indicates that all the soluble Chloride has been transformed into insoluble
Silver Chloride.
The concentration of Chloride per liter of solution can be calculated from the following.
NaCl(grams per liter) = ['Add to' value from table + 1] * [cc's AgNO3 solution used]
KCl(grams per liter) = ['Add to' value from table + 1] * 1.276 * [cc's AgNO3 solution used]
Example: If the estimated value of Na Chloride was 150 g/l and 0.6 cc of AgNO3 solution was used
to precipitate all Chloride (permanent slightly red colour obtained), then the Na Chloride concentration is:
[199 + 1] * 0.6 = 120 grams per liter NaCl.
![[pictures of stages]](cl_tit.jpg)
If you need some practice with this system it is a good idea to make up a solution of 200 grams per liter
NaCl by weighing out 100 grams NaCl and dissolving in water. This solution is then taken up to 500ml. Practice on this solution to get an idea of when the colour change should be deemed to have happened.
Some points:
If taking samples from a cell to track CE make sure the cell volume is the same at each sampling time.
Always use needles on the syringes as they will be more accurate.
Use a dedicated syringe for the Nitrate and Chloride solutions.
Always eliminate bubbles from syringes.
Weigh the 2.00 grams Ag Nitrate as carefully and as accurately as possible.
Hyprchlorites or Chlorites do not interfere with the test but it should be noted that if you test a
sample from a cell and then test the same cell contents that has been boiled, there will be a small increase
in Chloride concentration due to destruction of the Hypochlorites. Boiling increases the amount of Na Chloride by approx. 6 grams per liter.
There is a more exacting Chloride titration procedure in the Sodium Chlorate section under "Collection of Graphs and Tables".
Chlorate determination
The Sodium Chlorate in a Chlorate cell can be calculated by knowing the starting amount of Na Chloride per liter and noting the fact that each gram of Chloride that is no longer present will have formed an amount of Chlorate equal to 1.82 * [Chloride no longer present] in grams per liter assuming the volume of the cell is the same as at the start.
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