TOCII CA72TOC Installation
Endress+Hauser 17
Procedure:
For an organic carbon solution with a concentration of 5,000 mg/l, dissolve 10.627 g of p.a. (or
better) KHP in 500-700 ml of deionized water in a 1-liter volumetric flask (other concentrations of
the solution are listed in the table below). Once the chemical has dissolved, add 4 ml of H
2
SO
4
(4molar) (CAS: 7664-93-9) and top up the mixture with water until the 1-liter mark is reached. Stir
the solution once more. Label the container, indicating the contents and the date of preparation.
The solution with a concentration of 5,000 mg/l is stable (particularly when stored in a cool dark
place). It is recommended to perform serial dilutions on the basis of a standard substance of
5,000 mg/l to reduce the concentrations if needed. Example:
• If 10 ml of a solution with a concentration of 5,000 mg/l is diluted with 90 ml deionized water,
this results in a concentration of 500 mg/l.
• If 10 ml of a solution with a concentration of 500 mg/l is diluted with 90 ml deionized water,
this results in a concentration of 50 mg/l.
• If 10 ml of a solution with a concentration of 50 mg/l is diluted with 90 ml deionized water, this
results in a concentration of 5 mg/l.
Serial dilution is the preferred method to create lower concentrations instead of diluting 1 ml of the
5,000 mg/l solution with 99 ml deionized water. The latter method can result in measurement
errors.
"
Caution!
Please note the following:
• Storable parent solutions with concentrations of 1,000 and 5,000 mg/l are relatively stable for
several weeks at room temperatures. Parent solutions must be stored in cool dark place.
• In the case of a solution with a concentration of 10 mg/l, on the other hand, the quality starts to
deteriorate at room temperature within 3 to 5 days. To give the KHP standard solutions greater
stability 4 ml H
2
SO
4
(4 mol) can be added to one liter (has a shelf life of up to 4 weeks).
• If parent solutions with a high KHP content acidify, there is the risk of the KHP precipitating.
• Make sure to keep the container with the crystalline KHP sealed at all times. If the crystalline KHP
comes into contact with the air, it absorbs water very quickly and must be dried before use.
Otherwise you will get inaccurate measurements since the concentration of carbon is lower in the
hydrous salt. KHP that has come into contact with air must be dried for one hour at 105 °C
(221 °F).
mg/l carbon g KHP Volume
5,000 10.627 1 l
1,000 2.1254 1 l
500 1.0627 1 l
100 0.21254 1 l
10 0.021254 1 l
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