Xylem Oxix Calibration - Manual (Page 7)

Item Oxix
Name: FW 846003-001
Release date: 12/07 2011
S/N at release date: 97060 Quick Guide for Oxix
Calibration
Version: 04-2012 KJ
EN 5.4 Oxix Quick guide for calibration 1204.doc 7/7
Guide to Oxygen-free Solution for Checking Oxix D.O. Sensor
Zero Point
Method
•
Clean Oxix® and its optical window thoroughly.
•
Dissolve 3 tablespoons Na
2
SO
3
in 4 litres of tap water in an open container (bucket).
•
Stir for about 1 minute.
•
Immerse the sensor and let it rest in the solution for at least 30 minutes. (Towards the
bottom with the window down; check that there are no air bubbles on the lens.
Notes
This solution actually contains a concentration of approximately 0.10 ppm dissolved oxygen.
In time, if the solution is left alone, stratification will occur so that the concentration will be higher
towards to the surface.
If you need a reference sample with a dissolved oxygen concentration close to zero (approx. 0.02
ppm), the reference sample must be made with demineralised water and the solution must rest for
12-24 hours before measuring it.
It is important that the sensor and the optical window are completely clean when zero-point or
calibration is conducted.
How it works
Na
2
SO
3
(sodium sulphite) removes oxygen from the solution since Na
2
SO
3
is oxidized by O
2
(oxygen) into Na
2
SO
4
(sodium sulphate) following the reaction:
2Na
2
SO
3
+O
2
→
2 Na
2
SO
4
Materials
Bucket
Measuring jug
Tablespoon
Chemicals/Reagents
Sodium sulphite, Na
2
SO
3
, CAS-Nr. 7757-83-7 (Supplier VWR, Bie & Berntsen)
Tap water (alternatively, demineralised water)
Safety Precautions
Safety instructions for Na
2
SO
3
: None. There are no R- or S-phrases for the product.