Chemistry Reference
In-Depth Information
Table 7.8
Changes in the iodine concentration of standards, blanks and drinking water
solutions made up in 0.3% potassium carbonate in different containers over a
period of days
Test solution
Container
Iodine concentration
µg
L
−1
After
1h
After
1 day
After
3 days
After
8 days
4µg L
−1
solution
Glass calibrated
flask
3.9
4.0
4.0
4.2
Polyethylene bottle
3.9
3.9
4.0
4.0
Polystyrene bottle
3.9
3.9
3.9
3.9
Blank solution
Glass calibrated
flask
0.0
0.2
0.4
0.5
Polyethylene bottle
0.0
0.1
0.2
0.3
Polystyrene bottle
0.0
0.0
0.0
0.0
Laboratory drinking water straight
from tap
Glass calibrated
flask
4.7
5.5
5.7
5.8
Polyethylene bottle
4.5
5.5
5.8
5.6
Polystyrene bottle
4.5
5.4
5.7
5.7
Cambridge drinking water
Glass calibrated
flask
5.4
-
5.8
6.1
Polystyrene bottle
5.4
-
5.5
5.4
Hertford drinking water
Glass calibrated
flask
4.4
-
5.0
5.0
Polystyrene bottle
4.5
-
4.6
4.5
Oxford drinking water
Glass calibrated
flask
5.6
-
6.0
6.0
Polystyrene bottle
5.7
-
5.9
5.8
Source: Reproduced with permission from the Royal Society of Chemistry [38]
Standard iodide solution—200µg L
−1
of iodide. Dilute 5ml of the standard iodide
solution (40mg L
−1
of I) to 1000ml with distilled water in a calibrated flask. Store in a
polythene or polystyrene bottle (stable for 1 month).
Working solutions—into 200-calibrated flasks pipette 5, 4, 3, 2, 1 and 0ml of standard
iodide solution (200µg L
−1
of I). Add 2ml of 30% m/V potassium carbonate solution and
dilute to 200ml with distilled water. These are the working standards. Store in
polystyrene bottles and prepare freshly every 2 weeks.
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