Grundfos DIT-M, Installation And Operating Instructions Manual

Page: 23 / 36

English (GB)
23
7.7.5 Chlorine, total
7.8 Chlorine dioxide,
0.02 - 11 mg/l ClO
2
7.8.1 Selection
7.8.2 Important notes
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent)
contain reducing substances, the subsequent determination of
chlorine dioxide may show lower results. To avoid any
measurement errors, only use glassware free of chlorine
demand.
Preparation: Put all applicable glassware into sodium
hypochlorite solution (0.1 g/l) for one hour, then rinse all
glassware thoroughly with deionised water.
2. When preparing the sample, the escape of chlorine dioxide
gases, e.g. by pipetting or shaking, must be avoided. The
analysis must take place immediately after taking the sample.
3. The DPD colour development is carried out at a pH value of
6.2 to 6.5. The reagent tablet therefore contains a buffer for
the pH adjustment.
Strong alkaline or acidic water samples must be adjusted
between pH 6 and pH 7 before the tablet is added.
Use 0.5 mol/l sulphuric acid and 1 mol/l sodium hydroxide,
respectively.
4. For concentrations between 11 and 19 mg, the photometer
shows that the measuring range (Overrange) has been
exceeded. Concentrations above 19 mg/l chlorine dioxide can
lead to results showing 0 mg/l. In this event, the water sample
must be diluted with water free of chlorine dioxide. 10 ml of
the diluted sample should be mixed with the reagent and the
measurement repeated (plausibility test).
5. If "???" is displayed at a differentiated test result, see section
8.1 Operating messages in the display (error display) .
6. All oxidising agents in the samples interfere, as they react in
the same way as chlorine dioxide.
7.8.3 In the presence of chlorine
Important notes
1. The conversion factor to convert chlorine
dioxide as chlorine to chlorine dioxide as ClO
2
is 0.38:
mg/l ClO
2
= mg/l ClO
2
[Cl] x 0.38
ClO
2
[Cl]
ClO
2
(Chlorine dioxide displayed as chlorine units ClO
2
[Cl] has its
origin in swimming pool water treatment, according to
DIN 19643.)
2. The total chlorine result given includes the contribution of the
chlorine dioxide (as chlorine) reading. For true total chlorine
value, subtract the chlorine dioxide (as chlorine) reading from
the quoted total chlorine reading.
3. See also section 7.8 Chlorine dioxide, 0.02 - 11 mg/l ClO
2
.
Measurement
1. Fill a clean vial (
∅
24) with 10 ml of the
water sample, close tightly with the cap.
2. Place the vial in the sample chamber
correctly. See fig. 4 .
3. Press the [Zero] key.
4. Remove the vial from the sample
chamber and empty it, leaving a few
drops in the vial.
5. Add one DPD No. 4 * tablet
(No 95727751 ) straight from the foil and
crush the tablet using a clean stirring
rod.
6. Add water sample to the 10 ml mark.
7. Close the vial tightly with the cap and
swirl gently several times until the tablet
is dissolved.
8. Place the vial in the sample chamber
correctly. See fig. 4 .
9. Press the [Test] key. Wait for a reaction
period of 2 minutes.
When the reaction period is finished, the
measurement starts automatically.
The result is shown in the display in mg/l
total chlorine.
*) One DPD No. 1 tablet (No 95727747 ) in
combination with one DPD No. 3 tablet
(No 95727750 ) can be used as an
alternative.
The following selection is shown in the
display:
for the determination of chlorine dioxide in
the presence of (with) chlorine.
for the determination of chlorine dioxide in
the absence of (without) chlorine.
Select the desired determination with the
arrow
keys and .
Confirm with the key.
1 0 0
prepare Zero
press ZERO
Zero accepted
prepare Test
press TEST
∅
24
Countdown
2:00
1 2 0
Chlordioxid
with Cl
without Cl
>> with Cl
>> without Cl
>>
1. Fill a clean vial (
∅
24) with 10 ml of the
water sample, close tightly with the cap.
2. Place the vial correctly in the sample
chamber. See fig. 4 .
3. Press the [Zero] key.
4. Remove the vial from the sample
chamber and empty it.
5. Add one DPD No. 1 tablet
(No 95727747 ) straight from the foil and
crush the tablet using a clean stirring
rod.
6. Fill a second clean vial with 10 ml of the
water.
7. Add one Glycine tablet (No 95727752 )
straight from the foil and crush the tablet
using a clean stirring rod.
8. Close the vial tightly with the cap and
swirl gently several times until the tablet
is dissolved.
9. Transfer the contents of the second vial
into the prepared vial.
10. Close the vial tightly with the cap and
swirl gently several times until the tablets
are dissolved.
11. Place the vial in the sample chamber
correctly. See fig. 4 .
1 2 0
prepare Zero
press ZERO
∅
24