English (GB)
21
7.5 Bromine, 0.05 - 13 mg/l Br
2
7.5.1 Important notes
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent)
contain reducing substances, the subsequent determination of
bromine 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 bromine gases,
for example by pipetting or shaking, must be avoided.
The measurement 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 reagent
is added. Use 0.5 mol/l sulphuric acid and 1 mol/l sodium
hydroxide, respectively.
4. For concentrations between 13 and 22 mg, the photometer
shows that the measuring range (Overrange) has been
exceeded. Concentrations above 22 mg/l bromine can lead to
results showing 0 mg/l. In this event, the water sample must
be diluted with water free of bromine. 10 ml of the diluted
sample should be mixed with the reagent and the
measurement repeated (plausibility test).
5. All oxidising agents in the samples interfere, as they react in
the same way as bromine.
7.5.2 Measurement
7.6 Chloride, 0.5 - 25 mg/l Cl
-
7.6.1 Important notes
1. Ensure that all particles of the tablet are
dissolved. Chloride causes an extremely fine distributed
turbidity with a milky appearance.
Heavy shaking results in bigger sized particles which can
cause false readings.
2. High concentrations of electrolytes and organic compounds
have different effects on the precipitation reaction.
3. Ions which also form deposits with silver nitrate in acidic
media, such as bromides, iodides and thiocyanates, interfere
with the measurement.
4. If necessary, highly alkaline water should be neutralised using
nitric acid before measurement.
7.6.2 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.
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. 1
tablet
(No
) 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.
9. Press the [Test] key.
The result is shown in the display in mg/l
bromine.
8
0
prepare Zero
press ZERO
Zero accepted
prepare Test
press TEST
∅
24
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.
.
3. Press the [Zero] key.
4. Remove the vial from the sample
chamber.
5. Add one
Chloride T 1
tablet
(No
) straight from the foil to
the water sample, crush the tablet using
a clean stirring rod and dissolve the
tablet.
6. Add one
Chloride T 2
tablet
(No
) straight from the foil to
the same water sample and crush the
tablet using a clean stirring rod.
7. Close the vial tightly with the cap and
swirl gently several times until the tablets
are dissolved (see section
, note
1.).
8. Place the vial in the sample chamber
correctly. See fig.
.
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
chloride.
9
0
prepare Zero
press ZERO
Zero accepted
prepare Test
press TEST
∅
24
Countdown
2:00
Summary of Contents for DIT-M
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