44
amplifier, now, is a measure of the conductivity
of the solution being measured.
3.2.5.2 Materials Required
1. Conductivity meter with conductivity cell
2. Beaker
3. Stirrer
4. KCl
3.2.5.3 Operating Procedure
(a) Calibration of the instrument
(b) All the controls are marked on the instrument.
(c) The instrument be switched on. The indicator
lamp glows.
(d) The CAL/READ switch be kept in CAL
position and the CAL control be adjusted to
full-scale reading (100) on the meter.
(e) After thoroughly cleaning, the ‘cell’ (conductivity cell) be immersed in the standard
KCl solution, say, 0.1 N KCl which has a
specific conductivity of the order of 0.01412
millimhos (14.12 micromhos)/cm at 30 °C.
(f) The CAL/READ control be put in the READ
position. The meter needle should deflect.
(g) The range control be turned in the counterclockwise direction starting from 300
micromhos range to get a range where the
needle will show maximum deflection. The
maximum deflection of the needle could be
obtained in the range of 0–30 micromhos.
The standard table supplied with the
instrument be referred to in order to determine the conductivity of the solution at 30 °C.
(h) Then, the cell constant control be adjusted, so
that the meter reading corresponds with the
table value. In other words, the meter reading
be adjusted to read 14.12 micromhos.
Now, the instrument is calibrated for measuring the conductivity of the unknown sample.
The standard 0.1 N KCl solution is prepared
by dissolving 7.459 g of dried AR grade KCl in
1 l of DW.
3.2.5.4 Determination
of Conductivity
1. The instrument be switched-on.
2. The ‘scale selector’ knob be brought to
200-millimhos position (Maximum).
3. The ‘CAL/READ’ knob be brought to ‘CAL’.
4. The ‘CAL’ be operated to display 100 in the
display panel.
5. The cell be dipped in N/10 KCl (specific
conductivity of N/10 KCl at 30 °C is 14.12
micromhos/cm).
6. The ‘scale selector’ knob be brought to
20-millimhos position.
7. The ‘cell constant’ knob be brought to 0.95
position.
8. The ‘CAL/READ’ knob be brought to ‘Read’
position. The meter is supposed to display a
value which is little less than 14.12.
9. The ‘cell constant’ knob be adjusted, so that
the meter reads 14.12.
10. The ‘CAL/READ’ knob be brought to ‘CAL’
position.
11. The cell be rinsed with DW.
12. Next, the cell be dipped in sample water.
13. The ‘CAL/READ’ knob be brought to ‘Read’
position.
14. The ‘scale selector’ knob be rotated anticlockwise from 200-millimhos position
(highest value) gradually stage by stage to
the 20-micromhos mark (lowest value), till
the meter displays 1.0.
15. Now, the ‘scale selector’ knob be rotated
clockwise stage by stage and to be stopped at
that point where we get the highest value.
16. This value be recorded as the conductivity of
the sample water.
3.2.6 Carbon
Carbon atoms can be linked to other molecules or
atoms on four sides in long chains to form complex organic molecules. Carbon is the structural
basis of all living materials on the earth. Amount
of carbon fixed in a given time is an important
measure of productivity of a lake.
3.2.7 Productivity
Lentic bodies could be productive or unproductive in almost the same way as agricultural land.
When the input of nutrients in a lentic body
3 Lentic Water (Physico-chemical Characteristics of Water)
amplifier, now, is a measure of the conductivity
of the solution being measured.
3.2.5.2 Materials Required
1. Conductivity meter with conductivity cell
2. Beaker
3. Stirrer
4. KCl
3.2.5.3 Operating Procedure
(a) Calibration of the instrument
(b) All the controls are marked on the instrument.
(c) The instrument be switched on. The indicator
lamp glows.
(d) The CAL/READ switch be kept in CAL
position and the CAL control be adjusted to
full-scale reading (100) on the meter.
(e) After thoroughly cleaning, the ‘cell’ (conductivity cell) be immersed in the standard
KCl solution, say, 0.1 N KCl which has a
specific conductivity of the order of 0.01412
millimhos (14.12 micromhos)/cm at 30 °C.
(f) The CAL/READ control be put in the READ
position. The meter needle should deflect.
(g) The range control be turned in the counterclockwise direction starting from 300
micromhos range to get a range where the
needle will show maximum deflection. The
maximum deflection of the needle could be
obtained in the range of 0–30 micromhos.
The standard table supplied with the
instrument be referred to in order to determine the conductivity of the solution at 30 °C.
(h) Then, the cell constant control be adjusted, so
that the meter reading corresponds with the
table value. In other words, the meter reading
be adjusted to read 14.12 micromhos.
Now, the instrument is calibrated for measuring the conductivity of the unknown sample.
The standard 0.1 N KCl solution is prepared
by dissolving 7.459 g of dried AR grade KCl in
1 l of DW.
3.2.5.4 Determination
of Conductivity
1. The instrument be switched-on.
2. The ‘scale selector’ knob be brought to
200-millimhos position (Maximum).
3. The ‘CAL/READ’ knob be brought to ‘CAL’.
4. The ‘CAL’ be operated to display 100 in the
display panel.
5. The cell be dipped in N/10 KCl (specific
conductivity of N/10 KCl at 30 °C is 14.12
micromhos/cm).
6. The ‘scale selector’ knob be brought to
20-millimhos position.
7. The ‘cell constant’ knob be brought to 0.95
position.
8. The ‘CAL/READ’ knob be brought to ‘Read’
position. The meter is supposed to display a
value which is little less than 14.12.
9. The ‘cell constant’ knob be adjusted, so that
the meter reads 14.12.
10. The ‘CAL/READ’ knob be brought to ‘CAL’
position.
11. The cell be rinsed with DW.
12. Next, the cell be dipped in sample water.
13. The ‘CAL/READ’ knob be brought to ‘Read’
position.
14. The ‘scale selector’ knob be rotated anticlockwise from 200-millimhos position
(highest value) gradually stage by stage to
the 20-micromhos mark (lowest value), till
the meter displays 1.0.
15. Now, the ‘scale selector’ knob be rotated
clockwise stage by stage and to be stopped at
that point where we get the highest value.
16. This value be recorded as the conductivity of
the sample water.
3.2.6 Carbon
Carbon atoms can be linked to other molecules or
atoms on four sides in long chains to form complex organic molecules. Carbon is the structural
basis of all living materials on the earth. Amount
of carbon fixed in a given time is an important
measure of productivity of a lake.
3.2.7 Productivity
Lentic bodies could be productive or unproductive in almost the same way as agricultural land.
When the input of nutrients in a lentic body
3 Lentic Water (Physico-chemical Characteristics of Water)