Conductivity (Type-IV)
OIV-MA-F1-01 Conductivity
Type IV method
- Principle
The electrical conductivity of a column of liquid defined by two parallel platinum electrodes at its ends is measured by incorporating it in one arm of a Wheatstone bridge.
The conductivity varies with temperature and it is therefore expressed at 20°C.
- Reagents
Use only reagent grade chemicals
2.1. Purified water for laboratories, with specific conductivity below 2 μS cm-1 at 20°C, for example EN ISO 3696 type II water.
2.2. Reference solution of potassium chloride.
Dissolve 0.581 g of potassium chloride, KCl previously dried to constant mass at a temperature of 105°C, in demineralised water (2.1). Make up to one litre with demineralised water (2.1). This solution has a conductivity of 1 000 μS cm-1 at 20°C. It should not be kept for more than three months.
A commercial preparation can be used.
- Apparatus
3.1. Conductivity meter enabling measurements of conductivity to be made over a range from 1 to 1 000 microsiemens per cm (μS cm-1).
3.2. Water bath for bringing the temperature of samples to be analysed to approximately 20°C (20 
2°C).
-
Procedure
- Preparation of the sample to be analysed
Use a solution with a total sugar concentration of 25 0.5 % (m/m) (25° Brix): weigh a mass equal to 2500/P and make up to 100 g with water (2.1),
P = percentage (m/m) of total sugars in the rectified concentrated must.
4.2. Determination of conductivity
Bring the sample to be analysed to 20°C by immersion in a water bath. Maintain the temperature to within ± 0.1°C.
Rinse the conductivity cell twice with the solution to be examined.
Measure the conductivity and express the result in μS cm-1.
- Expression of the Results
The result is expressed in microsiemens per cm (μScm−1) at 20°C to the nearest whole number for the 25% (m/m) (25° Brix) solution of rectified concentrated must.
5.1. Calculations
If the apparatus does not have temperature compensation, correct the measured conductivity using Table I. If the temperature is below 20°C, add the correction; if the temperature is above 20°C, subtract the correction.
- Characteristics of the method
Repeatability (r)
- r = 3 μS/cm
Reproducibility (R)
- R = 16 μS/cm
Table I
Corrections to be made to the conductivity for temperatures different from 20°C (μS cm−1)
|
Conductivity |
Temperature (°C) |
|||||||||
|
20.2 19.8 |
20.4 19.6 |
20.6 19.4 |
20.8 19.2 |
21. 19.0 |
21.2 18.8 |
21.4 |
21.6 |
21.8 18.2 |
22,0(1) 18.0(2) |
|
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
50 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
2 |
2 |
2 |
|
100 |
0 |
1 |
1 |
2 |
2 |
3 |
3 |
3 |
4 |
4 |
|
150 |
1 |
1 |
2 |
3 |
3 |
4 |
5 |
5 |
6 |
7 |
|
200 |
1 |
2 |
3 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
|
250 |
1 |
2 |
3 |
4 |
6 |
7 |
8 |
9 |
10 |
11 |
|
300 |
1 |
3 |
4 |
5 |
7 |
8 |
9 |
11 |
12 |
13 |
|
350 |
1 |
3 |
5 |
6 |
8 |
9 |
11 |
12 |
14 |
15 |
|
400 |
2 |
3 |
5 |
7 |
9 |
11 |
12 |
14 |
16 |
18 |
|
450 |
2 |
3 |
6 |
8 |
10 |
12 |
14 |
16 |
18 |
20 |
|
500 |
2 |
4 |
7 |
9 |
11 |
13 |
15 |
18 |
20 |
22 |
|
550 |
2 |
5 |
7 |
10 |
12 |
14 |
17 |
19 |
22 |
24 |
|
600 |
3 |
5 |
8 |
11 |
13 |
16 |
18 |
21 |
24 |
26 |
|
(1)Subtract the correction. (2)Add the correction. |
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