Manufacturer of laboratory equipment and techniques since 1975

 

OPERATIONAL TECHNIQUE SULPHUR DIOXIDE SO2 (RIPPER METHODE)


MATERIAL:

BURETTE STAND GAB INOX

BURETTE CLAMP WITH BOSSHEAD

BURETTE 25 ml WITH PTFE KEY

PIPETTE 25 ml 2 CIRCULAR MARKS CLASS "A"

PIPETTE 5 ml GRADUATED

PIPETTE 10 ml GRADUATED

ERLENMEYER FLASK 250 ml NORMAL NECK

RUBBER STOPPER

SULPHUR DIOXIDE ANALYSIS PACK SO2

RED PIPETTE PUMP 25 ml


CHEMICAL CONCEPTS:

The advantage of this method is to get a fast estimation of the content of SO2, turning it into a rutine method, effective for its daily use. This method can be used for any kind of wines and is based in the redox reaction in which sulphur dioxide (SO2) reacts with iodine.

The use of a highly stable in time titration solution such as potassium iodate solution is a novelty compared with iodine.

The iodine/iodate that has not reacted turns into a dark blue colour in combination with starch and the persistence of this colour during 10-15 sec. indicates the end of the analysis.

By contrast it is slightly less precise than the oficial aspiration method (Paul-Rankine) for red wines as some iodate reacts with SO2 and the rest iodate might react with phenols, sugars, aldehydes and other reducing substances, the quantity of each varies depending on the composition of each wine.


OPERATIONAL TECHNIQUE FREE SO2:

1. Fill and top the 25ml burette with titration liquid.

2. With the help of a pipette pour in the erlenmeyer 25ml of the wine or must sample to be analysed, 1-2ml of starch solution and 5ml of acid solution. 

3. Set the erlenmeyer under the burette and titrate untill the change of colour which must persist during 10-15 seconds.

4. Multiply by 10 the spent volume to get the quantity of free SO2.


OPERATIONAL TECHNIQUE TOTAL SO2:

1. Proceed as step 1. free SO

2. Pour in the flask 25ml of the sample and 10ml of alkali.

3. Cover it, shake it, and let it rest during 15 minutes.

4. Past the time pour 1-2ml of starch solution and 5ml of acid solution.

5. Titrate it the same way as the previous case, steps 3 and 4, to get the total SO2 quantity.


OBSERVATIONS

One of its advantages is that the result is obtained multiplying by 10 the spent milliliters (1ml equals to 10mg/l of SO2, see table).

The change of colour turns into a deep blue-purple, hardly seen in red wines. Observation can be improved by adding some distilled water in the sample and with the help of a lamp through the sample.

Caution should be taken in order not to touch the walls of the erlenmeyer with the starch pipette because when returning the pipette to the bottle it will pollute the liquid and it will acquire a bluish colour.  Also be carefull not to mix pipettes from different bottles.

The end of the analysis is determined when the sample is maintained in a dark blue colour during 10-15 seconds.

Ripper method can’t be used if the sample contains ascorbic acid (C-Vitamin) thus it reacts in large quantities with iodate, use then SO2 Inhibitor ref. 1006012.

Use the table of multiplier coeficients in case you use a different concentration of iodine/potassium iodate or if you use a different sample volume: 


TABLE OF MULTIPLYING COEFICIENTS

 
 

  VOLUME OF THE SAMPLE mL.

 
        

10

15

20

25

50

100

             
IODINE N/10

320

213

160

128

64

32

IODINE N/32

100

66.6

50

40

20

10

IODINE N/50

64

42.6

32

25.6

12.8

6.4

IODINE N/64

50

33.3

25

20

10

5

IODINE N/100

32

21.3

16

12.8

6.4

3.2

IODINE N/128

25

16.64

12.5

10

5

 

 

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