Vinotest Acidometer
Congratulations on your purchase of the VINOTEST acidometer. The VINOTEST acidometer is a fast and accurate titrametric
method to measure the total acid content as well as the total sulphite content (SO2
content) of wines, cider, sparkling wines, etc.
Read these instructions carefully before starting. Always keep this sheet with your
set. This set is complete and contains the following components: Special measuring glass with 2 coloured scales Synthetic pipette Carrying basket 5x 100 ml reactives
SAFETY PRECAUTIONS
Certain reactives have a caustic or irritating effect.
ALWAYS KEEP THE REACTIVES OUT OF THE REACH OF CHILDREN.
Preferably always use gloves and possibly a pair of safety goggles when carrying out the measurements.
PREPARATION
Measuring the degree of acid (total acid content)
The reading of the acid content will appear on the RED scale of the measuring glass. Fill the measuring glass with wine up to the bottom red stripe (0). Slowly add first per ml, then by the drop, the reactive
CAUSTIC POTASH SOLUTION. Shake evenly so that the reactive is mixed well with the wine. Repeat this process until the colour
of the wine changes from (dark) green to blue. Attention: as the colour change approaches, you must be increasingly accurate
with your dosing: the change from green to blue can happen by adding 1 drop. Once the colour change has happened, you
simply read the value on the RED scale division. This value will give you the acid degree of your wine, in grams/ litres (expressed
in tartaric acid).
Measuring the free sulphite content (free SO2)
Reading the free sulphite content is done on the YELLOW scale of the measuring glass. Fill the measuring glass with wine up to
the bottom yellow stripe. Add the STARCH-ACID REAGENT up to the next yellow stripe (0). Shake the measuring glass well, so
that the reactive and the wine are well mixed. Then immediately begin to titrate (=slowly add) the reagent JODIT-JODAT. Add
this reagent first by the ml and then by the drop, while regularly shaking, until the colour change BLUE-VIOLET stays for 10
seconds. The content of free SO2 is read from the yellow scale in milligrams / litre. Measuring the TOTAL (= free + bound) sulphite content
Reading the total sulphite content is done on the YELLOW scale of the measuring glass. Fill the measuring glass with wine up to the bottom yellow stripe. Add the LYE REAGENT up to the GREEN stripe. Shake the
measuring glass well, so that the reactive and the wine are well mixed. Wait 10 minutes, then add the ACID REAGENT up to the
next YELLOW stripe. Shake the measuring glass well, so that the reactive and the wine are well mixed. Then immediately begin
to titrate (=slowly add) the reagent JODIT-JODAT. Add this reagent first by the ml, then by the drop, while regularly shaking,
until the colour change BLUE-VIOLET stays for 10 seconds. The obtained value on the YELLOW scale indicates the total sulphite
content, expressed in milligrams / litre.
COMMENTS
Store the reactives closed tightly in a dark place.
Titrating is usually easier for white wines. The colour change is easy to see. For red wines, the colour change is often more
difficult to see. You can mitigate this by first diluting the wine to e.g. 50%. Take exactly e.g. 10 ml wine and mix with 10 ml
water. Then multiply the outcome by 2.
Before reading a value on the measuring glass, sit straight in front of it. Reading a value is done on the underside of the
meniscus of the liquid.
Determining the SO2 content must be done at 20 °C. Lower or higher temperatures may give a different result.
For the determination of the acid content it is important that any carbonic acid (CO2) that may be in the wines is first
disposed of. For this, allow the wine to sit uncovered for a while and then regularly shake it until all the carbonic acid is
evaporated.
For wines to which ascorbic acid (vitamin C) has been added, an accurate SO2 content reading cannot be obtained. The
ascorbic acid will react with the reactive and will give a result that is too high.
