Hanna Instruments HI 84102 - Manual (Page 6)

6
PRINCIPLE OF OPERATION
The determination of total acids in wine is made according to a neutralization reaction, that is the
reaction between the acids found in wine and a base. This type of reaction forms the basis of titration
methods of analysing acids.
Titratable acidity is measured on a degassed sample at the end-point of 8.20 for Australian requirements
and 7.00 to fulfil the requirements of the European Union. Both results are expressed as g/L tartaric
acid.
For precise results it is very important to know the exact sample volume, titrant volume and concentration.
The peristaltic pump has a good repeatability but the dosing volume depends on many factors as the
diameter of the tube or the tube streching. To compensate for all this errors, the pump need to be
calibrated. The calibration of the pump is also needed in order to have high precision of the titrations.
It is important to calibrate the pump at the pH value you want to use as the endpoint of the titrations.
The calibration procedure is in fact the analysis of a known solution. By doing this, the instrument
makes a differential analysis between the standard and the wine sample. The pump volumetric debit
and the real concentration of the titrant is compensated. Only the sample volume has to be precisely
known.