Winegrowers Supplies - Instructions for the 'Sulfacor' test
Determination of Total acidity in juice, wine or cider, by Dr. Stührk's method:-
The drink to be analysed should be as clear as possible and free from carbonic acid (carbon dioxide in solution). It must be shaken (or heated to just below boiling point) until the CO2 comes out.
Pour the drink into the cylinder, accurately up to the '0' mark (approx 10 ml).
The lowest part of the meniscus must just touch the '0' mark.
Add the Blaulauge (blue alkali solution) turning the cylinder gently.
Eventually the colour changes from brownish to pale green. A further 1 to 2 drops are then added carefully and the contents of the cylinder mixed thoroughly by covering the top of the cylinder and inverting it slowly. This is repeated until the colouration changes further from green to blue-green, the determination is then complete.
The Total acidity ('tartaric equivalent') in grams per litre is then read off the scale; at the lowest part of the meniscus.
After the test the dropping bottle must be closed tightly with the sealing cap, otherwise the liquid can change composition.