Winemaking and technical services to the wine industry

Formol Titration method

Supplied by Michael Liedtke of Laffort

Apparatus and reagents

Aqueous solution of NaOH (N)- mother solution
Aqueous solution of NaOH 0,1 N
Aqueous solution of pure Formaldehyde (35% minimum)- Its pH will be adjusted to 8,5 (every day before use)
Solution of Peroxide (30%), H2O2


1. Take 50 ml of juice (if you already added SO2 in the must put 2 or 3 drops of H2O2 in before starting)
2. Adjust the juice to pH 8,5 with the solution of NaOH (N)
3. Add 20ml of formaldehyde adjusted to pH 8,5
4. Wait a few minutes
5. Titrate to pH 8,5 with a solution of NaOH (0,1 N)

The value titrated will be "n" ml

Total assimilable N=n x 28mg/L

150mg/L of assimilable N is the minimum required to avoid any problem of stuck fermentation due to lack of nitrogen.

A more detailed discussion with some variations can be obtained from the Zoecklein site.

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Feel free to contact Loftie Ellis on any wine related subject by Email at or contact us at

Tel: 021- 883 9017
Fax: 021-882 9487
Cell: 082 825 2489

Wine Quality Consultants
P.O. Box 6231
South Africa

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