Sigma-Aldrich

A 5 L or 10 L VOLPAC container consists of a flexible polyethylene bag with an outlet tap and a cubic cardboard supporting frame. No volume compensation by access of air is necessary during emptying of the bag, thereby eliminating the possibility of contamination. All our VOLPAC containers are supplied with a special adapter to allow direct connection of the titration tube to the VOLPAC container.

The endpoint of a titration can often be indicated only by using auxiliary substances. These so-called indicators are added to the titration medium and show the endpoint of the titration through easily recognizable visual changes like color change, clouding or fluorescence. Indicators are used primarily in volumetric titrations.

Advantages of non-aqueous titration:

• Enlargement of solubility range: many substances that are not soluble in water, can be easily titrated in water-free media (e.g. fats and oils).

• Enlargement of application range: weak bases and acids can be easily titrated.

• Substance compositions that cannot be separately determined in aqueous media can often be titrated in non-aqueous media.

The titration techniques can be classified along the chemical reactions they are based on:

• Acidimetric / alkalimetric titration - protons are transferred from acid to base.
• Redox titration - electrons are transferred from reducing agent to oxidizing agent.
• Complexometric titration - ions form chelate complexes with ions or molecules.
• Precipitation titration - sparingly soluble compounds are formed and precipitate.

Buffers keep the pH within a specified range, an important consideration for chemical and biochemical reactions that occur in aqueous solution. Buffers are typically mixtures of weak acids or bases with their salts or the salts of multi-alkaline acids. By dissolving these buffer substances in water that is free of salts and carbon dioxide, buffer solutions are created with reproducible pH values that remain stable for long periods.

The accuracy of Fluka buffer solutions is ensured by careful choice of the buffer substances, the use of deionized water with extremely low conductivity and subsequent calibration of the pH value with standard buffer solutions to DIN 19266.