ASTM D4901-99(2004)

1.1 This practice covers the preparation of a solution of liquid extract that is to be used in the tannin analysis of that extract.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

The concentration of tannin in extracts must be reduced to analytical strength (4 g tannin per L) for analyses.

Vegetable tannin extracts are heterogeneous mixtures of components with varying solubility.

The solubility of such extracts is influenced by temperature and concentration, which affect the degree of dispersion and size of the component particles.

While the solubility is better in hot water than in cold water, it is appropriate to dissolve and disperse an extract in hot water and then let the solution cool slowly to standard room temperature.