This test method is used to determine the proportion of the total soluble solids which are soluble non-tannins and the proportion which are tannins in a solution of tannin extract or in the water extract from raw or spent materials prepared for tannin analysis.

The specimens are aliquots from the analytical solutions prepared from tannin extracts or the water extract solutions prepared from raw or spent materials.

The soluble non-tannins are defined as the portion of the soluble solids which are not absorbed or bound by a prepared hide powder material.

The tannins are defined as the portion of the soluble solids which are absorbed or bound by a prepared hide powder material.

The results of this test method are dependent on a great many variables but particularly upon:

The temperature conditions under which the solutions were prepared and stored and the temperature at which the current analysis is performed;

The uniformity and consistency of the Kaolin paste layer deposited onto the filter paper;

The rate of solution run-out from the pipette;

Conditions related to the properties of the hide powder used to react with the tannin content of the solution; etc. It is, therefore, essential that the method be followed exactly in order to obtain reproducible results both among specimens within a laboratory and for analyses between laboratories.

1.1 This test method is intended for use in determining the quantity of soluble non-tannins and tannin in solutions of tannin extracts, water extracts of vegetable tanning materials, or tanning liquors. The method is applicable to the analysis of liquid, solid, pasty, and powdered extracts and to extracts of raw or spent materials.

1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.

1.3 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.