5.1 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.

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

5.3 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.

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

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

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

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

5.5.3 The rate of solution run-out from the pipette;

5.5.4 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.