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TAPPI T 428

Standard:  

TAPPI

Method:

TAPPI T 428

Title:

Hot water extractable acidity or alkalinity of paper

Scope

TAPPI T 428, based on the work of Kohler and Hall, measures the titratable acidity or alkalinity (end point at pH 7.0) of an aqueous extract of paper (filtered and extracted by boiling water for 1 hour). It specifies one extraction and so does not measure the total acidity or alkalinity of paper, for which exhaustive extraction is required. It may be applied to writing, printing, and sized industrial paper but is not intended for testing electrical insulating papers. This method measures the pH of the bulk extract as prepared in the method, and as such, measures the combined acidity and alkalinity of the base paper and any added fillers or coating materials.

Summary

This method consists of a boiling water extraction of the specimen followed by an alkalinity-acidity titration of the extract solution.

Significance

The pH determination measures the extent to which the paper alters the hydrogen-hydroxyl ion equilibrium of pure water, and the acidity-alkalinity determination measures the quantity of extracted ionic material that contributes to that equilibrium change. These tests are useful for routine acceptance testing, research work, or the evaluation and classification of different papers.

Samples

A minimum of 10 grams of paper is required to perform this test.

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