GB/T 8309-2013Tea -- Determination of alkalinity of water-soluble ash content (English PDF)

Foreword

This standard was drafted in accordance with GB/T 1.1-2009 given rules.

This standard replaces GB/T 8309-2002 "Determination of alkalinity of water - soluble ash tea." This standard compared with GB/T 8309-2002, the main technical changes are as follows.

--- Modify the repeatability requirement. the difference between the two measurement results, soluble ash alkalinity per 100g sample should not exceed 0.2g, Modify the absolute difference between the measurement results shall not exceed 10% of the arithmetic mean.

This standard uses redrafted law revision using ISO 1578. 1987 "Determination of alkalinity of water - soluble ash tea." This standard ISO 1578. 1987 compared to the main technical differences are as follows.

--- 5g sample quality measurement modify 2g; ashing process does not add vegetable oil;

--- Assay filtrate and washings from 60mL to modify the volume of 150mL;

--- Increase the repeatability requirement. the absolute difference between the measurement results twice in the same sample obtained under repeated conditions shall not exceed the arithmetic Average of 10%;

--- Increased Chapter 5 apparatus and appliances;

--- Increased 7.1 sampling;

--- Remove the ISO 1578. 1987, Chapter 8 test reports.

This standard also made the following editorial changes.

--- Remove the ISO 1578. 1987 Foreword.

The standard proposed by China Federation of Supply and Marketing Cooperatives.

This standard by the National Standardization Technical Committee of tea (SAC/TC339) centralized.

This standard was drafted. China Federation of Supply and Marketing Cooperatives Hangzhou Tea Research Institute, the National Tea Quality Supervision and Inspection Center.

1 Scope

This standard specifies the tea soluble ash alkalinity assay reagents and solutions, apparatus and appliances, measurement step and results calculated method.

This standard applies to the determination of tea soluble ash alkalinity.

2 Normative references

The following documents for the application of this document is essential. For dated references, only the dated version suitable for use herein Member. For undated references, the latest edition (including any amendments) applies to this document.

Preparation of GB/T 601 chemical reagent standard titration solution GB/T 8302 sampling Tea (GB/T 8302-2013, ISO 1839. 1980, NEQ) GB/T 8303 Tea grated dry matter content of the sample preparation and measurement (GB/T 8303-2013, ISO 1572. 1980, MOD) GB/T 8306 Tea Determination of total ash (GB/T 8306-2013, ISO 1575. 1987, MOD) GB/T 8307 tea-soluble ash and water - insoluble ash content (GB/T 8307-2013, ISO 1576. 1988, MOD)

3 Terms and Definitions

The following terms and definitions apply to this document.

Soluble ash alkalinity alkalinityofwater-solubleash and the amount of water-soluble ash leachate desired acid, alkali or the equivalent amount of the acid content.

Principle 4

Using methyl orange as indicator, titrated with standard hydrochloric acid solution from a solution of water-soluble ash.

5 Apparatus and appliances

5.1 Buret. capacity 50mL.

5.2 Erlenmeyer flask. 250mL.

6 Reagents and solutions

6.1 HCl. 0.1mo1/L standard solution, according to GB/T 601 Preparation and calibration.

6.2 methyl orange indicator. methyl orange 0.5g, diluted to 1L with hot distilled water to dissolve.