Reaffirmed 2022

NATIONAL FOREWORD

This Indian Standard (First Revision) which is identical with ISO 4793: 1980 ‘Laboratory sintered (fritted) filters – Porosity grading, classification and designation’ issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Glass, Glassware and Laboratoryware Sectional Committee and approval of the Chemical Division Council.

The system for porosity grading and designating laboratory sintered (fritted) filters was of classification in grades from G-00 to G-5. The Technical Committee responsible for preparing this standard decided to formulate this standard aligning it with ISO 4793: 1980 to assist the purchaser and user of the laboratory sintered (fritted) filters. This standard was originally published in 1988. The comparison between the then old and new designation were shown graphically in that standard.

Considering the importance of following uniform practices globally, the committee felt the need of revising this standard and also felt that it would be more convenient to prepare this standard by adoption of ISO 4793 on dual number basis.

The text of ISO standard has been approved as suitable for publication as an Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker, while in Indian Standards the current practice is to use a point (.) as the decimal marker.