Indicates the conditions under which the test sample shall be prepared and relates to particular properties which require particular precausions: the samples shall be taken rapidly in a dry atmosphere, storage in an airtight bottle. The bottle shall be made from an inert material such as polyethylene. Preparation of the main solution with distilled carbonat- free water. If the silica content is to be determined the test portion shall be dissolved in a container made from silica-free material such as polyethylene or silver. Cancels and replaces ISO Recommendations R 977/1969 and R 978/1969.
https://www.iso.org/standard/8392.html
