xmlns:atom="http://www.w3.org/2005/Atom" xmlns:atom="http://www.w3.org/2005/Atom"
50 mm, in case of heat treatment in accordance with point 2(a); or
30 mm, in case of heat treatment in accordance with point 2(b).
They must then be mixed with formic acid to reduce and maintain the pH to 4,0 or lower. The mixture must be stored for at least 24 hours pending further treatment.