According to the standards of GOST 859-2001 (Russia) and ASTM B170 (USA), it is extremely difficult to achieve a result above 99.997-8%, at least guaranteed. Therefore, often the manufacturer for copper 5N and above sets its own specifications describing its / other / abridged list of elements for determining purity, and sometimes the "rules" for calculating purity. Such 5N-9N copper is typically / often not even 4N according to ASTM B170 and may have characteristics even worse than 3N according to these standards. For example, some catalogs present copper "Cu 99.9999% trace metals basis". The resistivity of this "Cu 99.9999%" is indicated by 1.673 μΩ * cm, 20 ° C. In this case, the conductivity is ~ 103.06% IACS. Copper about 99.995-8% according to GOST 859-2001 and ASTM B170 can have such electrical conductivity. Comments on Cu 5-9N in the "Documents" section.
In some problems it is permissible not to take into account some impurities, but these points must be distinguished. For example, in cryogenic, any impurity has an effect, to a greater or lesser extent.
Some various sources claim that for a very pure "correct copper 99.999%":
- Electrical conductivity ~103,4-6% IACS
- RRR >1000.