Top IPC subclasses
1
|
C02F
|
8
|
Treatment of water, waste water, sewage, or sludge
|
2
|
C22B
|
3
|
production or refining of metalspretreatment of raw materials
|
3
|
C25C
|
2
|
processes for the electrolytic production, recovery or refining of metalsapparatus therefor
|