Disclosed is an etching solution which enables the formation of a silicon substrate having fine pyramid-like depressions and protrusions (a textured structure) in a steady manner without requiring the use of any conventional etching inhibitor such as isopropyl alcohol. Specifically disclosed is an etching solution ...

A removing system for contaminant in air comprises: a pre-stage air washer 11 which employs a chemical liquid; a chemical liquid supply device 12 configured to supply the chemical liquid to the pre-stage air washer 11; a post-stage air washer 13 which employs a pure water as the absorbent; an ion exchange resin 14 t...