I am confused about the sequence of mixing these two chemicals. Some materials said add H2O2 to H2SO4 but others do it reversely. Who can help me to confirm it? Thanks! Sincerely, Zhiwei Zou -----Original Message----- From: Hongjun-ECE Subject: RE: [mems-talk] About the Piranha cleaning Please confirm that it is H2So4 added to H2O2, instead of H2O2 added to H2So4, which might be dangerous.