SiO2+HF= SO2+I2+H2O= NiS+O2= ZnS+HCl=
SiO2+4HF = SiF4+2H2O SO2+I2+2H2O=2HI+H2SO4 2NiS+3O2=2NiO+2SO2 ZnS+2HCl=ZnCl2+H2S