Is breathing a requirement for "life"?

Are you referring to it being a solid? Silicon dioxide would be a gas at some temperature - likewise CO2 is solid below -78.5c. Extraterrestrial life doesn't have to be anywhere near the same temperatures as us.

Also I don't see why you couldn't have an organism that "breathes" solid material.

I researched this topic for a while, and I came to conclusion that Si-based life is nearly impossible for several reasons.

> Silicon dioxide melting point: 1710 °C

No complex chemistry can survive these temperatures. SiO2 is only soluble in HCl and HF, which are very reactive, so no solubility either.

> Also I don't see why you couldn't have an organism that "breathes" solid material.

All of known biological chemistry relies on some sort of solubility for reagents. I don't think there's any known organism that can get rid of solid waste from the entire volume of the organism.

You could react silicon with fluoride instead of oxygen. Silicon tetrafluoride melts at −90 °C (and boils at -86).

You can also have chlorine as your oxidizer and make Silicon tetrachloride which melts at −68.74 °C and boils at 57.65 °C, that temperature range is perfect.

What else will change by having a chlorine instead of oxygen atmosphere?