Fused Silica is neutral to all halogens and acids irrespective of temperature or concentration except hydro-fluoric and phosphoric acid. Phosphoric acid affects fused silica only at high temperatures and can be concentrated successfully in silica vessels. For all ordinary purposes they can be used with phosphoric acid. Sulphuric, Nitric and Hydrochloric acids or any mixture of these acids, do not affect Fused Silica even at temperatures upto 1000ºC. Cleaning of Silica ware regularly can ensure good service.