Can hydrofluoric acid be heated to 150 degrees to remove silica?
The treatment of silicon dioxide with hydrofluoric acid is usually carried out in platinum dry pans (or platinum dishes), and the elevated temperature can evaporate the four fluorinated silicon as soon as possible and accelerate the reaction speed. In order to remove all silica, it is usually added excessive hydrofluoric acid, plus a few drops of sulfuric acid (1+1), to be heated in a water bath or a low temperature hotplate. The first is water and four volatile silicon tetrafluoride gas heated to run, finally, sulfuric acid starts to decompose, three sulfur dioxide white smoke cigarettes, until no three sulfur dioxide white smoke, can stop heating, the silica have all become four silicon tetrafluoride gas to volatilize, thoroughly remove the silica.
In chemical analysis, this reaction is often used to remove silica and eliminate interference. It can also be used for the determination of silica in quartz sand or other samples by differential weight method, and the weight reduction part is pure silica.
Hydrofluoric acid and silicon dioxide react at room temperature to produce four fluorinated silicon gas and water. The heating is designed to drive off four of fluorinated silicon, speeding up the reaction rate and removing silica. The reaction is as follows:SiO2 + 4 HF = SiF4 + 2 H2O
The entire reaction temperature should not be too high (less than 100 degrees Celsius), if the temperature is too high, the reaction is severe, easy to cause sample splash loss.
