Production and Principal Reactions
The commodity chemical hydrogen fluoride is produced from fluorspar by treatment with sulfuric acid. As a by product, approximately 50 kg of H2SiF6 is produced per tonne of HF owing to reactions involving silica-containing mineral impurities. H2SiF6 is also produced as a by-product from the production of phosphoric acid from apatite and fluorapatite. Again, some of the HF in turn reacts with silicate minerals, which are an unavoidable constituent of the mineral feedstock, to give silicon tetrafluoride. Thus formed, the silicon tetrafluoride reacts further with HF. The net process can be described as:
- SiO2 + 6 HF → H2SiF6 + 2 H2O
Hexafluorosilicic acid can also be produced by treating silicon tetrafluoride with hydrofluoric acid.
Neutralization of solutions of hexafluorosilicic acid with alkali metal bases produces the corresponding alkali metal fluorosilicate salts:
- H2SiF6 + 2 NaOH → Na2SiF6 + 2 H2O
The resulting salt Na2SiF6 is mainly used in water fluoridation. Related ammonium and barium salts are produced similarly for other applications. With excess base, the hexafluorosilicate undergoes hydrolysis, so the neutralization of the hexafluorosilicic acid must guard against this easy hydrolysis reaction:
- Na2SiF6 + 4 NaOH → 6 NaF + SiO2 + 2 H2O
Read more about this topic: Hexafluorosilicic Acid
Famous quotes containing the words production and, production, principal and/or reactions:
“The heart of man ever finds a constant succession of passions, so that the destroying and pulling down of one proves generally to be nothing else but the production and the setting up of another.”
—François, Duc De La Rochefoucauld (1613–1680)
“The problem of culture is seldom grasped correctly. The goal of a culture is not the greatest possible happiness of a people, nor is it the unhindered development of all their talents; instead, culture shows itself in the correct proportion of these developments. Its aim points beyond earthly happiness: the production of great works is the aim of culture.”
—Friedrich Nietzsche (1844–1900)
“I would urge that the yeast of education is the idea of excellence, and the idea of excellence comprises as many forms as there are individuals, each of whom develops his own image of excellence. The school must have as one of its principal functions the nurturing of images of excellence.”
—Jerome S. Bruner (20th century)
“Cuteness in children is totally an adult perspective. The children themselves are unaware that the quality exists, let alone its desirability, until the reactions of grownups inform them.”
—Leontine Young (20th century)