Are fluorides soluble

Structural formula
Surname Sodium fluoride
other names Fluorosodium, fluorol
Molecular formulaNaF
CAS number 7681-49-4
Brief description white crystals or colorless single crystals
molar mass 41.99 g mol-1
Physical state firmly
density 2.79 g cm-3
Melting point 995 ° C
boiling point 1700 ° C
Vapor pressure 87 Torr (1426 ° C), 531 Torr (1655 ° C), 756 Torr (1761 ° C)
solubility good in hydrofluoric acid, water (42.2 g / L at 18 ° C), not in alcohol
safety instructions
R and S phrases

R: 25-32-36 / 38
S: 22-36-34

MAK 2.5 mg m-3
LD50 (Rat, oral) 52 mg / kg
LDlo (Human, oral) 75 mg / kg
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions.

Sodium fluoride is a sodium salt of hydrofluoric acid.


The colorless sodium fluoride crystallizes in the sodium chloride structure and can be "grown" into single crystals. It is permeable to infrared and UV light. It is only sparingly soluble in water at all temperatures. Heating hardly increases the solubility. It does not dissolve in ethanol. In concentrated sulfuric acid it is converted to sodium sulfate and hydrogen fluoride. As a result of partial hydrolysis, the aqueous solution of sodium fluoride has a slightly alkaline reaction. Sodium fluoride acts as an insecticide and is poisonous.

Sodium fluoride forms with sodium chloride, sodium carbonate and calcium fluoride melts with one eutectic, with sodium sulfate melts with two eutectics. Liquid sodium fluoride conducts the electrical current, the resistance decreasing with increasing temperature.


Sodium fluoride and sulfuric acid react to form sodium sulfate and hydrogen fluoride.

The high toxicity of NaF compared to other sodium halides (e.g. sodium chloride) is due to the effect of the fluoride anion as a strong Lewis base. The fluoride binds to all iron-containing enzymes and thus blocks them.


Neutralization of concentrated hydrofluoric acid with sodium hydroxide solution

Excess hydrogen fluoride leads to the formation of sodium hydrogen fluoride:

Conversion of hydrofluoric acid with sodium carbonate:

Starting from the sodium salt of hexafluorosilicic acid, sodium fluoride can be obtained by thermal decomposition.


Sodium fluoride is used as a wood preservative and to preserve adhesives. In the electrolytic extraction of aluminum it is used as a flux, in metallurgy as a slag additive for molten metal.
Other uses:

  • Opacifiers and fluxes in glass production
  • For cleaning other fluorides by binding excess hydrogen fluoride
  • Fluorinating agents in organic chemistry.
  • Single crystals are used in instrumental analysis as filters, lenses and prisms
  • In photometry as a masking agent for iron ions
  • Fluoridation of drinking water, table salt, toothpaste, etc., fluorine tablets
  • Purification of uranium hexafluoride during reprocessing
  • As a phosphatase ingredient in molecular biology


Sodium fluoride is poisonous. Avoid inhaling dust. Gloves should be worn when working with sodium fluoride. An amount of 15 mg / kg body weight is considered lethal.[1]


  1. Fluorine compounds in oral hygiene products

Categories: Toxic Substance | Sodium compound | Fluoride | Drug