Borates, salts or esters of boric acids. The salts are characterized in that they BO33 or a condensed form thereof, in their lattice ions as an anion, the borate ion ( for example, B4O5 (OH) 42 -, tetraborate ) containing.

Borates form an independent mineral class.

Natural Occurrence

The degradation of boron-containing, usually hydrated minerals is termed borate degradation. The following minerals are important, used in industry and technology borates:

  • Boracite (magnesium -chloro- borate, anhydrous)
  • Borax (sodium tetraborate )
  • Pandermite (calcium borate)
  • Colemanite (calcium borate)
  • Sassolin ( boric acid)
  • Kernite (sodium tetraborate )
  • Ulexite (calcium -sodium borate )


A simple illustration of the reaction of orthoboric acid borates with sodium hydroxide solution (sodium hydroxide solution):


The isolated borate ion is BO33 - trigonal planar according to the VSEPR model (cf. figure).

There are a variety of structural variations in the borates; For example, the dimer B2O54 or the already mentioned tetraborate B4O5 (OH ) 42 -.

In addition, there are various metaborate, which are derived from the metaboric and the general formula ( BO2 ) nn - have. You can train both annular and polymeric chain structures.

By the reaction of boric acid with polyhydric alcohols ( for example, glycerol or mannitol) can be obtained cyclic ester ( chelate ) complexes.

Borates in which an oxygen atom is replaced by a Disauerstoffgruppe called perborates or perborates.


For the rapid qualitative detection of borates are added to the test substance in a test tube or porcelain dish, adds methanol and a few drops of concentrated sulfuric acid, boric acid trimethyl ester is formed. The rising vapors of methanol, which also contain the boric acid esters are flammable and burn with a green flame.

The presence of divalent copper ions can interfere with the detection.

For quantitative detection of borates in analytical chemistry, the curcumin method is suitable. Curcumin and boric acid are the red - colored complex rosocyanine whose concentration is determined colorimetrically. Therefore, the curcumin method is also suitable for the quantitative determination of boron after oxidative digestion of a sample of boron - containing material.


Various forms of borates are used in wood preservatives. Borates are also used as buffer substances (see: buffer solution ) were used. Perborate in detergents and bleaches used.