Dipotassium tetraborate

Crystal structure
__ K +      __ B 3+      __ O 2−
General
Surname	Dipotassium tetraborate
other names	Potassium tetraborate
Ratio formula	B 4 K 2 O 7
Brief description	white odorless solid
External identifiers / databases
CAS number 1332-77-0 12045-78-2 (tetrahydrate) EC number 215-575-5 PubChem 9816075 Wikidata Q15627938
properties
Molar mass	233.44 g mol −1
Physical state	firmly
density	1.911 g cm −3
Melting point	> 500 ° C
solubility	soluble in water (16% by mass at 20 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 361d P: 281
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Dipotassium tetraborate is an inorganic chemical compound of potassium from the group of borates .

Extraction and presentation

Dipotassium tetraborate can be obtained by reacting potassium hydroxide , water and boric acid .

properties

Dipotassium tetraborate is a crystalline white odorless solid. It crystallizes in a triclinic structure ( space group P 1 (space group no. 2) ), which consists of a three-dimensional network of trigonal-planar BO ₃ and tetrahedral BO ₄ groups, in whose cavities the potassium ions are located. Its tetrahydrate has an orthorhombic crystal structure with the space group P 2 ₁ 2 ₁ 2 ₁ (space group no. 19) .

use

Dipotassium tetraborate is an excellent solvent for metal oxides at high temperatures. In metallurgy it is used for the production of special welding, soldering and soldering fluxes made of stainless steel or various non-ferrous metals in order to avoid the "glare" associated with sodium borate . It is also used in lubricants and as an absorber for the emergency shutdown of nuclear reactors.

Risk assessment

Dipotassium tetraborate was included by the EU in 2015 in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation in the Community's ongoing action plan ( CoRAP ). The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The reasons for the uptake of dipotassium tetraborate were concerns about consumer use , exposure of workers , high risk characterization ratio (RCR) and widespread use as well as the suspected dangers of reproductive properties. The reassessment took place from 2017 and was carried out by Lithuania . A final report was then published.

Individual evidence

1. ↑ ^{a b c d e f g h} Entry on dipotassium tetraborate in the GESTIS substance database of the IFA , accessed on August 9, 2018(JavaScript required) .
2. ↑ ^{a b} Borax: Potassium Tetraborate - Borax , accessed on August 9, 2018.
3. ↑ J. Krogh-Moe: The crystal structure of potassium diborate. In: Acta Crystallographica , B28, pp. 3089-3093, doi: 10.1107 / S0567740872007459S .
4. ↑ M. Marezio, HA Plett Inger, WH Zachariasen: The crystal structure of potassium tetraborate tetrahydrate. In: Acta Crystallographica. 16, p. 975, doi : 10.1107 / S0365110X63002619 .
5. ↑ European Chemicals Agency (ECHA): Substance Evaluation Conclusion and Evaluation Report .
6. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): dipotassium tetraborate , accessed on May 2, 2020.