Potassium disulfate

Structural formula
General
Surname	Potassium disulfate
other names	Potassium pyrosulfate Dipotassium disulfate
Molecular formula	K 2 S 2 O 7
Brief description	white, odorless solid
External identifiers / databases
CAS number 7790-62-7 EC number 232-216-8 ECHA InfoCard 100.029.288 PubChem 62681 ChemSpider 56432 Wikidata Q423545
properties
Molar mass	254.32 g mol −1
Physical state	firmly
density	2.28 g cm −3
Melting point	419 ° C
solubility	soluble in water; reacts with decomposition
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 314-331 P: 280-301 + 330 + 331-304 + 340-305 + 351 + 338-308 + 310
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium disulfate or potassium pyrosulfate K ₂ S ₂ O ₇ is the potassium salt of disulfuric acid .

Properties and appearance

Dipotassium disulfate is a hygroscopic, moisture-sensitive, white and odorless solid that is soluble in water, whereby its aqueous solution reacts strongly acidic.

The result of heating potassium hydrogen sulfate :

${\displaystyle \mathrm {2\ KHSO_{4(s)}\longrightarrow K_{2}S_{2}O_{7(s)}+H_{2}O_{(g)}} }$.

With further heating, the potassium disulfate breaks down at approx. 600 ° C into potassium sulfate and sulfur trioxide :

${\displaystyle \mathrm {K_{2}S_{2}O_{7(s)}\longrightarrow K_{2}SO_{4(s)}+SO_{3(g)}} }$.

Upon contact with water, potassium disulfate decomposes into sulfuric acid and potassium sulfate:

${\displaystyle \mathrm {K_{2}S_{2}O_{7(s)}+H_{2}O\longrightarrow K_{2}SO_{4(s)}+H_{2}SO_{4}} }$.

use

Potassium disulfate is used, for example, for the acidic digestion of salts in the heat:

${\displaystyle \mathrm {3\ K_{2}S_{2}O_{7(s)}+Fe_{2}O_{3}\longrightarrow 3\ K_{2}SO_{4(s)}+Fe_{2}(SO_{4})_{3}} }$.

The iron (III) sulfate formed is water-soluble.

Individual evidence

1. ↑ ^{a b c d e f} Entry on potassium disulphate in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
2. ↑ SB Rasmussen, KM Eriksen, G. Hatem, F. da Silva, K. Ståhl, R. Fehrmann: Conductivity, Thermal Measurements, X-ray Investigations, and Phase Diagram of the Na ₂ S ₂ O ₇ -K ₂ S ₂ O ₇ system. In: The Journal of Physical Chemistry B. 105, 2001, pp. 2747-2752, doi : 10.1021 / jp0039262 .
3. ^ ASTM International: A Manual for the Chemical Analysis of Metals. ASTM International, p. 86 ( limited preview in Google Book search).