Dipotassium hydrogen phosphate

Structural formula
General
Surname	Dipotassium hydrogen phosphate
other names	Potassium monohydrogen phosphate Potassium phosphate secondary Potassium phosphate dibasic DIPOTASSIUM PHOSPHATE ( INCI )
Molecular formula	K 2 HPO 4
Brief description	colorless, odorless solid
External identifiers / databases
CAS number 7758-11-4 (anhydrous) 16788-57-1 (trihydrate) EC number 231-834-5 ECHA InfoCard 100.028.940 PubChem 24450 ChemSpider 22858 DrugBank DB09414 Wikidata Q403721
properties
Molar mass	174.18 g mol −1 (anhydrous) 228.22 g mol −1 (trihydrate)
Physical state	firmly
density	2.44 g cm −3
Melting point	> 180 ° C (decomposition)
solubility	very light in water (1600 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Dipotassium hydrogen phosphate is a chemical compound from the group of hydrogen phosphates . It is in the form of a colorless and odorless solid and is the secondary phosphate of ortho - phosphoric acid . It also occurs as a trihydrate .

Extraction and presentation

Dipotassium hydrogen phosphate can be obtained by neutralizing phosphoric acid with potassium hydroxide or potassium salts ( e.g. potassium carbonate or potassium chloride ).

properties

An aqueous solution of dipotassium hydrogen phosphate has a slightly alkaline reaction. When heated, dipotassium hydrogen phosphate changes into the corresponding tetrapotassium diphosphate with elimination of water :

${\displaystyle \mathrm {2\ K_{2}HPO_{4}\longrightarrow K_{4}P_{2}O_{7}+H_{2}O} }$

use

Dipotassium hydrogen phosphate is used for the production of buffer solutions together with potassium dihydrogen phosphate or as a component of bacterial culture media .

Dipotassium hydrogen phosphate is used in food technology as a complexing agent , acid regulator and melting salt . Together with primary (KH ₂ PO ₄ ) and tertiary potassium phosphate (K ₃ PO ₄ ), it is approved in the EU as a food additive under the common number E 340 ("potassium phosphate") for certain foods, each with different maximum quantity restrictions. According to the Additive Admissions Ordinance , these are - largely uniform for most of the approved phosphates - individual specifications for a wide range of numerous different types of food. The maximum permitted amounts vary from 0.5 to 50 grams per kilogram (in creamer for vending machines) or the lack of a fixed limit ( quantum satis - as required, for food supplements and sometimes for chewing gum). Phosphoric acid and its salts are suspected of causing hyperactivity , allergic reactions and osteoporosis . A permissible daily dose of 70 milligrams per kilogram of body weight was set for the total amount of phosphoric acid and phosphates ingested.

It is still used as a fertilizer.

Individual evidence

1. ↑ Entry on DIPOTASSIUM PHOSPHATE in the CosIng database of the EU Commission, accessed on June 27, 2020.
2. ↑ ^{a b c d e} Entry on dipotassium hydrogen phosphate in the GESTIS substance database of the IFA , accessed on February 4, 2018(JavaScript required) .
3. ↑ CASO broth: casein peptone-soy flour peptone broth for microbiology. Merck Millipore , accessed August 14, 2019 .