ANNEX I

E 450 (v) TETRAPOTASSIUM DIPHOSPHATE

Synonyms

Potassium pyrophosphate

Tetrapotassium pyrophosphate

Definition

Chemical name

Tetrapotassium diphosphate

Einecs

230-785-7

Chemical formula

K4P2O7

Molecular weight

330,34 (anhydrous)

Assay

Content not less than 95 % on the ignited basis

P2O5 content

Not less than 42,0 % and not more than 43,7 % on the anhydrous basis

Description

Colourless crystals or white, very hygroscopic powder

Identification

A.

Positive tests for potassium and for phosphate

B.

Solubility

Soluble in water, insoluble in ethanol

C.

pH of a 1 % solution

Between 10,0 and 10,8

Purity

Loss on ignition

Not more than 2 % after drying at 105 oC for four hours and then ignition at 550 oC for 30 minutes

Water-insoluble substances

Not more than 0,2 %

Fluoride

Not more than 10 mg/kg (expressed as fluorine)

Arsenic

Not more than 3 mg/kg

Cadmium

Not more than 1 mg/kg

Lead

Not more than 4 mg/kg

Mercury

Not more than 1 mg/kg