Monopotassium phosphate

• Kaliumbiphosphat
• Monopotassium phosphate
• Mono- potassium orthophosphate
• Primary / monobasic potassium phosphate
• KDP

Odorless and colorless crystals

Fixed

2.34 g · cm -3

253 ° C ( decomposition)

Readily soluble in water: 222 g · l-1 (20 ° C)

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Potassium dihydrogen phosphate is a colorless and odorless potassium salt of phosphoric acid. It is composed of a potassium cation ( K ) and a dihydrogen phosphate anion ( H2PO4 ). It thus belongs to the dihydrogen.

• 3.1 potassium cation
• 3.2 dihydrogen phosphate anion

Properties

Chemical Properties

Potassium reacts acid in water: pH 4.4 cent at a 5% solution. Anhydrous potassium dihydrogen phosphate is hygroscopic.

Use

Is potassium, especially in biochemistry and related sciences, the use for the preparation of buffer solutions. Often it is used here together with dipotassium hydrogen phosphate, which reacts basically in contrast to potassium. The associated basic phosphate is potassium phosphate. By combinations of the three salts leads to the aqueous phosphate solution having a defined pH value. Potassium hydrogen phosphates may be substituted for the corresponding sodium hydrogenphosphates, if potassium ions are not desired.

Potassium is used in the food industry as an acidity regulator. It is together with the secondary dipotassium phosphate ( K2HPO4 ) and tertiary potassium phosphate ( K3PO4 ) in the EU as a food additive under the joint number E 340 ( " potassium phosphates " ) approved for certain foods, each with different maximum quantity restrictions. After the additive approval regulations are the - for most approved phosphates largely uniform - individual specifications for a wide range with many different types of food. The approved maximum amounts vary from 0.5 to 50 grams per kilogram ( in coffee whiteners for vending machines ) or the lack of a fixed restriction ( quantum satis - as needed, nutritional supplements and partly in chewing gum ). Phosphorus is in hyperactivity suspected of causing allergic reactions and osteoporosis. It was determined an allowable daily dose of 70 milligrams per kilogram of body weight for the total amount of recorded phosphoric acid and phosphates.

Further potassium dihydrogen phosphate is used as a fertilizer.

In nonlinear optics sectional potassium crystal plates are used for frequency doubling at certain angles. In the way of parametric fluorescence and frequency halving is possible. For the experiments on the development of laser - ignited inertial confinement fusion at the National Ignition Facility more potassium dihydrogen phosphate crystals were grown with each 318 kg mass per crystal.

Proof

Potassium cation

Potassium can be detected as other potassium salts on the violet flame coloration.

Very specific, albeit not very sensitive potassium can be detected with perchloric acid. It turns out sparingly soluble potassium perchlorate.

Dihydrogen phosphate anion

If you give ammonium heptamolybdate to a nitric acid, phosphate-containing solution, falls yellow from Ammoniummolybdatophosphat.

Arsenic acid interferes with this proof, since it is partially analogous to the phosphate precipitated as Molybdoarsenat.

If the solution is first neutralized, further possibilities for evidence:

With silver nitrate, a yellow precipitate of silver phosphate, which dissolves in weak acids forms.

The addition of barium chloride Bariumhydrogenphosphat white precipitates, which readily dissolves in acetic acid.