Potassium biiodate
| Potassium biiodate | |
|---|---|
| IUPAC name | potassium µ-hydridobis(trioxidoiodate)(1−) |
| Other names | potassium hydrogen iodate |
| Identifiers | |
| InChI | InChI=1/2HIO3.K/c2*2-1(3)4;/h2*(H,2,3,4);/q;;+1/p-1 |
| InChIKey | ACAYDTMSDROWHW-REWHXWOFAC |
| Standard InChI | InChI=1S/2HIO3.K/c2*2-1(3)4;/h2*(H,2,3,4);/q;;+1/p-1 |
| Standard InChIKey | ACAYDTMSDROWHW-UHFFFAOYSA-M |
| CAS number | [] |
| EC number | |
| ChemSpider | |
| Properties[1] | |
| Chemical formula | KH(IO3)2 |
| Molar mass | 389.91 g mol−1 |
| Appearance | white crystals |
| Solubility in water | 1.33 g/100 ml (15 °C) |
| Hazards[2][3][Note 1] | |
| EU index number | not listed |
| GHS pictograms |   
|
| GHS signal word | DANGER |
| GHS hazard statements | H272, H302, H314, H318 |
| GHS precautionary statements | P210, P220, P221, P260, P264, P270, P280, P301+312, P301+330+331, P303+361+353, P363, P304+340, P310, P321 |
| Flash point | Non-flammable |
| Related compounds | |
| Other compounds | Potassium iodate Iodic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Potassium biiodate, KH(IO3)2, is a primary standard strong acid in analytical chemistry.[4][5]
Contents
[hide]Chemistry
The biiodate anion is a hydrogen-bonded species formed from the reaction of an iodate anion with undissociated iodic acid (pKa = 0.75).[6]
- IO−3 + HIO3 → [H(IO3)2]− Kc ≈ 4 dm3 mol−1
Hence, in dilute aqueous solutions, potassium biiodate can be considered to be a mixture of potassium iodate and iodic acid: however, it dissolves and recrystallizes coherently from water.[7]
Preparation
Potassium biiodate is commercially available in analytical grade. However it may be conveniently prepared by simply mixing hot concentrated solutions of potassium iodate and iodic acid and allowing the potassium biiodate to crystallize.
Ferroelectricity
Potassium biiodate forms a ferroelectric phase below the Curie point of TC = 223(2) K.[8] The second-order phase transition appears to be associated with the ordering of the hydrogen bonds in the crystal structure.[9]
Notes and references
Notes
- Jump up ↑ Hazards were assessed as for an equimolar mixture of potassium iodate and iodic acid.
References
- Jump up ↑ CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p B-133. ISBN 0-8493-0462-8.
- Jump up ↑ HSNO Chemical Classification Information Database, <http://www.ermanz.govt.nz/Chemicals/ChemicalDisplay.aspx?SubstanceID=1913> (accessed 9 September 2010), New Zealand Environmental Risk Management Authority. (potassium iodate)
- Jump up ↑ HSNO Chemical Classification Information Database, <http://www.ermanz.govt.nz/Chemicals/ChemicalDisplay.aspx?SubstanceID=12620> (accessed 9 September 2010), New Zealand Environmental Risk Management Authority. (iodic acid)
- Jump up ↑ Kolthoff, I. M.; van Berk, L. H. The Use of Potassium Bi-iodate as a Standard Substance in Alkalimetric and Iodimetric Titrations. J. Am. Chem. Soc. 1926, 48 (11), 2799–2801. DOI: 10.1021/ja01690a006.
- Jump up ↑ Processing KODAK Motion Picture Films, Module 4 – Potassium Biiodate; Kodak, <http://motion.kodak.com/motion/uploadedFiles/US_plugins_acrobat_en_motion_support_processing_h244_potBiiod.pdf>. (accessed 9 September 2010).
- Jump up ↑ Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; p 1010. ISBN 0-08-022057-6.
- Jump up ↑ Smith, Sterling B. Ternary Systems. VIII. Potassium Iodate, Iodic Acid and Water. J. Am. Chem. Soc. 1947, 69 (10), 2285–86. DOI: 10.1021/ja01202a013.
- Jump up ↑ Petrosyana, A. M.; Buscha, A. A.; Chechkina, V. V.; Volkova, A. F.; Venevtsev, Yu. N. Ferroelectric phase transition in potassium Bi-iodate. Ferroelectrics 1978, 21 (1), 525–26. DOI: 10.1080/00150197808237316.
- Jump up ↑ Barabash, A.; Baran, J.; Gavrilko, T.; Eshimov, K.; Puchkovskaya, G.; Ratajczak, H. Structure and dynamics of crystal α-modification of potassium biiodate. J. Mol. Struct. 1997, 404 (1–2), 187–91. DOI: 10.1016/S0022-2860(96)09380-5.
