Rubidium dichromate

Structural formula
General
Surname	Rubidium dichromate
Molecular formula	Rb 2 Cr 2 O 7
Brief description	red triclinic or yellow monoclinic crystals
External identifiers / databases
CAS number 13446-73-6 EC number 236-602-7 ECHA InfoCard 100.033.261 PubChem 61606 Wikidata Q2171581
properties
Molar mass	386.924  g · mol -1
Physical state	firmly
density	3.021 g cm −3 (monoclinic) 3.125 g cm −3 (triclinic)
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 350i-317-410 P: ?
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Rubidium dichromate is a chemical compound made of rubidium , chromium and oxygen .

Extraction and presentation

Rubidium dichromate can be produced by the reaction of rubidium carbonate and chromium (VI) oxide

${\displaystyle \mathrm {Rb_{2}CO_{3}+2\ CrO_{3}\longrightarrow Rb_{2}Cr_{2}O_{7}+CO_{2}\uparrow } }$

or ammonium dichromate can be obtained with rubidium chloride.

${\displaystyle \mathrm {(NH_{4})_{2}Cr_{2}O_{7}+2\ RbCl\longrightarrow Rb_{2}Cr_{2}O_{7}+2\ NH_{4}Cl} }$

properties

Physical Properties

Rubidium dichromate occurs in two different crystal structures:

• A triclinic modification with the space group P1 (C _i ¹ ), which has the lattice parameters a = 13.554  Å , b = 7.640 Å, c = 7.735 Å, α = 93.64 °, β = 98.52 °, and γ = 88, 80 °. In the unit cell there are four formula units.
• A monoclinic modification with the space group P2 ₁ / n.

Chemical properties

Rubidium dichromate reacts with chromium trioxide to form rubidium tetrachromate .

${\displaystyle \mathrm {Rb_{2}Cr_{2}O_{7}+2\ CrO_{3}\longrightarrow \ Rb_{2}Cr_{4}O_{13}} }$

With rubidium forms Rubidiumchromat .

${\displaystyle \mathrm {Rb_{2}CO_{3}+Rb_{2}Cr_{2}O_{7}\rightarrow 2\ Rb_{2}CrO_{4}+CO_{2}\uparrow } }$

use

Rubidium dichromate is used to make elemental rubidium. To do this, it is reacted with zirconium in a high vacuum at 500 ° C :

${\displaystyle \mathrm {Rb_{2}Cr_{2}O_{7}+2\ Zr\longrightarrow \ 2\ Rb+2\ ZrO_{2}+Cr_{2}O_{3}} }$

Individual evidence

1. ↑ ^{a b c} Dale L. Perry, Sidney L. Phillips: Handbook of inorganic compounds . CRC Press, 1995, ISBN 978-0-8493-8671-8 , p. 334 ( limited preview in Google book search).
2. ↑ Entry on chromium (VI) compounds in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
3. ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling it falls under the group entry Chromium (VI) compounds, with the exception of barium chromate and of compounds specified elsewhere in this Annex in the Classification and Labeling inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
4. ↑ ^{a b} Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1526.
5. ↑ N. Ch. Panagiotopoulos, ID Brown: Crystal structure of triclinic rubidium dichromate, Rb ₂ Cr ₂ O ₇ . In: Canadian Journal of Chemistry . 48 (4), 1970, p. 537, doi : 10.1139 / v70-089 .
6. ^ Robert L. Carter: "Comparison of the vibrational spectra of K ₂ Cr ₂ O ₇ , Rb ₂ Cr ₂ O ₇ and Cs ₂ Cr ₂ O ₇ " in Spectrochimica Acta A 1973 , 29 (2), pp. 253-262 . doi : 10.1016 / 0584-8539 (73) 80069-8
7. ↑ Percy Löfgren: "The crystal structure of rubidium tetrachromate, Rb ₂ Cr ₄ O ₁₃ " in Acta Cryst. 1973 , 29 , p. 2141. doi : 10.1107 / S0567740873006242
8. ^ Mary Eagleson: Concise encyclopedia chemisry Berlin; New York: de Gruyter, 1994, ISBN 3-11-011451-8 , p. 958 ( limited preview in Google book search).