Silver chromate

Structural formula
General
Surname	Silver chromate
other names	Silver (I) chromate
Molecular formula	Ag 2 CrO 4
Brief description	red-brown solid
External identifiers / databases
CAS number 7784-01-2 EC number 232-043-8 ECHA InfoCard 100.029.130 PubChem 62666 Wikidata Q416277
properties
Molar mass	331.73 g mol −1
Physical state	firmly
density	5.63 g cm −3
solubility	almost insoluble in water
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 272-317-350i-410 P: 201-220-273-280-308 + 313-501
Thermodynamic properties
ΔH f 0	−731.7 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Silver chromate is a chemical compound from the group of chromates .

Extraction and presentation

Silver chromate can be produced by reacting silver nitrate (AgNO ₃ ) and potassium chromate (K ₂ CrO ₄ ). When silver nitrate solution is dripped onto a chromate-containing gel, periodic rings of silver chromate are created around the dripping point, which are called Liesegang's rings after their discoverer Raphael Eduard Liesegang .

${\displaystyle \mathrm {2\ AgNO_{3}+K_{2}CrO_{4}\longrightarrow Ag_{2}CrO_{4}\downarrow +\ 2\ KNO_{3}} }$

properties

Silver chromate has an orthorhombic crystal structure with the space group Pnma (space group no. 62) and the lattice parameters a = 1006  pm , b = 703 pm and c = 554 pm.

In 1798 Louis-Nicolas Vauquelin discovered the sensitivity of silver chromate to light.

use

Thanks to its characteristic red-brown color, silver chromate is used as a reagent in detection reactions. It is mainly used in the quantitative determination of chloride by titration according to Mohr .

The creation of Liesegang rings is an example of the creation of periodic structures by chemical reaction and is accordingly carried out as a demonstration experiment.

See also

• Silver dichromate Ag ₂ Cr ₂ O ₇

Individual evidence

1. ↑ Jander, Blasius: Introduction to the inorganic-chemical practical course . 14th edition. S. Hirzel Verlag, Stuttgart, Leipzig 1995, ISBN 3-7776-0672-3 .
2. ↑ ^{a b} Silver chromate data sheet (PDF) from Fisher Scientific , accessed February 13, 2014.
3. ↑ ^{a b} Data sheet Silver chromate from Sigma-Aldrich , accessed on May 12, 2017 ( PDF ).
4. ↑ 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 .
5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-4.
6. ↑ Oscillating and periodic reactions at seilnacht.com
7. ^ Marvin L. Hackert, Robert A. Jacobson: The Crystal Structure of Silver Chromate . In: Journal of Solid State Chemistry , 1971, 3, pp. 364-368, doi: 10.1016 / 0022-4596 (71) 90072-7 .
8. ↑ History of Photography (English) ( Memento from June 19, 2008 in the Internet Archive )
9. ↑ Jander, Blasius: Introduction to the inorganic-chemical practical course . 14th edition. S. Hirzel Verlag, Stuttgart, Leipzig 1995, ISBN 3-7776-0672-3 .