Ammonium thiocyanate

Structural formula
General
Surname	Ammonium thiocyanate
other names	Ammonium rhodanide
Molecular formula	NH 4 SCN
Brief description	colorless, hygroscopic, monoclinic tablets or leaflets; Different colorations can occur when stored in air
External identifiers / databases
CAS number 1762-95-4 EC number 217-175-6 ECHA InfoCard 100.015.614 PubChem 15666 Wikidata Q415464
properties
Molar mass	76.12 g mol −1
Physical state	firmly
density	1.3 g cm −3 (20 ° C)
Melting point	149 ° C
boiling point	Decomposition: 170 ° C
Vapor pressure	<1 h Pa (20 ° C)
solubility	very light in water (1600 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302 + 312 + 332-318-412 EUH: 032 P: 273-302 + 352
Toxicological data	500 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Ammonium thiocyanate (outdated: ammonium thiocyanate ) is the ammonium salt of hydrocyanic acid (outdated: hydrofluoric acid, HSCN) with the formula NH ₄ SCN.

properties

Ammonium thiocyanate forms colorless, odorless, hygroscopic crystals that are easily soluble in water and ethanol and have a density of 1.3 g / cm ³ .

Manufacturing

Ammonium thiocyanate can be made from carbon disulfide and ammonia under pressure and elevated temperature:

${\displaystyle \mathrm {CS_{2}+2\ NH_{3}\longrightarrow NH_{4}SCN+H_{2}S} }$

use

It is used as a stabilizer for photographic developers , as a vulcanization accelerator , as an accelerator for mortar and concrete and in herbicides .

In analytical chemistry it is used as a detection reagent for iron (III) ions. The very intense red color in aqueous solution is due to the presence of undissociated [Fe (SCN) ₃ (H ₂ O) ₃ ] in addition to the ions [Fe (SCN) ₂ (H ₂ O) ₄ ] ⁺ and [Fe (SCN) (H ₂ O) ₅ ] ²⁺ .

properties

From a temperature of 70 ° C it is partially rearranged into thiourea , analogous to Wöhler's urea synthesis from ammonium cyanate . Thiourea can be obtained by concentrating an aqueous solution.

safety instructions

In 2013, ammonium thiocyanate was included by the EU in the Community's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are reassessed and, if necessary, follow-up measures are initiated. The reasons for the uptake of ammonium thiocyanate were concerns about high (aggregated) tonnage, high risk characterization ratio (RCR) and widespread use as well as the dangers arising from a possible assignment to the group of CMR substances and as a potential endocrine disruptor . The Czech Republic carried out the re-evaluation from 2015. The final report revealed no need for EU-wide regulatory measures.

Individual evidence

1. ↑ Entry on ammonium thiocyanate. In: Römpp Online . Georg Thieme Verlag, accessed on May 2, 2014.
2. ↑ ^{a b c d e f g} Data sheet ammonium thiocyanate (PDF) from Merck , accessed on January 19, 2011.
3. ↑ Entry on ammonium thiocyanate in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
4. ↑ European Chemicals Agency (ECHA): Substance Evaluation Conclusion and Evaluation Report .
5. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Ammonium thiocyanate , accessed on March 26, 2019.