On the reaction of calcium with thiocyanate-liquid-ammonia solutions

✍ Scribed by F.E. Rosztoczy; C W. Tobias

• Publisher: Elsevier Science
• Year: 1966
• Tongue: English
• Weight: 479 KB
• Volume: 11
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(66)87060-3

✦ Synopsis

The stoichiometry of the dissolution of Li, Na, K, Mg and Ca in liquid ammonia solutions contaming NH,SCN or KSCN has been determined. In the temperature range between -20 and -45"C, and in the concentration range of 15-30 mol-% thiocyanate, calcium reacts with NH,SCN solutions according to the stoichiometric equations Ca + 2NH,+ + Caa+ + Hn + 2NHs, Ca + SCN-+ CaS + CN-.

Li, Na, K and Mg react with NH$CN solutions forming only HI. Li, Na, K and Ca react with KSCN solutions forming only sulphide and cyanide, while Mg reacts extremely slowly, and yields only hydrogen.

Although the calcium appears to react with the solute at all thiocyanate concentrations, the rate of dissolution decreases with increasing thiocyanate concentration.

This observation may be explained by assuming that the rate-controlling step is Ca + n NH8 -. [Caa+(NHs),]e,P-. R&snm&StoechiomCtrie de la dissolution de Li, Na, K, Mg, Ca dans NH, liq. contenant NH&X ou KSCN. Entre -20 et -45'C, pour des concentrations de 15 a 30mol % de thiocyanate, Ca reagit avec NH&XV selon Ca + 2NH1+ -, Gas+ + HII + 2NHJ et Ca + SCN-+ CaS + CN-. D'autre part, Li, Na, K, Mg rbgissent en n'engendrant que Ha, dans les solutions de NH$CN, mais Li, Na, K, Ca reagissent en n'engendrant que des sulfures et des cyanures dans les solutions de KSCN tandis que Mg ne r&agit qu'ext&mement lentement, en n'engendrant que Hp. Bien que Ca paraisse magir 21 toute concentration de tout thiocyanate, sa vitesse de dissolution decroit quand s'accroit cette concentration, ce qui peut s'interpreter en supposant l'etape mgulatrice Ca + n NH8 --+ [Cas+(NI-13]e,B-.