The Effects of Alkali Metal Ions and Alkaline Earth Metal Ions on the Adduct Formation of Thiocyanato-N Cobaltate(II) Complexes with Nonionic Surfactant

Abstract

On adding Triton X-100, a nonionic surfactant, to an aqueous solution of cobalt (II) containing some alkali metal or alkaline earth metal thiocyanates in excess, a deep blue tarry gel deposited. The gels were stoichiometric adducts such as M^J₂ [Co(NCS)₄] ⋅ 2Triton or M^II [Co (NCS)₄]⋅ 2Triton. These compositions remained essentially constant despite using various concentrations of Triton except barium salt. Counter ion of thiocyanate had a serious effect on gel formation. Lithium, magnesium, and calcium thiocyanates produced no analogous gels, while barium thiocyanate formed non-stoichiometric Triton adduct, which precipitated even without cobalt (II). The yields of such blue gels were observed in the following order: Ba²⁺ > K⁺ =Rb⁺ > Cs⁺ > NH⁴⁺ > Sr²⁺ > Na⁺. The recovery of cobalt (II) remaining in the supernatant liquid was minimized for all counter ions when the initial addition was conducted at a molar ratio of Triton/Co (II) =2.