Graphite rod atomization and atomic fluorescence for the simultaneous determination of silver and copper in jet engine oils

S-Methyldithizone(5-methylmercapto-1,5-diphenylformazan) reacts with the chlorides of copper(II), mercury(II) and phenylmercury(II) to give the 1:1 chelates CuCl(MeDz), HgCl(MeDz) and C₆H₅Hg(MeDz)] and with nickel(II) and palladium(II) to give the 1:2 chelates, M(MeDz)₂. All these complexes are intensely coloured in chloroform solution. No complexes are formed from cobalt(II), manganese(II) or zinc(II) or from the nitrates or acetates of copper and mercury. Coordination increases the reactivity of the sulphur atom in dithizone. Whereas dithizone is unaffected by methyl iodide, nickel dithizonate, Ni(HDz)₂, gives Ni-(MeDz)₂ when heated with methyl iodide in ethanol in the presence of sodium acetate; palladium dithizonate behaves similarly. The 1:1 adduct of nickel dithizonate with 2,2'-bipyridyl gave only Ni(MeDz)₂ on treatment with methyl iodide, and this complex would not form an adduct with bipyridyl. On standing in the light, Ni(MeDz)₂ reacted photochemically to give the yellow isomer of S-methyl-dithizone.