XCIV.—Nickelo- and palladio-dithio-oxalic acids
Journal of the Chemical Society Transactions
XN a former paper (this VOI., p. 62) the preparation and properties of a number of highly coloured salts derived from the complex nickel* and palladio-dithio-oxalic acids were described. The salts were found to be derived from dibasic acids, M"(COS),H" dilute aqueous solutions of which had a higher electrical conductivity than equivalent solutions of sulphuric acid. The solutions when hea.ted decomposed and lost their colour; attempb t o evaporate the solvent under diminished pressure in the
... pressure in the cold also resulted in partial decomposition. Finally, however, these difficulties were overcome, both acids were isolated in well-defined crystals, and their properties have been studied. Nickelodit hio-o x d i c A cid, Ni(C0 S),H"4H20. The barium salt, Ni(COS),Ba,4H,O, in quantities of about 1 gram a t a time was finely powdered and stirred with the calculated quantity of a 3N-solution of sulphuric acid, the solution was filtered through a Gooch crucible, placed in a flat dish in a vacuum desiccator over quicklime, and allowed to remain until most of the solvent had evaporated. Long, lustrous, black prisms, often exceeding 1 centimetre in length, were thus obtained: 0.4031 gave 0.1900 CO, and 0.0920 H,O. 0.3320 " 0.8305 BaSO,. S=34*6. Ni(COS),H2,4H,O requires C = 12.87; H =2*68; S=34.3 per cent. ! I he acid dissolves readily in water, giving the characteristic, deep magenta-coloured solution like the metallic salts previously described. The solution is strongly acid; on addition of barium chloride the barium salt is precipitated, and on addition of ammonium carbonate the ammonium salt is precipitated and carbon dioxide is evolved. On heating the solution of the acid, the colour disappears, hydrogen sulphide and carbon monoxide are evolved, a green precipitate of nickel oxalate separates, and the solution was found to contain oxalic acid. Quantitative experiments showed that on boiling the solution 1 gram-molecule of the acid gave 4 gram-molecules of hydrogen sulphide and 1 gram-molecule of nickel oxalate, but that the relative quantities of oxalic acid and carbon monoxide were variable. In solutions of about normal strength 1 gram-molecule of acid gave 0.5 gram-molecule of oxalic acid and 0.5 grammolecule of carbon monoxide ; but in approximately decinormal C= 12.85 ; H = 2-54.