an oily viscous product that portion of solvent which is part of the complex does not evaporate during removal of excess solvent for example in the production of a complex of calcium nitrite with dimethylformamide the solution containing the complex in excess dimethylformamide was subjected to heating at 105 u00b0 c under 10 mm hg absolute pressure to drive off the excess solvent the resultant product contained 28 percent by weight nitrite 11 6 percent calcium and 58 3 percent dimethylformamide the analysis for the nitrite was carried out spectrophotometrically the analysis for calcium was carried out titrimetrically and the analysis for the solvent was carried out by the kjeldahl nitrogen analysis another method for preparing the chemical complex of this invention is to bubble dinitrogen trioxide gas through a slurry of a basically reacting metal salt in a selected polar organic solvent after bubbling the n 2 o 3 through the slurry the slurry is filtered to give a solution containing the complex excessive dinitrogen trioxide is undesirable due to the formation of other nitrogen oxides the solution may be concentrated by heating under reduced pressure to remove the excess solvent the concentrates of the complexes may be incorporated in organic media and lubricants.