Colored reagent complex and method of detecting a rust removing agent in metal working fluids using the same

A method of detecting an amount of a rust removing agent in a sample, the method comprising the steps of:

• forming a colored reagent complex from a reaction of a transition metal salt and a salicylate salt or acid, or a derivative thereof;
• preparing a first reagent solution comprising the colored reagent complex and a second reagent solution comprising the colored reagent complex, wherein the first reagent solution and the second reagent solution contain the colored reagent complex in substantially equivalent concentrations;
• adding a standard solution containing a known amount of the rust removing agent to the second reagent solution and developing a color to make a reference solution;
• adding the sample to the first reagent solution to make a test sample solution;
• determining an absorption value of the test sample solution at an optimal wavelength of the colored reagent complex and an absorption value of the reference solution at the optimal wavelength;
• comparing the absorption value of the reference solution and the absorption value of the test sample solution.

A kit for determining when a sample is depleted of a rust removing agent, comprising:

• a concentrated solution comprising a transition metal salt;
• a concentrated solution comprising a salicylate salt or acid, or a derivative thereof;
• a standard solution containing a known amount of the rust removing agent;
• and instructions;
• wherein, when combined, the transition metal salt and the salicylate salt or acid, or a derivative thereof, react to form a colored reagent complex.