[Jarmerfohn]

Hey All,
  If there are any helpful analytical chemists I've got a puzzle for you.  I am looking for a way to confirm that I have lubrication where I need it to be.  I'm applying a diester based lubrication, diluted 98% in a solvent which is used as a carrier to apply a thin film over a metallic surface.  My ideal solution is to buy or make a solution I can drop or swab in different areas so I can confirm the presence of the lubrication. 

  I tried to use a few ph indicators but the surface of the metal is yellow, which eliminates most of the indicators out there.  I also found that the indicators I tried were not soluble in the oil or the carrier solvent I'm using so there was no way to get a reaction.  I'm thinking using pH as the identifying characteristic might not work.  Is there any way I can use the fact that it's a diester to get a color reaction?

Thanks for any help.

Possibly important info about lube:
Acid number, mq KOH/g: .1
Measured pH: 4.14

[wildfyr]

So it's just an alkyl diester? No other molecular features?

[Jarmerfohn]

Thats the only information about the composition they give on the data sheet.  They probably want to keep the details to themselves.  You might be able to get some more clues from the SDS. 

https://www.chempoint.com/products/lanxess/royco-lubricants/royco-ester-lubricants/royco-885

Thanks,
Jr

[MOTOBALL]

The SDS says that the formulation contains barium compounds at 1-5%.
In inorganic wet chemistry, barium is detected by the white precipitate of barium sulphate formed by reaction with IIRC, dilute sulphuric acid.
Swab your lubricated, metal surface with a cotton tip and place into a test tube.
Swirl with dilute sulphuric acid to see a ppt.
You should first perform the test with the lubricant itself, to make sure that you can generate the ppt.

Regards,
Motoball