Ri liquids

I appreciate some one help me please
I have this issue of finding RI liquid suitable to testing rough stones. I have no idea which manufacturer makes the odorless or less harmful liquid to both hands and gems . I live in UK and have not seen except on eBay , which seller recommend that this liquid will penetrate into some stones so I am in doubt if the liquid works or not for Aqua, Tourmaline, Sapphire and Garnets.
Does anyone can help me to identify what should I buy and where?
This is the liquid I seen on eBay and I was told that , I can wash the stone after testing under kitchen cleaning agent, and let it out for 24 hrs in the air. RI=1.79
Kind Regards