[gastando]

Hello, I am trying to find a surfactant that I can use to lower the surface tension of a mineral oil blend that I am using in my research. I am not adding water to the solution. The only restriction is that the final solution has to be clear.

In my experiment I am trying to precipitate granules of quartz through the air and into the oil blend. But at the moment the fine granules sit on top of the oil until enough of them accumulate to break the surface tension and drop into the solution. The only problem is that when this happens, trapped air bubbles fall into the solution which is not a desired effect.

I am a civil engineer and my chemistry knowledge is basic. So I would really appreciate any advice or direction to follow.

Thanks

[Arkcon]

Maybe, instead of using a surfactant, you could use a lighter (less dense) grade of mineral oil, so that the solids sink faster.  Or maybe try another nonpolar solvent.

[Enthalpy]

Could you impregnate the quartz granules before throwing them at the oil? Then, I expect pretty much any hydrocarbon would let the particles sink, like Diesel oil or decalin - choose one for health.

[gastando]

Thanks for your responses. The problem is that whatever I add to the oil blend or the quartz particles has to be transparent and mixed in a way that the refractive index of the entire sample is the same. For this i can vary the proportions of the oils plus the additives, but anything that I add has to be uniform within the entire sample.

[curiouscat]

Heat the oil?

[Enthalpy]

I meant, pre-impregnate the quartz particles with your mineral oil.

If investigating the option of additives, you could have a look at the ones used for synthetic hydraulic fluids like polyethylene glycol, phosphates... These ones, not obtained from crude oil, are less good at wetting so they become often additives to improve that.

Did you consider pure biodiesel as the oil? Its ester part would be more compatible with an oxide ceramic than a hydrocarbon is.

You might also give a try to other oils like polyethylene glycol-based ones. If water wets your quartz quickly, it's an indication in favour of these watery fluids.