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I have faced this problems when I was working in lab with hexane for the first time.

I was trying to guide dispersion of nano-particles in hexane solution to a fluid cell (vacuum chamber) with a syringe and a flexible tubing (about 2mm or 3mm diameter). All the materials that I use are hexane resistant. The fluid cell is kept on very low pressure, so the goal is not to have any bubble formed in it. When I inject hexane fluid, midway before it reaches the chamber, the vapor bubble are formed ( I think because of low boiling point of hexane ) , which is bad I don't want any bubbles go in the chamber. However, I figured that if the flow is not horizontal or parallel to the ground (i.e when i inject vertically up ward to chamber) I can avoid the bubble flow.

I also thought to do the injection process fast, however the whole flow has to be very slow for the experiment. I would like to know what exactly causing it and what are your suggestions to avoid the bubble formation in a horizontal flow.

I was thinking maybe adding some other solution with higher boiling point would be a case to avoid it. But I don't know exactly what solution. And also it is important to keep in mind that hexane solution contains magnetic nanoparticles and I don't want any effect (like aggregation and so on) of added solution into the dispersion nanoparticles.
Thank you,

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    $\begingroup$ If you continuously evacuate the chamber, the partial pressure of hexane will be lower than at equilibrium. So hexane will evaporate and probably form bubbles. This is how nature works. $\endgroup$ – aventurin Apr 5 '18 at 19:48
  • $\begingroup$ Probably didn't explain well enough and vacuum chamber is a misleading term, i mean fluid cell. The fluid cell is in constant pressure prior to the injection of the fluid. Two independent process. The bubble formation inside the flexible tubing is formed even without attaching it to the fluid cell (or chamber). $\endgroup$ – Racaio Cmoto Apr 5 '18 at 19:57
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As you state, hexane has a low boiling point. If the bubbles are hexane vapor, as opposed to an air leak, then cool the fluid and apparatus more. You might pre-chill the hexane in a dry ice bath. The sublimation temperature of $\ce{CO2}$ at 1 atmosphere is about 195 K, and the melting point of a mix of hexane's various isomers is about 179 K, so there should be no problem with crystals blocking the flow.

Be careful with the cold -- frostbite is not painful at first, but is as damaging as a burn!

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