Quick way to identify fluid (of 3 possible fluids)
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Question

Quick way to identify fluid (of 3 possible fluids)

Ray H (Chemical)

(OP)

16 Jan 17 19:59

Hi, I am looking for some advice on how to determine what fluid is in a container (possibilities are isopropanol, MEK, or mixed xylene). Any measurements taken don't really need to be exact so long as they are able to differentiate between those three fluids.

The idea I came up with is to differentiate between the three by using viscosity, using a Zahn cup viscometer. I know that generally these are used for higher viscosity fluids like paint, but I have found a few manufacturers that do make ones for very low viscosity applications that might work for my purpose (.4 to 2cp).

Alternatively, I do not see any other property that separated the three fluids but could possibly use two tests in conjunction to determine the fluid (eg test freezing point to rule out xylene and then look at refractive index to determine between MEK and isopropanol).

Does anyone else have any suggestions or experience either with these fluids or Zahn cup viscometers?

jari001 (Chemical) · Answer 1 · 2017-01-16 21:48:13

Your freezing point test could tell you the difference between all of them with a somewhat sensitive methodology. Boiling point test might be an easier experiment to do, but it would be a bit complicated if you can't lose any amount of the sample. You're sure that it can be only one of the three possibilities?

Compositepro (Chemical) · Answer 2 · 2017-01-16 21:48:46

They all smell very different from one another. Perhaps you were not taught in chemistry class the proper technique for smelling the contents of bottles. Hold the bottle a foot away from your face and use your hand to gently waft some odor toward your nose.

jari001 (Chemical) · Answer 3 · 2017-01-16 22:10:35

Wafting would work, though I always get a second wafter to verify lol

moltenmetal (Chemical) · Answer 4 · 2017-01-17 00:02:05

Mixed xylenes are immiscible with water. Isopropanol is miscible with water, and MEK dissolves to a substantial extent (24%) but is not fully miscible, so you could eliminate the xylenes right quick with an eye dropper and a test tube or jar. The odour of xylenes is quite distinctive too- once you've smelled xylenes you won't mistake it for the other two.

Assuming it's down to MEK or isopropanol, it would be easy to tell them apart by the odour, and fairly easy by the solubility- but a similarly easy way would be to put a few drops on a piece of styrofoam. MEK and xylenes should both dissolve it readily- isopropanol will do nothing, just roll right off.

Ray H (Chemical) · Answer 5 · 2017-01-17 19:53:21

Thanks for the great answers everyone. I should have made my original post a little more clear, but I wanted something more objective than smell because an operator will be in charge of testing each container. The Styrofoam and miscibility tests are a great idea and easy to implement.

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Quick way to identify fluid (of 3 possible fluids)
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