Sciencemadness Discussion Board

Is it generally safe to openly evaporate heptane or does it pose an explosion hazard?

NaK - 17-12-2020 at 13:22

RustyShackleford - 17-12-2020 at 13:50

Openly evaporate where? in a closed small room, certainly an explosion hazard. In a garage with good ventilation, moderaly. Outside, no. Fumehood, depends on the fan type and airflow.

Consider if you would be ok with a can of butane or propane just sitting around leaking where you have it.

zed - 18-12-2020 at 14:35

Ummm. Pour it in your car's gas tank and, use it for fuel.

clearly_not_atara - 18-12-2020 at 15:07

^don't do that

Heptane flows along the floor because it is a very heavy gas. It can remain somewhat concentrated and find a spark, leading to a spreading deflagration. An explosion in the precise sense is unlikely, but you should have an open garage door at the very least, and don't plug anything in or unplug anything while the heptane is evaporating. Really it's best to be outside or have a fume hood/distillation setup.

karlos³ - 18-12-2020 at 15:12

Quote: Originally posted by zed  
Ummm. Pour it in your car's gas tank and, use it for fuel.

Thats not a good idea with heptane, at least not without using an antiknock-agent because it tends much to cause knockin.
This can, and over time likely will lead to damage on piston and cylinder heads, which can result in very problematic, dangerous, and definitely expensive damages.

If you would have said toluene instead, on that I concur very much.
Recycled toluene is very good high octane fuel.
Although highly illegal I think, and definitely will result in a lynchmob of green people of they would know :D
Even though burning that stuff inside your car is a very clean method to get rid of the toluene, much better than having it sit in some chemical waste depot, maybe even seeping out slowly into the environment.

Low boiling solvents are not well suited for the car, they tend to ignite prematurely(knocking) and this is why certain engine parts suffer a lot if this happens repeatedly over time.
Although, with the right mixture of various waste solvents.... it might be a superior fuel with good attributes.... :o

DavidJR - 19-12-2020 at 15:34

Quote: Originally posted by karlos³  

Thats not a good idea with heptane, at least not without using an antiknock-agent because it tends much to cause knockin.
This can, and over time likely will lead to damage on piston and cylinder heads, which can result in very problematic, dangerous, and definitely expensive damages.


Probably fine though if you only mix a small amount with a tank full of petrol?

karlos³ - 19-12-2020 at 16:43

I'm not a mechanic and actually, my knowledge is limited about these things.
But yes, I would guess so, if the dilution is right it would probably only boost the octane numbers of the tank load.
Although I wouldn't guarantee it, as it might still lead to engine knocking.

I think a good diesel engine can stand many things like solvents being added to the fuel though.
But I would be careful still.

Metacelsus - 19-12-2020 at 19:12

Quote: Originally posted by karlos³  
I'm not a mechanic and actually, my knowledge is limited about these things.
But yes, I would guess so, if the dilution is right it would probably only boost the octane numbers of the tank load.


Actually it would decrease the octane. Heptane is used as the standard for octane 0 on the octane rating scale. Probably not a good idea to put in your engine . . .

Diesel engines might be OK with it but I wouldn't count on it.

[Edited on 2020-12-20 by Metacelsus]

Fyndium - 20-12-2020 at 01:24

It is generally NOT safe.

Only environment I'd actively evaporate a flammable liquid solvent is outdoors. In all other instances, I evaporate it by distillation.

Only exception is when drying solids with residual moisture of such solvents. The amount evaporated is usually very controlled and small and pose little risk other than possible odor. Active evaporation for example in oven on the other hand is off limits, because of ignition risk. For these matters, the amount of solid to be dried is a factor of course, evaporating 100g of solid vs 10kg is a different matter.

By far the biggest reasons for lab fires and explosions, be they legitimate or not, is evaporated solvents. Seldom any reaction itself is the culprit. I've seen inputs where people just simply boil off stuff like ether indoors, and many syntheses just describe "evaporate off" a solvent, and for the uninitiated this translates to boil it off, in worst case with open flame. Calling these a mere risks is a very serious underestimation of the danger. 100g of hydrocarbon contains energy worth 1kg of TNT, and with bad luck, mixed nicely with air and going off by spark even at sub-detonation speeds it easily rips down half a house.