Sciencemadness Discussion Board

can ether/hexane starting fluid be used as is?

overload - 29-9-2011 at 14:05

The question is "Can ether/hexane starting fluid be used as is in place of ether when ether is called for in extractions and as a solvent. (Keeping in mind that tests should be done to detect impurities such as lube.) I understand that hexanes cannot replace ether if ether is being called upon as a reagent.

An example of a situation someone may be in which can be made simpler if the answer to question above is yes.

(just an example)
I used the ether from starting fluid once before in a science experiment. The hexanes boil at 78c and the ether at 38c so I assumed I could just distill the ether from the hexanes. It seemed that things went well. I did not distill the ether again after fractionally distilling it out of the starting fluid. I just added magnessium sulfate and stored it until I needed it. When used as the extraction solvent it worked fine but the final yeild was lower than expected. Could the reason be the ether was contaminated with hexanes?

Magpie - 29-9-2011 at 15:11

Normally a fractionating column is used to separate two liquids when the boiling point difference is less than 100C. I presume you didn't use one.

Did the boiling point of the 1st cut lock on at 38C, or was there a range around this temperature. If a range then your ether is likely contaminated with hexane.

Whether this lowered your extraction efficiency or not is difficult to predict without knowing the specifics. What are you comparing to - a previous extraction with pure ether, or a literature value. My guess is that a small percentage of contamination with hexane wouldn't make much difference in extraction efficiency.

BromicAcid - 29-9-2011 at 18:00

Hexanes pop up at least in my line of work as a wonderful anti-solvent. Ether is a wonderful solvent for numerous compounds that hexanes just don't fit the bill for. Yes, the presence of hexanes will reduce the solubility of some compounds in your ether however as Magpie said, without knowing the specifics it's difficult to predict. In my experience though when someone fails at an extraction it's because they try to do it all at once with no concept of a partition coefficient ;)

overload - 29-9-2011 at 18:16

The only method I have ever used to get pure ether was from sulfuric acid and ethanol but it takes so long and is expensive. Recently I've found these cans of starting fluid which are 50% ether / 50% hexanes and have a little over 300ml in each. A case of 12 costs about 44 bucks plus shipping. That means there is over 1.5 ltrs of diethyl ether to be had for under 100 bucks. The only downfall is the gas they use to compress the can has to be released and stinks up all the air so it must be done at night plus the hexanes. I have done this before by turning the can upside down which makes the straws opening above the liquid inside the can. Now when you release the gas a small amount of liquid is released since the straw had a little bit in there. Then you puncture the can where you know there is gap between the fluid and the can. (for anyone interested in do this)

I have never tried to use a fractioning column mainly because I dont understand how it works. You are saying that it will be possible to separate the ether using a fractioning column. I think I have what I need to do that.

overload - 29-9-2011 at 18:39

Quote: Originally posted by BromicAcid  
Hexanes pop up at least in my line of work as a wonderful anti-solvent. Ether is a wonderful solvent for numerous compounds that hexanes just don't fit the bill for. Yes, the presence of hexanes will reduce the solubility of some compounds in your ether however as Magpie said, without knowing the specifics it's difficult to predict. In my experience though when someone fails at an extraction it's because they try to do it all at once with no concept of a partition coefficient ;)


I want to extract benzaldehyde from a sodium carbonate solution that contains traces of benzalchloride and some sodium chloride.

Partition coefficient.

section removed due to dumb

[Edited on 30-9-2011 by overload]

Dr.Bob - 29-9-2011 at 18:47

First, the hexanes will make the ether not work as well for many extractions as stated above. In fact, hexane is frequently added to cause dissolved compounds crystallize out.

Second, if the mixture is hard to get out of the can, perhaps you could cool the can to lower the pressure, then spray the mixture into a large, cooled flask via the straw through a septa/stopper with a hole, and have a condenser going out of it to help condense the ether and avoid it from evaporating. Then vent the gas from the top of the condenser out a window or away from you.

Then distill the solvent and collect the lower fractions. The hexanes are likely a mixture of several isomers. A fractionating column (Vigreux for example) simple gives a better distillation, as if you distilled the material several times.

Lastly, be careful, all of these compounds are highly flammable, and fires start easily with ether and its mixtures, don't do this in a garage near a hot water heater, furnace, etc. please do think ahead of what can go wrong and avoid it to start with. I have seen too many fires from people doing things without thinking them over well. A few minutes planning beats a fire extinguisher anytime.

Bob

overload - 29-9-2011 at 19:21

So from what I'm reading a simple Vigreux condencer (or a condencer packed with glass beads) can dramaticly reduce contamination of the distilled ether and that hexanes do not have the same properties as ether when it comes to their use as an extraction solvent. That are actually used in some cases to cause the precipitation of compounds from ether.

If I add water to the hexanes/ether before fractional distilation will it have any effect? In other words will it help retain more hexane vapor than just a fractioning column alone?

Magpie - 29-9-2011 at 19:33

I trust you've seen this, which gives a procedure for both making ether from ethanol, and separating it from starting fluid:

http://www.sciencemadness.org/talk/viewthread.php?tid=9747

I used Len's method on two cans of Johnsen's starting fluid, which had heptane as diluent and propane as propellant. As I recall this method worked well. However, the propane was a bit of a nuisance as it messed up the boiling point of the ether and would bubble out of the pot sporadically.

Next time I need ether I will try the Valvoline brand. It has CO2 as propellant and therefore might behave better.

Edit: For a fractionating column I used a Hempel column packed with glass shards obtained by breaking up a glass jar wrapped in a towel with a hammer.

[Edited on 30-9-2011 by Magpie]

[Edited on 30-9-2011 by Magpie]

Endimion17 - 30-9-2011 at 07:38

Quote: Originally posted by overload  
So from what I'm reading a simple Vigreux condencer (or a condencer packed with glass beads) can dramaticly reduce contamination of the distilled ether and that hexanes do not have the same properties as ether when it comes to their use as an extraction solvent. That are actually used in some cases to cause the precipitation of compounds from ether.

If I add water to the hexanes/ether before fractional distilation will it have any effect? In other words will it help retain more hexane vapor than just a fractioning column alone?


The bead-packed column is called a Hempel column. I think it's far better to use that instead of a Vigreux column when distilling such mixtures.

I doubt water will help. Try, if you have enough of the mixture. Can't hurt.

peach - 30-9-2011 at 11:24

Have a look at the table on this page.

Generally, you can swap the solvents around to whichever is close by on the table and best fits the job (e.g. density, miscibility and boiling point); it is not universally true, but there is usually more than one solvent that will function for a task.

Combine it with the table on this page to make sure the two are actually immiscible prior to adding another.

I strongly suspect the main reason for your low yield is;

a.) you haven't shaken the two thoroughly
b.) the thing you're extracting has very little benzaldehyde in it to begin with
Quote:
Second, if the mixture is hard to get out of the can, perhaps you could cool the can to lower the pressure, then spray the mixture into a large, cooled flask via the straw through a septa/stopper with a hole, and have a condenser going out of it to help condense the ether and avoid it from evaporating. Then vent the gas from the top of the condenser out a window or away from you.


Judging by the salt and benzaldehyde in there, I would guess the temperature at which the mixture freezes is either down near 0C or below that.

Put the solution in the freezer overnight and see if it solidifies or turns to slush. If it does, try the fridge overnight. Get it as cold as possible whilst keeping it as a liquid.

Then spray the can (via the straw) directly into the solution, which will not only help trap the ether but also ensure the two phases are mixed.

overload - 30-9-2011 at 13:26

A Hempel column is a collum with a ridge or a pinch to allow for the column to be filled with glass beads or what ever else. I'm not sure how I will make one of these since I dont think my condensers have a ridge. I checked those pages out peach. Both of them are interesting and were added to favorites.

overload - 30-9-2011 at 13:31

The starting fluid I have now is Johnsons Premium starting fluid. The contents of the container are Diethyl ether 60-29-7 / Heptane 142-82-5 / Propane 74-98-6 / Iso-butane 75-28-5 / Carbon dioxide 124-38-9

You dont want to breath these in at all... If you try this try really hard not to breath any of the fumes in and try even harder not to expose other to the fumes. For example your doing this in the back yard in the middle of the after noon on a weekend when the person who lives behind you is having a barbeque. I just brought the can into the house for a few minutes and I can already tell I have absorbed some fumes.

The heptane boils at 98.42 °C and the diethyl ether at 34.6 °C. Thats a difference of 63.82 °C which should be enough to simply distil the ether from the heptane. After reading the posts above I think I understand now that when working with these types of materials there will most likely always be some contamination due to the fuming nature of the chemicals. Ether and Heptane both evaporate quickly so as the ether is distilling out of the heptane there will be fumes or vapor of heptane exiting into the condenser with the gaseous diethyl ether. One way to prevent this is a fractioning column which will prevent the higher boiling point fumes to condence out of the gaseous diethyl ether before reaching the condencer. I have not read anywhere that this method has the ability to completely prevent contamination. In the future I may have a lab test a sample of the ether for me when I get around to experimenting with this.

[Edited on 1-10-2011 by overload]

peach - 1-10-2011 at 10:58

You could piss into the flask and use that to extract an organic layer, seriously. ;) That's mainly water, and water is frequently used in extractions. Might not give a superbly clean result, but the blowers have kind provided openings for such appendages to fit through.

Heptane can certainly be used to extract things.

Generally, the cleaner the solvents and solutions and the fewer unknowns in them, the easier and better the separation will go. For instance, if you left soap in the glassware, and then shook it, the two layers would blend together.

Butane, pentane, hexane, pentane and onwards up are all used as solvents. They're all the same thing, just getting longer by one carbon and few hydrogens each time.

Butane is a gas at room temperature & pressure, so that needs special handling.

Pentane is a liquid, but boils at 36C.

Hexanes are used so frequently because they won't evaporate or boil off quite so readily, but can be made to do so when needed.

Heptane just has a very slightly higher BP.

QuickFit sell little coils to slide into columns and support packing. £5.10 each, plus vat, plus delivery, plus you're never getting one because Sigma will not sell to the public; which means anyone without a VAT code and registration at companies house.

You can instead use chunks of broken glass that happen to be the right size, or a loose wad of fibreglass.

But again, you can skip all this, because benzaldehyde is soluble in toluene, xylene and it should have gone into those other solvents too.

If you're trying to extract a domestic product in the US, keep in mind that benzaldehyde is a listed chemical there, so you are unlikely to find any significant amount of it in anything that's come from a manufacturer of domestic products. They are aware that people will try to extract it and only add as much as is needed to give the product it's smell or taste. As benzaldehyde has a very strong odour, they need only add a minute amount. You could extract an entire bottle of something with 100% efficiency and only get 1ml out.

overload - 2-10-2011 at 10:07

Quote: Originally posted by peach  
You could piss into the flask and use that to extract an organic layer, seriously. ;) That's mainly water, and water is frequently used in extractions. Might not give a superbly clean result, but the blowers have kind provided openings for such appendages to fit through.

Heptane can certainly be used to extract things.

Generally, the cleaner the solvents and solutions and the fewer unknowns in them, the easier and better the separation will go. For instance, if you left soap in the glassware, and then shook it, the two layers would blend together.

Butane, pentane, hexane, pentane and onwards up are all used as solvents. They're all the same thing, just getting longer by one carbon and few hydrogens each time.

Butane is a gas at room temperature & pressure, so that needs special handling.

Pentane is a liquid, but boils at 36C.

Hexanes are used so frequently because they won't evaporate or boil off quite so readily, but can be made to do so when needed.

Heptane just has a very slightly higher BP.

QuickFit sell little coils to slide into columns and support packing. £5.10 each, plus vat, plus delivery, plus you're never getting one because Sigma will not sell to the public; which means anyone without a VAT code and registration at companies house.

You can instead use chunks of broken glass that happen to be the right size, or a loose wad of fibreglass.

But again, you can skip all this, because benzaldehyde is soluble in toluene, xylene and it should have gone into those other solvents too.

If you're trying to extract a domestic product in the US, keep in mind that benzaldehyde is a listed chemical there, so you are unlikely to find any significant amount of it in anything that's come from a manufacturer of domestic products. They are aware that people will try to extract it and only add as much as is needed to give the product it's smell or taste. As benzaldehyde has a very strong odour, they need only add a minute amount. You could extract an entire bottle of something with 100% efficiency and only get 1ml out.


So the heptane / ether mixture should be able to extract the benzaldehyde? That's good to know since now I don't have to worry so much about column distillation. If I do this I will just distill the ether and hope the small amount of heptane that contaminates it doesn't cause any problems. I would prefer to work with ether instead of toluene since it boils at 35c. I'm aware of the schedual 1 status of benzaldehyde how ever I don't think that it is illegal to own or purchase as long as you aren't producing illegal compounds. Benzaldehyde is the reason I found this site in the first place. I'm pretty sure you can make it legally but you cant sell it.