Sciencemadness Discussion Board

Methanol Concentration

Ramblesthegoat - 18-2-2012 at 17:57

I bought some denatured alcohol from a hardware store that I planned on distilling to purify it. Before I did i looked up the msds and found out that is was half ethanol and half methanol. I tried to distill off the methanol at just above 65 degrees and got what would assume to be methanol, but i don't have the glass necessary to do a fractional distillation. Is there any way to tell the concentration of it or how pure it is that i can do with reasonably easy to get supplies/chemicals?

zoombafu - 18-2-2012 at 19:31

If you have a good enough scale weigh it in a graduated cylinder and calculate the density. If you are looking for pure methanol, I usually just buy HEET (a gasline antifreeze) it is almost pure methanol (just a small amount of water I believe).

marko - 18-2-2012 at 19:35

The density is pretty close, though, I'd think it would be hard to measure, and even a little water in there would screw the numbers up?

copper sulphate is soluble in methanol but not ethanol - IIRC - but that will only work if it's anhydrous, as it's soluble in water too. Maybe there is something that is insoluble in water and one of the alcohols, but I'm not sure...

Bot0nist - 18-2-2012 at 20:23

You won't be getting copper sulfate to dissolve in EtOH or MeOH!

entropy51 - 18-2-2012 at 21:59

There is a thread on distinguishing methanol fom ethanol:

http://www.sciencemadness.org/talk/viewthread.php?tid=12624

[Edited on 19-2-2012 by entropy51]

Ramblesthegoat - 19-2-2012 at 04:59

Thank you guys so much! A lot more copper sulfate dissolved in the distilled stuff than the untouched hardware store stuff. After doing some math i think i can safely assume that my methanol is about 85-90% pure, which is good for what i need it for.

bahamuth - 19-2-2012 at 05:35

Quote: Originally posted by Ramblesthegoat  
Thank you guys so much! A lot more copper sulfate dissolved in the distilled stuff than the untouched hardware store stuff. After doing some math i think i can safely assume that my methanol is about 85-90% pure, which is good for what i need it for.


Do not think you can safely assume anything, not before you atleast have established a boiling point, density and preferably a spectra of sorts.

Just by estimating how much that solvates of a solute does not give you squat of information. It could very well be that you have ethanole with let's say 10% water in it, how could you know if it is not? By solvating something that dissolves very well in water and fairly well in methanol?

Not to flame anyone but one can not assume anything, it is just stupid and ignorant. But guess those that assumes to much will figure it out after a while, or just leave chemistry since it never gives expected results.

I would just use the stuff you distilled for marker removal, and just buy some HEET or any other kind of mostly methanol.

PS, you need to share that math of yours that determines purity of a compound by its solvent power, especially when it very well might be a tertiary solvent system..

Halcyon - 19-2-2012 at 23:06

If you're after methanol (not ethanol), just go to a performance garage - the stuff they sell here for race fuel is 99.85% pure.

zoombafu - 19-2-2012 at 23:08

Quote: Originally posted by bahamuth  

PS, you need to share that math of yours that determines purity of a compound by its solvent power, especially when it very well might be a tertiary solvent system..


Yes please!

Ramblesthegoat - 20-2-2012 at 11:44

Well I just figured if one liter of methanol can dissolve 10.4 grams of copper sulfate at 18 degrees, than 20ml should be able to dissolve about .208 grams at 18 degrees, so I measured .2 grams because my scale isn't very accurate and dissolved as much as I could. Around 85% of it was dissolved and there was no way that there was any water in it (all my glassware was 100% dry, and the untouched stuff had no water in it according to the msds) and for the reaction I want it for I don't need it to be very pure, i want to make methyl salicylate, I know it will get some ethyl salicylate in it if my methanol has ethanol in it, but I just want it because it smells cool, not as a reagent.

zoombafu - 20-2-2012 at 11:52

Quote: Originally posted by Ramblesthegoat  
Well I just figured if one liter of methanol can dissolve 10.4 grams of copper sulfate at 18 degrees, than 20ml should be able to dissolve about .208 grams at 18 degrees, so I measured .2 grams because my scale isn't very accurate and dissolved as much as I could. Around 85% of it was dissolved and there was no way that there was any water in it (all my glassware was 100% dry, and the untouched stuff had no water in it according to the msds) and for the reaction I want it for I don't need it to be very pure, i want to make methyl salicylate, I know it will get some ethyl salicylate in it if my methanol has ethanol in it, but I just want it because it smells cool, not as a reagent.


Your scale isn't accurate enough to get that kind of resolution (sig figs). The best you could get is between 50% dissolved and 99% dissolved.

Ramblesthegoat - 20-2-2012 at 11:59

Quote: Originally posted by zoombafu  
Quote: Originally posted by Ramblesthegoat  
Well I just figured if one liter of methanol can dissolve 10.4 grams of copper sulfate at 18 degrees, than 20ml should be able to dissolve about .208 grams at 18 degrees, so I measured .2 grams because my scale isn't very accurate and dissolved as much as I could. Around 85% of it was dissolved and there was no way that there was any water in it (all my glassware was 100% dry, and the untouched stuff had no water in it according to the msds) and for the reaction I want it for I don't need it to be very pure, i want to make methyl salicylate, I know it will get some ethyl salicylate in it if my methanol has ethanol in it, but I just want it because it smells cool, not as a reagent.


Your scale isn't accurate enough to get that kind of resolution (sig figs). The best you could get is between 50% dissolved and 99% dissolved.



Like I said, I don't need very high purity at all.

zoombafu - 20-2-2012 at 12:02

Just go buy some HEET, its usually like 2 for a dollar.

Hexavalent - 20-2-2012 at 12:22

Or buy it on eBay.

Could a dichromate salt be used to determine methanol concentration just as it used for ethanol?

Ramblesthegoat - 20-2-2012 at 12:30

I think I'll just buy some HEET. Trying to distill the stuff i have is just too much work for a not so pure product.

bahamuth - 20-2-2012 at 12:48

Quote: Originally posted by Ramblesthegoat  
Well I just figured if one liter of methanol can dissolve 10.4 grams of copper sulfate at 18 degrees

Not to bug you but what "kind" of copper sulfate, pentahydrate or anhydrous. Asking because I found alot of varying values floating on the net..(never trust MSDS, they are inaccurate and often made by the company themselves to save money).
Quote: Originally posted by Ramblesthegoat  
I think I'll just buy some HEET. Trying to distill the stuff i have is just too much work for a not so pure product.

If you do it properly the reward is so much more sweet, just knowing that you put your mind and soul into it is what will keep you in amateur chemistry, and it is kinda good to struggle with a problem and finishing it properly.
Quote: Originally posted by Ramblesthegoat  
I want it for I don't need it to be very pure, i want to make methyl salicylate, I know it will get some ethyl salicylate in it if my methanol has ethanol in it, but I just want it because it smells cool, not as a reagent.

Beware of the salicylates, they are quite toxic, and passes fairly readily through skin. The increased bleeding tendencies is actually the biggest worry IMO. Though you'll not die from a drop, a large spill on your pants or similar may be very bad.

Hexavalent - 20-2-2012 at 13:21

Some muscle rubs take advantage of the tendency of methyl salicylate to penetrate the skin to enhance the efficiency of the product.

Lambda-Eyde - 20-2-2012 at 13:30

Quote: Originally posted by bahamuth  

Beware of the salicylates, they are quite toxic, and passes fairly readily through skin. The increased bleeding tendencies is actually the biggest worry IMO. Though you'll not die from a drop, a large spill on your pants or similar may be very bad.

I was not aware of that. One time I spilled a quite large quantity of ethyl benzoate on me (the stopcock on the sep funnel popped out in the direction of my hand), and I'm planning on making some salicylates too. I've never considered those compounds as such a hazard. I guess it just shows that I should really read the MSDS when I encounter an unknown compound. Probably the nicest smelling spill I've had, though... :P

Edit: That should be stopper, not stopcock of course... I wonder what Freud would say about this...

[Edited on 21-2-2012 by Lambda-Eyde]

Hexavalent - 20-2-2012 at 13:39

I did the same with some n-propyl acetate. The garage smelt of pears for about a week:)

bahamuth - 20-2-2012 at 14:06

Quote: Originally posted by Lambda-Eyde  

I was not aware of that. One time I spilled a quite large quantity of ethyl benzoate on me (the stopcock on the sep funnel popped out in the direction of my hand), and I'm planning on making some salicylates too. I've never considered those compounds as such a hazard. I guess it just shows that I should really read the MSDS when I encounter an unknown compound. Probably the nicest smelling spill I've had, though... :P


As I've mentioned in an old ester thread I/we tested alot of esters for a student lab, and I cannot agree that wintergreen is a nice smell anymore, sensitized so to speak. The whole lab smelled like a tuttifrutti factory, overwhelming. As a plus we got intoxicated and started giggeling from the most stupid dry jokes, though none of the other two would acknowledge it at the time..

Remember the smell of an simple ester that smelled raspberry when in high concentaration and the most "true" pear when dilute, like quickly passing some nice smelling chick in the hallway dilute:P

Halcyon - 21-2-2012 at 03:01

I remember back in highschool we were synthesising esters, and I was particularly fascinated with the ethyl butyrate I'd just made.

When we were told to dump our stuff and pack up, I decanted it into a small glass phial and went to slip it into my blazer pocket while keeping a weather eye on the teacher...

I forgot about the bloody labcoat, didn't I? Slipped straight down my front and smashed, splashing all over my shoes. I smelled like candy bananas everywhere I went for the next month.