Testing Methanol For Purity

In this article we’ll be discussing how to test the purity of methanol. Because methanol is a key ingredient in making Biodiesel, it needs to be as pure as possible or else it can cause problems with the reactions and cause poor conversions.

Why Test Methanol?
If the methanol isn’t pure enough, it can lead to poor Biodiesel conversions and higher than normal soap levels when reacting your oil into Biodiesel. This is because the contaminant in the methanol is usually water. Water plus oil plus catalyst makes soap (and sometimes lots of it!) Unfortunately, methanol LOVES to suck up water (that’s one of the main reasons methanol is used in fuel drying additives–ie. HEET fuel dryer), so it’s important that you know just how pure your methanol really is.

In most cases, if you purchase methanol new in a sealed container, you usually won’t have to worry about its purity. However, if you’re using recovered methanol or you’re using an old drum of methanol that’s been around for a while, it’s possible for water to have crept into it. As there are many things that can cause contamination to methanol, it’s always a good idea to test it for purity.

To test methanol’s purity, you will need the following:
Methanol Test Kit
1- A methanol hydrometer
2- A glass cylinder
3- A thermometer accurate to 1 degree
4- A methanol purity chart
5- A calculator
6- Some scratch paper
7- And some methanol to test.

It’s also helpful to use a stand to support the thermometer with, but it isn’t 100% necessary.

Step 1 – Add methanol sample to glass cylinder and insert the hydrometer
Testing Methanol

Step 2 – Allow the hydrometer to stabilize in the methanol (at least 1-2 minutes) and then read where it interfaces with the methanol level and record the reading
Methanol Test

Step 3 – Insert the thermometer into the methanol and let it stabilize (about 2-3 minutes) and take a reading and record it.
Temperature of methanol

Step 4 – Compare your reading to the methanol purity chart.

At 75 deg. F, the methanol should have a specific gravity of 0.7875
We recorded 0.789

Step 5 – Calculate the purity of the methanol

Subtract the standard from your reading (0.789 – 0.7875 = 0.0015)
Divide the difference by 0.00285 (0.0015 / 0.00285 = 0.5263)
Subtract the result from 100 (100 – 0.5263 = 99.4737)
This result is the purity of the methanol (99.47% pure)

The 0.00285 is the amount the specific gravity of methanol increases for every percentage point the methanol decreases in it’s purity.

100% pure methanol at 75 deg. F has a specific gravity of 0.7875
99% pure methanol at 75 deg. F would have a specific gravity of 0.7847

Making Biodiesel & Methanol Purity
When making Biodiesel, you really want to use as pure of methanol as possible. However, it is possible to make Biodiesel from lower grade methanol; however, it may not fully convert and you may create quite a bit more soap. In general, we recommend using methanol that is at least 97% pure or better when making Biodiesel. Much lower than that and you’re asking for problems.

Be sure to check out our Methanol Test Kits!
Our kits come with complete instructions and everything you’ll need to perform accurate methanol purity tests! We also sell the individual parts as well.

Methanol Test Kit
Click here to see the kits

Watch a methanol test demonstration!

Link to video

About Utah Biodiesel Supply

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21 comments on “Testing Methanol For Purity

  1. Graydon,
    Very interested in your methanol. I’m a shop teacher, usually make my biodiesel in summer time when I can. Last several years I’ve picked up a summer job and I’ve been away from bio d for a couple years. Ready to start up again this summer and have about 45 gallons of methanol that I’m not sure I can use or not. Going to test it at school with the chem teacher. If I find it’s not very “pure” anymore, is it still usable? Can I do anything to improve it to make it usable?
    Nick in WI

  2. I appreciate your quick reply and eager to make some biodiesel.Actually I am from Pakistan not US.I bought one Liter of Spirit which is extracted from Sugarcane.I do not know if it works or not.

  3. I never Ever found someone so helpful like you.I wish I was in US to payback the favour you are doing.I finally found a Local supplier who is selling Methanol and Stats they are showing on there website are (Methanol 99.85 %(w/w) Water 1000 ppm Ethanol 100 ppm Acetone & Aldehydes 30 ppm Acidity 30 ppm Non volatile 10 ).I do not understand any of this but as you mentioned in your videos that minimum of 97% pure is required and this is 99% if i am not wrong.I think this can do the trick.once again thanks to you for being so helpful,and sorry for my bad English as it’s not may native language.

  4. Hello Dear
    Today i read about use of algae oil for biodiesel.I have plenty of uncultivated land and waste waters to produce algae.Can you tell me is it worth to do so.

    Thank you.

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