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:
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
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
Step 3 – Insert the thermometer into the methanol and let it stabilize (about 2-3 minutes) and take a reading and record it.
At 75 deg. F, the methanol should have a specific gravity of 0.7875
We recorded 0.789
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.
Watch a methanol test demonstration!