How does one accomplish this?

I would like to know what the purity of the methanol recovered is going to be before I use it for another batch of biodiesel.

I use a spirits hydrometer.

quote:

I use a spirits hydrometer.

Yep. That's the best way to do it. You will have a very small discrepancy due to the different densities of ethanol (0.789 g/cc, for which the hydrometer has been calibrated) and methanol (0.792 g/cc), but that difference is negligible. I don't think you can get any better than that for the same cost.

Thanks guys,

I knew the solution would be a simple one.

Yup, around ten bucks will get you one.

You can get a good one here:

http://www.eckraus.com/WINEMAKING/Wine_Making_Equipment...rs/Page_1/HY810.html

If you shop around you'll probably get a better price. Personally, I buy my winemaking supplies from these guys (not that I've been making much wine lately), and just their customer service and knowledge (and willingness to share it) is worth the extra bucks.

Spencnaz,

Once you get a hydrometer, you'll need to compare to something. Here's the table I use for purity:

Percent Methanol
% @20C
100 0.7917
99 0.7948
98 0.7976
97 0.8005
96 0.8034
95 0.8062
94 0.809
93 0.8118
92 0.8146
91 0.8174
90 0.8202

IMPORTANT: These values are for 20C or 68F. Hydrometers and specific gravity are VERY temperature sensitive. If your methanol is hot, you'll read PURER, if cooler, you'll think your purity is low.

Good luck!

Steve

Here is the best chart for methanol purity I have seen... Thanks to Graham Lamming

Those tables are great, if you want to determine methanol purity using a scale, but they're not needed with a hydrometer. They come already calibrated in % alcohol.

10-4 on what bernyjb said, just get one for checking spirits.

Here is a link to a hydrometer for light liquids for $7.50

"Hydrometers for liquids with different densities. Range .700-1.000 in .01 divisions, overall length 29cm. The hydrometers bulb and stem are made of chemical resistant glass.Requires a jar or cylinder to test liquids(et.al. hydrometer jar or graduated cylinder)."