Testing your product

Before you use your biodiesel, it must be tested to be sure it is of the best quality possible.
For most people, lab testing is just not cost prohibitive. Below are some test we have found to be very useful with repeatable and verifiable results. We have the UCO chemistry lab verify and quantify the results and we have ben pleased. All the tests listed here we were able to verify the validity of.

There are three items that we feel are the most important.

1. Specific Gravity, or the viscosity
2. PH. or the measure of the acidity content.
3. Free glycerin content.

Supplies you will need.
1. Hydrometer and cylinder
2. the pHLip test vials (found HERE)
3. Small glass vials that can be sealed and capable of holding at lease 35 milliliters of liquid.

The standard we are currently using today for the biodiesel we are producing is the

ASTM D 6751

Viscosity should be lower than .9 when measured with a hydrometer.

PH should be right at 7.0 or neutral.

1. Conduct your specific gravity test.
If your viscosity is higher than .9 this would indicate an incomplete reaction and you should not use this batch in your vehicle. It still probable has a glycerin content that exceeds the standard.

2. Conduct your pHLip test.
Follow the instruction exactly! Your product should pass this test easily. This test is only valid for a short period of time so throw it out (or recycle it) when you are through.

If your PH is too low, this indicates the presents of lye still in the biodiesel. You will need to continue washing until you can get it as close to 7.0 as possible.

3. Conduct the 3/27 test.

This is probably the most definitive test we have found for free glycerin. IT is a very good indicator of how complete your reaction actually is.

Here is how to conduct the test. REMEMBER - your measurements must be very accurate for the test to be valid.

1. In a glass vial, measure out EXACTLY 27 milliliters of methanol.

2. Measure out EXACTLY 3 milliliters of your finished product and add that to the methanol you measured out in step one.

3. Cap the vial and shake gently a couple of times.

4. Set the vial in a place where it will not be disturbed and watch it.

Results -

The methanol turns a light yellow/tan color and remains clear.
This is what you want. The biodiesel completely disolved in the methanol. Methelesters will disolve in methanol. Vegetabel oil will not. If you get this result after letting it sit for a couple of hours, congratulations! You have a complete reaction! YOU PASS!

Small droplets fall out and end up on the bottom of the vial -
This can indicate several things. The most accepted and what we have verified is that this is un reacted oil, or oil that still contains a large amount of glycerin. Means you have an incomplete, or partial reaction.
We have also found, to some extent, the amount of oil left in this situation is almost directly related to the percentage of oil left un reacted.
Example- 3ml of oil put in vial. What fell out was 1.5 ml. This means that only about 1/2 the oil was reacted, or 3ml put in, what fell out was 1ml. this would mean the the oil is 66%, or 2/3 reacted, and so forth. You get the idea.

Remedy -
Do the last 1/2 of the reaction again. This will react any remaining oil. you will use a little more of your catalyst and methanol, but you will have a better product.

More - do some experimenting here. Try some different things. Drop your methanol down, lower you catalyst level. add it a little at a time and kept repeating the test until you have one that will pass. then stop your reaction and drain glycerol off completely.

The vial becomes cloudy and/or milky in appearance -
This indicates, to the best we can tell, that there was too much catalyst used in the reaction. You may have good biodiesel, but the ph will probably be to high and net meet the ASTM standard.

Remedy -
Keep washing you biodiesel, either water or dry. Retest and keep going until it passes.

 

Some things to remember.

This test is not a very "scientific" test. We have spoken with the Chemistry department and they have verified, in theory, that this test is valid. But there are limitation. What is not know (but we are working on) is weather what falls out is ONLY the tri-glycerides (oil) or a mixture of the mono and or di-glycerides.

Some mono and di-glycerides will be soluble in methanol and some wont be. Remember, mono and di-glycerides are also partially reacted oil. Obviously there is more work to be done in this field.

Also, temperature seems to play a big part in the apparent pass/fail indication of this test. Most tests are conducted around the 68 degree mark. This is becoming the widely accepted temp at which the test should be conducted.

Conducting the test at warmer temps could give you a false "PASS" and conducting the test at a colder temp could give you false "FAIL" result. More quantifying test will need to be, and is being done in this area.

Even with all this being said, it is a good test to use. We are currently using this test and doing all we can to control the parameters. We also try to get the same results 3 times in a row.