BioDiesel for all

We're now going to talk about doing a titration. When you collect waste vegetable oil from a restaurant or from anywhere that they use the oil, the oil is typically going to be well used, it's going to be somewhat acidic, and it'll be important to find out how acidic it is so that we can neutralize that acid with excess lye. 

We're going to talk about how we do it here on the board.

First of all we need to make a known amount of base. In theory what we're doing is we have an unknown amount of acid, and we can make a known amount of base. We're then going to take a sample of oil, we're going to add a pH indicator into it, and the one that we choose to use is called phenolphalene. It's very popular and the industry views it as the most scientific one. You can actually use phenol red, or tumeric, or pH strips, but the one I like to use is this phenol phaylene.

So I'm just going to label it phenol because it's a really long word, and if you want to know what it is look up on my site and I'll show you spell it. So, phenol is our pH indicator. Kay so basically what we're going to do is take some oil, we're going to add it to some alcohol, and the alcohol is neutral, so the alcohol is just going to be a solvent to put that we can put it in so that we can dilute it. So we've got an oil, alcohol and we're going to put a few drops of our pH indicator in there, and then we're going to add known amounts of our base solution in there. We're going to do that in milliliters at a time. What we're doing, what we're watching for is this pH indicator to change, or indicate a pH higher than about 8.5.

So what we're going to do is, as we add known amounts of the base, our goal is to figure out how much base solution it's going to take to neutralize that acid. You remember on a pH scale you've got zero to about fifteen, lower is acid higher is base. We're going to add known amounts of base to an acid until our pH indicator indicates that we've neutralized that acid. That known amount that we get is, I don't know, let's say about four milliliters. We're than going to plug into a formula to tell us how much lye we're going to use per liter of oil. If you remember from before, our formula for making biodiesel was O (oil) + 20% (methanol) + 7.5 g C (calalyst) if we're using potassium hydroxide.

If it's sodium hydroxide it was 5.5. Well, for a titration we're going to have something called our base, in other words, our starting amount. That starting is always 7.5 if we're using potassium hydroxide. So I know it's going to use 7.5 grams per liter of potassium hydroxide to react brand new oil with 20% methanol into biodiesel, which is what we do when we make a small batch. For titration, I'm going to add a known amount of this base solution until I get it to neutralize, and I measure that, then I add that amount to this base figure. So let's say that we got 5, so that would equal 12.5 (7.5 + 5 = 12.5) grams per liter. That means that I'm going to add an additional 5 grams of potassium hydroxide to neutralize the acid in that oil, so that I have enough lye left over, or potassium hydroxide to make biodiesel with, and that's all we're doing when we do a titration.

Now, to build our known amount of base we're going to make a .1 percent solution of KOH and distilled water. So we're going to add one gram of KOH to one liter of water, and this makes a .1 percent solution, and it's what we use to titrate with, or to add to our acid. This is our known amount. So with that, let's go ahead and we'll make our solution, and we'll do a titration.