quote:

Originally posted by im6under:

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Titrating will tell you how much FFA is in the oil. No one has determined FFA to be a problem in WVO. FFA are not corrosive like water soluble acids, I think it was Dana who did some tests on that.

It was my understanding you could also titrate for soluable acids...

Yes titrating shows soluble acids too, but it is not of much use for us, since it also detects all the FFA which are always present. I have not seen a method to titrate only for soluble acid and not for FFA. But thats OK since a simple PH test is easier anyway. A PH test will also detect if you have a base contamination, which titration with base would miss.

fair enough... I do both depending what I am doing...

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I use used oil, but I get it in the jugs it came in - I persuade the restaurant to do this by giving them the funnel and stand we sell on the 'site.

Craig

this may seem a stupid question... but how does the size of container prevent contamination???

In other words if the guys are trained to only put oil in your 55 or only put oil in your 5... it seems the key is simply educating the hillbilly as to what goes where...

The most common way for water to get into WVO is via rainwater getting into an uncovered or partly covered drum or dumpster that's outside, and that same drum or dumpster makes a handy place to dump any old crap the kitchen staff or janitorial service has in a bucket. Plus, most fryers hold just about 4.6 gallons, plus a little extra for the substance being fried, so if they're putting the used oil back in the 4.6 gallon jugs it came it, they're not going to have room for other stuff. We also urge our customers to leave the cardboard on the jugs (to make them easy to stack) but strip it off (and recycle it) right before pumping from them with our pump and filtering wand - so they can see what's on the bottom. If you notice a lot of lighter-colored stuff, that could be water (or lye.) (And the 70 micron filtering wand we sell stops short of the bottom by about 2-1/2", so if the food scraps or water that have settled are on the bottom 2-1/2", you by default won't suck them up. If there is a visible crud or water layer that's more than 2-1/2" thick/deep, simply lift the end of the wand up above the crud/water level.

Craig

that makes perfect sense...

my suction wand for my drums doesn't reach the bottom of the barrel and it has a clear section so I can shut it off before the tank if I see other than veg coming.

My drums have self closing lids so I haven't had a problem with rain water yet... but I did have a barrel once that a guy had dumped soapy water into from cleaning out the fryer. That took a polite reminder to fix.

Your method of dumpster diving is clever, and should be widely imitated by others - ditto for the closed lids. McMaster-Carr sells a drum funnel that fits in a standard 2" drum bung and has a spring-loaded self-closing cover on the funnel, and I've thought that might be a way to prevent water from getting into the drum, unless of course a well-meaning but sadly misdirected kitchen staffperson opened the spring-loaded cover and poured a bucket of cleaning slop down the funnel.

Craig

quote:

Originally posted by SunWizard:
[QUOTE]Originally posted by im6under:
SNIP

Yes titrating shows soluble acids too, but it is not of much use for us, since it also detects all the FFA which are always present. I have not seen a method to titrate only for soluble acid and not for FFA. But thats OK since a simple PH test is easier anyway. A PH test will also detect if you have a base contamination, which titration with base would miss.

The titration for soluble acid or alkali uses a water wash to provide water for the water soluble matter to dissolve into. The water is titrated, not the oil.

Titration for acid is well documented on this forum. Titration for an alkaline solution requires that the titration solution (0.1% solution) be acidic. as acids are normally liquids, a 1mL per litre solution could be used to determine the quantity of acid to add to neutralise the caustic in the solution.

Keep in mind that a lot of times the water at the bottom of the container will be just as dark as the oil above it. The only way I can tell if I'm sucking water is by the flow rate. With water it comes out at about twice the volume as oil does. Another thing to remember is used oil doesn't usually smell rotten, but it will if there is a lot of water at the bottom, because that's where the bacteria can grow, and where the food chunks rot. If I open a dumpster and it stinks like a dead animal, I won't even attempt to pump it out.

Do that water-mix test listed in this thread, and then titrate the water. That should give you the water-soluble acids but not the FFA.

Does anyone know how centrifuge filtration will affect these caustic solutes? Hopefully they will come out with the water. I am new to running svo and have not ph tested anything yet. the oil i get is pretty nasty too. and I was hoping that the centrifuge would make it useable. Maybee i need to mistwash after all. I will do a miniwash and ph test to see where i stand on ph.

dan

quote:

Originally posted by Daniel Franke:
Does anyone know how centrifuge filtration will affect these caustic solutes?

My CF has been removing them, shown by a TDS meter test on a mini mistwash. See:
TDS meter testing to decide whether to mistwash