Can any one offer some help .I have just taken a sample from a fifty ltr batch of well stired used oil mixed 1 mil oil to ten mil ipa shook well then tested ph. it is 7.8 befor i add my water lye mix repeted test five times with the same result using ph meter and litmus paper does this meen i have the best waist oil ever or am i doing somthing wrong
rio rick

Rio Rick,

What do you mean by ipa ?
regards
dva

pH is of no interest. What you need to know is acid capacity. This is found by measuring the amount of base needed to achieve pH9.

quote:

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What do you mean by ipa ?
regards
dva

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Iso propyl alcohol. Joe

THANKS NEUTRAL BUT IF I PUT 3 DRIPS OF WATER LYE MIX IN TO MY SAMPLE, 02 OF 1 MIL IT CHANGES PH TWO 10 SO WHAT IS THE REQIRED FORMULA FOR FIFTY LITERS THANKS RIO RICK

It sounds like new oil.
Are you sure they gave you the USED oil??

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Originally posted by rio rick:
Can any one offer some help .I have just taken a sample from a fifty ltr batch of well stired used oil mixed 1 mil oil to ten mil ipa shook well then tested ph. it is 7.8 befor i add my water lye mix repeted test five times with the same result using ph meter and litmus paper does this meen i have the best waist oil ever or am i doing somthing wrong
rio rick

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30 000 KM in a '90 Mazda 2 litre diesel on SVO with biodiesel start/purge.

Rio Rick,
I don't quite understand what you are doing here. Ph testing is usualy carried out on the water wash. i.e a sample of the oil is added to water, shook up, and when settled out the Ph of the water is taken.
I believe I am correct in saying that taking the ph of the iso/oil mix with Naoh add won't help you much.
Can anyone else please elaborate on this ?
regards
dva

Sounds to me like he is doing a normal titration, to find the amount of caustic to add to the methanol. From the figures given it is very good used oil.
Try a test batch, 1l oil, 200ml methanol, 4g caustic/lye, 50degC. This is a bit over the new oil requirements.
For the record, my used oil looks good but titrates at 4.75g, ie 8.25g per litre of oil. This is not good used oil but I'm happy with it.

Simon
http://mysite.freeserve.com/simons_photos/

After a year and a half I have started doing titrations using phenol red of swimming pool fame ($5.00 for about 600 titrations worth) and ethanol of methylated spirits fame at $2.00 a litre which will give about 100 titrations.

I measure the ingredient using 2- $0.75 eyedroppers and mix in a $0.50 medicine glass.

All these ingredients except the methylated spirits bottle and the Dr Pepper bottle of 0.1% NaOH fits nicely in a "Kitchen Match Box".

How can I get "cheaper and dirtier" than that?

Tilly SBC/IBA

[This message was edited by Tilly on 01 July 2003 at 09:26 AM.]

Punto,
Guess I am having a denser than usual day today, but I still have a problem with Rio Rick's Ph.

here is the original....
I have just taken a sample from a fifty ltr batch of well stired used oil mixed 1 mil oil to ten mil ipa shook well then tested ph. it is 7.8 befor i add my water lye mix repeted test five times with the same result using ph meter and litmus paper does this meen i have the best waist oil ever or am i doing somthing wrong

Now, it does indeed look like a normal titration but there is no mention of Phenol Red or Phenophelein. Just the Ph meter and litmus paper.
And we are reliably informed that you can't do a meaningfull Ph test on oil, only on the wash-water.
Do you see what I am getting at ?
regards
dva

I first used an electonic ph meter and got good test results, but was later told they are no good, so stopped using it. I now use phenol red. I would have thought litmus paper should be as reliable as indicator, the reason electric gadgets are supposed to be no good is the amount of free ions for the gadget to measure, but mine seemed ok?

Simon
http://mysite.freeserve.com/simons_photos/

Litmus paper is very imprecise and is supposed to show neutrality, pH 7, which is well away from a pH around 9 which is what phenolphthalein shows, and is what you are looking for.

By the way there is nothing wrong with using a pH meter provided you put it in a watery environment, such as you have when titrating. It will not tell you anything useful however if you put it in the veg oil before you add any NaOH solution.

The main argument against the pH meter is that it costs money, needs skillful handling and maintenance, and for making biodiesel doesn't tell you anything you need to know that a few drops of indicator won't tell you.

It is also a damn sight harder to vigorously swirl the container while titrating if there is a fragile pH meter in it. Unless of course you buy a magnetic stirrer, but that will set you back a few hundred dollars. Why do it the hard way?

[This message was edited by neutral on 02 July 2003 at 03:55 AM.]

"I'm a chemist and I know that you just can't do an accurate titration at home for lack of standard solutions and accurate burettes and scales. It's just not done your way."

Tilly SBC/IBA

Would this be an accurate statement?

NO! Joe.

I was thinking about getting a digital ph meter for measuring the ph of used cooking oil. It seems like what people are saying is that it wont be able to function in the oil. Just wanted to ask and make sure.

Hello B100TDI, welcome to the forum

YOu are correct, reading the pH of biodiesel is as informative as measuring it's voltage.

On another note, part of my post from three years agop is missing.
It started out "Would this be an Accurate Statement?" as Joe repeated in his answer.

well i have used a PH meter to do the titeration test and to test the waste water after washing but on the point of titerating the oil am i right in thinking that this can be done with a PH meter or have i wrong?

Hello Stampy

pH is an index of the concentration of Hydrogen Ion (H +) in water. Since oil (biodiesel) is not an ionizing solvent, it has no free hydrogen ions and therefore, it does not have a pH per se.
If the oil contains materials which when mixed with water supply hydrogen ions to the water phase, then these will register when the pH of the water phase is measured.