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Some questions about ph and temperature
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Hi!

i have some questions about the measurement of ph and temperature of the oil produced in the tank.

I have read that ph is not so easy to find but there is some ph-meters able to do it?

and what you suggest for the temperature? what kind of instrument must i use?

thanks you.
 
Registered: April 18, 2012Reply With QuoteReport This Post
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Nicola,

You can't measure the pH of oil. There is no instrument that will. You can measure pH of contaminates in oil after it's dissolved in alcohol. We do that when we Titrate WVO. You can also measure the pH of water used to wash biodiesel. There are some old references on the Internet to measuring the pH of biodiesel after washing and before drawing. In this case you're actually measuring the pH of the water still in the biodiesel. Measuring the pH of wash water doesn't really tell us much.

There are electronic instruments that measure pH. pH meters need a lot of maintenance including routine calibrations and can be permenantly damaged easily. They are available from many sources and prices vary a lot. There are a few on the forum that use them and like them. I don't.

I use Indicator Dyes that change color with pH, specifically phenolphthalein, to titrate.

Rick

This message has been edited. Last edited by: RickDaTech,
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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quote:
Originally posted by RickDaTech:
Nicola,

You can't measure the pH of oil. There is no instrument that will. You can measure pH of oil dissolved in alcohol. We do that when we Titrate WVO.

Rick
I think I understand. If I titrate my oil and the titration is 1 then the pH of the oil is 1.
 
Registered: January 08, 2012Reply With QuoteReport This Post
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quote:
I think I understand. If I titrate my oil and the titration is 1 then the pH of the oil is 1.


It's a little more complicated than that. A better statement would be, "It takes 1ml of solution to bring the pH of the sample up to 8-8.5".
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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quote:
Originally posted by RickDaTech:
It's a little more complicated than that. A better statement would be, "It takes 1ml of solution to bring the pH of the sample up to 8-8.5".

Rick
What is the pH of the oil.
 
Registered: January 08, 2012Reply With QuoteReport This Post
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If you titrate your vegetable oil with sodium hydroxide aqueous (water) solution with a strength of 1 gram per liter, and your titration number is 1 then you used 1/40 of a mole of sodium hydroxide to react the free fatty acids with sodium hydroxide in your vegetable oil. Acid plus base makes salt plus water. The resulting pH is more like 9- 10 not 1. Sodium soap is basic. A pH of 1 is a strong acid. The titration number indicates the concentration of free fatty acids in the vegetable oil, not pH. A pH from greater than 7 to 14 is basic. You might be able to find the pH of sodium hexadecanoate (sodium soap) on the internet. pH is a measure of the hydrogen ion concentration in water. No water no pH. Vegetable oil has little water in it so measuring its pH is a problem.

This message has been edited. Last edited by: WesleyB,
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post



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You said that when we dissolve the oil in alcohol then we can measure the pH of the oil by titration. If a titration of 1 does not mean the pH of the oil is 1 then how is it measuring the pH of the oil dissolved in the alcohol?
 
Registered: January 08, 2012Reply With QuoteReport This Post
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Jackson 39.

You may be able to understand the explaination in this thread a little easier:

The World Famous Chopstick Titration Technique (Pat Pend)

Rick
 
Location: Cowboy Country | Registered: December 06, 2004Reply With QuoteReport This Post
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RickDaTech,
At the risk of being labeled pedantic, I would like to clear up this misunderstanding you have about titration being used to find the pH of the oil. This is not correct.
When we titrate we are actually determining the amount of NaOH or KOH that will be required to neutralise any acid that may be in the oil.
This is not the same thing as finding the pH of the oil.
I know that people with limited chemistry knowledge often find this difficult to understand.

Also, it is not necessary for the oil to dissolve into the alcohol to perform a titration. Methanol and ethanol will also work to perform the titration and the oil does not completely dissolve during the titration using these alcohols.

If you would like any other explanations of the chemistry just ask.
quote:
Originally posted by RickDaTech:
You can measure pH of oil dissolved in alcohol. We do that when we Titrate WVO.

Rick
 
Location: France | Registered: October 18, 2010Reply With QuoteReport This Post
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Jackson 39; Vegetable oil varies in its composition from batch to batch. So we titrate batches of vegetable oil to find out free fatty acid composition. The concentration of free fatty acids vary. There's a little water in most new vegetable oil, maybe not much but a little. I expect that the pH of glycerol tri-fatty acid esters (the major component in vegetable oil) is neutral (pH 7), I'm not sure of that but I think its true. Also in vegetable oil are free fatty acids that do have a pH that's hard to measure. If these free fatty acids are isolated from the vegetable oil then oleic acid might be the major component. If you dissolve 2.82 grams of oleic acid in one liter of distilled water then the pH is about 3.51 at 25 degrees centigrade. That's what my math said. But there's only a little water in the vegetable oil, not a liter. I'm not sure what the pH of vegetable oil is, figuring it on paper is the only way I can figure how to get a range.I would guess that the pH of new vegetable oil is between 6 and 7. The little bit of water in vegetable oil has a pH to it probably, but how is it to be measured? Dillan "When we titrate we are actually determining the amount of NaOH or KOH that will be required to neutralise any acid that may be in the oil." Acid plus base makes salt plus water. KOH + FFA does not make a neutral product. Potassium soap is about pH 10- 10.5. It is not exactly a neutralization reaction. Neutral is pH 7. Another acid base rule is a weak acid plus a strong base makes a basic salt. Thanks for clearing up this misunderstanding. If I have made an error please point it out. I'm still learning this stuff also.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
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WesleyB,

quote:
Originally posted by WesleyB:
I would guess that the pH of new vegetable oil is between 6 and 7.
pH is an index of the concentration of Hydrogen Ion (H +) in water. Since oil 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.

quote:
Dillan "When we titrate we are actually determining the amount of NaOH or KOH that will be required to neutralise any acid that may be in the oil." Acid plus base makes salt plus water. KOH + FFA does not make a neutral product. Potassium soap is about pH 10- 10.5. It is not exactly a neutralization reaction. Neutral is pH 7.
In chemistry, neutralisation is a chemical reaction in which an acid and a base react to form a salt. Water is frequently, but not necessarily, produced as well.
Neutralization reactions do not necessarily imply a resultant pH of 7
If a weak acid and a strong base participate in a neutralization reaction, the resultant pH will be greater than 7.
 
Location: France | Registered: October 18, 2010Reply With QuoteReport This Post
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pH is a measure of the acidity or basicity of an aqueous [ie. water] solution. Oil can't have a Ph. Water dissolved or suspended in the oil can have a pH, but that's not a very useful indicator.

The titration we do to calculate a recipe to make biodiesel isn't measuring pH.
Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. In the case of titrating VO, we're determining the amount of additional caustic reagent needed to neutralize the FFAs so there is enough base caustic reagent left to do the transestrification of VO to biodiesel.



 
Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post



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quote:
Originally posted by RickDaTech:
You can measure pH of oil dissolved in alcohol. We do that when we Titrate WVO.
Rick
You are not measuring the pH of the oil when you titrate. You are actually conducting a test to determine how much Caustic will be consumed to neutralize the FFA's in the WVO.
 
Registered: October 06, 2010Reply With QuoteReport This Post
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realy, when you mix a sample for titration the ph # of that liquid gives no useful information as far as titration or the amount of ffa in the oil. I often measure ph of the sample with a meter as I add each ml of caustic solution, the higher the ffa content the greater number of mls you can add without any change in ph. the end point is all you have to be concerned with, when the meter reads 8.5 count the mls of caustic solution to get there. I have used ph meters for many year, they are quite slow to respond, but if you are not in a rush the results are always good. as has been mentioned above you are only measuring the ph of the contaminants in the oil, oil has no ph.


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Thanks for correcting RickDaTech's mistake john galt.
I am happy to see that someone knows the chemistry involved.
quote:
Originally posted by john galt:
pH is a measure of the acidity or basicity of an aqueous [ie. water] solution. Oil can't have a Ph. Water dissolved or suspended in the oil can have a pH, but that's not a very useful indicator.

The titration we do to calculate a recipe to make biodiesel isn't measuring pH.
Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. In the case of titrating VO, we're determining the amount of additional caustic reagent needed to neutralize the FFAs so there is enough base caustic reagent left to do the transestrification of VO to biodiesel.
 
Registered: January 08, 2012Reply With QuoteReport This Post
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