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The World Famous Chopstick Titration Technique (Pat Pend)
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The World Famous Chopstick Titration Technique (Pat Pend)

Hi Everyone.
I first posted these instructions in 2005 and the original posting is now in the archives here. http://www.biodieseldiscussion...owthread.php?t=33574

Over that time a few things have changed, especially that most people now use KOH instead of NaOH in the reaction.
With that in mind I have gone through the original instructions and updated them as needed and re-posted it here."


On With the Show

Titration is a simple test to determine how much KOH is required to neutralize the FFA's (and any other acid) in one litre of oil. This amount of KOH which is called the "titration amount' is added to the Methanol as an extra amount of KOH beyond what is required to perform the transesterification.
The amount of KOH required to perform the transesterification reaction for one litre of oil is normally called the “base amount” of KOH.

You add the Base amount to the titration amount to arrive at the total amount of KOH required to react 1 litre of oil

Please Note
I have written this procedure for titrations using KOH.
If you are going to use NaOH in the reaction, just substitute NaOH for the KOH in the directions.
Also change the base amount from 7g KOH adjusted for purity to 5g NaOH

A Word About using KOH
Many people use a base amount of 7g KOH for KOH with a purity of 100%
KOH rarely comes with a 100% purity. More often it is around 90% purity.
If your KOH is 90% purity, increase the base amount of KOH to 7.8g KOH per litre of WVO and then add the titration amount to this.
If your titrating fluid is made from the KOH you will use to react the oil, you do not need to adjust the titration amount of KOH.

If you are using NaOH the base amount is 5 and normally NaOH has a purity greater than 99% so no adjustment is normally required to the base amount if you are using NaOH

[

Please Note
If you use ethanol for the titration, all the oil will probably NOT dissolve into it. That is fine, the titration will still work although extra mixing vigour is recommended.

MATERIALS NEEDED

ALCOHOL
1- bottle of isopropyl alcohol (isopropanol).

In the USA, Iso-HEET Premium Fuel System Dryer & Antifreeze, is 99% isopropyl alcohol.

Rubbing alcohol is also isopropanol but might be a fairly low purity. If that is all you can get give it a try

Cleaning fluid sold to clean electronics in places like radio shack is also often isopropanol
OR
1- bottle of Ethyl Alcohol (Ethanol).

In Australia and many other countries, "methylated spirits", commonly called "Metho" is 95%+ Ethanol and only about $4 a litre.

In a pinch, you can use methanol for the titration.

1 Box Flat Wooden Tooth Picks

INDICATOR
1 container of Ground Turmeric

Turmeric is a spice and is readily obtainable from all Fine Grocery Stores.
OR
1- bottle 1% Phenolpthalein indicator

Good luck finding it.
OR
1- bottle of Phenol Red

Phenol Red is normally used to check the pH of swimming pools, is a liquid, and is easily available from all fine Pool Shops.

1-litre of "Titrating Fluid"
"Titrating Fluid" is made by dissolving 1g KOH into 1 litre of distilled or Rain Water. In a pinch, tap water will work too.
To make your titrating fluid use KOH from the bag of KOH you will use to perform the reaction.
As you might not have particularly accurate scales, one way of achieving greater accuracy is to measure out 10g KOH and dissolve this into 1 litre of distilled or rain water.
Now take 100ml of this water and mix with 900ml distilled or rain water.
You now have pretty close to the 1g KOH in 1 litre of distilled or rain water.
Or, go to your local High School Science Dept and ask them to do the measuring for you.

EQUIPMENT NEEDED

1- 50ml medicine measuring cup
with ml graduations marked on the side From local pharmacy. I think the tapered cone shaped ones are best.

1- glass 1 ml eyedropper with graduations marked on the side. From local pharmacy

1- 3ml Syringe (no sharp) From local pharmacy

1- plastic chopstick From local Chinese restaurant.

Total equipment cost should be under $10 and is good for hundreds of titrations.
No fair counting the cost of a meal at your favourite Chinese shop to steal a chopstick.

Be aware that because Phenol Red, Turmeric and phenolphthalein all change colours at a different pH, a slightly different titration technique is required with each one.

THE PROCEDURE USING PHENOLPTHALEIN

1. Pour about 10ml of room temp alcohol (Isopropyl or Ethanol} into the 50 ml medicine measuring cup.

2. Place 3 or 5 drops of Phenopthalein solution into alcohol

3. Fill the syringe with "Titrating Fluid" and while using the chopstick to vigorously stir, slowly, drop by drop, add "Titrating Fluid" to the alcohol until the alcohol just starts to turn a permanent pink colour and then STOP.
You have just performed the "Blank Titration" The "Blank Titration" neutralizes any acid that may be in the alcohol.
You are now ready to titrate the oil in question.

4 Using the 1ml eyedropper, add exactly 1ml of the oil to be titrated to the alcohol.

5. Place into microwave oven and microwave until the First Bubble appears (5 or 10 seconds)STOP Note: This step is not absolutely necessary.

6. Now, always filling the syringe with exactly 3ml of "Titrating Fluid", start dropping the "Titrating Fluid" into the medicine measure while stirring vigorously with the chopstick.
I find an up and down motion which breaks the oil up against the bottom of the medicine glass works best.
Do not stop stirring

7. Keep track of how many ml of "Titrating Fluid" is needed for the liquid to turn and remain a light pink for about 20 seconds before the colour fades.

This is your titration number which you then add to the base amount of KOH to find out how many grams of KOH is needed per litre of WVO.

It takes longer to read it than to do it.

THE PROCEDURE USING TURMERIC

1. Pour about 10ml of room temp alcohol (Isopropyl or Ethanol} into the 50 ml medicine measuring cup.

2. Scoop out a small amount of Ground Turmeric on the wide end of a toothpick.
Put the turmeric into the alcohol and use the Chopstick to stir it well into the Alcohol for about 5 seconds.
The Alcohol should now be a nice yellow colour.

3 Fill the syringe with "Titrating Fluid" and while using the chopstick to vigorously stir, slowly, drop by drop, add "Titrating Fluid" to the alcohol until the alcohol just starts to turn a permanent pink colour and then STOP.
You have just performed the "Blank Titration" The "Blank Titration" neutralizes any acid that may be in the alcohol.
You are now ready to titrate the oil in question.

4 Using the eyedropper, add exactly 1ml of the oil to be titrated to the alcohol in the medicine cup..

5. Place into microwave oven and microwave until the First Bubble appears (5 or 10 seconds)STOP Note: This step is not absolutely necessary.

6. Now, always filling the syringe with exactly 3ml of "Titrating Fluid", start dropping the "Titrating Fluid" into the medicine measure while stirring vigorously with the chopstick.
I find an up and down motion which breaks the oil up against the bottom of the medicine measuriing cup works best.
Do not stop stirring

7. Keep track of how many ml of "Titrating Fluid" is needed for the liquid to turn and remain it's darkest red for 20 seconds before the colour starts to fade.

This is your titration number which you then add to the base amount to find out how many grams of KOH is needed per litre of WVO.

It takes longer to read it than to do it.

THE PROCEDURE USING PHENOL RED

1. Pour about 10ml of room temp alcohol (Isopropyl or Ethanol} into the 50 ml medicine measuring cup.

2. Add 3 to 5 drops of phenol red to the alcohol.

3 Fill the syringe with "Titrating Fluid" and while using the chopstick to vigorously stir, slowly, drop by drop, add "Titrating Fluid" to the alcohol until the alcohol just starts to turn a permanent pink colour and then STOP.
You have just performed the [/b]"Blank Titration"[/b] The "Blank Titration" neutralizes any acid that may be in the alcohol.
You are now ready to titrate the oil in question.

4 Using the eyedropper, add exactly 1ml of the oil to be titrated to the alcohol in the medicine measuring cup..

5. Place into microwave oven and microwave until the First Bubble appears (5 or 10 seconds)STOP
Note: This step is not absolutely necessary.

6. Now, always filling the syringe with exactly 3ml of Titrating Fluid, start dropping the Titrating fluid into the medicine measure while stirring vigorously with the chopstick.
I find an up and down motion which breaks the oil up against the bottom of the medicine measuring cup works best.
Do not stop stirring

7. Keep track of how many ml of "Titrating Fluid" is needed for the liquid to turn and remain its deepest, darkest purple/ red for at least thirty seconds.

This is your titration number which you then add to the base amount to find out how many grams of KOH is needed per litre of WVO.

It takes longer to read it than to do it.</span>

While I am assured that the Turmeric Titration is more accurate than using Phenol red, and phenolpthalein is more accurate still, tests I have performed shows that Both Turmeric and Phenol Red give virtually identical titration results and are also virtually identical to the results obtained when using Phenolphthalein.
__________________
Saint Tilly






 
Location: ลึก ประเทศอินเดีย | Registered: March 03, 2001Reply With QuoteReport This Post
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