Acid Value

AIM:

To determine the Acid value of given oil. PRINCIPLE:

 Acid value is the number of mg of KOH required to neutralise the FFA present in 1g of the sample REAGENTS:

Neutral alcohol, 1% phenolphthalein,Stan phenolphthalein,Standardised dardised .1N NaOH PROCEDURE:

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Weigh accurately about 10 gm of oil into a 100ml conical flask. Add 50 cc of neutral alcohol & heat on a steam bath till the oil dissol dissolves. ves. Cool for a while,add 4 drops of phenolphthalein. With constant shaking titrate the contents in the flask against 0.1N NaOH solution from the burette till a pink color persists. FFA% & Acid value is calculated from the above procedure

There a number of ways of titrating WVO so as to get the right amount of KOH to add so as to neutralise the Free Fatty Acids contained in the oil Of course the Dr Peppers Chopstick technique (Pat Pending) using Turmeric is widely used by a lot of biodiesel makers worldwide, Tilly from paradise will confirm this We have now gone through a few of these issues in the series, this being no 7, with titration of the oil as one of the early ones A lot of us know how to titrate however we come across a few people asking how the percentage of FFAs can be found. It can of course be established quite easily, it is found by doing a titration Here is a procedure one can use so as to establish the percentage of Free Fatty Acids in his oil commonly referred to in the oil industry as the t he Acid Value Keep in mind this is only to measure the amount of the ffas, in the batch of oil been tested The amount of base so as to catalyse the oil must be added on top if you are going to do a reaction with that oil so as to make biodiesel relaying on this titration alone, which is ok

We need, 2 very clean as well as dry clear glass jars or beakers of about 500600 ml capacity A titrating pipette or dropper both graduated in ml Some isopropyl alcohol, about half a litre Some toluene, about half a litre again Phenolphthalein indicator A couple of stirrers, glass or plastic Titrating solution based on KOH, normality of 0.1 N A very accurate set of scales 0.1 g divisions to 25 Grams, The $10.00 from e buy are fine Procedure: 1. Prepare a solution of 50% isopropyl alcohol with 50% of Toluene. Total of  about 300 ml 2. Get two 500 ml clean glass jars or beakers if you have them 3. Place 125 ml of the solvent in each jar 4. Take 5 grams of the oil, add it in only one of the jars, weigh it out very accurately 5. In both of the jars add 2 ml in each of phenolphthalein indicator 6. Start titrating in both jars with 0.1 n KOH until the indicator turns pink, the colour should persist for a few seconds at least, keeping count of the amount added 7. We can now proceed to find out the percentage of Free Fatty Acids in the oil, the std formula which we are going to use for the Acid Value of our oil is AV= (A-B) x N x 56.1/W Explanation of the formula is as follows; AV= Acid Value A= Amount in ml of KOH to neutralise the jar/ beaker with our sample in it B= Amount in ml of KOH to neutralise the blank jar/beaker, the one with no oil in it N= Normality of our titrating solution in this case 0.1 W= Weight of our sample in grams It

is very important to remember % of FFA is half the AV

An extrapolation based on our findings will determine the amount of KOH needed so as to neutralise the FFAs for the quantity of oil we have

It is of course necessary to use weight for the oil if you are working in litres you can figure out the weight by using the SG of the oil If you have been following or printing out the posts in the series the information is there in so far as SG of materials are concerned It is also important to keep in mind the upper limit of FFAs to be neutralised via the addition of extra KOH as elaborated upon in a previous post in the series