Estimation of acid and sopinification value of oil:-

*Principle:-
 Saponification value is defined as the number of milligrams of KOH required to completely hydrolyse (saponify) one gram of the oil.
The acid value is determined by directly titrating the oil in an alcoholic medium against standard potassium hydroxide solution.
Acid value refers to the amount of "free" fatty acids in the oil. Saponification value refers to the amount of esters that can be hydrolysed and turned into soap. Both these values are given as mg KOH per g of oil .

In practice a known amount of the oil  is refluxed with excess amount of standard alcoholic potash solution and the unused alkali is titrated against a standard acid.
The neutralization reaction between the fatty acids in oils and bicarbonate in an ethanol (80%) aqueous solution was performed in a closed headspace sample vial, from which the carbon dioxide generated from the reaction was detected by HS-GC. It was found that the addition of ethanol can effectively improve the reaction of fatty acids in oils with bicarbonate, conducted at 75 °C for 30 min. 

*Protocol:-
Estimate saponification value of oil

1)    Weigh 1g of oil in a tared beaker  and dissolve in about 3ml volume of [ethanol(95%) /ether] .
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2)    Quantitatively transfer the contents of the beaker three times with a further 7ml of the solvent.
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3)    Add 25ml of 0.5N alcoholic KOH and mix well, attach this to a reflux condenser.
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4)    Set up another reflux condenser as  the blank with all other reagents present except the oil.
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5)    Place both the flasks in a boiling water bath for 30 minutes . 
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6)    Cool the flasks to room temperature .
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7)    Now add phenolphthalein indicator to both the flasks and titrate with 0.5N HCl .
               
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8)    Note down the endpoint of blank and test .

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9)    The difference between the blank and test reading gives the number of millilitres of 0.5N KOH required to saponify 1g of oil.
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10) Take saponification value of oil


*Protocol :-
Estimate the acid value of oil-
10 g substance add in 50ml  mixture of equal volume of ethanol (95%)and ether 

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Now neutralized with 0.1M KOH to phenolphthalein solution.
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If the sample does not disolve in the cold solvent , connect the flask with a reflux condenser nd warm slowly, with frequent shaking, until the sample disolve 

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Add 1 ml of phenalophthalein solution and titrate with 0.1M KOH until the solution remains faintly pink after shaking for 30 second .
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Calculate the acid value from the expression

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