Determination of Saponification Value of a Fat or Oil

BS (Hons) 2nd Semester

Organic Chemistry Practical Practical Manual

Experiment Title: Determination Determination of saponificati saponification on value of a fat or oil. Theory Saponificatiin is the process by which the fatty acids in the glycerides of oil are hydrolysed by an alkali. Each mole of triglyceride uses three moles of KOH for saponification as per the following equation: CH2

O

O

CH

CH2

O

COR

COR

CH2

+

COR

Triglyceride

3KOH

CH

CH2

OH

OH

+

3RCOOK

OH

lycerol

!otassium salt of 

fatty acid "Soap# Saponification $alue is %the amount "mg# of the alkali required to saponify & g of an oil or fat'. This $alue is useful for comparati$e study of the fatty acid chain length in oils. ( known known quant quantit ity y of the the oil oil is refl reflu)e u)ed d with with a known known e)ce e)cess ss of alco alcoho holi licc KOH. KOH. (fter  fter  Saponification* the remaining KOH is estimated by titrating it against a standard acid. Materials 1. Alcoholic KO KOH: +iss +issol ol$e $e KOH KOH ",",- g# in dist distil ille led d alco alcoho holl "& litr litre# e#** keep keepin ing g the the o temperature below & / while the alkali is being dissol$ed "&0#. 2. 0.5 H!l* accurately standardi1ed. ". #henolphthalein in$ in$icator:  &2 in 32 ethanol %. Air con$ensers #roce$ure 4eigh igh completely dry liquid sample ",. g# into a flask. 1. 4e 2. (dd alcoholic KOH "- ml# slowly from the burette into the flask. ". Simultaneou Simultaneously sly** process process another another flask flask in the same way without adding the sample* connect air condensers to the flask and boil b oil the contents gently on steam bath for about an hour. %. (llow the contents to cool at the room temperature and rinse the inside of the condensers with a little distilled water and then remo$e the condensers. 5. Titrate the solutions against -.0 H/l using phenolphthalein as indicator. &. The end point is the 5ust appearance of pink colour "pink to 5ust colorless#. difference between the titration titration $alues of the blank flask flask and the flask containing containing 7. 6rom the difference the oil* the amount of KOH in mg "saponification $alue# that has been used for &g of the oil* can be calculated. !alculatons

Saponification $alue 7

 89.- "titre $alue of blank −Titre $alue of sample# 4eight of sample "g#

Dr. Muhammad Muha mmad Aslam Asl am & Dr. (ssistant !rofessor/hemistry !rofessor/hemistry ;ni$ersity of Education* Township /ampus*