How Does Soap Made From Vegetable Oil Differ From Animal Fat
Experiment 8
Saponification and the Making of Soap - An Example of Bones Catalyzed Hydrolysis of Esters
Objectives
In today's experiment, we will perform a reaction that has been used for millennia: the making of soap. Animal fat and vegetable oils are composed principally of esters of the long chain fatty acids and glycerol (glycerin; ane,2,three-propantriol). Hydrolysis of these triglycerides (triacylglycerides; TAG) in base (e.g., NaOH) yields glycerol (a saccharide) and the sodium salts of the fatty acids. Because the fatty acids are ions, they are soluble in low concentrations in h2o (actually they are soluble because they class micelles), but in loftier concentration form insoluble aggregates called soap. You will start with a vegetable oil and volition use NaOH to hydrolyze these triglycerides. Bones hydrolysis of esters is chosen saponification. The reaction for this experiment is shown:
The triglycerides most commonly used to make soap commercially are from animate being sources, such as tallow, although plant fats from coconut, palm and other vegetable oils can be used. Pure coconut oil yields soap that is very soluble in water considering information technology contains predominately myristic and lauric acids (fourteen- and 12-carbon fat acids, respectively). Soaps made from animal and other vegetable sources contain more xvi- and 18-carbon fatty acids and are more often than not harder and like shooting fish in a barrel to form into shapes. To soften these harder soaps, coconut oil is oft included in the saponification reaction to make the soap softer.
Procedures
Caution: When y'all prepare the soap you volition demand to eddy the mixture until nigh of the h2o is evaporated. This may lead to splattering so be careful that the hot mixture does not splash on you. Follow the precautions listed below.
- Regulate the rate of boiling to maintain a steady boiling (set up the estrus knob to "ane" setting). Keep your hands and face up away from the peak of the flask. Disposable gloves tin be worn, if available. Although the boiling must be vigorous, as the liquid evaporates, be enlightened of the danger of splattering, and that the soap does non burn.
- Make sure that the flask does not tip over, such as if a stirring rod is left in the chalice. You tin can place an O-ring or clench around the flask to secure it. A chalice can be inverted as a cover to keep the soap from splattering out likewise.
- Try to avoid splattering, and e'er wear your goggles.
- Continue heating until the liquid is mostly gone.
Preparation of Soap:
Annotation: If desired the soap for this experiment may exist prepared for the lab by the instructor or a specific educatee group in a larger portion. Inquire your instructor whether each grouping will ready their own soap, or if soap will be prepared for the entire lab.
Prepare a mixture of 15 mL of 20% (5 M) sodium hydroxide and 10 mL of vegetable oil in a 150-mL flask. Add a stirring bar to the flask, to prevent explosive humid of the NaOH-oil mixture. Turn the stirring hot plate on at any setting to get it humid, and then switch to the lowest setting when boiling begins. Turn on the stirrer to let the stirring bar rotate. Eddy the mixture, observing the precautions listed above. Carefully command the heating, but you should oestrus the mixture high plenty to maintain a constantly boiling mixture. The saponification is complete if a wax-like solid begins to form that on further cooling becomes hard and somewhat breakable. On the other mitt, if the mixture cools to a syrupy liquid, saponification is not complete, and heating and stirring must exist resumed. It might be advisable to add more (5 mL) 20% NaOH and boil the mixture until its h2o is expelled. Saponification should exist consummate by thirty-45 min (but it may have only 15-20 min).
While the mixture is heating, prepare a concentrated common salt solution by dissolving 50 g of NaCl in 150 mL of distilled water in a 400-mL chalice. (Prepare this solution immediately so that it is gear up when your soap is ready.) When the saponification reaction is consummate, remove the flask from the rut source using HotHandsTM to hold the hot flask. Pour the reaction mixture chop-chop into the saturated salt solution (yous may have to scrape the solid into the NaCl solution using a scoopula). Stir the mixture thoroughly for several minutes; and then, collect the precipitated soap on a B�chner funnel. Launder the soap twice with 10 mL of ice-common cold distilled h2o (cool the water with ice, simply don't add the water ice to the distilled h2o). After yous take collected and washed the soap, continue to draw air through the lather for several minutes to help dry it. Save the soap for use in the evaluation section.
Evaluation of Soap
Deliquesce about 1 g of your lather in 50-60 mL of boiling distilled h2o (this is the Lather Solution). Add most 1 g of detergent (provided by the lab) into most 50-60 mL of distilled water (use hot water if information technology is solid detergent, or room temperature water, if liquid); this solution will exist the Detergent Solution. If either the soap or detergent solution is cloudy, this solution must be filtered prior to being used in the procedures outline below (rinse your filter flask and filter your cloudy solution through a pocket-sized B�chner funnel, collecting the filtrate for experimental purposes).
Experiment 1: Emulsification (dissolving) of Oils
Place iv drops of mineral oil in each of three tubes. Add five mL of distilled h2o to one tube, 5 mL of your soap solution to another, and 5 mL of your detergent in the last tube. Milkshake the tubes briefly and observe how well the oil is emulsified in each. Tape your observations in the table below.
| Tube #1: Water | Tube #2: Soap Solution | Tuber #3: Detergent Solution |
Experiment two: Reaction with metallic ions
Although the sodium and potassium salts of mutual soaps are soluble in water, the metal cations Mg2+, Catwo+, and Iron3+, which are typical components of "hard" water, form insoluble complexes. The insoluble complexes grade a scum on the top of the water, and lead to the "ring around the tub" problem. Most detergents, however, do not respond in a like mode, and can be used in both "hard" and "soft" h2o.
Place five mL of your soap solution in each of three test tubes. Add together to each tube 2 mL of a 1% solution of CaCl2, MgClii, and FeCl3 and notation whether a precipitate forms. Milkshake each tube and observe what happens. Echo using the detergent solutions.
| Tube #1: Soap plus Mg2+ | Tube #2: Soap plus Ca2+ | Tube #3: Lather plus Fethree+ |
| Tube #1: Detergent plus Mg2+ | Tube #2: Detergent plus Ca2+ | Tube #iii: Detergent plus Atomic number 263+ |
Experiment 3: Is lather bones or acidic?
Since soap is a sodium common salt of the fatty acids, you will determine if the acid class of these fatty acids (in contrast to their anionic forms) is soluble in water. Get-go, add a driblet of phenolphthalein (a chemical which turns pink in basic solution, with pH greater than seven.0, merely which is colorless in acidic solutions) to a 5-mL sample of your lather and of your detergent. Note any observations. Remember that a pinkish color indicates that your solution is basic (with a pH greater than seven.0).
(You can employ the tubes from to a higher place, with the phenolphthalein in them, for the side by side part of the experiment.)
Reaction with acid: 2nd, test a five-mL sample of your soap solution and a sample of your detergent solution past adding five mL dilute (3 1000) HCl. (If the color of the solution is still pink, due to the phenolphthalein, and then keep adding acid until the pink color disappears.) When the pink color is gone, the solution will be acidic. Notation your observations (i.due east., is the contents of the tube clear? is it cloudy? does it bubble?).
| Tube #ane: Soap plus phenolphthalein | Tube #two: Detergent plus phenolphthalein |
| Tube #one: Soap plus HCl (pinkish color is gone) | Tube #2: Detergent plus HCl (pink color is gone) |
If there will exist a single, lab-scale training of lather for the lab, your instructor, or designated group, should follow the procedure beneath:
Prepare a mixture of 75 mL of 20% (5 M) sodium hydroxide and fifty mL of vegetable oil in a 500-mL Erlenmeyer flask. Add together a large stirring bar to the flask, to prevent explosive humid of the NaOH-oil mixture. Turn on the stirrer to let the stirring bar rotate. Turn the stirring hot plate on at whatsoever setting to get it boiling, and and then switch to the lowest setting possible when boiling begins. Boil the mixture, observing the precautions listed above. Carefully control the heating, but you should heat the mixture high enough to maintain a constantly boiling mixture. The saponification reaction is complete when a wax-similar solid begins to form, that upon farther cooling becomes hard and somewhat brittle (like soap). On the other hand, if the mixture cools to a syrupy liquid, saponification is not consummate (oil is remaining). Continue heating and stirring your reaction, and it might exist advisable to add more than (15-20 mL) 20% NaOH to the humid mixture. Saponification should be consummate past 30-45 min (but it may take only fifteen-20 min).
While the mixture is heating, ready a concentrated salt solution by dissolving 100 1000 of NaCl in 250 mL of distilled (DI) water in a 600-mL chalice. (Prepare this solution immediately so that it is set up when your soap is ready.) When the saponification reaction is consummate, remove the flask from the estrus source using HotHandsTM to hold the hot flask. Pour the reaction mixture quickly into the saturated common salt solution (yous may have to scrape the solid into the NaCl solution using a scoopula). Stir the mixture thoroughly for several minutes; and then, collect the precipitated lather on a B�chner funnel. Wash the soap (in the funnel) twice with 50-100 mL of water ice-cold distilled water (cool the water with ice, but don't add together the ice to the distilled water since the ice is made from tap water). After you take collected and washed the soap, keep to draw air through the soap for several minutes to help dry it. Save the lather for utilize in the evaluation section.
Dispense small amounts of soap to each student grouping for apply in their experiments.
Become To Experiment: 1 2 iii 4 five six vii 8 9 10
Return to Chem102 Experiments Index
Copyright � Donald L. Robertson (Modified: 09/x/2009 )
Source: http://home.miracosta.edu/dlr/102exp8.htm
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