The group was assigned several tasks with several goals leading to an overall goal of composing and determining a soap (or detergent) that will help clean birds affected by an oil spill, and will help prevent the buildup of soap scum. The more specific goals from this project included testing the solubility of fats, oils, soaps, and detergents, comparing desirable properties, latherability, etc., of the soaps and detergents, observing and examining the environmental effects from soaps, detergents, and their wastewater, determine the cause of scum and a solution for it, and lastly, picking the best soap or detergent for the environmental group whose job is to clean up the oil spill.
The group composed soaps and detergents for the same goals, however, while the two commonly used cleaning items share some similarities, such as being surfactants, substances that can gather together on the surface of water and change the properties there, they have some distinct differences.1 Detergents are made synthetically by combining chemicals such as Lauryl Alcohol, sulfuric acid, and sodium chloride, and lauryl alcohol, sulfuric acid, and sodium hydroxide, and this differs from the composition of soaps which are precipitates of fatty acids and contain carboxylic groups while detergents have more concentrated sulfate groups.2 So, while each substance has a similar purpose, they each contain molecular and chemical makeup that differs from the other.
Each soap and detergent yielded both a solid and liquid filtrate due to the chemical interactions that created a precipitate and saponified the materials, meaning that within each reaction where the soaps were composed, the reactants interact to form an insoluble solid, a precipitate. This is beneficial because it allowed several types of testing to be performed to ascertain the ideal qualities and properties of each type of substance whether that be by solubility tests, pH tests, or titrations. With solubility testing being the first test conducted (the procedure outlined in the Solubility Tests section), the results in Table 1 show that olive oil-based soap and vegetable-oil based soap were the only soaps that were soluble in water, with the lard and shortening-based soaps not being soluble in water. This could be because the lard and shortening based soaps contained a higher amount of fatty acids which are insoluble. However, all four soaps were soluble in alcohol which indicates that the substances have polar properties, but not enough as sufficient to be soluble in water, as the results show that not all the soaps dissolved in water. This could speak to the functional groups that exist in both soaps and detergents as well as alcohols, indicating that the hydrocarbons and alcohols react in a way that causes dissolution of the hydrocarbons. The detergents were not subjected to solubility tests due to an oversight by the group, but would likely have been soluble in water and alcohol because detergents, like soaps,
must contain a hydrophilic component in their makeup which will attach to water while the hydrophobic part will attach to another substance, such as dirt.3
The soaps and detergents also underwent pH, latherability, cleansing effectiveness, residue, dispersion, and titration tests. The pH test, as outlined in pH Tests , determined, as presented in Table 2 , that Detergent 1, composed according to the first method outlined in the lab manual, was the only acidic solution, its strip turning red and approximating its pH at about 1. The shortening-based soap and Detergent 2 both had a pH level of about 11, and the vegetable oil, olive oil, and lard-based soap solutions had the most basic pHs of 12. These levels were indicated by the intensity of the color on the pH strip, for example, detergent 1’s pH strip prior to titration was red, indicating its acidity, and the lard-based soap’s was navy, showing its basicity. A matching pH table was located on the lab wall with example colors of the pH scale, and this led to the recorded values being reputable because of the given chart that allowed students to compare the pH of the strip they had tested to that of scientifically recognized values. Latherability consisted of rubbing the solid filtrates onto gloved hands and running them under the sink water, continuing to rub them a few seconds after the water was turned off to see the amount and type of bubbles produced. This procedure is outlined in the Latherability section, and results are presented in Table 4 , showing that vegetable-oil based soap had the most latherability, lard-based soap had greasy and white bubbles, and the rest of the soaps and detergents had regular white and foamy bubbles. The cleansing effectiveness test was then conducted, its procedure given in Cleansing Effectiveness and its purpose to determine which soap would best affect IMFs of oil as to break up the particles. This data is located in Table 4 with shortening, vegetable oil, and Detergent 2 removing oil while the rest did not.
The residue test aimed to see which of the solid filtrates would remain behind after being rinsed. Table 5 shows that the lard-based soap was the only substance to have any residue leftover after the rinsing process. The dispersion test and titration were a bit more complex. The dispersion test determined whether or not the soap or detergent could truly disperse oil, as it contained the soap liquid filtrate and oil, and the group examined the results after a test tube was shaken to see if any oil droplets remained. This would mean that the oil would have separated from itself due to the soap or detergent’s hydrophilic components that grab onto water molecules and hydrophobic components that can pick up dirt or oil. Table 5 shows these results, that Detergent 1 and the olive oil-based soap had the least amount of dispersion while the rest dispersed well. Lastly, the titration was determined based on the results of the pH tests. The acidic solution of Detergent 1 was placed under a buret and titrated with a base (Sodium Hydroxide) while the other five soaps and detergent 2 were titrated with Hydrochloric Acid. The purpose of titration was to determine the solution concentration and then neutralize it, detecting the point of equivalence.4 As shown by graphs of each soap, of the titrations completed thus far, Detergent 1 required 61 drops of the titrant, bringing its pH to 10.65, the shortening-based soap required 688 drops of titrant which
led to a final pH of 1.33, and the vegetable oil-based soap required 1223 drops of titrant, bringing its pH to 1.42. Meanwhile, the olive oil-based soap, had 138 drops of the titrant until the solution was neutralized to a pH of 1.91, Detergent 2 experiences 442 drops before reaching a pH of 2.10, and the lard-based soap required 743 drops of titrant until it reached a pH of 1.63. These results lead to the determining of the volume of titrant needed for each solution of soap or detergent, and to further identify where the neutralization occurred, these were:at about 2.4 mL of titrant for detergent 1, 20.5 mL for detergent 2, 34 mL for the lard-based solution, 5.7 mL for the olive oil, 30 mL for the shortening titration, and 53 mL for the vegetable oil solution’s titration.
Scientific Explanation of Claims/Support
Creating soaps from four different starting substances and detergents through two differing methods ensured that the group could perform the task at hand which would ultimately lead to determining which soap or detergent was the “best” fit for the environmental group looking to help clean up animals after an oil spill. Creating six slightly different substances meant that each soap or detergent, though similar in use and concept, had some differing properties, whether those be latherability, pH, cleansing effectiveness, or more, stemming from their differences in makeup. For example, the soaps whose origin lay in vegetable and olive oil were the only two soaps of the four that were soluble, as referenced in Table 1 , due to their abundance of hydrophilic molecules in comparison to those of the insoluble soaps of lard and shortening.
Beginning with solubility tests after the soaps and detergents were composed, vegetable oil and olive oil soaps were the only ones who were soluble in water. Soaps are all composed of either fats or oils which contain triglycerides and hydrocarbon chains that have hydrophilic and hydrophobic ends.5 The interactions between water and other materials such as grease and dirt are, in essence, the basis of cleaning with soaps and detergents because the hydrophilic parts of molecules within soap attach themselves to water and the hydrophobic parts attach to dirt.3 Since the lard and shortening-based soaps contain larger amounts of solid, specifically composed of more hydrophobic groups, after creation than the olive and vegetable oil, they tested as insoluble in the lab, with the olive and vegetable oil’s more liquid properties allowing the triglycerides more of an opportunity to locate oil and water, thus being soluble. Next, the pH test, relied solely on the composition of the soaps and detergents, and as the results show, the only substance to test as acidic was Detergent 1. This was because its method of preparation differed from that of the other detergent in that it was mostly composed of acidic solutions (lauryl alcohol, sulfuric acid, sodium chloride, and just some sodium hydroxide) while Detergent 2’s procedure omitted the sodium chloride additive, making it more basic. The pH test, reliable due to the provided pH strip color scale in the lab, determined what the soaps’ liquid filtrate would be titrated with. If they were acidic, they would be titrated with Sodium Hydroxide, and if they were basic, Hydrochloric Acid, and this is because a solution with an opposite pH of that being observed
must be used to titrate since it can neutralize and balance out the pH of the solution being titrated.
Titrations allow a solution to be balanced out, or neutralized, by an opposing concentration to ensure that the substances being made are safe enough for their intended use, such as the soaps in the lab which could be harmful if they are too high or low of a pH and used on skin.5 Detergent 1, shortening-based soap, and the vegetable oil-based soap were titrated initially, with the Detergent 1 requiring titration with Sodium Hydroxide and the rest needing Hydrochloric Acid. The graphs of the titrations show a trend indicating that the number of drops needed for the solution to neutralize increased dramatically with each trial. This could be natural, due to the amount of solution needing to be titrated or the strength of the pH that is being neutralized. It is significant due to the increase of volume of titrant needed to oppose and neutralize the strength of each substance’s pH.
Tables 4-7 show the plethora of other tests, including latherability, cleansing effectiveness, residue, and dispersion tests. These were all necessary to ascertain the specific and differing properties among the soaps and detergents. The latherability test showed the soaps and detergents yielding white and soapy lathers when tested, with the lard differing having a white and greasy lather and the vegetable oil producing the most lather. The bubbles that occur throughout the test are due to the fact that when soap molecules interact with water and an outside stimulus causing friction, lathering occurs.6 The vegetable oil-based soap could have had the best latherability for a number of reasons, including a varied amount of air coming in contact with the soap creating bubbles, or human variability and force when lathering. This type of seemingly-subjective outcome could also be seen with the results of the residue test since the lard was the only soap to have residue. This is due to its dense and greasy properties, coming from excess fatty acids, since it is essentially oil fat.
Lastly, the cleansing effectiveness and dispersion tests finished the testing process to discern differences in soap and detergent properties. The cleansing effectiveness allowed the group to see whether or not the soap successfully removed drops of oil when mixed. Remembering that soaps and detergents are surfactants, it can be trusted that they can dissolve in the water upon which they were once aggregated and create an uniform congregation of round particles, micelles, that can form with a high concentration of the surfactant and trap the oil.1 The shortening-based soap, vegetable oil-based soap, and Detergent 2 were the only substances to remove the oil droplets while the lard, olive oil, and detergent 1 did not have effective cleansing powers. This is due to acidic portions of the substance that had greatly decreased cleansing action because the soap’s fatty acids separate and become free and ineffective, as well as micelles and their properties.7 ,1 The dispersion test relates to the cleansing effectiveness test because it, too, allowed the soaps to interact with oil to see whether or not they would “clean” or
disperse the oil. Table 6 shows that detergent 1 and the olive oil soap were the only soaps with effective dispersive properties because they did not show a distinct layer of the water, soap, and oil that had been mixed, but their molecule grabbed the oil particles and interacted with them in a way that separated and dispersed them. The other four samples may not have had strong dispersion due to the amount of the soap sample present, since all the beginning compositions yielded different amounts of filtrates, and the strength of the soap.
The best detergent based on behavior throughout several tests was Detergent 2 because it, among other factors, did not leave behind residue, lathered well, and dispersed oil better than detergent 1. The better soap was the one composed from vegetable oil because it had the best lather, did not leave residue, and cleaned effectively. When deciding between soap and detergent for the use of cleaning up the oil spill, the vegetable oil-based soap is the best because detergents are slightly harsher on the environment, and this soap had the overall best results from all of the tests.
Sources of error could exist in several areas, since the group has four people, ran several tests, went a day without a group member, and relied on technology. Each test was run by a different person, which can lead to variability with yields and results as well as with perceptions and preferences in reading measurements. This could have occurred when putting liquids in beakers or cylinders, transferring the substances between containers, or misreading measurements, for example, not reading the bottom of the meniscus of the fluid in the measurement container or estimating incorrectly by not reading the measurement at the meniscus. The titration program, Capstone, could have led to an error as well because it is difficult to work with, and while it leads to the elimination of human error, technology glitches occur, and machines are not infallible.