Carbon and its Compounds | Soaps and Detergents
How to Study the Chemistry of Detergents
Detergents are a class of chemical compounds that are used for cleaning because of their dual hydrophobic and hydrophilic properties. Due to its chemical structure and reactivity, a detergent can bind to an oily stain and be washed away in water, making it ideal for cleaning.The chemistry behind a detergent is pretty basic and can be understood with little effort.
Understanding the Composition of Detergents
Define surfactants.A surfactant is a special chemical that reduces the surface tension of water. You have probably seen water form beads on a window or table. This happens because of the surface tension of the water. If you add a surfactant, the water will spread and wet more of the surface.
- Surfactants can be classified by their ionic properties or electrical charge: anionic (negative charge), cationic (positive charge), nonionic (no charge), and amphoteric (either positive or negative charge).
- Soap is an anionic surfactant while detergents are made up of one or more surfactants of various charges.
- In the simplest terms, a surfactant reduces surface tension, so that water soaks the garment evenly. When the garment is properly wet, it is easier for the surfactant to remove dirt and grease.
Learn about fats and oils.Detergents are made up of fatty acids and sodium or potassium salts. Triglycerides are compounds derived from animal or plant fats and oils composed of three fatty acids and glycerine.
- Fatty acids are weak acids composed of a hydrocarbon chain attached to a carboxylic acid group (one hydrogen, two oxygens, and one carbon). They are considered surfactants, so they will float on top of water and reduce the surface tension.
Study alkali salts.An alkali salt is a soluble, basic (pH > 7.0) portion of an alkali metal such as sodium or potassium. Alkali salts are able to react with and neutralize acids due to their basic chemistry. Sodium hydroxide and potassium hydroxide are the two most common salts used to make soaps and detergents.
- The alkali salt attaches to the carboxylic acid group to form carboxylate. The entire molecule of carboxylate and fatty acid is soap.
- These chemicals are very caustic and can cause severe injury if handled improperly.
- Sodium hydroxide is used to make harder soaps, while potassium hydroxide is used to make softer, liquid soaps.
- In water, the alkali salt is more soluble than the fatty acid is.
Define hydrophobic and hydrophilic.In chemistry hydrophobic compounds are ones that “run away” from water. They are not water soluble. Hydrophilic are “water loving” compounds and are soluble in water. Soap is unique in that it has a hydrophobic end (fatty acid chain) and a hydrophilic end (carboxylate).
- The hydrophobic end is capable of binding stains such as grease and oil that are also hydrophobic, while the hydrophilic end is attracted to water and allows the stain to be washed away.
- Detergents work better when washing with hard water (water with mineral salts) because they have multiple surfactants.
Learning the Chemistry of Detergent-Making
Obtain the necessary materials.To make a detergent, you need fat and sodium hydroxide. Fats can be obtained from animals in the form of tallow and/or plants such as coconut or palm oil. Sodium hydroxide is also known as lye and is an essential component for making soap.
- Sodium hydroxide, or lye, is extremely caustic and must be handled properly. Wearing gloves, goggles, and long sleeves is essential while making detergents.
Use proper safety when working with lye.Because lye is a caustic substance, you want to use caution when working with it to avoid injury. When making a detergent, never make it near children or pets. Work in a well-ventilated area with open windows and doors. Because lye is a strong base, you always want to add it to the water. Adding water directly to the lye super heats the water and can cause explosions.
- Work near a water source to quickly clean up any spills.
- If you get any lye in your eyes, you must rinse them for at least 15 minutes to make sure all of the chemical is washed out.
Mix the fat with sodium hydroxide and heat.The first step of detergent-making is called saponification. The fat and oils contain fatty acid chains and triglycerides necessary for the detergent. When mixed with the sodium hydroxide and heated, the glycerine molecules are removed and the sodium hydroxide combines with the carboxylic acid of the fatty acid.
- The resulting soap is a long chain of carboxylic acid.
Add salt to remove the glycerine.The detergent is not very soluble in salt water, while glycerine is highly soluble. Most of the glycerine is removed because it is valuable, although a little is left in the soap to make it smoother. When the salt is added the mixture separates into two layers: crude soap and brine/glycerine.
- The soap rises to the top of the solution while the brine/glycerine sinks to the bottom.
- This process is usually repeated multiple times to remove as much glycerine as possible.
Neutralize the base with a weak acid.At this stage, the soap is not nearly as caustic as pure lye, but it is still too high to use. The base can be neutralized using a weak acid such as citric or phosphoric acid. The acid removes the remaining sodium hydroxide and makes the detergent safe for use.
- After neutralization, the soap is dried and then ready for use.
Deepening Your Knowledge
Use memory aids.The most important concept related to the chemistry of detergents is the fact that they have both a hydrophobic end and a hydrophilic end. To remember which part does what, remember that a phobia is a fear of something. Since hydro, refers to water, hydrophobic means “water-fearing.”
- If you can remember what hydrophobic is, you just have to keep in mind that hydrophilic is the opposite and means “water-loving.”
Learn the properties of anionic and cationic detergents.Anionic detergents have a negative charge on the hydrophilic end while cationic detergents have a positive charge on the hydrophilic end. They are considered more harsh because they modify protein structures.Cationic detergents are also capable of killing microbes and work very well to neutralize residual anionic detergents molecules.
- Anionic detergents are commonly used for scrubbing floors.
- Cationic detergents are commonly used to wash clothes and in shampoo.
Know the properties of nonionic detergents.Nonionic detergents are a subgroup of detergents that have no electrical charge. Because of this lack of charge, they do not react with hard water ions making them less useful for washing clothes. They tend to foam less than ionic detergents as well.
- They are generally used as dish-washing liquids.
Video: Soaps and Detergents
Your Top 11 Kitchen Essentials Checklist to Cook Healthy Recipes
This Husband Took Some Oh-So-Sensual Dudeoir Pics as a Valentines Day Gift to His Wife
How To Deal With A Hairy Back
5 Totally Useless Things We All Do To Protect Ourselves From Germs
Stylish Scarves To Keep You Warm This Winter
10 Must-Have Products for Sweat-Proof, Waterproof Makeup
Zo herstel je je in de was gekrompen trui
Text Mistakes You’re Making
How to Stay Warm when Sleeping in a Tent
Make Your Own Marinades and More