[Chemistry Class Notes] Lye Pdf for Exam

Lye is an alkaline solution that is produced by the reaction of wood ashes and water. The process is called leaching. Lye is commonly used for making soaps and washing. It can also be considered as a strongly alkaline solution like potassium hydroxide or sodium hydroxide.

Pellets of Caustic Soda Lye

Uses of Lye

The lye chemical has been widely used for several purposes. Many industries consider a separate unit for making lye as they need the chemical as a part of their processing. Let us look at some of the applications of lye in our daily life.

1. Soap Production

Sodium hydroxide lye (or caustic soda lye) and potassium hydroxide lye are widely used in soap production. In general, potassium hydroxide soaps are more readily soluble in water and are softer than the caustic soda lye. These caustic lye soaps are not found to be interchangeable; they have separate sets of properties and are widely used for different purposes. 

Hot process washing is a unique process of washing. It uses a lye soap as the chief ingredient in the process. In this preparation, the lye particles are added to water. Since it is an exothermic reaction (reaction of alkalis with water generates heat), the solution is cooled down before it is added to butter and oils. This mixture is then heated over a period of one to two hours, and the molten solution is then poured into molds. The heating process needed to be slow for gradual and even heating, especially in a slow cooker.  

2. Food Industries

Although lye is mainly used as lye soaps, it has several applications in the food industry as well. It is used in curing several types of food like olives, Nordic lutefisk, lye rolls, bagels, pretzels, century eggs, hominy, mandarin oranges (canned), and Kabak tatlisi (a traditional Turkish dessert using pumpkins). It is also used as an effective tenderizer in different food like Japanese ramen noodles, Chinese noodles, zongzi (dumplings made up of glutinous rice wrapped in bamboo leaves), and Cantonese mooncakes. 

It is called Karwi in Boro and Khar in Assamese and is used in different food preparations, curing, medicines, and even in soaps. In the U.S., different grades of lye chemical are available. The higher grades are used in the food processing industries, while the lower grades are used for cleaning drains, oven cleaners, and de-cloggers.

3. Household Use of Lye

Since lye has several cleaning properties, it has found its application for different household purposes. Lye can react with fats and grease and dissolve them. This chemical reaction is called alkaline ester hydrolysis. These grease-dissolving properties are mainly used for commercial purposes like openers for clogged drains and oven cleaners.

Many households use lye for cleaning purposes. They apply lye solutions to tough grease and stains. After the grease gets dissolved in the lye solution, it is easily removed by rinsing. 

4. Tissue Digestion and Decomposition

The process of alkaline hydrolysis can also be applied to the digestion and decomposition of living tissues and animal carcasses. The carcass is placed in a closed and sealed chamber, and the lye solution in water is added to the chamber. Heat is provided to fasten the process.

 At the end of the reaction, the chamber will have a fluid that looks like coffee. Some remains of the carcass, like bone hulls, might be present. These bones are made up of calcium phosphate, which can be crushed with little force. Since lye is cheap and is readily available, it is commonly used in decomposing carcasses from roadkills. Many bodies can be treated at once in this process.

5. Identification of Fungus

Potassium hydroxide solution (3-10%) can exhibit a change in color in some species of mushrooms like Boletes, Cortinarius, and some species of Agaricus.

Safety Concerns Associated With Lye Solutions

Since Lye solutions are alkaline in nature, they are coarse on human skins. Therefore, proper care must be taken while handling lye solutions. Lye can cause skin blisters when coming in contact. It can also lead to tissue decomposition if a high concentration of lye solution is in contact with the body. 

Therefore, safety precautions are a must for handling lye solutions. Safety gloves, equipment, and covers are necessary. Proper access to washing and medicinal kits must also be kept handy while handling lye solutions.