Chemistry at home - Making soap while recycling
Normally I like to write here about code recipes.
But today I thought to bring a chemichal recipe, that can help us saving waste and learn some chemistry on the way!
And if somebody told you that its too complicated…
…dont worry.
The proportions I tried were:
are 6:6:1 with water,oil and NaOH.
The good thing?
You can also play around with the proportions, even adding perfume to it!
This is what we are going to create:
The Chemistry of Lye
Before we get started, lets understand what we are doing.
This beauty right here, is the one doing the job:
$$ NaOH(s) \xrightarrow{H_2O} Na^+(aq) + OH^-(aq) + \text{heat} $$
More details about the chemistry behind Lye 📌
The chemical reaction of NaOH (sodium hydroxide) with water is a dissolution process.
Not a typical chemical reaction (where new covalent bonds are formed).
Explanation:
NaOH(s): Solid sodium hydroxide.\xrightarrow{H_2O}: Indicates that the process occurs in the presence of water.Na^+(aq): Sodium ions dissolved in water (aqueous solution).OH^-(aq): Hydroxide ions dissolved in water (aqueous solution).\text{heat}: Represents the release of heat.
Is it exothermic?
Yes, the dissolution of NaOH in water is highly exothermic.
This means it releases a significant amount of heat, causing the water to become very hot.
See how Ive done lye (the temperature rises when mixing adding the water!)
I could see the water (3L) to get up to ~46C from ~19C
How much energy is released to heat water that way? 📌
Let’s calculate the energy required to heat water from 19°C to 46°C.
Given:
- Initial temperature (T1) = 19°C
- Final temperature (T2) = 46°C
- Specific heat capacity of water (c) = 4.186 J/g°C
- We’ll assume a mass (m) of 1 gram of water for simplicity. If you have a different mass, just multiply the result by that mass.
Calculations:
Temperature Difference (ΔT):
- ΔT = T2 - T1
- ΔT = 46°C - 19°C
- ΔT = 27°C
Energy Required (Q):
- Q = m * c * ΔT
- Q = 1 g * 4.186 J/g°C * 27°C
- Q = 113.022 J
Result:
- It requires approximately 113.02 Joules of energy to heat 1 gram of water from 19°C to 46°C.
KaTeX Formulas:
Temperature Difference:
\Delta T = T_2 - T_1
Energy Required:
Q = m \cdot c \cdot \Delta T
Where:
- Q = energy (Joules)
- m = mass (grams)
- c = specific heat capacity (J/g°C)
- ΔT = temperature difference (°C)
That was 113J/g * 3000 g = ~339KJ or 0.3MJ
For reference: One liter of gasoline contains approximately 32-34 megajoules (MJ) of energy (x100 times more).
Output:
The output of this process is an aqueous solution of sodium ions (Na+) and hydroxide ions (OH-), along with the release of heat.
The increase of OH- ions, makes the solution highly basic.
More details about Lye
Making soap with NaOH (sodium hydroxide), also known as lye, is a process called saponification.
It involves a chemical reaction between fats or oils and a strong alkali.
Chemical Formula:
The overall saponification reaction can be represented as:
- Fat/Oil + NaOH → Soap + Glycerin
More specifically, a triglyceride (the main component of fats and oils) reacts with sodium hydroxide:
(RCOO)₃C₃H₅ + 3NaOH → 3RCOONa + C₃H₅(OH)₃
Where R represents a long-chain alkyl group (the fatty acid part of the oil).
(RCOO)₃C₃H₅ is a triglyceride.
NaOH is sodium hydroxide (lye).
RCOONa is the soap (sodium salt of a fatty acid).
C₃H₅(OH)₃ is glycerin.
Important Safety Precautions:
- Lye is caustic: NaOH is extremely corrosive and can cause severe chemical burns. Always wear safety goggles, gloves, and long sleeves when working with lye.
- Ventilation: Work in a well-ventilated area to avoid inhaling lye fumes.
- Accurate measurements: Use a digital scale to accurately measure lye and oils. Incorrect measurements can result in soap that is either too caustic or too soft.
- Water and lye: Always add lye to water, never the other way around. Adding water to lye can cause a violent exothermic (heat-releasing) reaction, potentially splashing lye solution.
- Children and pets: Keep children and pets away from the soap-making area.
Basic Soap-Making Process:
Prepare lye solution:
- Carefully measure the required amount of NaOH.
- Measure the required amount of distilled water into a heat-resistant container.
- Slowly add the lye to the water, stirring constantly. The solution will heat up.
- Set the lye solution aside to cool.
Melt oils:
- Measure the required amounts of your chosen oils (e.g., olive oil, coconut oil).
- Melt the solid oils (e.g., coconut oil) in a stainless steel pot.
Combine oils and lye solution:
- Once the lye solution and oils have cooled to the appropriate temperatures (typically around 100°F), slowly pour the lye solution into the oils, stirring constantly.
- Use an immersion blender to blend the mixture until it reaches “trace” (a light pudding-like consistency).
Add additives:
- At trace, you can add essential oils for fragrance or other additives like colorants.
Pour into mold:
- Pour the soap mixture into a mold lined with parchment paper.
Insulate and cure:
- Cover the mold and insulate it to retain heat.
- Allow the soap to saponify for 24-48 hours.
- After this time, remove the soap from the mold and cut it into bars.
- Place the bars on a rack to cure for 4-6 weeks. During this time, the soap will harden and become milder.
Ph testing: before using your soap, it is very important to test the ph level, to make sure all of the lye has been reacted.
Finding Recipes:
- There are many soap-making recipes available online and in books. It’s crucial to use reliable recipes that provide accurate measurements.
- Using a lye calculator is also very important, these calculators allow you to insert the types and amounts of oil you want to use, and it calculates the precise ammount of lye that is needed.
My Experience
What I tried was with: 3L water + 3L used Oil + 0.5Kg NaOH (90%)
The costs?
1kg of NaOH is ~2$ and thats all you need to get those 3kg + 3*0.91 + 0.5 ~~ 6.23kg
What can you do with this?
For every 100g you are saving 1$ in soap, thats a x30 return on the money you placed on the project.
Or…mix it with more water and make gel?
With 200g you can make 1.5L of gel confortably (just adding more water).
In this case, you are saving 3$ in gel for every piece, thats a x90 return!